View Full Version : Rifle length upper w/ UBR lower

06-18-2010, 1:11 PM
Hey all, I just bought a new rifle-length upper from JohnnyUSA and I'm wondering if I need to buy a different buffer for my lower w/ a UBR stock. Does a regular A2 buffer work in there? I currently have just a regular old carbine buffer that I've been using with my mid-length upper. I know people run rifles w/ UBR's instead of A2's, so what is the procedure? Thanks!

Here's the upper from JohnnyUSA - I ordered it today and it's already on the way!

20" Lothar Walther stainless barreled upper with 13" Troy TRX hand guard

20 Match Grade Lothar Walther LW-50 Stainless Barrel 1-8 twist Wylde match grade chamber. Safe to fire 5.56 Nato or .223 Rem.
Polished extended feed ramps.
Matched bolt. The barrel was specifically head spaced to the bolt at the barrel factory.
Pinned Gas Block .
Smith Vortex flash hider
Troy 13" TRX forearm.
Built on a Noveske forged upper receiver w/ extended feed ramps.
Test fired to ensure function.
MOA or better accuracy capable with Match Ammo and good quality scope.
1 year limited warranty against malfunctions.

gun toting monkeyboy
06-18-2010, 1:13 PM
You can normally just swap out uppers and make no other changes. The buffer assembly that you have for one should work with any other, regardless of barrel length.

06-18-2010, 1:16 PM
I guess I should have made it a little more clear, but the new one is a rifle-length gas system while the old one was mid-length gas... Still okay in general? Thanks for the quick reply!

You can normally just swap out uppers and make no other changes. The buffer assembly that you have for one should work with any other, regardless of barrel length.

06-18-2010, 1:32 PM
To put it simply, the buffer assembly has nothing to do with the gas system. The length of the gas system doesn't matter, they all trap gas and put it back into the actions. The buffer assembly just returns the bolt forward. There is a rifle length buffer and spring because the rifle extention tube is longer and the carbine tube is shorter so it needs a short spring and buffer. Gas system length only deals with the location of the gas port and the length of the tube so that it can tap that gas back to the upper.

06-18-2010, 1:43 PM
Doesn't the UBR come with it's own "buffer tube"?

06-18-2010, 2:01 PM
Doesn't the UBR come with it's own "buffer tube"?
Yep, it comes with it's own buffer tube, but not the actual buffer.

And thanks, Josh3239, that did indeed make it perfectly clear!

gun toting monkeyboy
06-18-2010, 2:22 PM
Josh pretty much nailed it. I swap my uppers around whenever I get bored, or need a specific combination. I have an Exile Machine set up and a Solar Tactical grip on another one. I use those for when I need detachable magazines. Both have rifle buffer tube set ups. I use many of the same uppers that I normally run on carbine set up lowers, less the forward hand grips and other evil features. It doesn't make any difference. Rifle, mid length, carbine. 5.56, 6.8, 7.62x39. One works just as well as another as far as compatability is concerned.

06-18-2010, 2:53 PM
I have a similar setup. Use a carbine spring n buffer.

06-18-2010, 3:06 PM
Cool! Thanks everyone for the info's!

06-18-2010, 3:37 PM
On a 20" upper system the buffer doesn't matter unlike the Carbine which cycles much faster and benefits from the heavier buffer.

06-18-2010, 4:58 PM
The rifle buffer is for an rifle length BUFFER TUBE.
The carbine buffer is for a carbine length BUFFER TUBE.
You are good to go on you lower to shoot your new upper !!!
Looks very nice ... Put some pix up when everything comes together, it should look awesome !!!