Inconsistent OAL - 9mm

M

mpmo

New member
Hello,
New to handloading/reloading. Just did my first batch of 9mm, around 100 rounds with 2 different formulas. I noticed that the Cartridge overall length was inconsistent and I'm wondering what factors might contribute to that.
Setup:
Brass: New Starline 9mm. (measured each one. All were pretty consistent at .750".
Bullets: Hornady, 115 RN FMJ
Powder: Acc7, and Power Pistol (2 different formulas, not used in at same time)
Primer: CCI 500 Small Pistol
Press: RCBS single stage (gifted to me used)
Dies: Lee Carbide set of 4. Used the gap, seat and crimp dies.
Primer setup: One batch I did on the press, one with a Lee primer tool. Primers did not feel proud using either method.

OAL was between 1.099 and 1.111

Measured after seating, if it was off by more than 0.005, I re-seated but that didn't change anything.

I know I'm probably being too picky, but I want to get things right and exact first before I decide how much variation I'm willing to live with.

Note, I've fired around 70 of these rounds. They fed and fired flawlessly in 2 pistols.
 
9mm reloads

Did you measure the new rounds before reloading them?

Are the new shells from the same manufactured lot?

Was the fired brass measurements the same for a particular gun?
IE is brass from gun #1 all the same size and brass from gun #2 the same size?

If so, it could be the gun. Check headspace, etc.
 
ammo.crafter said:
Did you measure the new rounds before reloading them?

Are the new shells from the same manufactured lot?

Was the fired brass measurements the same for a particular gun?
IE is brass from gun #1 all the same size and brass from gun #2 the same size?

If so, it could be the gun. Check headspace, etc.
Click to expand...
By rounds, do you mean bullets? This is new brass, not reloads. I did not measure the bullets. I would assume it is all from the same batch. It came in a box of 500 from Midway earlier this month. Either way, I did measure the brass in advance and it was consistent. And even if the rounds were different lengths, wouldn't the seater die press it to a consistent OAL?

All measurements above are during the reloading process, so guns wouldn't be a factor.
 
Bullets are not perfect. You might check the bullet diameter at the point that your seating stem contacts the bullets. That most likely will change the dimensions that you are concerned with.
 
Are you handling these a while (loading them in mags, etc) after you load them and are you taper crimping?

I'm wondering if you don't have enough neck tension and you are getting bullet set back.

Also, are you loading compressed loads?
 
Dufus said:
Bullets are not perfect. You might check the bullet diameter at the point that your seating stem contacts the bullets. That most likely will change the dimensions that you are concerned with.
Click to expand...
Holy moly. That makes a lot of sense! Good chance it could be off by that much?

And at what point should I be concerned with a change in pressure?
 
It would not take much difference in diameter at the point the seating stem contacts the bullet to throw your OAL off a bit.

Since you are at 0.002" extreme spread on your reload OAL, you should be good to go. Haven't you already proven that? 70 shots fired should tell you something about it with no malfunctions.
 
Are these variations straight off the press?

Are your shortest COL's below the min specified in the recipe you are using?
 
0.012"

Twelve thousandths of an inch.

Is that a significant amount?? Might be, might not be.

Consider this, seating dies normally do not contact the tip of the bullet. The seating stem bears on a point on the ogive of the bullet. IT is not impossible for the seating stem to be uniform in its contact point, (meaning the base of the bullets are all seated to the same depth in the case) while the length of the bullets from where the seating stem contacts them to the tip can vary.

This would result in a measurable difference in COL, but no difference is seating depth. So you can have ammo with bullets all seated to the same depth in the case, but overall length of the loaded round varying slightly.

Measure the length of the bullets you re using, base to tip, before you load them. I'd be surprised if they are all exactly the same.
 
The forest:
They fed and fired flawlessly in 2 pistols.
Click to expand...

The trees: 0.012" OAL variation.

Yeah, that's a bit more than one would expect; but twelve thousandths of an inch is not enough to raise my eyebrows. I've measured 9mm factory ammo (both Remington and Winchester) and got more variation than that.

It's about the forest ;)
 
mpmo: I was going to suggest that you measure ten or twenty rounds of factory ammo and see how much variation there is. I don't think you have anything to worry about.

mpmo said:
Dies: Lee Carbide set of 4. Used the gap, seat and crimp dies.
Click to expand...
You have me confused. I use Lee 4-die sets. The four are:

1. Resizer
2. Powder-through flare
3. Seating
4. Factory crimp

So ... if you have a four-die set, why aren't you using four dies? And which three are you using? There is no "gap" die.
 
Another common factor is bullets going into the case slightly tilted. Use the Lyman multi-expander (for powder-through) or their M-die for your caliber to expand the case mouth. These dies put a small step in the case that lets the bullet sit upright in them. If the bullet is straight when seating starts it generally stays straight through the seating operation, eliminating some of that OAL variation.

The easy way to tell if you have this problem is to look at your cases where the bullet base stops after seating. You can usually see a slight bulge there from the bullet expanding the brass down to the bottom of its base. I that bulge is only visible on one side for some of your cartridges, but not others, you have variable bullet tilt.
 
Aguila Blanca said:
mpmo: I was going to suggest that you measure ten or twenty rounds of factory ammo and see how much variation there is. I don't think you have anything to worry about.
Click to expand...

I measured around 15. They were pretty much all different sizes in that range 1.099-1.012.

Aguila Blanca said:
You have me confused. I use Lee 4-die sets. The four are:

1. Resizer
2. Powder-through flare
3. Seating
4. Factory crimp

So ... if you have a four-die set, why aren't you using four dies? And which three are you using? There is no "gap" die.
Click to expand...

Sorry, I meant Powder-through flare when I said gap. So, Powder-through flare, seating and factory crimp. I am skipping the re-sizer since it is new brass. That is correct right?
 
That should be fine. But do look for the bullet base bulge and see if it is even. If not, that could account for the whole difference even if the bullets are uniform in length.
 
I could see a very slight bulge on just one of the rounds.

And, unfortunately I am out of bullets! So I can't measure any more in that batch. Having a hell of a time finding stuff. I started with the 115 fmj just becuase it was all I could find. I'm looking for the Hornady HAP and the Berry's competition loads but can't find them anywhere! I can't find any 9mm competition bullets. I've been pretty much looking every day...
 
I am skipping the re-sizer since it is new brass. That is correct right?
Click to expand...

Some folks say yes, some say no. If it works, fine. Do be on the lookout in case it doesn't.

9mm is short and fairly sturdy, Packed loose (like in bags) the brass seldom gets deformed. Other rounds, like .45-70 are long and thin and often get flattened and out of round case mouths from being packed loose.

I size new brass before loading it. Not necessarily because I need to but to have it uniform, sized in my dies.
 
OP inconsistency in oal too. I’m willing to bet nearly everyone does to a degree... unless they load a flat meplat and a flat nose seating stem. .012 is a bit on the large side of a large variation but not too bad. If they fed fine, grouped well, and weren’t loaded hot as fire I would go with it.

This is one of those reasons why I don’t push handgun loads too hard. And Ogive variance could absolutely lead to variance in oal AND seating depth.
 
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