Why I Crimp

[tribb]

I discovered that many years ago. Particularly true for 223/5.56. My solution to that happening was to just take .005" or so off the bottom of the sliding collet. Works like a charm! That way, I can always trim to minimum length and still get a solid crimp on every case.

The sliding collet on what? Tribb

 

[Teri Anne]

It was a couple of years ago that ButterBean and I discussed whether to crimp or not. I was working up loads for the Tikka 270 at the time and without any crimp was able to get 0.070 to 0.075 groups. Got a Lee Crimp Die and gave it a try with just a light factory style crimp. Group size dropped down to 0.55 to 0.60. Have been lightly crimping everything since, 223, 270, 30 and now 338 with fantastic results.

 

[RegionRat]

I was working up loads for the Tikka 270 at the time and without any crimp was able to get 0.070 to 0.075 groups. Got a Lee Crimp Die and gave it a try with just a light factory style crimp. Group size dropped down to 0.55 to 0.60.

Teri Anne, I'm pretty sure I follow your drift, but it looks like the zeros slipped on the 0.070 to 0.075?
It makes more sense if that was really 0.70 to 0.75 such that it improved with 0.55 to 0.60.

 

[ButterBean]

Thanks Bean I'm gonna try it for sure. On bullets with grooves like hammers do you want to have the crimp in the groove or on other part of bullet that's between the grooves.lm thinking on the hump between the grooves. Am I correct? Tribb

You are correct

 

[ButterBean]

The sliding collet on what? Tribb

They can be "Tuned" if needed, I'm set up to do that if need be

 

[ButterBean]

It was a couple of years ago that ButterBean and I discussed whether to crimp or not. I was working up loads for the Tikka 270 at the time and without any crimp was able to get 0.070 to 0.075 groups. Got a Lee Crimp Die and gave it a try with just a light factory style crimp. Group size dropped down to 0.55 to 0.60. Have been lightly crimping everything since, 223, 270, 30 and now 338 with fantastic results.

I'm just glad you had an open mind and tried it, so many on here are not

 

[tribb]

They can be "Tuned" if needed, I'm set up to do that if need be

Roger that thank you

 

[Teri Anne]

Teri Anne, I'm pretty sure I follow your drift, but it looks like the zeros slipped on the 0.070 to 0.075?
It makes more sense if that was really 0.70 to 0.75 such that it improved with 0.55 to 0.60.

You are absolutely correct, sometimes those zeros have a tendency of getting out of control late at night when one should be in bed sleeping instead of trying to stay awake to read, "just one last post."

 

[RichCoyle]

I'm and small increments. Therefore, I didn't choose 8th turn but rather 16th turns on the die. At 7/16 turn the groups all of a sudden shrank. It was like the rifle was waiting to show me it's best potential.

 

[nicholasjohn]

The crimp isn't enough to create a pressure spike, at least you shouldn't be crimping that hard. You can get a significant spike if the bullet jams the lands prior to full ignition. I can feel it when I'm shooting. The slight crimp that @ButterBean recommends just prevents this from happening. Once we figured out what was going on and started using the LCD, the false pressure signs went away and we were able to increase the powder charge till we got to normal consistent pressure signs before backing off and finding a safe, stable load. Since some would jump prematurely into the lands and some would not, we were getting flyers until we started crimping. This pulled everything together remarkably. That was the 124 HH in a CM. Not all of our rifles had the same degree of trouble.

Thanks for the explanation. It may be that the pressure signs that signaled max to me were due to this spike, and I might have backed off from a point that wasn't really maximum in my rifle. This makes sense to me, since I may have more complete ignition with the crimp before the bullet engages the lands. This would probably eliminate the pressure spike. When I try the crimp it's quite likely that I'll find that I can keep advancing my powder charge for a slightly higher velocity that is closer to true maximum.