How much should I crimp a 10mm?

Y

Yosemite Steve

New member
My hornady seating die was creating a bur on the mouth of the case when crimping. I ended up chamfering to eliminate the little lip. There are no cannelures on my bullets so it's hard to tell if it's right. Am i doing it wrong?
 
Little to none if you're shooting it in a semi-auto. It should be head-spacing on the case mouth. A factory crimp or taper crimp is what you need.
 
I get mixed instructions. Hornady tells me to do it all in one press. Others say it's best to crimp after seating. I guess if it's not really crimping but resizing the flare it could be done in one stroke, hence the die that is designed to do so. I'm at a point of retraining habits from loading other ammo. The 10 mm is new to me. The 44 mag has cannelures and take a good crimping. What I have now is .0005 less than the added dimensions of the bullet and case thickness times two. I will measure a round after repeated firings to see if it moves from recoil.
 
Hornady tells me to do it all in one press. Others say it's best to crimp after seating.
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Both answers are correct. You can do it in one step; but it's best to do it in separate operations. And if you're just getting started (I'm curious how much overall handloading experience you have), all the more reason to do it in separate operations; as to "isolate" your processes for troubleshooting/learning purposes. Seating and crimping in one operation is done after you've worked out the kinks in your processes.

I'm at a point of retraining habits from loading other ammo. The 10 mm is new to me. The 44 mag has cannelures and take a good crimping.
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When it comes to crimping, your 44 Mag habits won't serve you well. The 44 Mag uses a roll crimp; the 10 uses a taper crimp. Apples n Oranges.

I wish I had the magic advice for you. Crimping (roll or taper) is a "feel" thing and there is no substitute for experience. You just need to learn when it feels right. When taper crimping, less is generally better. Take out the flair, and maybe just a touch more. Just a touch.
 
Steve, I'll try to shed a bit of light if possible. I've been reloading for 30 years and have been following the 10 since Mr. Cooper came up with it and the Bren10 chamber it.

Semi automatic cartridges like the 9mm, 10 [and it's little brother 40SW] get seated in the chamber and "headspace" - meaning the case stops going any further down the bore - by the mouth of the case hitting a point in the chamber. Look down the barrel of your 10mm and you will see where the case hits it. If you crimp too much, the mouth no longer hits that point, but goes further. This causes 2 issues 1- chamber pressure increases because the case mouth cannot expand fully, as it is now in the narrower part of the chamber designed for the bullet. 2- the primer has to extend further to hit the case, as it is too far into the chamber.

Revolver cartridges, like your 44 headspace using the rim of the case. The cartridge can only go to far, regardless of the crimp, because the rim stops it from going any further. So you will often see revolver bullets with cannelures. The cannelures are there so the case can be crimped [the mouth is actually rolled into the cannelure]. Because the case depends on the rim to position it in the chamber, the mouth of the case can be rolled into the bullet.

The reason some people tell you to crimp after and yet other tell you to crimp in 1 step is partly due to personal preference and part due to the hardness of the bullet. If you are using soft bullets, or those with a fragile exterior [plated, lead, cast], the chances of scraping the bullet is greater when you crimp and seat in 1 step. As you raise the press ram, the bullet is being pushed into the case while the case is being squeezed - you will get some scraping of the bullet. This is a huge problem with semi-autos and cast bullets. Why? As the bullet scrapes, it builds up at the case mouth. Remember the case mouth determines the position of the cartridge in the chamber. If you crimp too much, the cartridge goes too far down the chamber. If the cartridge doesn't go far enough [excess bullet material scraped up against the mouth], then the gun will not go into battery. You will see the slide slightly open and the gun will not fire.

If you are using hard, FMJ, soft points, etc. or loading revolver cartridges, it is not as important. If a little build up occurs, the gun will still fire - again, the revolver depends on the rim, not the case mouth.

For me, rule of thumb -

Loading for semi autos or accuracy rounds - seat then crimp
Loading for plinking revolvers - seat and crimp at the same time.

Hope this helps.

Rick
 
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It's only necessary to seat and crimp in separate steps if your not sure how to adjust the seating die to accomplish both with the seating die. That is, if you are applying a roll crimp into a crimping groove or cannelure for revolver loads that headspace on the case rims. But that wouldn't usually apply to 10mm auto loads.

The 10mm is an extended .40 and both follow the same rules as other autos that space on the mouth of the case, just crimp enough to remove any flare, thereby leaving a straight case at the mouth. I have a Smith 10mm revolver in addition to an auto and I do crimp on rounds for the revolver, mostly using Hi-Teks coated bullets. The rounds do headspace within the cylinder so a heavy crimp is not used, or probably not even needed.
 
Wow, guys. Great advice! Northof50, you in particular! I wish that Hornady had your explanation in the directions for the dies. I also wish I had a progressive press. I'm using an RCBS Rock Chucker and this is taking a long time.

Also, with my Bulge Buster, it says in the instruction to resize before debulging. Why? I have been debulging first because my resizing die will crease the case near the head if I don't.
 
You can seat and crimp in one step easily, as others have said, with a properly adjusted die. Just remember case lengths are important, they all need to be the same length to get the same crimp result.
 
Steve - No problem. We've all been there. Cannot tell you how long it took me to realize that the hard-cast material was building up on the mouth of my cases.

Don't be too concerned. I still use my RockChucker and wouldn't trade it for anything. I eventually purchased RCBS's PiggyBack system, which converted the single to a progressive. I used that for years. I only recently [past 5 years] moved to the Pro2000. That RockChucker is outstanding.

I've been shooting my Glock 20 since '94. I've loaded it with everything from 155 hard cast [yes, yes, I know - you cannot shoot cast bullets in the Glock - OK] @ 900fps up through 180XTP bullets @ over 1400fps. I have never used a "bulge buster," nor do I have the desire. Full length resize, bell the mouth, seat/crimp. Provided your crimp is just taking out the bell, you can seat/crimp in the same process [and you are not loading cast bullets].

FYI - I mean no offense to anyone, as I am relatively new here - but I have read some ridiculous stuff within these pages with respect to "reloading process." You will develop your own style of reloading and determine, based on your own experiences what works and what does not.

Good luck.
 
Just enough to remove the bell. Pull a bullet from a finished round, if you deformed the bullet with your crimp, you are crimping too much.

With no cannelure, neck tension is what is holding the bullet, not crimp.
 
I crimped separately using my lee carbide crimp die. I screwed it in until it met the case and then another 3/4 turn. It does it's thing but does not affect case mouth diameter. .401 bullet, .010 wall thickness. After seating it's .420" no change after the crimp. When I taper the mouth it is just barely enough the set the bullet. Seating the bullet seems to deal with the taper as the wall thickness is reduced the .0005" resulting in a .420" measurement after seating. Even if i give the crimp die a full turn i still get the same measurement. Lee says 1/2 to 1 turn.
 
FYI - I mean no offense to anyone, as I am relatively new here - but I have read some ridiculous stuff within these pages with respect to "reloading process." You will develop your own style of reloading and determine, based on your own experiences what works and what does not.
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That's forums for ya. Take it all with a few grains of salt. I will say that I have gotten some very good advice here. I hope nobody takes offense at my questioning their advice. If I know "why" with the "what" I learn a lot more. I have some serious OCD so I might spend a great deal of time over thinking something before I can feel comfortable with it.
 
"...creating a burr on the mouth..." That shouldn't happen assuming the seating plug isn't damaged. Suggests there's something in the die or it's otherwise damaged. The 10mm headspaces on the case mouth just like a .45. Look in the die for crud assorted or just clean it.
"...my Lee carbide crimp die..." Only the sizer die is carbide.
 
Bulge Buster

Also, with my Bulge Buster, it says in the instruction to resize before debulging. Why?
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I don't know. I bulge bust my 10mm. I've always busted first, then resized. I don't recall the instructions stating otherwise; and I'm sure I have tossed them years ago.

Bulge bust first. Trust me on this one. It works exactly as intended (or at least, needed) doing it that way.
 
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