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1Luv4SF
02-13-2012, 8:46 PM
I assembled my DPMS pattern LR308 from parts. Meaning that I didn't buy it as a whole rifle. I spent 8 months accumulating the best parts that I could afford to build my dream rifle. Anyways, I finished it up and dropped in the new BCG and lubed it all. Everything is new as well. I loaded some dummy rounds and slapped in the mag to function test it. So here are the issues...

1) The BCG sounds like it grinds when I slowly rack it with the CH.
2) The gun feeds from my CProducts 10/20 but not my Pmag 10/20. With the PMag the bolt gets stuck on the lip of the mag.
3) The Cproducts mag gets really stuck in the magwell and takes a tremendous amount of force to take out.
4) The front take-down pin also takes serious force to pull out.
5) It's hard to pull the bolt back. The spring is so damn stiff.

So any advice? I'm seriously hoping that the rifle just need to break-in and the parts wear into each other because they are new. The tolerances on the lower are so tight and it seems like nothing is as easy as it should be to insert/remove. The rifle is a DPMS upper, 24" SS barrel, chrome BCG and TM lower receiver. Any suggestions would be appreciated. Thanks in advance. You guys always really help me out and I learn so much from the CGN members =]

C.G.
02-13-2012, 9:02 PM
You might want to change your title to either DPMS or LR308 then the people that have them would chime in. I actually thought you had an AR-10, which you don't, with which I probably could have helped.

1911su16b870
02-13-2012, 9:17 PM
Remove magazine and see how it cycles.

Does the bolt hold open lever work when you hit the lower part and no magazine?

Dill45
02-13-2012, 9:24 PM
1: Describe the grinding noise? Mine makes some noise but it just sounds like metal moving on metal.

2: Is there a round in the mag when the bolt gets stuck back or is it empty? If its empty its supposed to lock back into place.

4: I have a set up quite similar to yours as well, and the front take down pin is pretty tight on mine as well. It has loosened up a bit since I finished but it just needs to be broken in.

5: Yep, have yet to feel a AR-10/LR-308 with an easy going buffer assembly. Or at least one as easy going as an AR-15

ott1
02-13-2012, 9:32 PM
My chrome BCG is a little tight also. I think it just needs break-in. My black phosphate bcg is just fine.

CIV Tactical
02-13-2012, 9:55 PM
try to locate where you bcg is grinding. look for the wear marks on your bcg and upper receiver and polish them accordingly, this should help smooth the area and prevent abnormal friction and wear. as far as your magwell goes I suggest you find the mag that functions best and stick with it. If the Cproducts functions properly and is just tight in the magwell you can polish that area as well to reduce the friction. As far as the front take down pin goes you can slightly ream the holes or just give it time. Lightly lube the buffer and buffer spring to. Hopefully this helps smooth you out and yes your right part of all this is break in. Good luck and have fun poppin 308 rounds.

1Luv4SF
02-13-2012, 9:58 PM
The bolt catch works fine when there is no mag. When the bolt gets stuck there usually is a round in the mag too. And sometimes the round gets stuck on the feedramp. And as for the grinding noise yeh, it sounds like metal and metal contact. My AR15 is super smooth but the 10 makes this sound that is like grinding.

Dill45
02-13-2012, 10:07 PM
So is it not feeding the next round? Or is the bolt getting stuck in the locked back position?

There's a lot more metal moving in a 308 BCG than an AR-15's BCG. A lot more to grind on and make noise.

CIV Tactical
02-13-2012, 10:43 PM
The grinding you can polish out and thats not that big of a deal. It sounds like you have a feeding problem. When the bolt sticks with a round in the mag is it sticking on the bolt catch or is it sticking behind the round because it is not pushing the round into battery? `I have a feeling its not pushing the round into battery. If this is the case, check your extractor and ejector functions and check your feedramps in the barrel extension for misalignment or burrs. Those can all contribute to a feeding problem. With no rounds in the action does the bcg cam into position correctly?

motorwerks
02-13-2012, 11:07 PM
Clean it and lube it up real good... then sit and watch your favorite show while you cycle the action a few hundred times. I bet it loosens up and polishes the rough spots out.

edit... if you're lowers number is lower then my first TM lower 245 (the new one is a little higher) it was tight too, I sent it back and they fixed me up.

hornswaggled
02-13-2012, 11:20 PM
Honestly none of these things sound like they are a show-stopper for your AR yet.

If you're slowly riding the bolt up and down using the charging handle, I would expect a lot of resistance and even trouble feeding a round off the magazine. What if you just insert the magazine and hit the bolt carrier release to let it charge full force?

I have magazines that stick in the mag well pretty tight and need to be jiggled out hard. Both my front pivot pin and takedown pin are tight, just tap them with a punch when disassembling.

Have you even shot the rifle yet?

Jpach
02-13-2012, 11:46 PM
IIRC this is common with many DPMS builds. For whatever reason that chrome bcg is just nasty tight and seems to give people issues. I had a DPMS .308 once and I never had problems, but then again I didn't go crazy doing mag dumps and I had a phosphate BCG.

Your rifle may just need to be broken in a bit more. I have no explanation for your magazine issues, they should not be happening.

Dhena81
02-13-2012, 11:59 PM
I'd go shoot 1000 rounds and then clean it your problem will probably be solved.

NewbieDave
02-14-2012, 12:05 AM
I would grease it up and go shoot couple rounds from it... since it's a mix-master, it's hard to judge it unless it wears in. Remember, your parts are not made using one set standard... like mil-spec. There's going to be some rub-wear that will take time to work itself out.

I would load a round in the mag, charge it full force, makes sure it's seated... then fire it. It should fire, eject the case & lock the bolt back. Then load two rounds and repeat, this time... it should fire, eject, load round, fire, eject and lock bolt back. Continue with three rounds and so on until you work up to a full mag. If you have any issues during this... document and bring it back here.

FeuerFrei
02-14-2012, 12:08 AM
Mag/bolt catch issue is my best WAG. Back track it's install.
Tight pivot/take down pins wil loosen up over time. Use lube on them and work the pins. Detents were lubed during install?
I've seen too many "hokey" 10/20 mags causing jams to trust them. Normal PMags are the standard IMHO. Modding them to 10/20 is easy to DIY.
Grinding sounds...sounds right to me for new carrier+CH. Lube and shoot it. When jamming situation get fixed.
308 rifles are not as plug and play as 223/556.
Good luck.

lwbyo1
02-14-2012, 12:52 AM
Check the follower to see if there are any burrs that might be catching on the mag body.

If that's not the problem, it might be the BCG. If I remember correctly, you bought an aftermarket BCG. That could be the cause of some of your problems. Maybe a fellow Calgunner in your area has a DPMS BCG (and other mags) they'll let you cycle in your upper to see if the feeding problem goes away. Make sure you check the headspace. I ordered an aftermarket BCG last year just to check one out. I ended up sending it back, and the replacement one they sent, because they wouldn't even come close to headspacing correctly.

As for the grinding, it could be the BCG or it could be the charging handle. I wouldn't worry about that too much, unless it's more of a metal digging into metal.

Rock6.3
02-14-2012, 7:08 AM
Find a local person with a similar build, compare rifle behavior, swap parts to see if the magazine binding problem moves to the other rifle.

I lightly grease the entire bolt carrier on the outside. (Apply lubriplate, rub it in, then wipe it all off with finger. This leaves a minimal level of grease in the phosphate surface.)

Yes the buffer spring is going to be really strong compared to the AR-15.

Sicarius
02-14-2012, 7:44 AM
It sounds like it needs to break in a bit. Like mentioned before, pop the mag out and cycle it by hand and see if the sound is still there. If so you narrowed it down to the firearm itself. You can lube the hell out of individual parts and see if the noise goes away and find out which part it is binding on. ARs in general like to be run wet so keep that in mind. Typically on a new gun, the metal parts that wear against each other need to mate to a point... the grinding noise can be as simple as the charging handle if you are not pulling it back perfectly straight. Also lube the buffer tube area.
Kevin

goodlookin1
02-14-2012, 8:02 AM
Needs break in. Mine did as well. There's more surface area of metal on metal rubbing, so it will be stiff. Oil the heck out of the thing, in the buffer tube, in the upper receiver, etc, etc. Take the mag out and just rack it back and forth a few hundred times.

The magazine issue is different...Either the mag is out of spec, or your lower is out of spec. It should drop freely and not be so tight as to need you to pull it down to get it out. The bolt should only be held back if the mag follower is pushing up on the bolt catch.....if there is a round in the mag and it is still not feeding because the bolt is getting stuck on the feed lip, something is wrong with your mag or the lower. Talk to Nathan Krynn with TM....he'll be able to sort you out. He's a member here.

Also, since you put this together yourself, you NEED to make sure you have all the lower parts correct: You should not have any AR-10 parts as they are not interchangeable. They need to be from a DPMS LR-308 parts kit (or other DPMS compatible trigger assembly). Any Armalite (AR10) mag catch will mess things up. Make sure you used the right stuff.

Rock6.3
02-14-2012, 8:05 AM
1) The BCG sounds like it grinds when I slowly rack it with the CH.

Don't rack it slowly. Run it at full speed or not at all, preferably with the force provided by gunpowder.

4) The front take-down pin also takes serious force to pull out.
Agreed, mine is that way too, but it gets easier over time. Better tight than loose.

5) It's hard to pull the bolt back. The spring is so damn stiff.
This is normal.

coltn46920
02-14-2012, 11:03 AM
Break it in:37:

cabinetguy
02-14-2012, 12:36 PM
do you possibly have a rifle buffer spring in a carbine tube?

1Luv4SF
02-14-2012, 6:42 PM
Thanks guys. I'll work with it some more and report back after my range trip on Friday. I have to rifles to break in so that should be fun =/

1911su16b870
02-14-2012, 7:07 PM
That sounds great! Looking forward to your AAR from the range.

FWIW AR10s do not need to be babied...run them hard, cycle the charging handle with authority and hopefully everything will iron out with 100 or so rounds down the tube.

blazeaglory
02-14-2012, 7:16 PM
Yeah of course if you "rack it slow" bad things will happen. Rack that sumofabeetch with some athoritah!

1Luv4SF
02-14-2012, 11:15 PM
Lol okay. It's kinda funny how much force is needed to rack it and how tiny the handle actually is. I need something bigger. Like a PRI CH or BCM.

NewbieDave
02-15-2012, 12:05 AM
Are you racking it this way?

http://1.bp.blogspot.com/_k07pirzBU34/TFMD_fdCuOI/AAAAAAAAFdw/ML5-6KK3Lks/s1600/m16a2+charging+handle+cropped+492.jpg

Or this way?

http://4.bp.blogspot.com/_k07pirzBU34/TFMEfZF1L3I/AAAAAAAAFd4/361ZSeqQhsk/s1600/racking+2009+500.jpg

The second way is better, IMHO... I usually place stock under arm pit, seat mag, rack the handle all the way back with my support hand using a finger hook method... then let that bad boy fly home.

Never a single issue... unless I had a crappy magazine.

osis32
02-15-2012, 1:08 AM
Sounds to me like you have tight fitment new springs and a funky mag. Shoot it and see if you actually have problems. Hope everything works out for you.

Calplinker
02-15-2012, 8:43 AM
My first AR build also had fitment issues between the upper and lower to where the pivot pin had to be hammered in to place. After an embarrasingly long time, the solution finally occurred to me. Rather than ream out the lower or touch it at all, I just ground down the pin on a sander. I have a stationary grinder, but figured that would take off too much material.

Took about 15 minutes or so of lightly taking off material on a disk sander, holding the pin with gloves (it get's hot). Finally, it slid home nice and smooth and stays put. Hit it with back to black and you're done.

Mess it up and take off too much? No problem. New pins are something like $3. Mine's been great for 3 years now and if memory serves, I think I did ruin one by sanding a flat on one side. :rolleyes:

Much better than futzing with the lower. It'd really be a bummer to bugger it up.

speeddreamz
02-15-2012, 9:11 AM
I would probably say it needs to break in, but perhaps you've misaligned the gas block (misaligning the gas tube as well)

Sicarius
02-15-2012, 9:45 AM
I also noticed on my DPMS that the finish is really rough. The anodization method they use likely adds material and "tightens" a lot of holes and makes operation not so smooth. My pins are harder to push in more than any other AR I have. Just use it and break it in.
Kevin

Nathan Krynn
02-15-2012, 12:12 PM
I assembled my DPMS pattern LR308 from parts. Meaning that I didn't buy it as a whole rifle. I spent 8 months accumulating the best parts that I could afford to build my dream rifle. Anyways, I finished it up and dropped in the new BCG and lubed it all. Everything is new as well. I loaded some dummy rounds and slapped in the mag to function test it. So here are the issues...

1) The BCG sounds like it grinds when I slowly rack it with the CH.
2) The gun feeds from my CProducts 10/20 but not my Pmag 10/20. With the PMag the bolt gets stuck on the lip of the mag.
3) The Cproducts mag gets really stuck in the magwell and takes a tremendous amount of force to take out.
4) The front take-down pin also takes serious force to pull out.
5) It's hard to pull the bolt back. The spring is so damn stiff.

So any advice? I'm seriously hoping that the rifle just need to break-in and the parts wear into each other because they are new. The tolerances on the lower are so tight and it seems like nothing is as easy as it should be to insert/remove. The rifle is a DPMS upper, 24" SS barrel, chrome BCG and TM lower receiver. Any suggestions would be appreciated. Thanks in advance. You guys always really help me out and I learn so much from the CGN members =]

We thank you for purchasing one of our lowers and please feel free to contact me if you or anyone needs anything from me. Latly I have a little too busy to be on here but I did see this and will try to answer some of these in order.

1) like others have said you need to run rounds through it and don't slowly rack.
2) Like someone else said as well when people block pmags sometimes it does weird things. I am wandering what will happen under live fire though.
3) C-products are hit an miss with buldging and I am wandering if that is the issue, or if you have a REALLY old lower.
4) I hate repeating stuff but like someone said the anodize can be thick in the hols for the take down pin and repeated use will break it in, or ream it.
5) make sure you have the right spring and buffer combo, they are not the same as the AR-15.

Please if you need anything at all call or email me.

ott1
02-15-2012, 3:51 PM
DPMS .308 Buffer Spring, Standard Length, 12.75 Inch 39 Coil

Buffer:
.223 rifle length 5-7/8” – weight 5.2 oz
.308 rifle length 5-3/16” – weight 5.4 oz

1Luv4SF
02-15-2012, 10:54 PM
To answer the buffer spring questions, yes I'm using a 308 rifle length spring for my PRS.

joeyalex
02-16-2012, 12:54 PM
in regards to the mag issues...

I've run into issues with blocked P Mags before... I had some that were blocked in a way that made the spring sit on top of the block. This seemed to cause some issues with feeding and such.

As a result, the mag would work great if I loaded 9 rounds in it. Completely messed up with 10 in it. I couldn't get the mags to lock in when the bolt was forward, and the feeding of the first round was iffy at best. I believe the fact that the spring was placed on top of the block put too much tension on it, much like a 30 round mag with 31 rounds in it. (Or a GI mag with 30 in it that has to be "downloaded" to 29 or 28 to function correctly).

So now I order the mags myself as rebuild kits and then use mag blocks from http://www.magazineblocks.com.

Those work great, because it allows the spring to sit at the bottom of the mag, where it should be.

H2O MAN
02-16-2012, 1:57 PM
You should have bought an FAL

http://www.falclan.yolasite.com/resources/JG-KA-FAL-lg.jpg















Just kidding ;)









.

1Luv4SF
02-16-2012, 5:00 PM
An FAL is on my list. Next is a remy action in a AI chassis.

SkiTTleKiLLeR
02-16-2012, 5:48 PM
5) It's hard to pull the bolt back. The spring is so damn stiff.


thats normal, it takes alot more force to pull this 308 bolt back then the 223. I dont mind that, just lets me know i'm dealing with a big boy toy lol:cool2:

motorwerks
02-16-2012, 9:31 PM
IIRC this is common with many DPMS builds. For whatever reason that chrome bcg is just nasty tight and seems to give people issues. I had a DPMS .308 once and I never had problems, but then again I didn't go crazy doing mag dumps and I had a phosphate BCG.


My Chrome DPMS BCG has been nothing less then perfect from day 1 it was always never real tight.

motorwerks
02-16-2012, 9:36 PM
Nathan for President!! :)

1Luv4SF
02-17-2012, 9:19 PM
Okay I went to the range and here's my AAR. The AR308 shot perfect. Not 1 single malfunction. And the mags were running flawlessly. Couldnt ask for more. Here's a pic of my target. I think it's pretty good considering it's shot with an unbroken-in rifle and mil-spec trigger. The cluster is from the 1st 7 shots. The 3 fliers were the result of realizing there was 30 seconds left in the volley to shoot. I should have stopped at 7 haha. But still great accuracy IMO for the 1st range trip with a **** trigger. Btw my shoulder is bruised =D
http://img.tapatalk.com/a6cd8b4f-34d3-55e2.jpg

osis32
02-18-2012, 12:45 AM
Glad it wasn't as bad as you thought. Nice first group my tm10 with dpms 18" lower does about the same group wise. I can't believe you bruised your shoulder on it though I've had 140 pound girls not get bruised. Not trying to be a jerk just surprises me.

1911su16b870
02-18-2012, 12:11 PM
http://img.tapatalk.com/a6cd8b4f-34d3-55e2.jpg

AWESOME!

Congrats and isn't this one of the best feelings in the world? You built and delivered excellent accuracy on YOUR rifle! :D

1911su16b870
02-18-2012, 12:12 PM
...oh and please add ... it functions GREAT to the thread title! :D