To crimp or not

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To crimp or not

Post by Multiracer on 6/23/2017, 8:04 pm

I have a need to know what the net result of NOT crimping 45 SWC lead or JHP bullets is ?
Anyone want to chime in ?
Thanks
Ron

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Re: To crimp or not

Post by Wobbley on 6/23/2017, 8:23 pm

Accuracy goes down, velocity variation goes up.

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Re: To crimp or not

Post by Jack H on 6/23/2017, 9:28 pm

Your brass MUST secure the bullet in place somehow.  If not, the bullet may creep from recoil.  Or move ahead on chambering.  The rounds may not feed at all.  I had to increase the crimp on yellow box Winchester JSWC to not bite the side of the chamber in a 1963 Gold Cup. 

Then you get into the crimp needed for best accuracy in your gun.
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Re: To crimp or not

Post by SteveT on 6/23/2017, 9:44 pm

You must crimp enough to straighten out the bell in the case. Not doing so will result in lots and lots of jams as the flared case is too large for the chamber. Don't ask me how I know... On a completely unrelated topic did you know that you can switch the seating and crimping dies in a Dillon SDB press, which doesn't remove the flare in the case? In my experience you are most likely to make this mistake the night before leaving for Canton and Camp Perry.

Most of the recently developed JHP loads call for very little crimp. There seems to be a trend. Years ago people called for heavy crimps. Now days it seems many people are getting better results with light crimps. I don't know what changed.
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Re: To crimp or not

Post by jmdavis on 6/23/2017, 10:36 pm

I crimp everything to .469-.4695, swc's, jhp's. If it goes in my 45s it is .469. In line with what Steve said above, you can also flare a case too much on a single stage that the crimper won't fix it and you will need to resize to use the brass. 

It's all part if the learning process.
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Re: To crimp or not

Post by Multiracer on 6/24/2017, 10:06 am

Very good gentlemen, Thank you.
I have been loading with no more crimp other than to straighten any bell I induced in the case.
There was no measurement difference top to bottom of the cases.
I stumbled upon this by setting up my Dillon RL550B.
I now induce a slight .004 crimp and during testing yesterday the accuracy went up on LSWC at 25 yards.
Thanks for the info.
Ron

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Re: To crimp or not

Post by zanemoseley on 6/24/2017, 10:09 am

What's interesting is nobody crimps hand loaded rifle ammo used for long range shooting. Of course they don't bell the cases either, perhaps that's the main difference.

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Re: To crimp or not

Post by bdas on 6/26/2017, 4:10 pm

Multiracer wrote:Very good gentlemen, Thank you.
I have been loading with no more crimp other than to straighten any bell I induced in the case.
There was no measurement difference top to bottom of the cases.
I stumbled upon this by setting up my Dillon RL550B.
I now induce a slight .004 crimp and during testing yesterday the accuracy went up on LSWC at 25 yards.
Thanks for the info.
Ron

I'm no reloading expert, but according to my reading of the SAAMI specs, the 45 Auto case is not truly straight-walled.  Just above the extractor groove, the diameter should be 0.4760, and at the case mouth, the diameter should be 0.4730, with a note that says "unless otherwise noted, body dia. -.006".   See [url=http://saami.org/specifications_and_information/publications/download/Z299-3_ANSI-SAAMI _cfpandr.pdf#page=65]http://saami.org/specifications_and_information/publications/download/Z299-3_ANSI-SAAMI%20_CFPandR.pdf#page=65[/url]
The 45 Auto spec is on the 65th page of the PDF file, and is the page numbered 56 in the document itself.

So, if you were not measuring any difference between the diameter just above the extractor groove and at the case mouth, you might not have been removing the bell all the way.

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Re: To crimp or not

Post by Multiracer on 6/26/2017, 5:30 pm

Correct sir,
I discovered the two measurements by chance. I was only measuring from the center to the crimp area and seeing very little change. I now crimp to .470+- 
Thanks for the reply and the saami info.
Ron

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Re: To crimp or not

Post by noylj on 6/26/2017, 6:11 pm

Take a look at factory ammo and see how "much" crimp is used--like NONE. They just have a straight case mouth.
Bullets don't walk out of semi-auto cases. The only real issue with semi-autos is the bullet hitting the feed ramp and moving deeper in the case. Even if you want to say the case tapers, you should be able to lay a ruler along it and not have air visible between the case and ruler at the case mouth.
To be sure that is sufficient bullet tension, I push down on the bullet after seating to ensure it doesn't move.
Unless it has a bottleneck, it is defined as a straightwall case.
When you put 9mm Luger rounds side-by-side, you can clearly see the taper.
All you have to do, if your eyes can't see the residual flare or you can't run your finger down the bullet and feel any residual flare, is make sure the case mouth is 0.473-0.470" for .45 Auto.

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Re: To crimp or not

Post by Jack H on 6/26/2017, 7:41 pm

"Take a look at factory ammo and see how "much" crimp is used--like NONE."


I had some whitebox hardball with a visible crimp.  I measured it as .465 on 230 FMJ factory.  It shot just fine though.
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Re: To crimp or not

Post by straybrit on 6/26/2017, 11:18 pm

Single datum - Canton/Perry 2015 - both CF & 45 long line I had called eights/nines in the 5 ring. Drove me crazy. Ended up buying a few boxes of factory ammo from Zero to finish up the matches (props to the Zero guys on commercial row who effectively reopened to take care of me).

Got home and measured the ammo - instead of the nominal .468 I normally use I had a nominal .471. Yeah - I check that crimp die a lot more frequently now. So for me, my gun and my grip - crimp is vital. YMMV.

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