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.223 and crimp

Sierra did a test not too long ago with the Lee Factory Crimp and without it. They found that some .223 bullets w/o the crimp were backset by as much as .2" in the chamber due to loading. This is from the "Experts" at Sierra. Take it for what its worth to you. Its a long article but well worth reading

http://www.exteriorballistics.com/reloadbasics/gasgunreload.cfm

Aim for the X

Stan
 
I CRIMP every .223 Remington case with a Lee Factory Crimp Die. Regardless of bullet brand, I believe a crimp allows a powder charge to build alittle steam before it releases a bullet. At 200 yards, accuracy is good (2" or less groups with ten rounds fired). Not crimping can cause excessive bullet run-out, bullet set-back in ARs, and varied velocity even with carefully-weighed handloads. This is my belief, but I've been wrong once before. I may be shaky, but my groups stay tight. Reducing locktime with a decent firing pin spring helps accuracy also. Cliffy
Old Post but I think you are correct and the rest are not. Cannelure is needed in AR that is why the military uses it. The BCG hits very hard and will actually move the bullet forward without a crimp. I tested in 4 different ARs from a 24" varmint AR to Colt 6920s. No amount of neck tension overcomes the kenetic effect.
Bullets go from 2.250" to 2.255"
Sometimes its the opposite they hit the feed ramp hard or maybe rough feed ramps and it resets the bullet to something shorter than it was.

It does not happen on the 55gr with Cannelure but it does on 53gr 55 and 69gr non Cannelure bullets I tested.

I think you have to single feed them to avoid that effect. They don't know because they never bothered to try it and measure. The guns still shoot but the pressures have to be affected by it.
 
I have been experimenting with crimping, even on precision single feed bolt guns for FTR. I am not through all of my testing (trying on all platforms and calibers I have) but so far, I agree with another poster on here that it does help stabilize start pressure and therefore is more accurate and none of my bullets have the cannelure for the crimp.
We all stress about neck tension, the Lee crimp die in my mind is one way to “add” neck tension and even out pressure.
Here is my 2000+ rd savage FTR, 6 shots at 100, win brass, Hornady 178 and Shooters choice precision. It did very well at 600yds, better than my Berger loads (not crimped fwiw).
 

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My toys and shooting is not at the level of many here, but I crimp every round that I load since most of my shooting is with semi-auto toys. Never have to worry about setback or a bullet walking forward in a revolver. Makes for very consistent loads which translates to better accuracy in my toys. Eliminates any questions about neck tension.
For best results, trim brass to the same length before loading and crimping.
In the one rifle I load for precision shooting, a crimp is still used and insures initial pressures will be nearly identical between rounds. The rifle is an old Mosin M-44 that is a 1.5 MOA gun with my hand loads after some work to the stock and hand guard.
 

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