The 6UM

[Ryan Avery]

I ended up going with 66.7 out of my 18" 40*. Im at 3160

.7 with 570

 

[Gstew1930]

.7 with 570

I never said I was smart

 

[treillw]

Alright. I'm still trying to nail down an action length for building a 6um-40. Defiance Anti X or Ti X action.

What is the appropriate length? Short or medium?

Seems like you guys are seating the bullets well shorter than where they touch the lands.

Sounds like it touches the lands at around 2.970" COAL, but that is unrealistic because the bullet wouldn't be embedded into the case neck?

What is the longest expected COAL?

I want to be absolutely certain that I don't have issues with the bullet tips being smashed in the magazine under recoil, like I have with two other rifles.

Thank you!

 

[PathFinder]

Alright. I'm still trying to nail down an action length for building a 6um-40. Defiance Anti X or Ti X action.

What is the appropriate length? Short or medium?

Seems like you guys are seating the bullets well shorter than where they touch the lands.

Sounds like it touches the lands at around 2.970" COAL, but that is unrealistic because the bullet wouldn't be embedded into the case neck?

What is the longest expected COAL?

I want to be absolutely certain that I don't have issues with the bullet tips being smashed in the magazine under recoil, like I have with two other rifles.

Thank you!

I've seated DTACS anywhere from .020"-.120" off. They do not care one bit. Just seat them in the general neighborhood of .060" off and call it good. The bullet would still be in the neck at 2.970. I've never seated mine longer than 2.950, even with the new heavy TMK.
The best way to avoid smashed bullet tips is properly designed magazines with shoulder stops. I've only had the 6 UM in Tikka actions, so I'm not much help there.