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View Full Version : Thoughts on 20" uppers on carbine lowers


Mossy Man
06-25-2012, 10:30 PM
Saw this video

lSHlofN5EAU

and have been considering trying one.

i have a 16" M4 profile rifle, and was thinking of trying this out with the less expensive DSA upper

http://www.dsarms.com/DSA-ZM4-A3-Upper-Receiver-20-FLuted-Barrel-M4-Feed-Ramps---ZM4CBU20FLUTE/productinfo/ZM4CBU20FLUTE/


can just pull my existing BCG/CH, slap it into the 20" a3 flat top 20" upper, and use it with my carbine lower?

thoughts on this setup?

I'm kind of a bigger guy, 6'1 250 lbs and i tried using an AFG forward-style grip but its just not possible with my arm length even with the stock fully extended.

plus, it might be kind of cool to not have a 16" like everyone else all the time.

edwardjames
06-25-2012, 10:39 PM
i've always liked the look and really.... its something different to try out.
unless you're going to go clear a room full of bad guys with it, i would say go for it

p.s. all the components will interchange between the two uppers

gmcal
06-25-2012, 10:40 PM
It's not a good idea to use the bolt is 2 uppers. Could cause unsafe headspace issues.

Have you considered turning your 16" upper into a dissipator?

Mossy Man
06-25-2012, 10:42 PM
It's not a good idea to use the bolt is 2 uppers. Could cause unsafe headspace issues.

Have you considered turning your 16" upper into a dissipator?

i'm mostly concerned with messing with the FSB

from everything i've heard its a real pain to remove

loosewreck
06-25-2012, 10:53 PM
You might need a heavier buffer like a H2 or H3, or you might not.

It might also be wise to order a new bolt with the 20" upper if you plan on shooting either a lot.

If you do a google search along the lines of "rifle gas with carbine extension" you'll find everything you need.

The Canadian military use this set up its called a C7A2.

Mossy Man
06-25-2012, 10:54 PM
Might just be better to get a lo-pro gas block and ff guard.. i mainly just want more hand real estate.

AmpedUp
06-25-2012, 11:01 PM
Might just be better to get a lo-pro gas block and ff guard.. i mainly just want more hand real estate.

Easiest way I have seen to do this is to just chop the FSB.

Mossy Man
06-25-2012, 11:07 PM
Easiest way I have seen to do this is to just chop the FSB.

I'm afraid to take it off lol.....do people chop it down while still attached?

Dhena81
06-25-2012, 11:12 PM
A Vltor A5 will basically runs anything. If your concerned with headspace issues using an old BCG you could just buy a new bolt. I would consider looking at Palmetto state armory also at that price point.

loosewreck
06-25-2012, 11:14 PM
I'm afraid to take it off lol.....do people chop it down while still attached?

Some have. If you're confident with your craftsmanship its possible.

I have a Bushmaster Dissy that I recently added a DD Omega rail to. The gas block was a simple pre-ban that was chopped down by BM and was too big to fit under the narrower Omega rail. I was too lazy to punch out both the pinned FS and GB so I just masked around the GB and ground it down. Afterwards, before removing the mask, I hit it with black rustolium. Presto.

Mossy Man
06-25-2012, 11:16 PM
At that point I'd have to chop off the hand guard retaining cap and get a free float that attaches to a standard Delta ring?

Dhena81
06-25-2012, 11:19 PM
I'm afraid to take it off lol.....do people chop it down while still attached?

Depending on your rail system your probably going to have to take off the front sight gas block anyways because a lot of rail system companies have a proprietary barrel nut. If you go with a quality manufacture its a good thing because the standard GI barrel nut wasn't necessarily designed for an extended FF rail. A lot of companies make a beefier designed barrel nut in an effort to minimize rail flex.

To answer your other question yes you can chop it down while its still attached I would add some cold blue or other type of finish to help minimize rust.

loosewreck
06-25-2012, 11:21 PM
At that point I'd have to chop off the hand guard retaining cap and get a free float that attaches to a standard Delta ring?

DD Omega FF is one way to go. Or you can buy a "clamp on" front sight base and a new handguard retaining cap.

Most common clamp on FSB everyone is going with is made by Armalite (http://www.armalite.com/ItemForm.aspx?item=EU0240MPKIT).

The main problem you might run into is that most "clamp on" are made for .750 diameter barrels, so you might want to measure yours before you start.

loosewreck
06-25-2012, 11:26 PM
Diesel has a "how to" on the first page of the Dissipator thread (http://www.calguns.net/calgunforum/showthread.php?t=493277).

gmcal
06-25-2012, 11:33 PM
At that point I'd have to chop off the hand guard retaining cap and get a free float that attaches to a standard Delta ring?

If you don't want to remove the barrel you could cut off the delta ring and remove snap ring and weld ring. The samson evolution rail mounts to a standard barrel nut. Most rails have proprietary nuts/mounting systems that would require the barrel be removed. You would need to shave the fsb though.

SocomM4
06-26-2012, 12:42 AM
Vltor Casv/EL or /M. Done.

loosewreck
06-26-2012, 3:30 PM
i mainly just want more hand real estate.


Troy BattleRail Charlie (http://troyind.com/%20/rail-systemsaccessories/rails/ar15m16-rails/drop-in-rails/troy-battlerail-charlie)
Troy BattleRail Delta (http://troyind.com/%20/rail-systemsaccessories/rails/ar15m16-rails/drop-in-rails/troy-battlerail-delta)

I remembered these after I logged off last night. I found them when I was shopping around for a new rail for my Dissipator a couple of months ago.

They're "drop-in" FF rails like the DD Omega but have the FSB cut like some non drop-in FF rails from DD, Centurion, Troy, etc.

You won't have to do any disassembly past removing your carbine handguards and removing your sling loop.

BTW, I was in your situation a little over a year ago and went with a DD Omega X FSP rail for my M4 profile BCM upper. The installation would have involved some dedicated tools that I wouldn't have much use for afterward, so I just had Addax Tactical (http://www.addaxtactical.com/store/pc/ADDAX-SERVICES-c163.htm) do the installation for 50 bucks, the wait was only about an hour.

MXRider
06-26-2012, 3:36 PM
I have the Vltor A5 setup on my 20" rifle, very smooth shooter.

http://i149.photobucket.com/albums/s73/hownowbrowncow_02/Guns/IMAG0243.jpg

Mossy Man
06-26-2012, 3:38 PM
Troy BattleRail Charlie (http://troyind.com/%20/rail-systemsaccessories/rails/ar15m16-rails/drop-in-rails/troy-battlerail-charlie)
Troy BattleRail Delta (http://troyind.com/%20/rail-systemsaccessories/rails/ar15m16-rails/drop-in-rails/troy-battlerail-delta)

I remembered these after I logged off last night. I found them when I was shopping around for a new rail for my Dissipator a couple of months ago.

They're "drop-in" FF rails like the DD Omega but have the FSB cut like some non drop-in FF rails from DD, Centurion, Troy, etc.

You won't have to do any disassembly past removing your carbine handguards and removing your sling loop.

BTW, I was in your situation a little over a year ago and went with a DD Omega X FSP rail for my M4 profile BCM upper. The installation would have involved some dedicated tools that I wouldn't have much use for afterward, so I just had Addax Tactical (http://www.addaxtactical.com/store/pc/ADDAX-SERVICES-c163.htm) do the installation for 50 bucks, the wait was only about an hour.

those look pretty cool.

so they just attach to the existing D-ring?

loosewreck
06-26-2012, 3:45 PM
Yeah, according to their description. Maybe you should email Troy to find out more info or if they're actually in stock.

Mossy Man
06-26-2012, 3:46 PM
actually loose wreck, that looks like it might be the ticket for me.

I bought a complete rifle (S&W M&P15 Sport) and was thinking to get a longer rail i'd have to chop it up (voiding warranty?) or just get a separate upper to experiment with.

with the Troy battlerails charlie/delta, i can get what i want without voiding my warranty or having to buy a second upper.

i think i'm going to be getting one of these once i get paid next

thanks bro

Mossy Man
06-26-2012, 3:47 PM
just looked at it...only option for "add to wishlist"

hell i don't have the money right now anyway......so i can wait.

Mossy Man
06-26-2012, 3:50 PM
http://www.702shooter.com/shot-show/troy-industries-delta-battlerail-squid-grip-suppressors-2012-shot-show/

this link shows a video of the troy rep with the rail and an explanation on how it works.

looks good and has pictures

MXRider
06-26-2012, 3:55 PM
Well you really drifted from the original post, lol. Also look into the Centurion C4 rail here:

http://www.bravocompanyusa.com/Centurion-Arms-C4-Rail-System-FSP-12in-p/centurion%200609-fsp.htm

Mossy Man
06-26-2012, 3:56 PM
Well you really drifted from the original post, lol. Also look into the Centurion C4 rail here:

http://www.bravocompanyusa.com/Centurion-Arms-C4-Rail-System-FSP-12in-p/centurion%200609-fsp.htm

from what i understand it's easy to do with ARs ;)

maybe one day i can be like pokemon and catch them all

loosewreck
06-26-2012, 3:57 PM
http://www.702shooter.com/shot-show/troy-industries-delta-battlerail-squid-grip-suppressors-2012-shot-show/

this link shows a video of the troy rep with the rail and an explanation on how it works.

looks good and has pictures

Cool. Thanks


just looked at it...only option for "add to wishlist"

hell i don't have the money right now anyway......so i can wait.

Yeah, take your time. And call your doctor, you sir have BRD.

Peter.Steele
06-26-2012, 5:59 PM
A Vltor A5 will basically runs anything. If your concerned with headspace issues using an old BCG you could just buy a new bolt. I would consider looking at Palmetto state armory also at that price point.



+1 for the VLT0R A5 + 20" PSA setup. That's what I'm running, couldn't be happier with it.



http://img33.imageshack.us/img33/73/1021647.jpg