Inconsistent OAL - 9mm

Ran a new batch today. 16 rounds. Didn't have any more Hornady's left, but some Sierra 125gr FMJ RN came in the mail and I used those.

Made 2 other changes, 1 which could have possibly made a difference. I took off the collars with o rings on the Lee Dies and put in ones that lock with a set screw. I also did use the sizing die this time even though it is new brass.

I measured at every step.
-Initial brass, with in .0015" (.749-.7505
-brass after primer, no change
-bullet length - within .001"
-Final OAL, within .002"

I have a feeling it was either an inconsistency with how the bullets were initially seating or an inconsistency in the diameter where the bullet met the seating die.

I'm not going to loose sleep over it. I'm loading light, didn't have any problems and will continue to over measure the crap out of everything until I get more comfortable with my skills and results.

Thanks for all the help!
 
Over time your technique will become more uniform, which will help keep the C.O.A.L. more uniform. What I've noticed when setting up the seating die is that in initially setting it up, when I start with a setting that I know is too long and then use the same round while progressively turning the seating stem down by increments of a quarter or an eighth of a turn, is that I get to the exact cartridge length I want. Then I load two or three rounds, check them, and they're all too short.

Consistency includes not just having everything set correctly, it also includes doing everything smoothly and (more importantly) the same. Always pull the handle at the same speed and always be sure that the handle bottoms out at the end of each stroke.
 
I'm not familiar with the Lee dies they sell today, but you went from round nose bullets to flat nose bullets, the problem went away.

Did you change the seating stem when you did this or were you using a flat profile seating stem to load round nose bullets.

Seating round nose bullets with a flat nose profile on the seating stem will make the OAL all over the place. It will cause the bullets to seat crooked.

Just something else to look at.
 
OAL was between 1.099 and 1.111

Might want to try a different crimp die. I load 45 Colt with a Lee 4 die set & was having trouble with the FCD seating the bullet anywhere from .007" to .015" deeper. Inconsistent enough that I couldn't make allowances for it when seating the bullet.
After a lot of head scratching I tried the Lee Collet Style Factory Crimp Die. That did the trick. Bullets stayed right where I seated them.
I don't think Lee makes one for 9mm, but maybe try one from a different manufacturer.
 
LE-28 said:
I'm not familiar with the Lee dies they sell today, but you went from round nose bullets to flat nose bullets, the problem went away.
Click to expand...

Both were RN. Both .355. Hornady 115 FMJ RN, and Sierra 125 FMJ RN.

LE-28 said:
Did you change the seating stem when you did this or were you using a flat profile seating stem to load round nose bullets.
Click to expand...

I was not aware that there were different stems for flat vs round! There is no reference in the die manual to this. Is this something I should look for? I have some flat nose bullets on the way. Here is the die set I have:
Lee Deluxe Carbide Pistol Four-Die Set 90963 Caliber: 9mm Luger
Code:LEE-R6-90963
MPN:90963
UPC:734307909635
 
Lee Deluxe Carbide Pistol Four-Die Set 90963 Caliber: 9mm Luger
Click to expand...

I have the identical die set and use it to seat lead SWC bullets and never had any kind of issues with it.

As pointed out previously, you need to make sure your lever stroke is consistent and bottoms out on the press each evolution. The fact that your variances are now in the 1000s indicates that you are getting it down.
 
45 long said:
Might want to try a different crimp die. I load 45 Colt with a Lee 4 die set & was having trouble with the FCD seating the bullet anywhere from .007" to .015" deeper.
Click to expand...
I don't see how that's even possible. The FCD doesn't have a seating stem.

https://leeprecision.com/reloading-dies/hand-gun-dies/lee-carbide-factory-crimp-die/


I don't think Lee makes one for 9mm, but maybe try one from a different manufacturer.
Click to expand...
9mm doesn't need a collet style crimp die. 9mm takes a taper crimp, not a roll crimp.
 
What happens is the edge of the case mouth can grip the bullet so that as the case mouth is rolled in and down, it moves the bullet down with it.
 
.012 of an inch variation is nothing for me to be concerned about in a handgun that's shot at, what, a maximum of 25 yards?. It would be for rifle shooting at 300 + yards, but not a handgun.
 
I've done a lot of 50-yard slow fire bullseye target shooting, so I always look at 50-yard accuracy. But it still doesn't matter. A self-loading pistol or a revolver that can shoot under 2 moa at 50 yards is considered exceptionally accurate by most folks. A rifle that shoots under ½MOA at 100 yards is considered exceptionally accurate by most folks. That's a 4:1 difference in expectation. Small changes in seating depth may be noticeable on paper with the rifle, but you'll never be able to distinguish them with something shooting a factor of four wider spread to begin with.
 
This one is so common, and a new guy will go crazy trying to chase the OAL with the seater.
I always say pull ten or a dozen bullets out of the box and put the calipers to them, and you will find the variance there.
Even match bullets will vary due to manufacturing tolerances.
Since most seating stems do not index on the very end of the bullet that variance will match the set you put the calipers to.
It is simple math, and it is not important, at least not anything to fret about.
The important distance is from the ogive(the curved side/or side of the bullet) to the lands of the rifling in your chamber.
 
You must log in or register to reply here.
Back
Top