260 AI reloading questions

[rebel]

This is my first venture with an Improved case. I set my die to touch the shell holder. Fire formed around 12 factory ( Black Hills ) rounds. After sizing the case I found that the case grew about .002. I am measuring base to datum with a Hornady bushing. First. is this type of of case growth after sizing normal? Second, which bushing fits a 260 AI datum line the best?
Third, any other tips and tricks you may want to share.
Thanks in advance for your help.

 

[22BRGUY]

I use the 400 insert to measure my datum length. A .002 growth sounds ok on first firing and is usually the place to bump back to upon subsequent firings. I think you will notice that the case will grow more upon the second and third firings.
It sounds to me like you are doing everything right unless there is something else that concerns you but JMHO.

 

[ballison]

If your case is growing after resizing, your die is never touching the shoulder and needs to be lowered. The reason your case grows is that the die is squeezing the case and it grows in length. On a few of my dies, I had to grind some off the bottom so I could lower it.

 

[Joe R]

I use the 400 insert to measure my datum length. A .002 growth sounds ok on first firing and is usually the place to bump back to upon subsequent firings. I think you will notice that the case will grow more upon the second and third firings.
It sounds to me like you are doing everything right unless there is something else that concerns you but JMHO.

He nailed it.

Regarding the head space gauge, this wont help you, but you may want to keep it mind for next time. I had my gunsmith make me one with the same reamer that he chambered my rifle.

Joe

 

[rardoin]

He nailed it.

Regarding the head space gauge, this wont help you, but you may want to keep it mind for next time. I had my gunsmith make me one with the same reamer that he chambered my rifle.

Joe

+++

However, I would hold off on grinding the die until you find your fired brass is starting to resist bolt closure. I would keep the die at the present position until the shoulder pushes forward enough to produce resistance to chambering. You may find you don't need to modify the die.

 

[22BRGUY]

If your case is growing after resizing, your die is never touching the shoulder and needs to be lowered. The reason your case grows is that the die is squeezing the case and it grows in length. On a few of my dies, I had to grind some off the bottom so I could lower it.

Same principle but I find it easier to grind off the shellholder instead of the die.

 

[rebel]

He nailed it.

Regarding the head space gauge, this wont help you, but you may want to keep it mind for next time. I had my gunsmith make me one with the same reamer that he chambered my rifle.

Joe

This was a gun traded here in my shop I decided I needed. The fellow seemed knowledgeable, but didn't think to ask the builder of this. I have them for other custom barreled guns I own and they are superior to any gauge manufactured. This is a Shilen barreled Tikka Master Sporter. Neat rifle.
Thanks for all the replies guys, much appreciated. I'll set the die lower to bump back the shoulder and hopefully won't need to attack the shell holder.