9mm COL

sfl_gunner

sfl_gunner

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Joined
Jul 18, 2020
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I'm loading a known recipe that has shot well for me in the past.
Hornady 124 gr XTP 9mm
Bullseye 4.3 gr
CCI Small pistol
COL 1.060
My only significant change is my brass. I'm loading a mixed batch of brass. I haven't messed with my dies. The vast majority of my loaded rounds COL is 1.060.
However, some have come up as short at 1.045 and as long as 1.070. But they all pass the plunk test.

What can cause this amount of variance?Given this recipe, is the .015 variation significant enough to make these rounds unsafe?

Thanks
 
The seating stem shape can cause that by deforming the bullet nose. If the brass has higher tension a round seater stem can close a hp nose letting it stick up higher in the seater. And low tension will be shorter.

If you are not at max probably be fine. Shows under max load according to some of my books.
 
Manufacturers, many from around the world have slightly different specs will "stretch" their brass differently. More countries than I can think of have produced 9mm for military and private use. Now, will it make a difference? Not usually. 9mm headspaces on the mouth of the case. After shooting the same cases a while doesn't seem to bother it either.
Many target shooters will sort by mfr. and by case length for target competition claiming it makes a minute improvement in accuracy.
 
Maybe you need a different/better seating stem. I do not see how different brass would affect COL since you push from the bottom and the top when seating the bullet.
 
Thanks everybody. I probably do need a better seating stem. I have noticed a small ring around the top of the bullets. I will try to post pictures later.
The crimp is set with the seating die, nothing excessive.
 
sfl_gunner said:
The crimp is set with the seating die
Click to expand...
You have potentially three or four things effecting the COL variation,
1) mixed head stamps resulting in varying force on the bullet.
2) seating and crimping in the same step, results in moving the bullet while you are trying to keep it form moving:confused:
3) seating stem, I use a flat nose profile seating stem for the 124gr 9mm XTP.
4) case length, will effect the crimp. when taper/roll crimping the bullet is being drawn deeper inside the case.
A process of elimination should get you a more consistent COL.
 
Last edited:
1) I've found that a lot of OAL inconsistency is simply being a novice reloader. You did not say how long you've been reloading, but concentrating on the op handle movement is critically important. It's sort of like pulling a trigger... an art that needs to be practiced in slow motion until the brain gains the "muscle memory".

Just focus on being slow and consistent with the motion of the op handle.

2) If you are using a progressive press, then most of the resistance that can throw off your "smooth and consistent" bullet seating is in the concurrent case sizing. Start using case lube.

3) Most dies don't have a seating anvil that is shaped correctly for the XTP. This can lead to some seating issues. that usually show up at OAL errors.
.
 
if you are on a single stage press try seating, spinning the round 90 degrees, seating again, repeat at least one more time for each round. sometimes the die and seating stem can be "out". spinning the round may even things out in the end.

luck,

murf
 
sfl_gunner said:
The crimp is set with the seating die, nothing excessive.
Click to expand...
Nothing excessive until you hit a case that's longer than the one you used to set the crimp. Longer cases will start crimping earlier in the seating process and resist fully seating the bullet and you'll get longer COLs. Shorter cases will have less resistance and you'll get shorter COLs.
Another thing that adds to inconsistent COL readings is primer seating. Any proud primers will add to the measured COL and give you a false reading.
 
rfwobbly said:
I've found that a lot of OAL inconsistency is simply being a novice reloader.
Click to expand...
I had some brass that had very tight primer pockets and not all of the primers were seated at or below the case head, so measuring off a high primer gave a longer COL.
When I began reloading I would hand tighten my dies in the press sometimes they would become loose, now I snug them up with a wrench. Seating with a loose die really messes with the COL:)
 
Notice that the hollow point appears to have been pinched closed slightly, too! I use a 5-die position progressive press to load my 9’s. The bullets are seated first, then crimped with a taper crimp die. I also separate cases by type and head stamps.
My OAL’s may vary by .013” which is the amount of play in the shell plate.
 
rfwobbly said:
1) I've found that a lot of OAL inconsistency is simply being a novice reloader. You did not say how long you've been reloading, but concentrating on the op handle movement is critically important. It's sort of like pulling a trigger... an art that needs to be practiced in slow motion until the brain gains the "muscle memory".

Just focus on being slow and consistent with the motion of the op handle.

2) If you are using a progressive press, then most of the resistance that can throw off your "smooth and consistent" bullet seating is in the concurrent case sizing. Start using case lube.

3) Most dies don't have a seating anvil that is shaped correctly for the XTP. This can lead to some seating issues. that usually show up at OAL errors.
.
Click to expand...

I have absolutely found this to be true. The sizing station is what causes all of the drama. I just don't do it anymore on the progressive. My juvenile slaves can size while they are watching TV with the hand press. This makes the rest of the operation on the progressive SO much easier.

Also, I have a space for a factory crimp die, which is last. I don't crimp at all with my seating die.
 
sfl_gunner said:
Hornady 124 gr XTP 9mm ... Bullseye 4.3 gr ... COL 1.060 ... some have come up as short at 1.045 and as long as 1.070

Given this recipe, is the .015 variation significant enough to make these rounds unsafe?
Click to expand...
Alliant/Speer load data lists 4.4 gr as max for longer 1.120" OAL for Gold Dot HP - https://www.alliantpowder.com/reloa...owderlist.aspx&type=1&powderid=1&cartridge=23
When my working OAL/bullet seating depth is shorter than published, I usually consider reducing my start/max charges by .2-.3 gr.

sfl_gunner said:
What can cause this amount of variance?
Click to expand...
  • Mixed range brass
  • Tilted bullet/seating stem profile contact during seating
  • Dirty bullet seating stem/die
  • Too much taper crimp
  • Bullet length/ogive variation
And if you are using progressive press, shellplate tilt/deflection can add to the OAL/COL variance.

To troubleshoot OAL variance issue:
  • Clean dies and be careful not to tilt bullet during seating
  • If OAL variance doesn't change, sort some same headstamp brass that's resized to same length
  • If using same sorted resized length headstamp brass eliminates OAL variance, cause could be mixed range brass and/or shellplate tilt/deflection during uneven resizing from different headstamp/length/work hardened brass.
  • If using pre-resized brass eliminates OAL variance on progressive press, tighten shellplate or check for play on ram/linkage.
 
There’s another variable in play, and that’s trying to measure COL. I’ve found it’s difficult to get a consistent COL reading on HPs in general just due to the nature of how the blades contact the tip.
I load a lot of mixed brass so I’ve dealt with the variances and found the seat and crimp in the same step is the biggest problem which is why I don’t do that anymore. The mixed neck tension can be alleviated a bit by lubing the brass first with a quick spritz of one-shot.
 
I've gotten variations due to different ogive shapes between different bullet manufacturers, using the same dies than anything else. Nothing that severe though.
 
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