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crimp or no crimp ?

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View Poll Results: Do you crimp or not for better accuracy?
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crimp or no crimp ?

Old 12-05-2009, 07:38 PM
Fork Horn
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Default crimp or no crimp ?

.223 for AR, getting ready to load some quantity what says the board?
In general are the more accurate handloads with or without crimp?
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Old 12-06-2009, 10:01 AM
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I'm not sure it really matters with my handloads, but i use a lee factory crimp die just because i like the idea of my loads being crimpped a bit.
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Old 12-06-2009, 04:32 PM
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I don't crimp hunting rounds, but I do crimp 7.62 reloads for my M1-A1. It was suggested to me years ago that semi auto's should be crimped and I just followed that suggestion. Don't know how much difference this makes in accuracy, because I have always crimped them, but the reloads are exceptionally accurate.
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Old 12-14-2009, 08:33 AM
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I crimp the AR 223 with great sucess with lee dies. 3 rounds @ 100yrds inside a quarter Took the same loads uncrimped 4 inches low with a 5 inch spread No brainer crimp for me
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Old 12-14-2009, 09:11 AM
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I don't crimp rifle cartridges, but I also don't load for any semi-auto rifles.

I really don't see how it would be strictly necessary, as long as the sizer die sizes the neck to give good tension. Also, be aware that rifle seater dies that have a crimp function are usually roll crimp. This being the case, you should never attempt to crimp unless the bullet has a cannelure, and then obviously the bullet must be seated such that the neck is crimped into said cannelure. Attempting to crimp a non-cannelured bullet will likely cause the neck to be bulged or crushed. If that happened, the best case is that the rounds won't chamber and the brass will be ruined, requiring you to pull the bullets and start over with new brass. Worst case is that the case could chamber but because the bulge causes less space for the neck to expand on firing, you could see dangerous pressure spikes... which are obviously not good.

The exception is the Lee Factory Crimp Die. It uses a collet to create a pinch like crimp in the neck. This is acceptable for both cannelured and non-cannelured bullets. Some folks swear by this die, saying it greatly improves accuracy and velocity consistency, but I'm not thoroughly convinced of its benefit.

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Old 12-16-2009, 06:51 PM
Fork Horn
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Neck Tension
When we stop to consider the vigorous (read, downright violent) chambering cycle a loaded round endures in a Service Rifle, it becomes pretty clear it suffers abuse that would never happen in a bolt-action. This is simply the nature of the beast. It needs to be dealt with since there is no way around it.
There are two distinctly different forces that need to be considered: those that force the bullet deeper into the case, and those that pull it out of the case. When the round is stripped from the magazine and launched up the feed ramp, any resistance encountered by the bullet risks having it set back deeper into the case. Due to the abrupt stop the cartridge makes when the shoulder slams to a halt against the chamber, inertia dictates that the bullet will continue to move forward. This is exactly the same principle a kinetic bullet puller operates on, and it works within a chamber as well. Some years ago, we decided to examine this phenomenon more closely. During tests here at Sierra’s range, we chambered a variety of factory Match ammunition in an AR-15 rifle. This ammunition was from one of the most popular brands in use today, loaded with Sierra’s 69 grain MatchKing bullet. To conduct the test, we chambered individual rounds by inserting them into the magazines and manually releasing the bolt. We then repeated the tests by loading two rounds into the magazine, chambering and firing the first, and then extracting and measuring the second round. This eliminated any potential variation caused by the difference between a bolt that had been released from an open position (first round in the magazine) and those subsequent rounds that were chambered by the normal semi-automatic operation of the rifle. Measuring the rounds before chambering and then re-measuring after they were carefully extracted resulted in an average increase of three thousandths (0.003") of forward bullet movement. Some individual rounds showed up to seven thousandths (0.007") movement. Please bear in mind that these results were with factory ammunition, normally having a higher bullet pull than handloaded ammunition.
To counteract this tendency, the semi-auto shooter is left with basically two options: applying a crimp or increasing neck tension.
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Old 12-17-2009, 01:51 AM
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I crimp only for tubular magazines myself.
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Old 12-17-2009, 02:40 AM
Fork Horn
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Thanks all , for the very informative replys.
I've been using the Lee crimp die all along , I will have to compare some non -crimped loads at range.
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