20” upper on M4 carbine lowers - what buffer weight

[.45's and .38's]

So I have a 20" aero upper

I want to use my aero lower with M4 stock assembly and carbine spring

What buffers are you all running for smoothest function

I don't want to dish out the cash for the A5 system I was hoping a carbine spring and different buffer weight will get this baby running as smooth as the rifle A2 stock setup

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[DirectDrive]

So I have a 20" aero upper

I want to use my aero lower with M4 stock assembly and carbine spring

What buffers are you all running for smoothest function

I don't want to dish out the cash for the A5 system I was hoping a carbine spring and different buffer weight will get this baby running as smooth as the rifle A2 stock setup

View attachment 1115233

My Internet Guess is an H2 using full power ammo (XM193 or M855) would be the sweet spot.
Or an H3 might be better.
The Internet really can't tell you.
Ideally you change them out until you get the cyclic rate/ejection pattern you like.

 

[titsonritz]

I was hoping a carbine spring and different buffer weight will get this baby running as smooth as the rifle A2 stock setup

That's not going to happen.

An H2 is a safe bet but as DD says an H3 might be better.

 

[Z-PDX]

seems like we're all circling around, "it depends".

I'd also point out that depending on who made the upper, gas port sizes can vary, which will affect the optimal buffer weight.

please keep us posted on what seems to work.

 

[.45's and .38's]

it's the M16A4 aero complete upper

I'll try a H3 buffer or I also heard 9mm buffer and my carbine spring and see what happens

 

[Bears]

Start at carbine. Clock it. Increase as needed.

Guessing that carbine is starting and will clock at 3.

 

[Pepe-lepew]

Most high power service rifle shooters run carbine buffer systems on a 20" upper. Many are running H2 with carbine spring. Some run a Tubbs spring with up to H2. In general they are all doing something to fix being over gassed. Ideally they would run an adjustable gas block but the rules do not allow it.

From my experience, I would tune to the heaviest spring It will run on a light buffer, then fine tune with the buffer weight. That is if I can't run a adjustable gas block.

 

[.45's and .38's]

Yeah I would rather keep my front sight post
Link me to which sprinco spring I need please
And buffer combo

 

[titsonritz]

Start at carbine. Clock it. Increase as needed.

Guessing that carbine is starting and will clock at 3.

All carbine buffer should be thrown in the ocean. If an AR can't run with a H buffer something is wrong with it. The reason carbine weight buffers exist is because they are cheaper to make for all the AR manufacturers pinching pennies.

 

[powermad]

A Tubbs flat wire spring and H1 would run well if it's gassed right.

I started playing the buffer game with mine then took the easy way out with a BRT gas drive.

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I got a tube to run with an A5H2 buffer and Tubbs spring.

 

[P7M13]

Take the buffer you have apart and play with the weights. I've tuned FL and adjustable stocks that way.

 

[Cerberus Group]

At least a H2...change out the spring to a Sprinco Blue.

With the rifle length gas system, it'll make a soft shooting rifle. Better yet, switch it out to a A5 system.

 

[Z-PDX]

Most high power service rifle shooters run carbine buffer systems on a 20" upper.

can you tell me more about how this all works? what the pieces and parts combo is and why the guys are doing it.

i don't know a thing about service rifle except i shot it once and did poorly. so use small words.

 

[Diamondback]

If memory serves, the mil-issue M16A4 telestock conversion kit uses standard spring and H6, which is similar weight to an H3 but has a spring in it for timing control in rock-n-roll.

My memory IS fuzzy, though, long on book reading short on hands-on experience. There used to be a piece in Preventative Maintenance magazine about this...

 

[titsonritz]

If memory serves, the mil-issue M16A4 telestock conversion kit uses standard spring and H6, which is similar weight to an H3 but has a spring in it for timing control in rock-n-roll.

My memory IS fuzzy, though, long on book reading short on hands-on experience. There used to be a piece in Preventative Maintenance magazine about this...

https://jerkingthetrigger.com/2013/07/20/h6-buffer-upgrade-kit-from-damage-industries/

 

[srxfan]

Try this guide out on the history of the 20" upper with carbine buffer:
A Builder's Guide to the M16A5: https://www.everydaymarksman.co/equipment/m16a5/

Skip to the section "Buffer System" if you want to skip the history part.

summary: Canadians used H2 buffer in carbine, US used H6 buffer mentioned above; A5 system also good

 

[titsonritz]

Better yet, switch it out to a A5 system.

That would be the thing to do, but the OP said he did want to spend the additional money.

 

[Pepe-lepew]

Service rifle use to be 20 inch rifles with fixed A2 stock using iron sights. Rules changed and now they can use up to 4.5 magnification optics and adjustable length of pull stocks. these Two things allowed them to fit the rifle better to them for each position. For example, lengthen the stock for laying down prone or shorten it when they stand.

Most flocked to the Magpul UBR stock since it was a heavy solid adjustable stock. It has a carbine buffer tube length. Therefore, they also converted and tune their rifles to a carbine buffer system. The general rule some said is to match the carbine buffer weight to the rifle buffers they used before. The rifle buffer was heavier and matched the heavier H2 carbine buffer weight better.

 

[titsonritz]

The general rule some said is to match the carbine buffer weight to the rifle buffers they used before. The rifle buffer was heavier and matched the heavier H2 carbine buffer weight better.

Not quite...

Buffer weights:

Carbine - 2.9oz
H - 3.8oz
H2 - 4.5-47oz
H3 - 5.3-5.5oz
H6 - 5.2oz
Rifle - 5.1-5.3oz
A5H0 - 3.8oz
A5H1 - 4.56oz
A5H2 - 5.33
A5H3 - 6.08
A5H4 - 6.83

 

[Pepe-lepew]

I over simplified. Both the buffer weight, spring rate and start and stop spring compression play into the buffer system dynamics. Rifles typically have a higher initial spring force than carbines, thus an offset in buffer weights for unlocking timing between the systems? Rifles also store more energy in the spring, similar to going to a flat wire in the carbine system. So a H2 with a flat wire may be closer to a rifle system in both unlocking and energy storage.