Swirling on Mec Jr. (20ga)

[Hiaboo]

Why is this happening sometimes, and sometimes not? I tried playing with the final crimp and nothing ever turned up.

Never had a problem with my 12's on a Grabber.

Remington HV low brass 20ga w/ claybuster WAA20 rep. 14gr unique w/ 7/8oz.

 

[rcmodel]

Look on the side of the cases and see if there is any sign of the case buckling when you put the final crimp pressure on it.

The off center spiral crimp is sometimes caused by the seating pressure causing the case wall to give, which pulls the seater off-center with the crimp.

The one on the left actually looks like there is a deeper crimp on the upper right side then the lower left side, and that can only be caused by a crooked / buckled case.

rc

 

[JimKirk]

I believe that what you're seeing is too much wad pressure. This results in the hull being too long at the crimp. The swirled crimp shows that the space left after the shot and wad is too long, this causes the bunched up look, that extra length go to the crimp. Modern wads really don't need much pressure other than to make sure they touch the powder good. Lighten up on the wad pressure and you'll see that crimp go away. If you see an open crimp where the fingers don't meet like the right shell(photo), then you would need more wad pressure.

Jimmy K

RCmodel, you can see that off center crimp in the right shell too, look at the 7 to 10 o'clock being thick and the and the 11 to 2 o'clock being thin.

 

[Hiaboo]

The drops of powder/shot are consistent, about .3 variation for powder - a bit but it's not that much..

Wad pressure, I adjusted that from nothing to 30 to 50 lbs and still same results.

Played with the final crimp and nothing really, it improved a bit yeah but nope..

I'll have to try backing off the pre-crimp.. I'm starting to think that it's just the overall length of the fired shells. *shrugs*

I'll have to check the guides (8pt/6pt). I was thinking of that as well.