Over Crimping 9mm

[Sharper2112]

I shoot Acme 124gr hi-tek coated bullets 99% of the time behind 4.0gr of Alliant Sport Pistol for practice and competition. I had some Acme 145gr hi-tek Coated RN bullets laying around from when I used to shoot those and thought I’d try them again today. I loaded two small batches; one with 3.3 grains of Sport Pistol and one with 3.4 grains of sport pistol. When I fired the first couple of rounds through the Chrono with the 3.3 grain load I was seeing velocities in the 1150 range. I immediately stopped because I knew that was very wrong for a bullet with this weight and charge. I figured I may have screwed up the loading or something so I moved on to the batch loaded with 3.4 grains. I fired one shot and got a reading over 1200 FPS. Needless to say I stopped again. I came home and pulled some bullets from both batches and they were all loaded correctly; nothing over the prescribed charge weight in any of the cases. My OAL was 1.10 to 1.11 which is what the load data calls for on Alliants sight. I’ve been racking my brain trying to understand what could have caused this. Upon Inspecting some pulled bullets I noticed that the crimp applied was indeed excessive as you can see from the photos below. I did not adjust my Dillon Crimp die from where I usually have it for the 124’s. Could over crimping cause excessive pressures high enough to push a 145gr Bullet to 1200 FPS with a standard charge? For good measure I also fired some of my 124’s through the Chrono today and they averaged 1040 which is right where I want them; 130 or so PF. I’m baffled

 

[Tcruse]

Crimp does not look all that bad based on your pictures. Since the heaver bullet is longer, you may be compressing the power in the case driving up the pressure. Did the fired cases show any signs of over pressure like flatten primers or budged cases?

 

[drband]

9mm will be way too hot before the case bulges. Velocities indicate you may be into +P pressures.

 

[Tilos]

I consider any mark/ring on the bullet as an over-crimp condition, jmo though.
That said, I don't believe the crimp is causing the higher than expected velocity.
What is the velocity listed for that load?(looked it up, should be less than 950!)
Not wanting to assume anything here, what are the measured bullet diameters?
A larger bullet diameter will receive more crimp than a smaller one, at the same die setting.

 

[murf]

what's your c.o.l.? here is the alliant load data: http://www.alliantpowder.com/reload...derlist.aspx&type=1&powderid=42&cartridge=189

luck,

murf

disregard, i read the rest of your post. i would check for bullet setback as, i agree, your 1100 fps is way too fast.

 

[sbwaters]

My OAL was 1.10 to 1.11

What happens in a plonk test? The OAL might match the recipe and get pushed shorter in the barrel.

 

[Sharper2112]

Crimp does not look all that bad based on your pictures. Since the heaver bullet is longer, you may be compressing the power in the case driving up the pressure. Did the fired cases show any signs of over pressure like flatten primers or budged cases?

I forgot to look at the damn fired cases. I was so shocked by the Chrono reading didn’t think to check

 

[Sharper2112]

What happens in a plonk test? The OAL might match the recipe and get pushed shorter in the barrel.

I consider any mark/ring on the bullet as an over-crimp condition, jmo though.
That said, I don't believe the crimp is causing the higher than expected velocity.
What is the velocity listed for that load?(looked it up, should be less than 950!)
Not wanting to assume anything here, what are the measured bullet diameters?
A larger bullet diameter will receive more crimp than a smaller one, at the same die setting.

I weighed a couple of th bullets to make sure they were 145gr. They were

 

[Tilos]

I weighed a couple of th bullets to make sure they were 145gr. They were

OK, actually looking for any difference in DIAMETER, ie the 145gr being larger, causing the crimp ring and high velocity.

 

[Sharper2112]

OK, actually looking for any difference in DIAMETER, ie the 145gr being larger, causing the crimp ring and high velocity.

Ok I did. They appear to be .356 as they should.

 

[Sharper2112]

I’m beginning to think this was just a fluke of some kind. I think I’ll fire a couple more rounds of the suspect ammo tomorrow, look at the cases, and then report back my findings.

 

[Blue68f100]

Have you done the Plunk test? To confirm their not into the rifling.

With a heavier bullet set at the same OAL is going to give you less case volume. Using Mixed brass will just add to the problem. May have to back the charge down.

 

[Sharper2112]

Have you done the Plunk test? To confirm their not into the rifling.

With a heavier bullet set at the same OAL is going to give you less case volume. Using Mixed brass will just add to the problem. May have to back the charge down.

Yes they plunk fine. I loaded them to the OAL that the load data said to. 1.10

 

[sbwaters]

Yes they plunk fine. I loaded them to the OAL that the load data said to. 1.10

Those are two different things. The bullets are shaped differently. They have a different ogive. They will touch the rifling in a different place.

If you take your barrel out and drop a reloaded bullet and case into the chamber. Does it twist freely and easily?

 

[Sharper2112]

Those are two different things. The bullets are shaped differently. They have a different ogive. They will touch the rifling in a different place.

If you take your barrel out and drop a reloaded bullet and case into the chamber. Does it twist freely and easily?

Yes. But if it didn’t that would generally mean I’ve loaded too long. It would seem counterintuitive to the issue I had to load shorter because that would increase pressure even more. In my experience a Beretta 92 (the gun I was firing) doesn’t have a really tight chamber like some other guns I’ve dealt with. You’re right though the load data is a guide only; there have been several guns I’ve had to load shorter than the printed data in order to plunk and adjusted the charge accordingly.

 

[Walkalong]

The crimp is not your issue.

 

[cheygriz]

I use a Lee factory crimp die.

 

[Sharper2112]

The crimp is not your issue.

Thanks. That’s what I really wanted to know. I’m going to test again tomorrow and see if maybe it was just the Chrono acting up today or something.

 

[Walkalong]

Chrono acting up today or something.

Could be, it happens. Too cloudy? Sun at a bad angle?

Double check your data, but if that is good, sure, try them again.

 

[kmw1954]

Yes they plunk fine. I loaded them to the OAL that the load data said to. 1.10

I think I would recheck this data. I load a 124gr plated bullet to 1.150" and 1.160" and those bullets look to be much shorter than those 145gr bullets you have there. I too believe the crimp looks normal.

 

[sbwaters]

there have been several guns I’ve had to load shorter than the printed data in order to plunk

Thanks for your reply. I'm glad it twists. It was a safety question I had to ask.

 

[Sharper2112]

I think I would recheck this data. I load a 124gr plated bullet to 1.150" and 1.160" and those bullets look to be much shorter than those 145gr bullets you have there. I too believe the crimp looks normal.

The data is right off of Alliant Powders website. Thanks for commenting on the crimp though. However I’ve read that it’s not good to be making that much of an indention into the Bullet like I did.

 

[LiveLife]

Acme 145gr hi-tek Coated RN ... OAL was 1.10 to 1.11 which is what the load data calls for on Alliants ... 3.3 grain 1150 [fps] ... 3.4 grains 1200 FPS ... I’m baffled

I would be too as Alliant's max charge lists 3.5 gr at 949 fps - http://www.alliantpowder.com/reload...wderlist.aspx&type=1&powderid=42&cartridge=23

9mm Luger 145 gr Acme RN-NLG (No Lube Groove) coated Sport Pistol OAL 1.100" Max 3.5 gr (949 fps)

9mm with small internal case volume can increase chamber pressure with small changes.

i would check for bullet setback as, i agree, your 1100 fps is way too fast.

I agree. It's not "finished OAL" that determines chamber pressure rather "chambered OAL" after any bullet setback when bullet nose slams on the feed ramp. I always check neck tension/bullet setback of my test rounds by measuring before/after feeding some dummy rounds from the magazine without riding the slide.

Before anything, I would suggest you check bullet setback of your 145 gr load to ensure you are not seating the bullet deeper when loaded from the magazine. Either load dummy rounds (no powder, no primer) or point muzzle in safe direction and load/chamber rounds from the magazine without riding the slide. If "chambered" OAL is shorter, it may explain the velocity increase.

I would also verify the accuracy of scale with check weights to confirm you are actually metering 3.3 and 3.4 grains using check weights set close to powder charge range being used.

Keep in mind, Alliant used 4" test barrel. So if your barrel is longer (like your Beretta 92), chrono velocities will be higher.

Have you done the Plunk test?

Yes they plunk fine. I loaded them to the OAL that the load data said to. 1.10

No.

The purpose of the "Plunk Test" is to determine the max OAL for the barrel you are using. Listed OAL of 1.100" in the published load data simply means that's the OAL used for pressure testing in a single shot test barrel fixture. For our pistols that must feed from the magazine and cycle the slide, we need to determine the "working OAL" that works with our barrels, magazine and pistols.

Use the barrel to first determine the "max OAL" that will allow the finished round to drop freely in the chamber with a "plonk" and spin without hitting the rifling. Next, determine the "working OAL" that will reliably feed and chamber from the magazine. Working OAL can be same as max OAL but often shorter.

 

[LiveLife]

I too believe the crimp looks normal.

Thanks for commenting on the crimp though.

We cannot verify the proper amount of crimp by "looking" with our eyes.

Since case wall thickness averages .011"+ (around case mouth), I usually add .022" to the diameter of bullet for proper taper crimp amount which will essentially return the flare back flat on the bullet - https://www.thehighroad.org/index.p...nd-bullet-setback.830072/page-3#post-10712225

So for .356" sized bullets, I use .378" taper crimp.

 

[Dudedog]

Just curious how did the 145s feel when you shot them?
If they really were 1150 I think you would have felt it on the first round and though what the heck and stopped before ever looking at the chrono.
If they really are that fast something is going on. (and pressures are to high for sure)