Consistent seating only with truncated cone - 9mm

[squidvet]

Hey guys,

Love the forums here. Been browsing for some time now, trying to soak it all in. Glad to find some knowledgeable folks on the BE site!

I've searched all around for similar topics, but I just can't find something like mine. Basically, I can't get consistent seating depths for consistent COL unless I'm using the truncated cone rounds. I'm using the Hornady 9mm carbide seating die with the microjust seating stem. I've also tried the Lee carbide 9mm seating die. I didn't want to purchase another die until I posted the issue here.

When I tried the MG 115 FMJ, MG 124 CMJ, MG 124 HP and PD 124 FMJ, I can get variance of +/- .013". Meaning I might seat a bullet at 1.110 (as an example), then seat another of the same bullet at 1.123 & the next of the same bullet at 1.097. Seems like too much of a variance to me, especially when trying to tune the load for IDPA, etc. If I use the same dies with the MG 147 CMJ (which is the truncated cone bullet), I get a variance of +/- .003. That's certainly perfectly acceptable to me.

I've tried the different inserts in the seating die, my bench is solid, my press is solidly mounted to the bench, I'm using the exact same motion when seating, I've hand-selected different brass (exact same length) from different manufacturers (10 at a time) with bullets that have the same length (10 at a time). I'm trying to rule out any possible variables. Anything else you guys can recommend? Don't get me wrong, I like how the MG 147 CMJ works in my pistol for IDPA.....but I'd like to be able to get some consistency with something else - anything else!!

Any ideas would be greatly appreciated - Thanks!

Edited February 15, 2011 by squidvet

[blue]

I'm a rookie but the only time I get inconsistent seating like that is when the die is dirty.

[squidvet]

I'm with you Blue. But the dies are nice and clean. I've cleaned them & seated my "problem" bullets and they seated poorly. Without cleaning the die again, I went right to the truncated cone MG 147 CMJ and seated quite well.

Edited February 15, 2011 by squidvet

[Graham Smith]

It almost sounds as if the bullet is not being seated perfectly straight for some reason.

[kevin c]

I don't use your press, and I understand they're build solidly, but I've had variations in OAL because of unrecognized problems in the press itself. That would be cracks in the frame, the handle, and the linkages.

If you've ever heard a sudden "crack" when working the press, I'd take a close look at the press itself. With a dummy round and bullet in place, run the ram to the end of its range of motion and apply and maintain some pressure. While in that position look to see if you can see hairline cracks anywhere that might not be obvious w/o stressing the press this way.

[blind bat]

Make sure you are setting your OAL with the entire shell plate loaded and fired (not already resized) brass in position one. I also haven't had good luck with MG 124gr CMJs but .013" seems excessive. I seem to remember the CMJs being in the +/- .005-.006" range. I don't have problems keeping MG 124 JHPs, Hornady HAP or Sinterfire 90gr Frang to >=90% within .003". I do notice round nose bullets are harder to get a precise reading from the micrometer. Like you, I find the 147gr MG bullets provide the most consistent OAL.

This is probably obvious but make sure your primers are below flush...