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dot429
10-12-2009, 10:11 PM
Greetings all,

Last week, I finally broke down under the immense pressure of my addiction and bought a Rock River Arms 9mm upper and their conversion kit from Riflegear.com. Those folks are great to deal with; I ordered and received everything form the UPS guy in two days. It's great having a dealer like that in Costa Mesa.

My build consists of:

- RRA 9mm mid-length upper
- RRA 9mm magwell conversion block, 9mm specific carbine buffer, hammer, and one 10 round RRA magazine
- KD stripped lower
- Magpul enhanced trigger guard
- DPMS LPK
- JP Enterprises reduced power fire control spring kit (yellow)
- Precision Reflex, Inc., Military charging handle latch ( http://www.brownells.com/.aspx/sid=21150/pid=8734/sku/Military_Latch__Only?mc_id=10000 )
- B-16 bullet button (uses JP anti-walk pin instead of the standard pin)
- ACE M4 SOCOM collapsible stock
- Hogue grip (not my favorite, but it's what I had laying around)
- Brownell's chrome silicon carbine action tube spring
- Aimpoint Comp M/L 3
- GG&G Accucam QD cantilever mount
- Brownell's rear BUIS w/Trijicon inserts (http://www.brownells.com/.aspx/pid=27024/Product/CAR_15_M4_FLIP_UP_TRITIUM_REAR_SIGHT)
- Specter Gear single point sling (attachment swivel comes with ACE stock)

The finished, unfired rifle:

http://s-prefix.smugmug.com/photos/674306021_d7cwY-XL.jpg

I've built more than a handful of AR-15s and one AR-10 (Armalite style), but this was my first 9mm AR-15 build. I learned a lot in the build, some things I was not expecting. First off, there is no gas impingement system in the RRA 9mm upper, which I understand was originally designed by Colt. It is a straight blow-back system and has a few peculiarities that I was not expecting. Aside from the lack of a gas impingement tube, the bolt carrier is truly massive; it is very heavy. In addition, the bolt carrier utilizes a spring-loaded inertial firing pin system, like that of the AR-10. The 9mm specific buffer is also quite heavy, I have not weighed it, but I'd guess it is more than twice the weight of a standard 5.56 buffer. One thing that surprised and, to some extent disappointed me is that the RRA magazine has no provision to lock the bolt back after the last round. The follower does not engage the bolt stop when it reaches the top of its travel within the magazine. I called Riflegear.com and spoke with a very knowledgeable guy name Brian, who explained that while the RRA mags do not engage the bolt stop after the last round, the C Products version do; so I ordered a few and hope to get them next week.

One issue that I ran into that I felt was of legitimate concern was that when I manually locked the bolt back, a slight tap on the rifle would send the bolt home. After closer inspection, I found that with the bottom of the bolt stop pushed in as hard as I could, I was getting only a few thousandths of engagement between the bottom of the bolt face and the bolt stop. On a side note, this build was the first in which I've used a DPMS LPK; I've always used RRA or Armalite LPKs in the past, and truth be told, I'm not that big a fan of DPMS's gear. The DPMS LPK was given to me and it's what I had laying around, so I figured I would try it out. I was concerned about the quality of the DPMS parts kit, however, as it turned out, the LPK was overall, quite good. As you will see in the following photos, I decided to change things up a bit after the initial build.

I have several spare AR-15 bolt stops, one of which was left over from the RRA LPK kit that I used for my AR-10 build. The AR-10 uses a proprietary bolt stop, so I had the RRA piece available to compare to the DPMS bolt stop. I removed the DPMS bolt stop and found that the RRA bolt stop was just a few thousandths taller, but after trying it, it too was not engaging the front of the bolt carrier enough to keep the bolt locked back. Once again, just a slight tap on the rifle would let the bolt fly home; once again, I felt this was unsafe. If I could not have found a work-around, I would have still used the rifle, but would either have run it sans any bolt stop or been extremely careful with it and certainly not used it for defensive or training purposes.

After some careful thought, I decided to make some adjustments of my own. Given that the vertical travel of the bolt stop is limited by its engagement of the frame, I decided to take one of the bolt stops and remove some material from the bottom back side of it, where it engages the frame and plunger. I started with a coarse diamond file, then a medium bastard file, and finished up with a fine diamond file to smooth it up and clean off any burrs. In addition, I used a pair of wire cutters to stretch the bolt stop plunger spring to about one third longer than its original length, to provide more tension on the bolt stop. As you will see in the photos, the modified bolt stop provides quite a bit more surface area to engage the face of the bolt carrier. I re-installed it and after doing so, when manually locking the bolt back, I get a very solid engagement of the bolt stop to the bolt carrier. The rifle will not send the bolt home, even with a very firm wrap or blow to its side. Like nearly any other AR, however, a solid bump of the butt end of the stock will cause the buffer to move rearward, allowing the spring pressure to be overcome by the weight of the bolt and buffer and the bolt and will fly home. I think that the inherent design of the 9mm upper, with its very heavy bolt carrier and buffer exaggerates that, and is simply the nature of the beast. Of course, I will need to test and ensure that the bolt will automatically lock back with the C Products mags once they arrive. I'll update this post regarding that when I can.

More pics:

http://s-prefix.smugmug.com/photos/674307224_Yhhso-XL.jpg

http://s-prefix.smugmug.com/photos/674308428_Af5iB-XL.jpg

http://s-prefix.smugmug.com/photos/674309566_Dbw4M-XL.jpg

http://s-prefix.smugmug.com/photos/674304801_ukVm9-XL.jpg

http://s-prefix.smugmug.com/photos/674310423_intmX-XL.jpg

dot429
10-12-2009, 10:11 PM
http://s-prefix.smugmug.com/photos/674304405_G7rhj-XL.jpg



There's nothing like having the right tool for the job. I use this punch when I build an AR. It's a half-round AR-specific punch from Brownells, there's no picture on their website at the moment, but I believe this is the correct product: http://www.brownells.com/.aspx/pid=26484/Product/BOLT_CATCH_PIN_PUNCH

http://s-prefix.smugmug.com/photos/674301174_SZy7i-XL.jpg


Here you can see a stock bolt stop (on the left) and the modified bolt stop with some material removed to allow for more engagement of the bolt carrier.

http://s-prefix.smugmug.com/photos/674301974_WhUQx-XL.jpg



This is the amount of vertical travel with a standard bolt stop. I was using the Brownell's punch to hold it in place for the photograph.

http://s-prefix.smugmug.com/photos/674300153_maBkf-XL.jpg



Here is the modified bolt stop; there is quite a bit more vertical travel, resulting in more positive engagement with the bolt carrier's face.

http://s-prefix.smugmug.com/photos/674300766_zt5sn-XL.jpg



Here is a look at the RRA magwell conversion block. I tested it on several lowers, this lower being new and unused. I found that with the lowers that I have used with 5.56 uppers and shot quite a bit, that the RRA block was loose, however, on this virgin lower, the block was very tight. You can also see the yellow JP Enterprises reduced power springs, which functioned perfectly.

http://s-prefix.smugmug.com/photos/674302158_WvSKu-XL.jpg

dot429
10-12-2009, 10:12 PM
Here is a look at the 9mm-specific RRA hammer that came in the kit. The masking tape is there so that if I slip with the hammer or punch, I won't tick the receiver; better safe than sorry.

http://s-prefix.smugmug.com/photos/674303053_jm8oA-XL.jpg



There is a hex set-screw in the conversion block that pushes upwards and outwards on two round pins that cause an interference fit that hold the block very tightly, so I don't think a virgin lower is necessary.

http://s-prefix.smugmug.com/photos/674304046_Javtd-XL.jpg



Note that the 9mm-specific buffer does not have cut-outs along the perimeter of its face like standard AR buffers do. The smudges on the buffer face are from a dab of Brownells Action Lube Plus: ( http://www.brownells.com/.aspx/pid=1147/Product/ACTION_LUBE_PLUS_reg_ ) I swear by that lube. A dab of it on any friction-bearing surface will do wonders, especially on a sear surface.

http://s-prefix.smugmug.com/photos/674302799_vGBhR-XL.jpg


I shot the rifle this past Friday and I am so thrilled with it that I can't believe it. I think that any AR enthusiast would have been on cloud nine! I cleaned the upper before the first range session and intended only to shoot the rifle enough to first: function fire the new rifle (only two rounds in the magazine to make sure it didn't double), to sight in the iron sights, and to sight in the red dot optic. I was having so much fun, however, that I shot over 200 rounds, I just couldn't help myself! This rifle came together as if it was meant to be. When I built the rifle and installed the rear BUIS, I eye-balled the windage to make the flip up portion centered on the receiver. Experience has taught me that centered doesn't mean much, but I thought that I should start there. After the function testing, the rifle did not double and I felt it was safe to load 5 rounds and start sighting in the BUIS. At 25 yards, from a rest the first 5 round string went nearly all through the same hole, with the windage being dead-on! The elevation was a bit low, however, I was pretty happy. I loaded another 5 rounds in the RRA mag and before I inserted it, I brought the front post up three clicks to start. Well, bang!, pun intended, the rifle was right on the money. I shot two more 10 round strings and they were point-of-aim, point-of-impact at 25 yards. On a side note, I may try the rifle at 50 yards, but given 9mm ballistics, I think a 25 yard zero is useful and sufficient. I proceeded to sight in the Aimpoint and within three more 5 shot strings, the rifle was sighted in.

I've never been one to beat up my rifles, as I stated my intention was to only shoot enough to sight it in, and then clean the bore thoroughly and return to the range for some serious fun at a later date. Well, I had so much fun shooting that carbine that I couldn't help myself. I had several other types of 9mm ammo with me and decided to try them. I shot 125gr tmj ball, 147gr +P Winchester Ranger ball, and some Fiocchi 158gr subsonic ball. The rifle liked all them pretty much equally, though I think the 147gr and 158gr were the most consistent. The barrel of the RRA 9mm upper is a 1:10 twist, which, quite frankly means nothing to me, as I have no idea what a 1:10 twist is optimized for in 9mm. One funny thing happened that was just great. When I was shooting the 158gr subsonic rounds, I noticed that the rifle would make no discernible "crack" when I fired it; there was more of a "whoosh" sound. At one point, a fellow shooter at the range tapped me on the shoulder while I was reloading the tiny 10 round mag and asked, "What kind of ammo are you shooting?" I figured that he didn't know it was a 9mm AR, so I said, "It's a 9mm upper, so it's not as loud as a .223/5.56." He said, "I realize it's not a .223, but whenever you shoot it, it makes a funny sound, a ""whooshing"" sound almost like a suppressed rifle." I laughed out loud, and told him that I noticed that too and explained that I was shooting some very heavy 9mm that was subsonic. I showed him the box of ammo and he smiled.

My overall impressions of the build are simply fabulous. I could (but would never do so!) throw away my other ARs and be content to shoot my 9mm RRA AR for many moons to come. 9mm ammo is much cheaper, the recoil, while more than I expected (likely due to the very heavy bolt carrier and buffer), was pleasant, and accuracy was fantastic. I lost count of how many 8 to 9 out of 10 rounds cut one ragged hole at 25 yards with me throwing one or two. There are some idiosyncrasies of the 9mm-based ARs that I have come know, but none of them cause enough concern to be a bother. The first is that when the brass is ejected from the upper, it is thrown out at tremendous velocities. I have never been thumped in the face, neck, arms, etc., by brass so hard in my life. (Wear the eye protection folks!) I was shooting indoors with a lane divider between me and the next guy, so the brass was bouncing off of the divider and coming right back at me most of the time. I'm guessing that if I shot that carbine outdoors, it would throw the ejected brass a good 15-20 feet. Also, given the straight blowback design, quite a bit of gunk was deposited in the lower receiver. I literally had to flush the lower out with M-Pro 7, scrub where I could, followed with compressed air, and a CLP rinse and repeat to get it clean. The 9mm upper throws enough gas and debris back at the shooter that when I was done shooting and went to wash my hands, I looked in the mirror and the right side of my face was speckled with soot and oil, he-he!, good times!

This was also my first build with the ACE M4 SOCOM stock, wow! What a substantial piece of gear; I can see why they are so expensive. It is a very well-built and a very well thought out collapsible stock. At this time, I can honestly say that I'm thrilled with this build and would highly recommend to my fellow Calgunners that they build one of their very own. If I had to gripe about anything, it would be that the match-up of the DPMS trigger and the RRA 9mm specific hammer was not the best. In spite of the reduced power springs providing a lighter than stock pull, the trigger feel was quite gritty. The let-off was reasonably crisp, however, after another range session, once a very good wear pattern is established between the two parts, I will burnish the primary sear surfaces with grey jeweler's rouge and that should help quite a bit. I've performed that on several other ARs and the difference has been worth the work. I may resort to getting out the stones, but I want to enjoy the rifle for a while before I tear it down again. The only other bother is that this is my first build with the B-16 bullet button and I can honestly say, no offense to the maker or anyone else, I don't like it as much as the Prince BB, not that I have any love of ANY bullet button, I found that the Prince is easier and faster in mag removal. Also, the hole on the B-16 is so small that I needed a punch to work it and on several occasions, I pushed too hard and the mag catch came out the left side of the frame and got hung up there. I suppose the difference in BBs is a minor thing and YMMV, but I'm going to switch the B-16 out the next time I work on the rifle. I'm also going to try the RRA 9mm upper on one of my lowers that has a Timney drop-in fire control group to see if I can run it that way. The Timney and other drop-in fire controls will spoil you over time.

I hope you have enjoyed my build/range report. I can't tell you how much fun it's been for me. I think that if any of my fellow Calgunners try a 9mm AR, they won't be able to sleep at night until the have one of their own.


I LOVE this rifle!!!

http://s-prefix.smugmug.com/photos/674308428_Af5iB-XL.jpg


Best,

Michael

GunPhonatic
10-12-2009, 10:16 PM
very nice, im thinking about getting an RRA Magblock. Im taking out my c-products one. Is there any play in the magwell or does the magazine sit in there tight?

Cyclepath
10-12-2009, 11:06 PM
Nice writeup. Out of my 5+ ARs, the 9mm is one of my favorites. I shoot it more than their .223 counterparts these days.

Gio
10-12-2009, 11:24 PM
Nice write up indeed, out of the 3 AR's I've had the 9mm is tied with my .22LR build.

I attached a pic of my 9mm, I like showing it off ;) Featureless FTW!!! :D

-Gio

hkdad
10-12-2009, 11:30 PM
great write up! i love my 9mm AR too. a lot of fun to shoot!

fliparch
10-13-2009, 7:38 AM
NICE! I would love to build one of these but I see the 9mm ammo being MORE scarce in Cali, I'm afraid I'd eat through my ammo supply faster. I hate Arnold! :7:

kaiserworks
10-13-2009, 8:07 AM
Mike,
I'm glad that the bolt stop mod you told me about worked out. Just doing assembly of parts that were individually sourced gives a certain amount of satisfaction, but, having to do a small bit of "gunsmithing" and having it work as expected is always a great feeling. Excellent write up as well, RRA should give you a commission check because everyone that reads this will consider buying their 9mm conversion.

Take care and have fun with that bang stick,
-Greg

Heavy_Grinder
10-13-2009, 8:08 AM
I have been "on the fence" thinking about a 9mm build for the past few weeks now.

I cant take it anymore! arrgghh!

Thanks for the great thread/read bro.

Chach
10-13-2009, 9:47 AM
Excellent review of the RRA 9mm conversion. Wish you had written it before I built mine up as it answered all of the questions I had before doing the build. ;)

In fact, I think i'm going to pull mine out of the safe and see if I can mod the bolt stop a bit as well. It bugs me to no end that it doesn't work like it should. Yes the cproducts mags hold the bolt back, but once you eject one to reload SLAM!!! the bolt goes forward. Can be a real PITA sometimes. But not enough of one to make me stop loving shooting it.

dot429
10-13-2009, 4:16 PM
Excellent review of the RRA 9mm conversion. Wish you had written it before I built mine up as it answered all of the questions I had before doing the build. ;)

In fact, I think i'm going to pull mine out of the safe and see if I can mod the bolt stop a bit as well. It bugs me to no end that it doesn't work like it should. Yes the cproducts mags hold the bolt back, but once you eject one to reload SLAM!!! the bolt goes forward. Can be a real PITA sometimes. But not enough of one to make me stop loving shooting it.

Thanks. To me, it was well worth the effort to remove the bolt stop and remove a little material from it, even if the C Products mags don't lock the bolt back. Simply from a safety standpoint, I want to know that the rifle can take a bump and retain the bolt in the reward position. I have to wonder why RRA designed it that way. Perhaps they were getting too many broken bolt stops, because the buffer and bolt carrier are so heavy?

Best,

Michael

Bladewurk
10-13-2009, 4:22 PM
Thanks. To me, it was well worth the effort to remove the bolt stop and remove a little material from it, even if the C Products mags don't lock the bolt back. Simply from a safety standpoint, I want to know that the rifle can take a bump and retain the bolt in the reward position. I have to wonder why RRA designed it that way. Perhaps they were getting too many broken bolt stops, because the buffer and bolt carrier are so heavy?

Best,

Michael

I see a Buffer tube spacer in your future..:cool:

dot429
10-13-2009, 4:34 PM
I see a Buffer tube spacer in your future..:cool:

Huh? According to RRA and riflegear.com, the spacer is needed with the full-length stocks, not carbine/collapsible stocks.

Am I missing something?

Best,

Michael

B Strong
10-13-2009, 4:37 PM
Good job, nice rifle, great report.

Cyclepath
10-13-2009, 4:38 PM
Huh? According to RRA and riflegear.com, the spacer is needed with the full-length stocks, not carbine/collapsible stocks.

Am I missing something?

Best,

Michael

If you are using a carbine length buffer tube and using a 9mm or carbine buffer, I would recommend using a spacer or a stack of quarters in the buffer tube. Usually somewhere between $1.75 to $2.25 worth of quarters is enough. Or you can use Spike's Tactical spacer. This will help with to prevent broken mag catches.

Cyclepath
10-13-2009, 4:43 PM
Like this one - http://www.spikestactical.com/z/index.php?main_page=product_info&cPath=68_71&products_id=174. I used the ST-9X 9mm heavy buffer. I think it is overkill but it does not require the spacer above.

CHS
10-13-2009, 5:35 PM
GREAT writeup!

I haven't had a chance to bring mine out yet, but I'm very happy with my 9mm build so far.

Mine's built on the CMMG dedicated 9mm lower, but I'm going to pop that bolt catch out immediately and do your mod! The exact same issue had been bugging me too, but I wasn't sure what to do about it until now! It's a 9mm-specific bolt catch, but the mod should work the same.

C Products mags have a built-in bolt stop, but also need a little work.

When you get your C Products mags you'll want to shorten each leg of the follower by about an 1/8th of an inch, otherwise the mags load up WAAAY too tight and sometimes can't even be inserted without only having 9 rounds in the mag.

Also, take a dremel with a 1/2" sanding wheel and carve out a little bit of the top of the follower where the follower meets the feed lip. This allows the follower to travel further upwards in order to engage the bolt catch more fully. This would be on the left-hand side of the gun.

dot429
10-13-2009, 6:12 PM
GREAT writeup!

I haven't had a chance to bring mine out yet, but I'm very happy with my 9mm build so far.

Mine's built on the CMMG dedicated 9mm lower, but I'm going to pop that bolt catch out immediately and do your mod! The exact same issue had been bugging me too, but I wasn't sure what to do about it until now! It's a 9mm-specific bolt catch, but the mod should work the same.

C Products mags have a built-in bolt stop, but also need a little work.

When you get your C Products mags you'll want to shorten each leg of the follower by about an 1/8th of an inch, otherwise the mags load up WAAAY too tight and sometimes can't even be inserted without only having 9 rounds in the mag.

Also, take a dremel with a 1/2" sanding wheel and carve out a little bit of the top of the follower where the follower meets the feed lip. This allows the follower to travel further upwards in order to engage the bolt catch more fully. This would be on the left-hand side of the gun.

I don't know... that sounds like way to much work for a stinking magazine.

Just kidding!

Thanks for the tips. I'll be prepared, just waiting for the box to come from my friendly neighborhood Postman...

Best,

Michael

CHS
10-13-2009, 6:33 PM
I don't know... that sounds like way to much work for a stinking magazine.

Just kidding!


Keep in mind there are only 4 magazines out there for 9mm AR's:

Metalform - Hi-cap only. Best choice if you can get them. Expensive.
RRA Uzi - no BHO, available in 10's
Promag - POS! Hi-cap only
C Products - Best choice for a factory 10 or rebuild kit to be converted to 10. Available, 3 C products mags for the cost of ONE Metalform mag.

Lead_Rain
10-13-2009, 6:56 PM
My 9 mil is usually the most popular of my AR's when my non-gun owning friends come out to shoot. It is dead accurate and with +P or NATO Ammo,
can hit steel plate at 200 yards with slight elevation adjustment.
I have a Aimpoint Comp ML2-2X mounted and it's perfect for a 9mm AR.

Nice detail in the Write Up!

xm177
10-13-2009, 7:21 PM
Thanks for the excellent write-up. :D Very clean build. I personally can't stand those stubby 9mm 10rd. mags.

Saym14
10-13-2009, 7:21 PM
Nice! they need a 10/30 mag tho.

dot429
10-13-2009, 9:07 PM
Thanks for the excellent write-up. :D Very clean build. I personally can't stand those stubby 9mm 10rd. mags.


Thank you. I decided not to Gucci-arize that rifle. I just wanted a clean straightforward shooter. I gotta say, that SOCOM stock, which I was at first not sure about, has grown on me quite a bit. I hate to say it, but I may just have to order another one. I wonder if they are still on sale at midway...

Yeah, those LAR 10 round mags look pitifully small in that massive magwell, kinda like a BB in a boxcar, no?

Heck, that tiny mag could give a less confident man MAGAZINE ENVY. :D

Best,

Michael

dot429
10-13-2009, 9:36 PM
If you are using a carbine length buffer tube and using a 9mm or carbine buffer, I would recommend using a spacer or a stack of quarters in the buffer tube. Usually somewhere between $1.75 to $2.25 worth of quarters is enough. Or you can use Spike's Tactical spacer. This will help with to prevent broken mag catches.

Sorry I missed your tip earlier. Thank you.

Sometimes my frain-barts... uh... correct me if I'm wrong but it seems counterintuitive to me, your suggestion of using a spacer in a carbine tube. Wouldn't that cause more compression on the spring? I'm thinking that the argument could be made that adding a spacer might reduce the rebound energy of the action spring, but at the same time, it would increase the static pressure of said spring and the issue of holding the bolt back would be further aggravated.

I've heard that Spike's has a good reputation, so perhaps I'll contact them for more information. The rifle has not been shot with magazines that would otherwise normally lock the bolt back; I'm waiting on their arrival.

Any other information you have on this would be interesting and appreciated.

Best,

Michael

Cyclepath
10-13-2009, 10:02 PM
9mm ARs are known for breaking bolt catches due to the additional travel of the 9mm bolt. This issue is not seen\less prevalent in .223/5.56 setups since the bolt carrier and bolt is longer so the bolt travels the rear of the buffer tube and has less of a "running start" against the mag catch on the last round. On a 9mm setup, when the bolt travels back against the rear of the buffer, it has more of a "running start" and slams into the bolt catch... thus causing more stress on the catch.

Try this... if you have a standard .223 AR, pull the charging handle back and manually engage the bolt catch. While further pulling on the charging handle, you will see that it probably has less than 1/8" more travel between the hitting the back of the buffer tube and before it will engage the catch.

Now try this, on your 9mm with a 9mm buffer\carbine length buffer, do the same as above and you will that there is more travel between the the buffer and the point it engages the catch. You will notice that there is more "play" before it engages the catch. This is what causes the issues with broken bolt catches.

jchen76@gmail.com
10-14-2009, 8:14 AM
Alternative is to use modified UZI magazines to prevent mag catch breakage. They don't bolt hold back feature on last round, so either you count your rounds or fire on a empty chamber, kinda like a AK style rifle. I have 3 uzi modified mags and c-products mags, the uzi modified mags have been 100% reliable so far.

CHS
10-14-2009, 9:46 AM
Alternative is to use modified UZI magazines to prevent mag catch breakage. They don't bolt hold back feature on last round, so either you count your rounds or fire on a empty chamber, kinda like a AK style rifle. I have 3 uzi modified mags and c-products mags, the uzi modified mags have been 100% reliable so far.

I would much rather have a BHO. Especially since C Products mags are so cheap compared to all the alternatives.

dot429
10-14-2009, 10:24 AM
9mm ARs are known for breaking mag catches due to the additional travel of the 9mm bolt. This issue is not seen\less prevalent in .223/5.56 setups since the bolt carrier and bolt is longer so the bolt travels the rear of the buffer tube and has less of a "running start" against the mag catch on the last round. On a 9mm setup, when the bolt travels back against the rear of the buffer, it has more of a "running start" and slams into the bolt catch... thus causing more stress on the catch.

Try this... if you have a standard .223 AR, pull the charging handle back and manually engage the bolt catch. While further pulling on the charging handle, you will see that it probably has less than 1/8" more travel between the hitting the back of the buffer tube and before it will engage the catch.

Now try this, on your 9mm with a 9mm buffer\carbine length buffer, do the same as above and you will that there is more travel between the the buffer and the point it engages the catch. You will notice that there is more "play" before it engages the catch. This is what causes the issues with broken catches.

Did you mean "bolt catch" or "mag release" ? I don't see how the bolt carrier could break a mag catch.

I've noted that w/the 9mm upper, there is more rearward travel than the 5.56 upper, beyond the point needed to move it to in order to lock it back.

I still don't see how adding spacer to a carbine buffer tube will help. If you have any further info or links on that subject, I would appreciate it.

Best,

Michael

Cyclepath
10-14-2009, 10:53 AM
Did you mean "bolt catch" or "mag release" ? I don't see how the bolt carrier could break a mag catch.

I've noted that w/the 9mm upper, there is more rearward travel than the 5.56 upper, beyond the point needed to move it to in order to lock it back.

I still don't see how adding spacer to a carbine buffer tube will help. If you have any further info or links on that subject, I would appreciate it.

Best,

Michael

That is correct... Bolt catch - my bad. It is well documented on Ar15.com and referenced many times. http://www.ar15.com/forums/topic.html?b=3&f=15&t=443951 is just one thread. There are many others. Also, take a look at the link I sent you from Spikes for the spacer. It explains the issue. It may or may not happen to you depending on the tolerances.

Also, another issue with 9mm ARs with non ramped bolts is that the shearing forces of the blow black design puts additional stress on the hammer pins and may cause it to "egg" out over time. Either ramping the bolt by sending it to Adco and\or adding KNS anti rotation pins will prevent the hammer pin from spinning from the additional shearing forces the 9mm design produces. Normally, I do not use KNS pins and think they are hype but in this instance it is cheap insurance.

Hope this helps. :)

Gio
10-14-2009, 11:15 AM
Good to know that Cyclepath, Ihave a Ramped Bolt in my 9mm AR and my friends have told me to use the KNS Pins. I think I might get them just for cheap insurance like you said.

-Gio

CHS
10-14-2009, 11:17 AM
Good to know that Cyclepath, Ihave a Ramped Bolt in my 9mm AR and my friends have told me to use the KNS Pins. I think I might get them just for cheap insurance like you said.


Ramped bolt + Rounded hammer + KNS pins = 9mm AR that will last forever :)

dot429
10-14-2009, 12:34 PM
That is correct... Bolt catch - my bad. It is well documented on Ar15.com and referenced many times. http://www.ar15.com/forums/topic.html?b=3&f=15&t=443951 is just one thread. There are many others. Also, take a look at the link I sent you from Spikes for the spacer. It explains the issue. It may or may not happen to you depending on the tolerances.

Also, another issue with 9mm ARs with non ramped bolts is that the shearing forces of the blow black design puts additional stress on the hammer pins and may cause it to "egg" out over time. Either ramping the bolt by sending it to Adco and\or adding KNS anti rotation pins will prevent the hammer pin from spinning from the additional shearing forces the 9mm design produces. Normally, I do not use KNS pins and think they are hype but in this instance it is cheap insurance.

Hope this helps. :)

Right now, I'm running the JP pin through the hammer with the B-16 BB. I would suppose that would suffice?

Cyclepath
10-14-2009, 3:38 PM
The JP pins are designed to keep the hammer/trigger pins from moving out of alignment and "walking" out of the lower receiver pin holes. They are cheap and offer good insurance that your hammer or trigger will not fall out like in Timney or other drop in triggers. However, in a 9mm application, "anti rotation" is more of an issue due to the shearing forces caused by the heavy bolt and steep ramp. The JP pins will not prevent anti-rotation and my opinion would be marginally better than the standard hammer pins. I would say use them for now, but if you plan on shooting tens of thousands of rounds through the 9mm, get the KNS pins instead. I have about over 5k rounds over the years on my 9mm and on all that I build for friends and family I always configure them as closely as $ permits.

dot429
10-14-2009, 8:31 PM
The JP pins are designed to keep the hammer/trigger pins from moving out of alignment and "walking" out of the lower receiver pin holes. They are cheap and offer good insurance that your hammer or trigger will not fall out like in Timney or other drop in triggers. However, in a 9mm application, "anti rotation" is more of an issue due to the shearing forces caused by the heavy bolt and steep ramp. The JP pins will not prevent anti-rotation and my opinion would be marginally better than the standard hammer pins. I would say use them for now, but if you plan on shooting tens of thousands of rounds through the 9mm, get the KNS pins instead. I have about over 5k rounds over the years on my 9mm and on all that I build for friends and family I always configure them as closely as $ permits.


Interesting... I have run several Timney's with bunches and bunches of ammo through them and some heavy-hitters too, I have one in my AR-10 and also in my .450 Bushmaster, and I haven't had a one of them budge. I am, however, very careful to make sure the set-screws and the cap screws are carefully torqued. At first, I was checking them every time I cleaned, but these days, I'll drop an allen wrench in on one of the cap screws maybe once in a blue moon. I think the Timney triggers are wonderful, though fiddly to install until you figure out the work-arounds. I do know that there was a recall of Timney AR triggers some time back, but I've had zero issues with mine. In spite of my love of them, the best AR trigger I have is one in which I used RRA standard parts, and followed the instructions in the AR Trigger Course DVD (AGI w/Bob Dunlap). Some very judicious stoning in combination with JP reduced power springs and a careful burnishing of the primary sear surfaces (after several hundred rounds to establish a good wear pattern -not included in the DVD) has created a truly wonderful trigger. Several of my friends who have shot and handled that AR with that want me to work over theirs, but as much as I love working on them, I don't want the liability. -uh, a bit of a drift there...

Back on point, as for the JP anti-walk pins, as far as I can tell, they have not rotated a bit. I'll make a witness mark to see, but they are locked in pretty tight. Truth be told, I much prefer the standard pins, the JP pins are fiddly to get in, because they are ever so slightly larger than standard pins.

I've got three more stripped lowers on the way and an RRA Predator Pursuit 5.56 upper that I've never even mounted on a lower. I was going to sell it, but the way this Country is going w/respect to gun laws, I think I'm going to hang onto pretty much everything and maybe get more.

Thanks for all your input, you've been very helpful, I always appreciate a fellow gunner who likes to get into the nitty-gritty details.

Best,

Michael

Cyclepath
10-14-2009, 8:39 PM
Not a problem and this is one of the purposes of this forum. I am just sharing experiences and info I received from others. Good luck on completing your build.

robairto
10-14-2009, 9:53 PM
I have 2 RRA 9mms and the only issue I've had are that the Cproducts and Metalform mags don't always stay in once I've stuffed them in the lower. It's the mag release and they both have RRA LPKs. The metalforms less so then my 20 rnd cproducts. The 9mm in the AR platform is cheap and fun.

Cyclepath
10-14-2009, 9:58 PM
I have 2 RRA 9mms and the only issue I've had are that the Cproducts and Metalform mags don't always stay in once I've stuffed them in the lower. It's the mag release and they both have RRA LPKs. The metalforms less so then my 20 rnd cproducts. The 9mm in the AR platform is cheap and fun.

Try giving the mag catch one more turn. If that doesnt work try a DPMS mag catch. That might fix the problem. I don't normally like DPMS LPKs but for 9mm ARs, they seem to work the best. I think you can just buy the DPMS mag catch from Brownells.

Sugarfoot47
10-15-2009, 5:10 AM
Saw this thread and thought I'd comment. I've seen a Collt carbine that was 9mm specific snap 3 bolt catches. Two were factory and one was from Garrison. Yes, it had to do with the distance between the bolt overtravel distance to the bolt catch. The Colt 9mm specific bolt catches are designed differently and are common to breakage under heavy use. The conversion type 9mm using a magblock and standard 223 bolt catch rarely if at all (as far as I've seen) has this problem. None the less, after about 1500 rounds on my 9mm build I bought the white nylon spacer from RRA that is normally used when using a FIXED stock with the shorter carbine buffer on a 9mm build and cut a piece off approx. 3/4 of an inch that when inserted into the buffer tube would duplicate the overtravel distance of a 223 bolt. I have fired almost 4500 rounds with absolutely no problems whatsoever. The bolt locks back securely after the last round and strips the rounds from a fresh mag as if it were going down on an empty chamber.On the subject off "egging" pinholes, I think that may be a problem when using the taller M-16 type hammers with an unramped bolt after a whole mess of rounds down the barrel. The shorter profile 9mm hammers in my opinion won't give you that problem. I have an approx total of about 6000 rounds through my 9mm upper and about 8000 rounds on my 223 upper using the same RRA 9mm hammer in a 17 year old registered Busmaster lower and I've yet to see any wear on my trigger and hammer pinholes. My 9mm bolt is a stock RRA ramped bolt. I've never had a single problem with C Products 9mm mags holding the bolt back securely even when dumpiing the mags during fast reloads in competition. I replaced the followers a little over a year ago with the 2nd generation type that C Products shipped to me for free, though I'm sure if the OP's mags are recent, it should have the improvements on it, mainly the higher profile where the trip contacts the bolt catch.