UMC Blackout

[pud-knocker]

Our set-ups seem very similar, even down to the powder being used but mine cycles with bullets as light as 175gr.
So....I don't buy the argument that you need heavier bullets to get it to cycle, that's just silly

This coming from an actual running example, not a computer model, although I have been told an extra half inch does make a difference

[carcass]

Originally Posted by pud-knocker

Our set-ups seem very similar, even down to the powder being used but mine cycles with bullets as light as 175gr.
So....I don't buy the argument that you need heavier bullets to get it to cycle, that's just silly

This coming from an actual running example, not a computer model, although I have been told an extra half inch does make a difference

It could be that your suppressor holds more back pressure...I am using an SRT Shadow .30 cal can. The gun certainly does not cycle without it when using subsonic loads. What can do you have? As for the larger dimensions, I understand it makes a difference whether it's in the length or diameter.

[pud-knocker]

Originally Posted by carcass

It could be that your suppressor holds more back pressure...I am using an SRT Shadow .30 cal can. The gun certainly does not cycle without it when using subsonic loads. What can do you have? As for the larger dimensions, I understand it makes a difference whether it's in the length or diameter.

Could be very possible. My set-up suffers from slight cross-pollination lol lol, I have a ....gulp...SSK can
It's a little longer than my other cans at 12", rated for full-auto, weighs about 26 lbs. lol lol
It is pretty effective.

[carcass]

Has anyone here experimented with a short piston system for the 300 BLK/Whisper?

[Recusance]

what mags are you using?

I have found that if you carefully file down the inside rib of a Pmag it allows more "space" for the heavy 220 SMK rounds to feed as it reduces contact on the ogive of the bullet.

I also use un-modified 20 round Pmags with better success.

it seems the new wrinkle in 200+ grain 300 BLK
loads is the magazines.

I contacted Magpul by email about making 300 blk mags that fit the heavier rounds. I have not heard back from them, nor do I think I will, as I am not an industry insider.

all the problems you have encountered described here I have also found with the 30 round Pmags and aluminum mags when loaded to capacity.

not enough umph to push the rounds up. I have even had the bolt stop at 1/2" rearward travel with a fully loaded mag. same rounds downloaded to 15 in the mag (30 rd mag)and the gun cycles fine.

20 rd mags seem to work fully loaded.