260 AI problems

[ssphoger]

Ok let me start at the begining
I got a MGM 260 AI TC Encore barrel used it came with 20 fire formed brass.
I got a set of dies from CH tool & die,$85.00!!!)

Also got 2 boxes of Rem 260 factory rounds.

Fired some of the factory 260 rounds they grouped around 1.25" at 100 yds.

Went to size the brass I fired and the stuff that came with the barrel. Wow they sized hard squeeling in and out of the die no matter what type or how much lube I tried. But got them thru any how,Need it for Deer season!!)

Took the loads to the range got it to shoot under 1" at 100 then one of the cases split in two about 3/4" from the rim. Well done for now,
Got home pulled the remaining bullets and checked the inside of the cases and found 4 more with a grove in the inside in the exact location.
Boxed the dies with several rounds -Fired factory,sized stuff and the sampels that came with the barrel, and shipped them back to CH will see what they say.
when measuring the brass I am getting .009" difference from the new brass and the fire formed stuff at the split point this seems a little much to me. Maybe the chamber is big or the dies are small.
Just putting this out there to see what feed back I get.
Thanks

 

[kevinj308]

I would make a cast of that chamber.
Hope you can make it work out .

 

[fivering]

It sounds like a classic case of setting the shoulder back way too far when resizing the fired case.
Get a good caliper, and a Stoney Point "Head 'N Shoulders" cartridge head space gauge.
Measure several of your fired cases to get a good base reference on your rifle chamber.
Then back off your sizing die until you are getting from .0005 to .0015 set back on the sized case. This should solve your problem.

 

[bsekf]

Case separation is not unusual in Encores. You are dealing with a break open gun so you get frame flex. Have you checked to see how much space is between your frame and the barrel, it can be as much as .005. So if you bumped the shoulder back too much, add in the distance between frame and barrel, factor in the frame flex, you may be stretching the case 0.01. Google Mike Bellm and read his stuff on headspace for TC guns. He sells a dial indicator to measure the amount you bump the shoulder back and lots of other stuff to help you make the Encore shoot.