9mm AR bullet setback

[Southpaw]

I tested my 9mm AR for the first time last week and noticed the bullets were getting dented pretty good when chambering and I measured a few when I got home and found bullet setback between .01-.02". I tried both my reloads and factory CCI Blazer Brass and both were getting dented and had setback.

I just tried manually chambering a few rounds and again had the same issue, pics of the rounds below. They have dents on both sides of the bullets, second pic might be harder to see, but it's the marks near the tips of the bullets. Dents were worse with plated reloads I was also testing it.

Has anyone ever had setback issues in their 9mm AR or dented bullets like this? Mine is a Glock mag New Frontier Armory lower.

[StealthyBlagga]

Yes, I have seen this cause feeding problems in several PCCs of different types, and in my open bolt subgun. For this reason, I take the following precautions:

1) Use true FMJ bullets (not plated)

2) Use a Lee U sizing die

3) Use a Lee Factory Crimp die

Even then, some brass has poorer neck tension than others (FC sucks). For serious matches I run factory ammo in my PCCs and subguns.

This topic really belongs in the PCC forum

Edited May 23, 2016 by StealthyBlagga

[Southpaw]

Thanks. I do use a U die and FCD, although was using plated bullets. I'm too cheap for FMJs . My reloads were getting around .01" of setback while the factory CCI was .02".

I just shipped my upper back to the guy who did some work on the barrel so we'll see what he finds. Hopefully he gets it sorted out!

This topic really belongs in the PCC forum

Definitely!

[Miranda]

.... plated bullets are lead bullets for most considerations.

your ammo cases do not look coke bottle or wasp waist-ed. so that does not help.

If your plated bullets are bigger than .355 do not use the FCD use a taper crimp.

you may want to use the taper crimp for a test batch to see if the FCD is swaging your plated bullets.

the dents... I have no good ideas for the cause

but it may not be helping with the setback problem.

the split here is that your ammo may be ok in a gun that does not dent the bullets

or you can try to make ammo that does not setback even with the dents.

miranda

[perttime]

There's got to be something wrong with a gun that dents bullets.

Everybody can make a pistol that doesn't cause dents - why not a carbine?

[Southpaw]

.... plated bullets are lead bullets for most considerations.

your ammo cases do not look coke bottle or wasp waist-ed. so that does not help.

If your plated bullets are bigger than .355 do not use the FCD use a taper crimp.

you may want to use the taper crimp for a test batch to see if the FCD is swaging your plated bullets.

the dents... I have no good ideas for the cause

but it may not be helping with the setback problem.

the split here is that your ammo may be ok in a gun that does not dent the bullets

or you can try to make ammo that does not setback even with the dents.

miranda

The above pics are from factory rounds which I also tested along with my reloads just to see if there was any difference (they both had setback, but less with my reloads). My reloads do come out wasp waisted. I don't have any other crimp dies, but I've loaded many thousands of rounds with Lee dies and never had bullet setback or dented bullets in any handguns. I think we've actually already discussed in another thread how my FCD doesn't swage bullets like yours does

And yes the dents are causing the setback. I wasn't trying to imply that they were two separate issues, sorry if that wasn't clear. The rounds are obviously not hitting the chamber opening properly, either at the wrong angle, too low, too high, or something like that. Was curious if anyone else has had this happen and how they solved it.

Edited May 24, 2016 by Southpaw

[Miranda]

Hi southpaw,

mark some ammo and set them into the magazine where you know the orientation.

I said that backwards put a round in the mag and sharpie mark the top at 1 o-clock

and cycle the round and find out what is making the dent.

I am thinking the leading edge of the ramp, buuuut who knows?

and chase a fix from there.

miranda

baaaad typo

Edited May 24, 2016 by Miranda