Help a noob with his 223 case preparation...

[Enzyme]

I am loading 80 gr Sierra Matchkings over 24.0 gr Reloader 15 to an OAL of 2.435 in. I am currently using new Winchester unprimed brass and CCI BR4 primers.

After resizing the brass in an RCBS full-length small-base die, I use a Giraud powered case trimmer to trim to OAL and perform the inside and outside chamfer. Though the OAL is correct, and the trimmer leaves no burr on either the inside or outside, the chamfer itself is uneven and inconsistent. I have spent hours trying to adjust he cutting blade to even out the chamfer, but am unable to do so. As I highly doubt the unit itself is defective, I am really starting to question the quality of the Winchester brass. Results with some resized once-fired Lake City '02 brass have been marginally better.

Am I being too anal wanting the chamfer to be even inside and out? Does the imbalance have an effect on accuracy? Should I try some of the expensive Lapua brass? Or should I simply ignore the issue since I'm shooting an AR15 service rifle?

 

[acloco]

Rotate the brass in the trimmer and see if that changes the width/eveness of the chamfer.

Remember, that machine indexes on the shoulder.

In your case, you have unfired brass,not formed to any chamber) and then you resized it in a small base die.

I have to ask, why are you using a small base die? Are these for an AR?

 

[Enzyme]

Indeed, these rounds are for an AR15. There are two actually, one is set up as a CMP service rifle and the other is set up as a match rifle.

I have tried rotating the rounds while in the cutter, but to no avail. The chamfer is still uneven, as if the cutter is on a slightly different axis than the shell holder. From what I understand, there are at least two possible reasons for this. The case shoulder may not be perfectly round, or the case neck may not be uniformly thick. Please let me know if there are other possible reasons.

In either case, it seems the brass may be to blame.

 

[BoydAllen]

Just for fun, get a hold of some fired brass and size it, and then see how the chamfer looks when you do it. Your new brass may be a bit crooked until it has been fired a couple of times. Putting in a die will only move brass that is larger than the die. Yours is probably too small to be straightened much.

 

[ronemus]

Whether you're using the original steel cutters or a replacement carbide cutter,Giraud's is highly recommended), the cut on the outer edge of the mouth is only intended to remove the burr; generally you can't see it without a magnifier. Trying to get the inner and outer cuts even is probably a large part of your problem.