9mm cartridge OAL

[93Bandit]

Hi guys, I'm reloading some of my cast and PC 9mm boolits. I set my seating die to an OAL of 1.12" per a load sheet I'm using. Several rounds came out to 1.12, but then I started getting a wide range of OAL, from 1.05 to 1.25. I checked to make sure the die was tight in the press, no issue. Long story short, I keep having to adjust the die up and down to get any sort of consistency.

So what could be causing this? Primer seating depth? Could the OC or how I cast the bullets be affecting the OAL? Lastly, should I even be worried about this range if OAL? The boolits are just for plinking under 25yds in my Pistol and all the OALs I was getting chamber just fine.

Any thoughts are appreciated!

[Willie T]

It could be the seating stem. If the seating stem is engraving the projectiles, seating depth will be inconsistent. If neck tension of the cases has a lot of variation, seating stem engraving compounds.
Getting bullet lube in the seating stem can give you wonky seating depth as well.

[Dusty Bannister]

The seating stem presses on the ogive of the bullet when seating. You mention powder coating. Uneven thickness of this can give different seating depths due to a thick application on the side of the bullet can result in uneven cartridge OAL. If you have uneven seating of the primer and the primer is proud of the case, you could experience a slam fire. Are you using a single stage or progressive reloader.

[93Bandit]

It could be the seating stem. If the seating stem is engraving the projectiles, seating depth will be inconsistent. If neck tension of the cases has a lot of variation, seating stem engraving compounds.
Getting bullet lube in the seating stem can give you wonky seating depth as well.

Ok, that makes sense. I am getting a slight engraving towards the tip of the boolit. Some worse than others but the amount is generally pretty consistent. I am not using lube as I've read it isn't necessary on PC boolits.

[93Bandit]

The seating stem presses on the ogive of the bullet when seating. You mention powder coating. Uneven thickness of this can give different seating depths due to a thick application on the side of the bullet can result in uneven cartridge OAL. If you have uneven seating of the primer and the primer is proud of the case, you could experience a slam fire. Are you using a single stage or progressive reloader.

Right, I think that's probably what's happening, Uneven PC.

As for primer, every time there's an OAL too high, I inspect the primer and to the eye it is not proud of the case, and the cartridge does not wobble when standing on a flat surface.

I am using a Lee turret press.

My main concern is functionality. Will this range of OAL have any negative impacts, or potentially be dangerous?

[Willie T]

Right, I think that's probably what's happening, Uneven PC.

As for primer, every time there's an OAL too high, I inspect the primer and to the eye it is not proud of the case, and the cartridge does not wobble when standing on a flat surface.

I am using a Lee turret press.

My main concern is functionality. Will this range of OAL have any negative impacts, or potentially be dangerous?

It depends: if your loads are at or near maximum, deep seating can spike pressure beyond maximum SAAMI pressure.

[93Bandit]

It depends: if your loads are at or near maximum, deep seating can spike pressure beyond maximum SAAMI pressure.

Im using Sport Pistol, the max charge is 4.2gn, but I'm using 3.9gn.

[fredj338]

Are you sizing or as cast? One reason i size is remove one variable. Also the M style or mbf expander gives a straighter bullet seating & seating & crimping in separate steps. Also mixed brass, always mixed oal results, because brass thickness varies.

[93Bandit]

Are you sizing or as cast? One reason i size is remove one variable. Also the M style or mbf expander gives a straighter bullet seating & seating & crimping in separate steps. Also mixed brass, always mixed oal results, because brass thickness varies.

I'm sizing with a Lee press through sizer, although I'm not sure how that would affect OAL?

I am using mixed brass, range pickup brass.

[fredj338]

I'm sizing with a Lee press through sizer, although I'm not sure how that would affect OAL?

I am using mixed brass, range pickup brass.

As i noted, if the bullets vary +/ 0.002” & going into mixed brass, resistance seating cause variation in seating. Mix brass, especially 9mm, all over the place in thickness.

[Hick]

Everyone covered most all the questions-- but one other situation would be if your bullets are sized too small. In a small pistol case, if you don't have much neck tension, the compressed air under the bullet will actually push it back some after seating (not likely-- just something to think about if all else fails to cure the problem).

[93Bandit]

As i noted, if the bullets vary +/ 0.002” & going into mixed brass, resistance seating cause variation in seating. Mix brass, especially 9mm, all over the place in thickness.

Ah, ok. I misunderstood your post the first time. I get it now!

[93Bandit]

Everyone covered most all the questions-- but one other situation would be if your bullets are sized too small. In a small pistol case, if you don't have much neck tension, the compressed air under the bullet will actually push it back some after seating (not likely-- just something to think about if all else fails to cure the problem).

I never would have thought about that, thanks for the idea.

[JonB_in_Glencoe]

SNIP>>>

My main concern is functionality. Will this range of OAL have any negative impacts, or potentially be dangerous?

93Bandit, welcome to the forum.

You might want to Plunk test all the finished ammo that has various OAL, to be sure they all chamber. If some have too long of a OAL and don't chamber, that is always a bummer to find that out at the range. Another thing, if a cartridge doesn't fully chamber, when you eject the case and the boolit sticks in the barrel, that's always a bummer too

[billmc2]

I'm not to far ahead of you in the experience department. I have a 9mm mold but haven't started to use it yet. I was having a very similar problem loading 32 S&W Long. Hick mentioned the possibility of trapping air within the seating stem. My question to you is what is the meplat shape?

I was using a Keith style bullet, powder coated, and couldn't get any consistency at all. I tried varying the amount of powder coat in an attempt to make the thickness the same. It didn't help. I then learned that seating stems can have different profiles. I got one that is flat and mates to the flat front on the Keith bullet. No more discrepancies. I've also been able to use it on other shapes of bullets as well, with no ill affects. Also, being flat, there is no place to trap any air.

You didn't mention which bullet you are using. My Lyman Cast Bullet Handbook, 4th ed, shows in the cartridge drawing an OAL off 1.169". Amongst the different bullets they list the OAL range is 1.010" - 1.160". The drawing shows the brass to have a length of 0.754" and indicates a trim to length of 0.751"

With the varying OAL you're stating, if the brass is all the same length, you'll be changing the interior volume of the case; less volume means higher pressure, more volume means lower pressure. I'm not experienced enough to comment on this being a problem or not, one of the other folks will have to do that.

[Kosh75287]

I'm not casting aspersions on the way you maintain your loading dies, but you might benefit from just pulling the seating stem from the die soaking both in solvent for a few minutes, pushing patches (or whatever) through the die until clean, and reassembling. I only had one time in which o.a.l. problems arose from a truly/discernibly dirty seating die, but when I get variations like the ones you describe, disassembly, cleaning and reassembly usually helps matters.

ANOTHER CONSIDERATION:
The 9mmP has a very small case capacity and operates at ~30,000 p.s.i. There is an old SPEER manual that cites a load, developing ~29,000 p.s.i., which then developed pressures in the 60,000 p.s.i. range when the o.a.l. was shortened by 0.020".
If your goal o.a.l. is 1.12" and some of your loads end up at 1.14", it isn't great, but I would expect no safety issues. If some of your load ends up at 1.10", I'D seriously consider pulling them and retrying their assembly.
Willie T was good enough to point this out before me, so I'm repeating it mainly for emphasis, and to relay a "real-life" incident in which persons who do this for a living could have had a very bad outcome. I just don't want to read about you experiencing a "ka-BOOM!" somewhere down the line, because I didn't loudly sound off about a possible hazard.

[BC17A]

Several rounds came out to 1.12, but then I started getting a wide range of OAL, from 1.05 to 1.25.

Am I reading this correctly, or are you not reading your mic/caliper correctly? A .200" difference in oal is HUGE! Shouldn't be too difficult to figure out what's causing it if in fact those numbers are right. What casting are you using? What die brand?

[kevin c]

That much variation means you need to reduce a lot of variables, many of which are mentioned above.

If you have fmj’s, single head stamp brass in good condition (pick and inspect some from your range brass), and a clean, appropriate seating stem, I’d run several dummy rounds (no powder, no primer) and check if they’re more consistent (be sure that you measure rounds that cycle through the press only with all stations full).

From personal experience, though, I only ever got that big a variance when the press itself failed: a cracked frame, press arm, or broken shell plate bolt.

[93Bandit]

93Bandit, welcome to the forum.

You might want to Plunk test all the finished ammo that has various OAL, to be sure they all chamber. If some have too long of a OAL and don't chamber, that is always a bummer to find that out at the range. Another thing, if a cartridge doesn't fully chamber, when you eject the case and the boolit sticks in the barrel, that's always a bummer too

Thank you for the warm welcome. I've been plunk testing most rounds and haven't ran into any issues yet, but you make a good point to test them before heading to the range.

I'm not casting aspersions on the way you maintain your loading dies, but you might benefit from just pulling the seating stem from the die soaking both in solvent for a few minutes, pushing patches (or whatever) through the die until clean, and reassembling. I only had one time in which o.a.l. problems arose from a truly/discernibly dirty seating die, but when I get variations like the ones you describe, disassembly, cleaning and reassembly usually helps matters.

You're not wrong to question the die's condition. However, as I am new to this, my dies are all new. I've only reloaded a hundred rounds or so of 9mm thus far with these dies. I cleaned them out before the first use, but maybe I should clean them again.

ANOTHER CONSIDERATION:
The 9mmP has a very small case capacity and operates at ~30,000 p.s.i. There is an old SPEER manual that cites a load, developing ~29,000 p.s.i., which then developed pressures in the 60,000 p.s.i. range when the o.a.l. was shortened by 0.020".
If your goal o.a.l. is 1.12" and some of your loads end up at 1.14", it isn't great, but I would expect no safety issues. If some of your load ends up at 1.10", I'D seriously consider pulling them and retrying their assembly.
Willie T was good enough to point this out before me, so I'm repeating it mainly for emphasis, and to relay a "real-life" incident in which persons who do this for a living could have had a very bad outcome. I just don't want to read about you experiencing a "ka-BOOM!" somewhere down the line, because I didn't loudly sound off about a possible hazard.

Thank you for the example, I'll definitely pull the shortest rounds. I know a shorter OAL will increase pressures, but wasn't sure how much.

Am I reading this correctly, or are you not reading your mic/caliper correctly? A .200" difference in oal is HUGE! Shouldn't be too difficult to figure out what's causing it if in fact those numbers are right. What casting are you using? What die brand?

Mr. BC17A discovered the biggest issue I'm having... I promise I can read a dial caliper, but for some reason I was reading it wrong the other day.
I measure several cartridges today and the range of OAL was 1.108 - 1.125. That's a delta 0.017" between the shortest OAL and longest OAL. To avoid losing an eye/finger or damaging my pistol, I'm going to pull all the boolits that come under my 1.12" target OAL but I'll probably shoot those that go over, as long as they pass the plunk test.

Mr. Dusty suggested I measure the max OAL using this boolit for my pistol and when doing so I ended up with a max OAL of 1.164"

[BC17A]

.017" variation?, that's more like it. What boolit are you casting? Doesn't sound unusual if you're using the shake/bake PC method since it causes more lumps and bumps when baked. What powder and charge weight are you loading with? .012" deeper seating depth won't increase pressure enough to worry about unless you're already at max with a very fast burning powder.