What buffer for a 18” barrel?

[bbbass]

Chics dig coil springs? ... Flatwire? Why don't Chics dig USGIs?

 

[titsonritz]

On the A5 system .
The BCM site has a kit with extension, spring and H0 buffer .
I take it that set up is for a 16" carbine gas system ?

14.5 middy is the driving force. The theory being even crap underpowered ammo will still function with a normal size gas port. If you look at Vltor kit it comes with A5H2 buffer.

 

[titsonritz]

You are running a CAR compatible butt stock? Start out with the OEM USGI CAR buffer.

Which is an H2 buffer for both M4 and MK18, the 6920 has an H buffer.

Be sure to use an OEM USGI spring.

Do not run cut off industrial wire. Find and use the OEM USGI buffer spring.

There is nothing wrong with USGI action springs, but Spinco springs are superior and will out last a USGI spring. Check them out.
Tactical Springs & Machine Gunners Lube

Also miking your barrel gas port diameter is a good idea so you know what you have at the other end.

Most do not possess a pin gage set to do it accurately, a micrometer will put you in the neighborhood but when we're talking about +/- .001" it is a pretty small neighborhood.

Ideally you want the slowest cycling speed with 100% function.

Agreed

The mid length is NOT USGI stock.

True, but this ain't rocket surgery and the mid length gas system has proven to be superior to carbine length gas system.
NSWC-Crane Mid-Length Gas System Testing Shows Increased Performance & Service Life For M4 Carbines - Soldier Systems Daily

 

[Tony617]

Exactly what did you order? Link?

"Standard" carbine buffer are complete garbage and should be banded from earth. The lowest weight buffer should be an H.

That said, anything I build for myself has an A5 system my standard go to buffer is an A5H2.

I ordered a from PSA. Here are the specs:

• Gas System: Mid-Length
• Barrel Profile: Heavy
• Barrel Steel: Hammer-Forged Chrome Moly Vanadium ("Machine Gun Steel")
• Chrome Lining: Yes
• Muzzle Thread: 1/2-28
• Chamber: 5.56 NATO
• Twist Rate: 1 in 7"
• Barrel Extension: M4
• Diameter at Gas Block: .750"
• Gas Block Type: Low-profile
• Muzzle Device: A2 Flash Hider
• Receiver Material: Forged 7075 T6
• Receiver Type: M4
• Handguard Type: PSA Precision 15" M-Lok Lightweight Rail

PSA 18" CHF Mid-Length Length 5.56 NATO 1/7 Heavy 15" Precision Lightweight M-Lok Upper - NO BCG/CH - 516444448

 

[titsonritz]

I ordered a from PSA. Here are the specs:

PSA can be all over the map with port size, but typically run on the larger side. As I posted earlier an H is the "safe" bet, but you should be ok with an H2 assuming you use something a little warmer than PMC Bronze.

 

[Tony617]

PSA can be all over the map with port size, but typically run on the larger side. As I posted earlier an H is the "safe" bet, but you should be ok with an H2 assuming you use something a little warmer than PMC Bronze.

No I shoot mostly M193 indoors. Outdoors I shoot M193 and M855. Whatever is cheaper at the time.

 

[oli700]

IDK... I dance with the girl I brought.

ARparts.com 18.5" stainless upper. El cheapo Blackhawk spring.
Hardened Arms 10.5" upper, Ebay spring.



Budget everything...

(Edit: But it all is working. lol )

That's a good thing . I like the gun running as smooth and slow as possible while still shucking all ammo. You can set your spring and buffer as light as possible and the gun will run good. However the wear and eventual broken lugs and such will come much sooner .
The benefits to tuning the gun out weigh " good enough" for me . The parts last longer , the rifle shoots much flatter a lot less jumpy and since I reload, just the life of the brass from a proper tuned AR is worth the price of admissions for me .
The absolute best set up is rifle gas and rifle buffer as Eugene intended .

 

[Sniper03]

Nothing at all wrong with H Buffers, H-2 Buffers or H-3 Buffers for the right application when needed. Obviously it would not hurt anything at all to use an H Buffer as mentioned. But the statement.

"Standard" carbine buffer are complete garbage and should be banded from the Earth. ????????

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[Geardo]

"Standard" carbine buffer are complete garbage and should be banded from the Earth. ????????

They are just way too light for anything but a race gun. I only run h2 or heavier. Look at how heavy the original rifle length buffer was! And then look at how people talk about how smooth the rifle length stock is. They think it's the apring but its really the buffer.

 

[DirectDrive]

you'll just have to run it see what it wants, going to depend on gas port size and ammo .

This
The Internet cannot answer this question.
Too many variables that only you can observe/control.

 

[titsonritz]

This
The Internet cannot answer this question.
Too many variables that only you can observe/control.

But factors can be controlled, that why I am very particular about which barrels I buy and know they have a properly sized gas port from the get go and why I own a pin gage set for those in question. It all boils down to gas port size, people assume/believe one can "fix" and over-gassed barrel with a heavy buffer and spring setup, not true, it is still over-gassed, heavier buffers and springs setups are a band-aid approach.

 

[Geardo]

But factors can be controlled, that why I am very particular about which barrels I buy and know they have a properly sized gas port from the get go and why I own a pin gage set for those in question. It all boils down to gas port size, people assume/believe one can "fix" and over-gassed barrel with a heavy buffer and spring setup, not true, it is still over-gassed, heavier buffers and springs setups are a band-aid approach.

What brands, in your experience, come with a proper sized port?

 

[titsonritz]

What brands, in your experience, come with a proper sized port?

Colt, BCM, SIONICS, SOLGW, new Daniel Defense (they use to be over sized).

Here are Mil-Spec correct gas port sizes...

18" SPR Rifle length gas .0995 +/- .001 (Crane spec)

14.5" and 16" Carbine length gas .063 +/- .001

20" Rifle length gas .093 +/- .001

10.3" and 10.5" Carbine length gas .071 +/- .001 MK18

14.5" and 16" Mid length gas .076 +/- .001 (ideal, no Mil-Spec standard)

 

[titsonritz]

They are just way too light for anything but a race gun. I only run h2 or heavier. Look at how heavy the original rifle length buffer was! And then look at how people talk about how smooth the rifle length stock is. They think it's the apring but its really the buffer.

For comparison:
standard carbine buffer- 3 oz.
Rifle buffer- 5.1-5.3 oz.
H3 Carbine- 5.3- 5.5 oz.
U.S Army H6 Buffer- 5.15 oz.
VLTOR A5H2 buffer- 5.33 oz

 

[Geardo]

Colt, BCM, SIONICS, SOLGW, new Daniel Defense (they use to be over sized).

Here are Mil-Spec correct gas port sizes...

18" SPR Rifle length gas .0995 +/- .001 (Crane spec)

14.5" and 16" Carbine length gas .063 +/- .001

20" Rifle length gas .093 +/- .001

10.3" and 10.5" Carbine length gas .071 +/- .001 MK18

14.5" and 16" Mid length gas .076 +/- .001 (ideal, no Mil-Spec standard)

Thanks!

 

[oli700]

Over gas is subjective . A " perfect gas" carbine has would run a standard carbine buffer and carbine spring . A rifle would run a rifle buffer and spring .
If you use anything different than that , not a perfect gas pulse based on one type of ammo .
Then ammo , so many kinds . I have used ammo that is the difference between over and under gas as far as unlocking .

As long as you get the unlocking slowed down then the goal is accomplished just like the factory does with h1 - h3.
In fact some argue that a system with more gas than less will run more reliable under more conditions and as long as you can slow down the unlock then you get a more authoritative gas pulse . So not messing with the gas pulse by going after springs and weight makes since . It's all different ways to approach more gas than needed to cycle with one particular ammo .

 

[Tony617]

I am using an H1 buffer on my 18" AR. I bought a fully assembled upper receiver from PSA.

 

[Sniper03]

I all of our correct Gas Port discussion one must remember other factors that might dictate the difference that is AMMUNITION!
Military us normally hotter than commercial ammunition. Then some military ammunition is hotter than other military ammunition. That is why the 5.56 NATO Chamber has Lead or some call it Free Bore. And the commercial Remington 223 Chamber does not. And the same with commercial ammunition some is hotter than others. This can have an importance effect of the proper operation of the rifle and gas port size used.
But your good manufacturers usually always have correct Gas Port sizes to accommodate most loads.
Any company using Wilson Barrels usually have no problems. No connection to Wilson Combat it is the Wilson Barrel Company on the East Coast. People like Rock River Arms and others exclusively use Wilson Barrels and have for years. IMO they are one of the best quality and have stood the test of time year after year.

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