Why are my reloads "growing"

[Grump]

Sorry, my post about the powder charge skipped that I was tracking down baesed on it being the longest, the 147. I don't remember it being explicitly stated, but it sounds like you are loading a 124-GR bullet.

You say the powder has a tiny bit more than .10 of room. Please double-check that.

But it what I don't see here (unless I missed it) is what your sized necks measure before seating the bullet and what they measure after seating the bullet. If there is no change, I bet you at least a doughnut that insufficient next tension is the real culprit here. Entrapped air can easily push bullets back out if there's hardly any grip.

[woody2]

The air gap between the top of the powder charge and the base of the bullet is about 0.107". I'll seat some bullets and measure case diameters tomorrow and let you know the results.

Today I chambered 10 rounds, measuring OAL before and after chambering to see if there was ant setback. Two had no setback, one had 0.001, three had 0.002, one had 0.003, and three had .004.

[blaser.306]

OK , I'll admit it. It is too early in the day and before work to go thru 3 pages of posts , so accept my apologies if this has been covered off. What kind of lube is being used? If it is a tumble lube , might it not just be lubing up the deriving bands ( bearing surface ) and helping the boolit with its exit plan. Those little bitty 9mm cases are tapered are they not?

[David2011]

OK, it's way past work and I read the whole thing. I recall seeing boolits come back out of the cartridges during a loading sessions some time ago. I seated a few and then noticed that they were longer than the seated length. Seated another, set it down and watched the boolit come back out a noticeable amount. I don't remember what cartridge I was loading or anything useful other than figuring out it was air pressure.

David

[woody2]

[QUOTE=David2011;3312952]OK, it's way past work and I read the whole thing. I recall seeing boolits come back out of the cartridges during a loading sessions some time ago. I seated a few and then noticed that they were longer than the seated length. Seated another, set it down and watched the boolit come back out a noticeable amount. I don't remember what cartridge I was loading or anything useful other than figuring out it was air pressure.

Thank you, thank you, thank you. That's exactly what I think is happening. Did you fire them and was everything ok?

[Wayne Smith]

I had this happen with the 45-70 that I was literally thumb seating boolits in fired cases without sizing. It was a Trapdoor. This was the most accurate way to load for that rifle, with no tension, and the weight of the boolit and the lube acting as glue. Every once in a while the situation would be that a boolit would start sliding up. I figured that the case was just a little tight and did not let the air escape as I seated the boolit. I had a couple that I could push the boolit down and feel the bounce of the air compression.

[opos]

I came in late...and I don't load 9mm any more but I got a question...or more of a comment/question. I read you say the brass is all R/P..correct? Are you using Lee dies?..here's why I ask...I was loading 38 special some time ago...loading with Lee carbide dies...I load one at a time in a single stage...I got to the bullet seating part and found that I had a random number of bullets that were loose in the case...didn't "look loose" but were "finger push" loose...went back through and found they were all R/P brass...measured all the brass "thickness" at the case mouth and found that the R/P brass was about .002 thinner than the other manufacturers brass on average....contacted Lee....sent them some of the brass..some of the bullets, etc...they found that their dies that I had were right at the limit for size and the brass was at the other end of the scale so the accumulated error was significant enough to cause the light throat tension..they replaced the sizer die with a different one and all has been right on target since...

I would think with the 9mm cartridge shape and no roll crimp that you might be seeing the bullets sort of "hydraulic" out of the cases from air pressure built up inside when you seat the bullets...

Just another place to look.

[woody2]

I came in late...and I don't load 9mm any more but I got a question...or more of a comment/question. I read you say the brass is all R/P..correct? Are you using Lee dies?..here's why I ask...I was loading 38 special some time ago...loading with Lee carbide dies...I load one at a time in a single stage...I got to the bullet seating part and found that I had a random number of bullets that were loose in the case...didn't "look loose" but were "finger push" loose...went back through and found they were all R/P brass...measured all the brass "thickness" at the case mouth and found that the R/P brass was about .002 thinner than the other manufacturers brass on average....contacted Lee....sent them some of the brass..some of the bullets, etc...they found that their dies that I had were right at the limit for size and the brass was at the other end of the scale so the accumulated error was significant enough to cause the light throat tension..they replaced the sizer die with a different one and all has been right on target since...

I would think with the 9mm cartridge shape and no roll crimp that you might be seeing the bullets sort of "hydraulic" out of the cases from air pressure built up inside when you seat the bullets...

Just another place to look.

Interesting. I'll measure some of the cases. I've reloaded some of these cases before, though, and everything was normal.