So i had a chance to take my AR to the range and sight it in yesterday. I put about 200 rounds through it, performed great. After it got a little dirty (pleannnnttyyyy of clp in there) I noticed that the bolt was not staying back on the last round. Didn’t bother me too much and still doesn’t, but would like to get to the bottom of it. I was using the federal xm193, 55 gr ammo. I also loaded up a few 63 grain Wolf loads. It held back fine using those.
My thoughts are as follows:
The bcg is a ym nm. So it is a half oz heavier than mil spec. I am using the buffer spring from my Vltor Emod kit. I believe it is a carbine buffer spring/tube. My system is a mid-length.
My guess is the lower grain ammo is not powerful enough to kit the bcg back far enough to catch on the magazine. I was also thinking that maybe the spring is too stiff since it is meant for a carbine length system?
If I wanted to solve this would I need a softer spring?
The XM193 is probably a hotter load than the Wolf, so I don’t know if that’s the issue. Did it happen with different magazines? The most common causes of failure to lock back are weak magazine springs or an issue with the mag catch.
I tried two diff pmags same thing happened. Weird thing is it held back fine a few months ago when I put about 60 rnds down range. I used the same ammo. It was holding back in the beginning of this shoot too, when it got dirtier it decided not to hold. Other than that the gun performed perfectly…
sounds like you’ve got too much weight for a mid-length, especially the mid-length you have, which is sure to have a good, small gas port. i’d switch to a C buffer. i’m very confident that’ll fix your problems.
You are definitely using good stuff! I know the Young BCGs do not do well on the chart, but I still like them. Of course when the Zombie Apocalypse starts, will pull out a Noveske for me and a Daniel Defense for the wife, so no issues there.
with a small-ported, mid-length barrel, a NM carrier, and an H buffer, i think the weapon is slightly “under-gassed”… causing a mild short-stroke. by replacing the H buffer with a lighter C, or carbine, buffer, you’re easing up on the DI action, allowing it to cycle a little harder. you could go about this a number of different ways- but replacing the buffer is definitely the cheapest and easiest… a C buff is less than $10
Thank you for the reply. Just realized C stands for carbine. I believe I am running one of those? I am using the one that comes with the Emod kit, which to my knowledge is a C buffer?
I’m not badmouthing the BAD lever or MagPul. I have a lot of their accessories and mags but at least on my rifle, the BAD lever didn’t work. Or rather, it created a problem.
oh- i thought i read that you had an H buffer. my bad. start checking for gas leaks. where’d you get the YM carrier from? if you got it directly from YM, it’s not staked, and WILL come lose at some point, perhaps already has. if you got it from Denny’s, it should be staked already, but i’d still look for carbon streaking at the base. also check for leakage at the gas block- there will probably be a little bit, as some gas almost always escapes, but it should not be building up. what kind of gas block do you have?