AR15 in 7.62x39 fixed stock or adj w/short buffer

[sansone]

fellas I need opinions please regarding the buffer & buffer tube length differences.
As you know the fixed stock AR has a longer tube & buffer, I'm building one in 7.62x39 and understand the bolt & buffer slam back a little harder than 223.
Sounds to me like the longer buffer tube would do better at slowing the bolt due to the added length.
Please don't argue the comparisons of 223 vs 7.62x39 or fixed vs adj stock.
I need your thoughts on the buffer & buffer tube question. THANKS

 

[desidog]

As long as you have the appropriate tube, spring, and buffer combo, both work fine.

I have 2 x39 AR's. and use rifle tubes, springs and buffers on both...not cause they're better necessarily, but because telescoping stocks are illegal in my state.

With a carbine stock, don't worry about buffer weight until the gun is fully assembled and not ejecting properly.

 

[sansone]

thanks desidog..
I like the magpul adj stock but been reading about the recoil increase with the x39 round.
My sons need shorter LOP so having adj means we can all shoot the same rifle.
No steel cases will go through this rifle and like the 30 cal option even with the 150yd limit

 

[rbernie]

I have converted my 7.62x39 and 6.8SPC ARs from fixed to adjustable stocks, so that my whole family can be fit to any given rifle just by adjusting the stock. I used the regular carbine buffer without issue, but recently updated most of them to a H buffer (which duplicates the weight of the rifle buffer).

The extra length of the rifle buffer does not do any appreciable good. The extra weight of the rifle buffer, on the other hand, can help if you have a stronger recoil pulse or want additional mass in front of the spring to help shuck heavier rounds from the magazine and stuff them into the chamber. Using a H or H2 carbine buffer can allow you to achieve the same results as the rifle buffer while staying within the carbine tube format.

 

[Birdmang]

Do the 762x39 AR15s shoot steel cased ammo reliably?

 

[sansone]

thanks rbernie that reply answers my original post exactly...

birdman from what I have read the AR will shoot the steel case ammo but I am a reloader, and always on a never-ending quest for that magic recipe

 

[desidog]

Do the 762x39 AR15s shoot steel cased ammo reliably?

Might depend on the make. But for my 2 guns with M1S barrels (16 &20) & bolts, YES, just not Wolf....Wolf primers are thicker or something, and 1/10 might be a light strike and it no go boom.

I mainly use the stuff on the bottom shelf, next to the Wolf stuff. Golden bear brown bear etc.

The bigger issue is mags that feed reliably. C-Products have been AOK for me; but i recently heard they went under.

 

[rifleman14]

I think that a carbine buffer tube and spring with a H3 buffer would probably slow down the bolt considerably more than just a standard rifle length tube and spring. The heavier buffers really make a difference in cycle rate. Some rifles in 223 wont even cycle with an H3 buffer because the ammunition doesn't have enough oomph to push the bolt all of the way back. If I went with a carbine tube i would just make sure to get a heavier buffer, H2 at the lightest. preferably H3

 

[rbernie]

Do the 762x39 AR15s shoot steel cased ammo reliably?

The issue with steel case ammo in the AR-pattern rifles is two-fold; chambers and firing pin protrusion. Some chambers are tight enough that steel cased ammo simply will not chamber, or will give issues during extraction. There is no way to know where you and your particular rifle fall relative to that issue until you try it. Steel cased ammo seems to also have deeper primer pockets and can give occasional light strikes unless the firing pin protrusion is increased (either by removing a wee bit of material from the bolt's tail end or by removing a wee bit of material from the firing pin's integral stop).

If I went with a carbine tube i would just make sure to get a heavier buffer, H2 at the lightest. preferably H3

This isn't one of those 'if big is good, then bigger is better' situations. The goal of the buffer is to add reciprocating weight (to slow the recoil pulse and to conversely increase the ooomph available to chamber a new round) and to provide a shock buffer to the end of the BCG travel. Increasing the mass of the buffer can help slow things down, but if you have a 18" barrel with a rifle gas system (i.e. short dwell) in a 7.62x39 bore volume (i.e. larger interior volume drops off pressure faster given the limited powder of the cartridge), you may find that getting too heavy on the buffer makes the rifle short-stroke and become unreliable.

The 7.62x39 AR gas port should be sized such that you don't NEED a heavy buffer. You may want to try one, and see if you like it. I did, but that's because I wanted the extra mass for feeding reliability. I would not move to a H2 or H3 buffer in any 7.62x39 rifle until you establish a good reliable baseline with a normal or H buffer.

 

[frankge]

H2 Spikes tungsten buffer in my 7.62x39 carbine. shoots steel case and surplus np. Hates hollow points.