help with Specs for polymer coated bullets

[track101]

I've been using poly coated bullets for about a year but recently had some problems (115gr, RN). Ran a few new polymer coated bullets for check and they would not fit into my case check completely. I coated the bullet and brass with a marker to see if I could find the problem. When I added pressure to push the bullet into the case check, there was a scuff mark just above the brass on opposite sides of the bullet, no marks on the brass. I contacted the manufacture and they suggested I use the following specs; COL down to 1.110"/flair .3815/crimp.389. After trying these marks, the bullets still do not seat all the way into the case check. This time when with pressure added, there is a thin scratch ring just above the crimp. Pulling the bullet does not show any damage to the coating. I measured the diameter of 10 bullets. They ranged from .356" to .357", the majority were .365". I then measured bullets from another company and they were consistently at .355". Length for both brands were inconsistent: ave .5515 for the problem bullets and .5620 for the other. I believe I will try to return the bullets but was wondering if others have any specs for 115 grain bullets they would be willing to share. THANKS

[Gringo Bandito]

It could be the crimp. I load .356 diameter bullets with a crimp at .379 and don't have any issues. Take a look at the Dillon website for a crimp calculator. IMO 389 is not enough.

[track101]

Thanks. Any idea why I'm only having problems with one brand? I've tried bullets from 4 manufactures previously without any problems with case check.

[M1NM]

Thanks. Any idea why I'm only having problems with one brand? I've tried bullets from 4 manufactures previously without any problems with case check.

Just a guess but probably that brand isn't the same as the other 3.

[checkenbach]

I use Blue Bullets and Black Bullets International, for coated, Extreme for plated and Precision Delta for jacketed.
The BBI’s are .356, the others are .355. I had accuracy issues form over crimping, then backed off the die to leave a very light mark on the bullets. I’m using a ..376-378 crimp...

[ar15barrels]

Thanks. Any idea why I'm only having problems with one brand? I've tried bullets from 4 manufactures previously without any problems with case check.

Bullets are too large.
The 0.355" ones don't cause you any problems, but the 0.356" ones do...

You shoot the ammo through the barrel, not the chamber gauge.
Try checking the rounds in your actual barrel instead of your chamber gauge.

[scotty99]

[track101]

Bullet length

For my test run on the black bullets, I used 1.142 /29mm for the overall length. That produced the scuff marks on the bullet. The second test run I used 1.110 as suggested by the manufacture. Instead of a scuff mark, the very thin scratch line the went around the bullet above the brass. I will use the suggestions given and run a few more test rounds and try them in my gun.
I used Blue Bullets to compare my diameters and they were the ones consistently measuring at .3550 diameter. I have used them a few times without problems. I should have stayed with them but the new bullets were suggested by another loader.
Thanks for all of your suggestions.

[checkenbach]

Also, my Springfield 9mm 1911 would choke (FTE) until I started using a Lee “U” die.