This forum has been a great resource, but I'm afraid you guys are gonna get sick of me.....

I did a search on setback and found plenty of threads talking about what it is, effects on pressure, crimp, etc. But nothing really answering my question.

I have my 9mm dies set. OAL is running consistent with what I want. Crimp SEEMS to be correct; drop/plunk test is good, the case mouth when loaded mic's at .375", when I pull the bullet I see a very faint line where the crimp is but not cutting into jacket or deforming bullet.

Yet, when I cycle these dummies in my XDM I get setback about .004 - .007 each time. Just out of curiosity I cycled two different brands of factory ammo. I also got setback on factory rounds, about .005" on average.

Am I being too paranoid about this? I thought with a proper set up I shouldn't get any setback. But if I'm getting setback on factory ammo, I'm wondering if I'm making more out of this than I should be. I'm not riding the upper limits of the load charts. Is .004-.007 setback a concern or am I over-thinking this?

Thanks.

Rick

Exactly what do you mean by set back?
Is the bullet being pushed 5 to 7 thousands into the case?
are you using a taper crimp?
How many times has the brass been fired?

Just a thought, but have you tried seating your bullets .010"-odd deeper and then checking for setback again? If the problem disappears, you may be looking at very tight freebore (that your rifling is actually stopping the forward travel of the cartridge, pushing the bullet deeper into the case as the slide goes into battery). In that case, accept the freebore you have, and develop (shorter) loads accordingly. You actually want (I believe) some clearance between a chambered bullet and the rifling. A bullet jammed into the rifling could cause pressure issues, not to mention possible issues ejecting an unfired case (should the rifling have 'bitten' into the bullet to an adequate extent that pulling the slide back leaves the bullet lodged in the lands, but ejects the primed case and dumps its powder on your magazine!

Just a thought - let us know what you find.

quote:

Originally posted by hivelosity:
Exactly what do you mean by set back?
Is the bullet being pushed 5 to 7 thousands into the case?
are you using a taper crimp?
How many times has the brass been fired?

Yes, bullet is being pushed back into the case.

Crimp is taper crimp.

Once-fired brass.

And to really confuse the situation, I'm seeing setback with brand new factory rounds also.

Rikkie-

I do have load data with a different powder that calls for a considerably shorter OAL. I'll try a deeper seating and see if it continues.

Thanks.

Rick

Something very strange going on here; factory bullets should never be pushed back into the cases; that can only be caused by the bullets hitting the rifling, which should not happen either. See if you have rifling markings on the bullets; If so, call the maker immediately. It will raise pressure; although 9mms are build strong enough to take it, it should not be happening. Either that or you have a hang up in feeding. Does it happen when you just drop one into the chamber; not cycling it from the mag?

Try coloring the bullet with a magic marker and then chamber and eject it and then look at where the marks are on the bullet.

quote:

Originally posted by Mark:
Try coloring the bullet with a magic marker and then chamber and eject it and then look at where the marks are on the bullet.

RE-READ Mark's excellent suggestion. Totally coat the bullet with a marking dye, or magic marker. The first question you need to answer is where the impact is occurring that is pushing the bullet back into the case.

How clean is the throat area? Is there a burr at the throat/chamber? Are the bullets jammed further into the case marked in some way (indicating the previous?) At what OAL does a dummy round touch the lands? Do NOT shoot any more until you understand what you've got/where you're "at"!

The nose shape of different bullets may require using different cartridge overall lengths. For example, a sharply pointed bullet can project way into the bore before it makes contact but a round nose bullet will make contact with the bore right away.

I like to make an extra long dummy cartridge (no powder or primer) for the particular bullet I am loading. Then I insert the dummy and close the action. When the bullet makes contact with the bore it gets pushed back into the case. Then I gently extract the dummy and measure the OAL. When I load cartridges with that bullet I load to a slightly shorter OAL than the extracted dummy.