What buffer for midlength upper?

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ny32182

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I am rebuilding my 16" AR from a carbine to a midlength. I will be running the carbine buffer tube... BCM upper is scheduled for delivery next week.

Do I need a regular carbine buffer, H buffer? I assume H2 is too heavy? What are you guys running? Thanks,
 
I am running a carbine buffer and it works fine for unsuppressed shooting. With the can on, I really need to be running at least an H buffer or the action cycles pretty violently for an AR.
 
Regular for mid-length. H is really only for carbine length gas systems. But double check to see where your brass is ejecting... should be around the 3-4 o'clock position.
 
A regular will likely work fine with a 16" midlength, but you could always buy an H buffer for the $22 or so it costs from BCM and try out both. If you are running hot ammo in your South Carolina climate it's likely that everything would work most or all of the time with the H buffer and you might find that you prefer the recoil and operation characteristics.
 
Is the US Military now ordering/using middys for their new procurments, or stil carbines? Also, can you even use a middy with a 14.5", or does the barrel have to be 16"+ to make it work with a middy system?
 
I'm sure I've got both sitting around in my "misc parts" bin; I'm mostly interested in making sure the system is going to be reliable. It is within the realm of possibility that I could one day want to use it with a suppressor, so if the "H" is just as reliable in normal use, I would probably want to use it all the time. If I am risking short-strokes with an "H" and a dirty gun, I will run the standard buffer 99% of the time.

Thanks for the input so far guys... sounds like the middy is kind of "on the edge" between the two?
 
No problems with reliability using either the H or carbine buffer unsuppressed. The really heavy buffers like the MGI 7oz hydraulic buffer will choke my MSTN midlength without the suppressor; but the MGI does OK (not great) in the CMMG mid unsuppressed. I would probably stay with the carbine for unsuppressed use or go with the H if I was switching back and forth.
 
This is a bit off topic, but can you use buffers to change the cyclical rate on full autos ?

I'm thinking of getting a Class 3 lower and running a 7.5" or 10.5" upper.
 
This is a bit off topic, but can you use buffers to change the cyclical rate on full autos ?
Click to expand...

Yes, you can. The most dramatic change will come from the heavier buffers like the MGI Rate-Reducing Buffer and the Endine Hydraulic Buffer.
 
If you have one of each you could weigh them, but typically they are marked on the face: nothing for standard, "H" for heavy, "H2" for next heaviest, etc.
 
I would start out with the H buffer myself and go from there to see if you are having any short stroke issues. Especially so if you shoot mostly true 5.56 ammo vs 223. More than likely the H2 buffer would be to much.
 
Colt's civilian M4 (6920) comes with an H buffer. They assume you'll be running true 556 ammo.

BCM also uses mil spec sized gas ports. So assuming you'll also be running true 556 in a middy, Id say you'd probably be ok with an standard or a H.

Rifles like my Bushmaster are over gassed, so I run an H2.

100_0813.png
 
Two things about the 6920:

1) It has a carbine gas system, so the gas pulse profile is different between that and a midlength.

2) It has a 16" barrel, which changes the dwell time and therefore the gas pulse at least a little from a milspec 14.5" carbine system.

Therefore you can't really draw any hard conclusions about a midlength system from a 16" carbine system. I am not done experimenting with buffers on my BCM midlength; based on this thread I have been running a regular weight buffer up till now. I will probably run an H for a while at some point just to see what happens.

It does eject forward in the ~2 oclock direction at this point; unlike any other AR I've ever owned.
 
It does eject forward in the ~2 oclock direction at this point; unlike any other AR I've ever owned.
Click to expand...

Hmm, that is what my MSTN mid does when I put the can on with a standard carbine buffer. If I switch to heavier buffers (or remove the can), it ejects back towards the 3-4 o'clock again, so I've assumed that the ejecting forward was a sign that the action is cycling harder/faster. However, I know some of the high power guys will also modify their ejector springs so that the brass ends up in the specific spot they want, so it might also be a case of a stronger/different ejector spring in the BCM bolt.
 
" Also, can you even use a middy with a 14.5", or does the barrel have to be 16"+ to make it work with a middy system?"

I have owned three 14.5" mid-lengths (still own two). All have been 100% reliable with H buffers.
 
I run a 9mm in my 14.5 middy with no problems. I run an H buffer in a 20" without any issues either, also on a different 20" target rig one of the Olympic compressed air buffers. All have been reliable.

I have never heard of being "over gassed" except after Mexican food. I thought all parts and ports for gasses were a standard size.
 
How much does an H buffer weigh compared to a rifle buffer?
Click to expand...
I took this info from somewhere else, and it seems to be correct:
Buffer weights-
Standard......... 3.0 oz.
Car H............. 3.8 oz.
Car H2........... 4.6 oz.
Car H3........... 5.4 oz.
RRA 9mm........ 5.6 oz.
 
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