Difference in receiver extension length?

[ike838]

Collecting parts for a 18" rifle length build with Odin Works adjustable gas block. Will I see any practical difference between a A5>rifle length>carbine length extension?

[98Z]

Yes, but the difference is in buffer weight. Rifle length buffer is 5.2oz, standard AR15 Carbine buffer is 3.0oz. Additional AR15 carbine buffers usually run H1 (3.8 ounces), H2 (4.6 ounces) and H3 (5.4 ounces). More weight = softer recoiling system, as long as the cartridge power can support it. Grendel can take some heavy weighted buffers.

VLTOR A5 is way different. It's a hybrid buffer length that uses a longer carbine receiver extension (than AR15 carbine) and longer buffers (than AR15 carbine buffers). You basically gotta know the difference in Carbine receiver extensions between Armalite AR-10 length and AR15 length to get the grasp on the VLTOR A5 system - because it's receiver extension is identical in internal depth to the Armalite AR-10 Carbine receiver extension.

There are 6 different A5 buffer weights, and they go further than AR15 rifle weight of 5.2 and carbine H3 weight of 5.4.

I can go on about this for hours, if you want. The VLTOR A5 system is superior on the 6.5 Grendel, if you're running a collapsible stock setup. I'm running an 18" RLGS BA barrel with this, and the VLTOR H1 buffer (about H2 weight, for an AR15 Carbine buffer). I may go heavier, time will tell. It's nice, though.

I experiment,so I'll keep going up until I reach a point of failure. I wish I had all the A5 buffers (in weight) now, but I don't.

[98Z]

To understand the A5 system, it was developed for the USMC. They were stuck (politically/policy-wise) on the 20" M16 barrel, but they needed something with a collapsible stock - because 20" barrels and A2 stocks suck, for the Marine Corps, in modern combat zones. VLTOR stepped in and developed the system that would mitigate the felt recoil of a 20" RLGS M16 with that collapsible stock.

It works wonders on a Grendel, which kicks just a little harder than a 5.56...

[ike838]

Thanks for the info. I didn't know that there that many buffer weights for the A5 system. Still wondering if the adjustable gas block will make a carbine extension as soft shooting as the A5. Carbine extensions seem to be quite a bit cheaper than Vltor ones and if I can just dial the gas back and get the equivalent result of the A5 system I could use the savings on other areas of the build.

[grayfox]

Hi Ike,
Here's what I did to soften up, still using the carbine buffer and tube. For collapsible stock, I put the JP centerless spring in with a T2 buffer (Spikes or Kaw). Some really like that SCS captured spring setup but I was looking for a bit more economy...
Then adjustable gas block, this actually also helped me. It isn't a fancy one just a joebob's but there are several name-brands like Syrac, seekins and others... I measured the #of turns from just-full-open (ie, having the setscrew just clear the port-hole-opening, not fully out) to closed (looking at the gas port inside the GB while uninstalled). Then start with that full-open setting and close down by 1/2 your current "turns open", or your choice, until your ammo doesn't allow full lock back of the bcg. Then tweak it open until you get lock back, then go +1/6 or 1/4 turn just to be sure. (Others go 1/2 turn or 1/4 turn at a time, just pick your method and keep notes.)
I tried to do this for a couple of my heaviest loads and then all the others cycled great. Brass goes to 3-4 o'clock. Nicer to shoot.

[ike838]

Hi grayfox, actually built a 18" Faxon gunner with a SLR .625 block last fall. The Odin works barrel and block were a Christmas sale impulse buy that started this build. Waiting for the weather to break to try out the first one and once I had the barrel the other parts just started showing up, lol. Pretty much have everything I need except furniture, extension system and stainless birdcage/. Sounds like carbine extension will be fine. If I go that route I was thinking of a Magpul CTR stock but am open to suggestions.

[grayfox]

I actually have settled on that CTR stock. I like the extra friction lock to cut down on any wobbles.
ps, make sure your butt-stock and carbine tube match diameters, ie, both commercial or both mil-spec diameter.
Mix and match doesn't work here...
Hope it odes well for you!

[ConcernedCitizen]

You might also take a look at the Magpul SL stock. It doesn't have a friction lock like the CTR, but it fits really snug, with almost no wobble at all.

It's my personal favorite, along with the ACS-L.

[ike838]

Ended up going with a Hogue overmolded carbine stock kit with extension for $83. Reviews seemed good.