PCC/PDW AR Buffers

[Albroswift]

Before my incredibly short attention span and Al-zimers moves me along to the next project,  I'm posting up some musings on blowback buffers. Not claiming to be an expert in the subject and by no means a complete dissertation.

Any-hoo:

Tried several different combinations of springs and buffers over 3 AR40's, 2 with 4" barrels and 1 with a 16" barrel.

First of all, 3-1/4" buffers don't quite work. End up with too much travel and with LRBHO the bolt is moving way too fast when it hits. First solution was a spacer to limit travel. Spikes sells one as well. Works OK, but space could be put to better use.

 

 

KVP has a 4-1/8" 7.5 oz solid SS or 10 oz Stainless with 4 tungsten weights. The solid didn't work well for us, too much bounce, my opinion the weights really help deaden the effect. The 10 oz (Mine weighed 10.29 oz) worked good and fair priced.

Problem with the KVP is it is designed for a spring that compresses to about 3-1/2" which as far as I know doesn't exist.

Then tried the Quarter Circle 10, 11.2 oz, tungsten weights, and the head is a little bigger so about the correct compression for a  Sprinco Red  or EA1095 spring. A little shorter overall then the KVP's and made out of material that rusts! Heavier then SS?

Ran really, really smooth in the 16" AR40/ red spring. Two problems with the QC10, damn thing is 120 bucks, and  when I was going to buy another one anyway, found out they quit selling them!  QC10 now only sells firearms it looks like. 

So, shop time. First bored the KVP 7.5 solid to hold 4 weights, came in even heaver then the QC10 or the KVP 10, possibly due to the bore was a little tighter. Added a collar to set spring compression. Also turned a monster that holds 5 weights, set up for a red or EA spring in a 7-11/16" extension tube. 

 

Some deductions:

If you are already running a KVP 10oz and a Sprinco orange, a SS collar can add some weight, 1.5 oz, +/- and sets the orange spring for full compression. (Sprinco Orange was designed around a 2-1/2" buffer in a 7" tube and 308 BCG I believe)

Sprinco Red and the KVP, a 5/8" 0 .75 oz spacer sets the spring compression and brings the total up to 11+ oz

Some more picks:

 

 

 

Some good information here:

The American PDW

https://10mmautocombat.wordpress.com/blowback-bolt-calculations/

 

 

Edited May 11, 2021 by Albroswift

[98Z5V]

This is amazing information...  

[unforgiven]

Outstanding job brother 🍺🍺

[CatFood]

Great post Al!

[DNP]

Holy hell...look what the cat food drug in. 

[Albroswift]

Looking through KAKs site, they have a 4 weight and 4 weight adjustable 4 inch buffers, the straight 10 oz with 4 tungsten weights isn't much more then buying the weights alone. 

 

 

 

 

 

[MikedaddyH]

I have a feeling I will be doing this to get my PCC guns cycling right.

Had nightmare problems with the 9mm bumpfire gun I used to own. Would eat buffer heads every trip to the range. Problem was solve with a$1.25 in Canadian quarters.

BTW the bumpfire buttstock lost a battle with a saw.

[392heminut]

On 10/9/2021 at 12:13 PM, MikedaddyH said:

I have a feeling I will be doing this to get my PCC guns cycling right.

Had nightmare problems with the 9mm bumpfire gun I used to own. Would eat buffer heads every trip to the range. Problem was solve with a$1.25 in Canadian quarters.

BTW the bumpfire buttstock lost a battle with a saw.

Riiiight!!!