Differences in 9mm ammunition Added a Picture

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mikld

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hard nose street cop said:
Kevin also keep in mind that ALL factory semi Auto ammunition is crimped, let that be your guide
How much is it "crimped"? Is it just enough to insure good feeding? Do you know how much neck tension a factory round uses? A process called a "crimp" is not necessarily a real crimp, where the case is squeezed against the bullet. I would be interested in knowing the factory dimensions for cases/bullets during their manufacturing process...
 

Rick Courtright

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Hi,

If you want to do some measuring, get a box of factory shells, and go to the SAAMI website (http://www.saami.org if I recall) and download the spec sheet for both the ammunition and the chamber. That will show you what you want, and should answer mikld's question, too.

These will tell you the range of sizes for various measurements, clearances, tolerances, and such. Measure the factory ammo, measure your ammo. If they're both within range, measure the chamber (might want to do a cast--Brownell's has the material) and measure it. You may have a tolerance stacking problem where the ammo's just a touch out of spec on the large side, the chamber's a touch out on the small side, and the two worlds are "colliding" in your case.

Shouldn't be too hard to do except the chamber cast will take a bit of time.

As for crimp: I try to learn from the people who know what they're doing. In the case of ammo, they would be the ammo factories. I know it's popular to say you don't need a crimp on xxxx caliber ammo. That's one of those Interwebs "truisms" that may prove true in certain individual cases, but won't hold up across the board in the big picture. To the best of my knowledge, I've NEVER seen a factory round that isn't crimped. The factories load more ammo in an hour than most of us will in a long lifetime, so follow their lead. BTW, the factories generally use more steps than we do for a couple of operations, such as the crimp. This lends some credence to the "seat bullet, crimp separately" approach of the Lee Factory Crimp Die and whatever similar approach other die mfrs use.

You can even duplicate that process with a single seating/crimping die if you don't mind some readjustments along the way: first, adjust your die so the crimp section doesn't touch the case, and adjust the seating pin to seat the bullet where you want it. Now adjust that pin out to where it doesn't touch the bullet, and adjust the die body to provide the desired crimp. Takes longer than having a dedicated die for each step, but it's doable.

Good luck!

Rick C
 

Enigma

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Kevin, when dealing with cast bullets, you have to realize that the specified weight is merely a goal to aim for. Unless you are using the exact same lead alloy that the manufacturer uses, there WILL be a weight variation. In this instance, three grains difference is negligible. Next, diameter. Cast bullets are normally used at .001-.002" OVER the barrel groove diameter. This allows for a complete gas seal, as they swage down to fill the bore. This prevents gas cutting, which causes leading.

Next, many/most 9mm barrels do NOT truly have a .355" groove diameter, per SAAMI specs. Many nominal 9mm pistol barrels will be found with a groove diameter ranging anywhere from .355" to .358". The only way to tell for sure what your barrel runs is to slug it and measure the slug with a micrometer. If I didn't have the means to slug a barrel and was shooting commercial cast bullets, I would use the largest diameter that would 1) chamber, 2) function and 3) NOT cause leading.

Lastly, here is a thread written about this very subject - shooting cast bullets in a 9mm pistol. It's rather long, but there's a lot of good advice and info in there:

http://castboolits.gunloads.com/showthread.php?121607-Setting-up-for-boolits-in-a-new-9mm
 

Mobuck

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Here's something to consider in the process of "crimping" 9mm(or any case that headspaces off the case mouth). The "crimp" is going to be minimal at best, however, seating/crimping in one operation may have a certain advantage that most overlook.
When the bullet is seated/crimped in the typical one step process, the crimp is applied during the final increment of seating. This may in effect cause a tiny bit of the outer bullet surface to be "bulldozed" ahead of the lip of the case mouth actually improving the resistance to bullet set-back during cycling.
Is this advantageous? I dunno. I'm just tossing out an observation of the actual mechanics of the process.
 

chuck

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A great big thank you to Recumbent, I didn't know they had such a thing. Im going to buy one.
 

mikld

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chuck said:
A great big thank you to Recumbent, I didn't know they had such a thing. Im going to buy one.
I got my first semi-auto quite a while ago and thought I needed a case gauge. Actually the gauge gave me more trouble than any feeding/chambering problems I may have had, so I tried the plunk test. I put the case gauge away and use the plunk test exclusively. For my 4, 9mm pistols it works quite well in all (I normally use the easiest gun to strip for a barrel test; my Ruger LC9). For my 45 ACP guns (two pistols and one carbine) I plunk test with my Ruger P90 barrel and the handloads work/feed quite well in the others. I've only got one 380 ACP and one 32 ACP, but I still plunk test my handloads for those too...
 

toysoldier

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Mobuck said:
In the future, don't toss those faulty rounds. You need them to determine the problem.

Good point. I was trying out a Hatfield shotgun with sub-caliber inserts this morning, and had problems with some .45acp reloads. The primers were dented, but failed to fire. The rounds were more difficult to extract. I think I had over-crimped them just a hair, and they were driven into the chamber when struck. Just eyeballing, the case mouth looked just a hair different from the other .45 loads I tried. You reload, shoot and learn.
 

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