How much crimp for 10mm ?

[Taterhead]

Taterhead, I too use the RCBS 10mm dies for 10 and 40S&W and they do a great job, but as I started getting "The so called GLOCKED brass" I did see a few that did fit most chambers but did not pass the case gauge.  In my Storm Lake 40S&W barrel I did have some show the slightest hold out of battery where a slight push on the slide sent them home.  Also as the chamber got fouled with soot it would get worst...

The pass-through system help with everything 10mm / 40S&W / 357Sig / 9x25Dillon, this restored the brass to a better state and actually improved primer pockets and case rims as it made them uniform in roundness.

Yes it was adding an extra step, but in my opinion it was well worth the troubles.  I usually sit at the table and pass through size every thing and toss in a big jug and place a piece of paper stating they were pass-through sized.

It is funny, since I am the kind of guy that looks for an excuse to "need" to buy a reloading tool. You might say that I have been guilty of looking for a solution to a problem I really didn't have. I, on more than one occasion, had the G-Rx die in my cart with the mouse pointer hovering above the "submit order" button. I talked myself out of it since my cases gage just fine. It sounds like you've run into issues here and there, so I can see the logic in what you're doing.

[cwall64]

I don't know if it is a necessary step or not, but I do use the Redding GR-X die with the bottle on top and love it!  Like Shadow said, it is a simple/mindless step and I can do it while listening to the nightly news.  Then set the cases aside with a label on the jug...

[gandog56]

Tight bullet fit is need however your taper crimp should be the same for all of your 10mm ammo.  The full seating of the bullet to it's proper depth without any crimp being applied should be done.  Afterwards in a separate step you can apply the taper crimp, to squeeze the casing closed, back against the bullet to finish.  This will provide the best bullet tension in the semi auto cases.

For the 10mm, my finished crimp measurement at the very edge of the case mouth usually measures 0.4215" to 0.4220".  You should see a slight shine on the very edge of the case mouth, where the casing makes contact with the tapered portion inside of the crimp die.

Hope this helps! 

Yeah, don't use a crimper to increase neck tension. I only use it to equalize neck tension. So every round is more uniform.

[The_Shadow]

Where most loaders get themselves in trouble is that they try seating and crimping in the same step like revolver rounds with a roll crimp.  However with semi auto cartridges the bullet is dependant on the "case to bullet fit" for proper tension.

What happens is the bullet is being guided into the casing, with a taper crimp seating die, as the bullet is still moving down into the casing the case encounters the tapered portion of the die and starts to close inward.  The edge of the casing being sharp and some bullets being soft as in cast or plated they begin to snag and this can cause several issues.

The copper plating or cast lead alloy can start to snag, shave or even roll up inside the casing as it is pushed further inside the casing.

Once the taper crimp starts to close and actually crimp to the bullet that is not at its final depth or COL, it can cause the casing to buckle and that can loosen the case to bullet tension along its entire length.

With true copper jacketed bullets, the surface is fairly hard and can resist snagging the case mouth.

When using two separate steps, you seat the bullet to its proper depth or COL with the taper crimp section raised higher (I use a 1/8" spacer ring or two different dies) With the crimp section not being engaged, the casing is less likely to snag or buckle.

Once the bullet is seated and then apply you final crimp, the bullet is not moving so the taper crimp is just squeezing the case closed against the bullet.  With most of my semi auto I like to see the slightest shine at the very edge of the case mouth showing some contact of full crimp section, that aids in better feeding as the case mouth edge is tapered ever so slightly to make smother transitions from magazine to chambing.

[tommac919]

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When using two separate steps, you seat the bullet to its proper depth or COL with the taper crimp section raised higher (I use a 1/8" spacer ring or two different dies) With the crimp section not being engaged, the casing is less likely to snag or buckle.
snip

yes.. it's great when you do two steps and I do on my 'special' loads.

But, on some presses (like the Lee pro1k) the process is both at once and that calls for very fine adjustment to work well and pass the go-nogo gauge. With the two-in-one you look for shaving and for me does it pass the 'push test' against the bench.  Then again,  that's the main reason I only use the Lee pro1k for just 10mm target rounds and don't touch any settings as it took long enough to get it perfect with the plated heads.

Ps ; yes I hear the comments on the 1K already... and I agree. Its a set once and leave alone cookie cutter but works well enough for target loads...and I wouldn't buy one for a friend. ( maybe that's why the wife bought me it as a gift !/? )

[Taterhead]

Where most loaders get themselves in trouble is that they try seating and crimping in the same step like revolver rounds with a roll crimp.  However with semi auto cartridges the bullet is dependant on the "case to bullet fit" for proper tension.

What happens is the bullet is being guided into the casing, with a taper crimp seating die, as the bullet is still moving down into the casing the case encounters the tapered portion of the die and starts to close inward.  The edge of the casing being sharp and some bullets being soft as in cast or plated they begin to snag and this can cause several issues.

The copper plating or cast lead alloy can start to snag, shave or even roll up inside the casing as it is pushed further inside the casing.

Once the taper crimp starts to close and actually crimp to the bullet that is not at its final depth or COL, it can cause the casing to buckle and that can loosen the case to bullet tension along its entire length.

With true copper jacketed bullets, the surface is fairly hard and can resist snagging the case mouth.

When using two separate steps, you seat the bullet to its proper depth or COL with the taper crimp section raised higher (I use a 1/8" spacer ring or two different dies) With the crimp section not being engaged, the casing is less likely to snag or buckle.

Once the bullet is seated and then apply you final crimp, the bullet is not moving so the taper crimp is just squeezing the case closed against the bullet.  With most of my semi auto I like to see the slightest shine at the very edge of the case mouth showing some contact of full crimp section, that aids in better feeding as the case mouth edge is tapered ever so slightly to make smother transitions from magazine to chambing.

You're right, and this is a great description of what is going on. To complicate matters further, mixed brass will have differing case wall thickness and lengths. So if the crimper is set at the perfect setting for brass A, along comes brass B and the setting is no longer perfect. You kind of have to find a spot where it is "pretty close" for most cases. Add the dynamics of simultaneously seating, and then (as you stated) you have to be concerned about shaving the bullet, and (worse case) buckling the case. Plated bullets can't tolerate being engraved or shaved at all. PLUS setting a die to seat and crimp in the same step is probably the most frustrating setup for new loaders.

Combining the steps can be made to work for machines that don't have enough stations, or for single stage loading. I think the key is to bias toward less crimp, but tight match chambers might not tolerate this. It really takes some trial and error. Pulling a few bullets out of brass of different headstamps will show if the bullet is being abused. If it is, turn out the crimp die a tad. Repeat as needed. If the round kerplunks and the bullet is unscathed, AND your seating depth is right, THEN you've found the right setting.

Glocks don't care if the case mouth is a tad wide, and this can actually be a HUGE time saver if loading for Glocks with a single stage. I have loaded thousands that way, and my Glocks can't tell the difference. Frankly, 1911s and XDs didn't notice either. The after-crimp case mouth measurement will need to be about 0.422" in order to avoid shaving the bullet.

I too seat/crimp in separate steps with seating in station 4 and crimping in station 5. It is the preferred practice. But I have made thousands of rounds of good ammo by combining the steps. Shadow, I think you did a great job explaining the pitfalls of loading this ammo this way.

[The_Shadow]

Thanks Taterhead!  that is my intention, to educate people about what is going on as they work through their issues.
You also write

You kind of have to find a spot where it is "pretty close" for most cases.

You are correct about the different makes of brass being thinner or thicker and even the slight differences in case lengths, all of which add to the problems.  Making cartridges using the two individual steps, makes that even more forgiving.

When I doing all of the pull-downs, I try to add the measurements where the crimp actually indented the bullets if any.  I was surprised just how much some were crimped inward.  When taking the case mouth edge measurements, anything less than 0.4215", tend to be where I see the most indentions on the bullets.  I have measured some at 0.4170" which is way heavy...and the bullets crimped in measurements 0.3940" on some.  If that would be a plated bullet it would have cut through the plating.

I will also comment on the LEE FCD being used as a final crimp die can squeeze the bullets smaller in diameter as the sit in the cartridge.  That can destroy accuracy.  Especially cast bullets, where we want the bullet to remain at its largest diameter fit.   Cast bullets at 0.4000" will lead the bore, because of the lack of bore seal and blowby gases eroding the alloy.

Just getting people to understand all of these various aspects, so they to can make better decisions and adjustments to their loading procedures is the ultimate goal!