25-06AI - throat depth?

[Shinbone]

I am having a Kimber Montana 25-06 re-barreled to 25-06AI. The new barrel will be a Broughton 1:8 twist. The gun will be used for hunting antelope through mule deer in the Rocky Mountain west. I am not looking for bench rest competition accuracy, but I do want an accurate hunting rifle. And, I am not going to be shooting past 500 yards, so I don't have much interest in the heavy-for-caliber bullets with the super high BCs. I am more interested in speed and flat trajectory.

The gunsmith asked me to send in a dummy round loaded with the bullet I plan to shoot seated at the depth I want, and he will cut the chamber accordingly. In particular, the gunsmith will cut throat depth based on my dummy cartridge. I've never done this, before, so any advise will be appreciated.

Gunsmith advised to choose bullet seating depth so:

1) a loaded cartridge will fit in the magazine box (obviously, but I'd forget if not reminded);
2) the bullet doesn't protrude into the case too much, which would reduce available powder volume;
3) I've got some "reserve" bullet shank/case neck engagement to chase the lands as they erode with use (i.e., the opposite consideration of #3).

I've got two candidate bullets in mind; Sledge Hammer 98gn (top), and Hammer Hunter 103gn (bottom). In the photo, below, are the aforementioned bullets, a 25-06 case, and a pair of calipers extended to the length of the magazine box.



Looks like I got plenty of length to the magazine, so I don't have to worry about that as a constraint. Next, my thought is to position the bullet's shank/boattail junction about 0.100" below the case's shoulder/neck junction as the best compromise between #2 and #3.

Comments and/or suggestions?

 

[nmkid]

I normally like the base of the bullet to not be below the half-way point of the shoulder. Ideally for me, not more 1/3 into the shoulder. I feel you are short-changing yourself with that twist and not using the 131 gr. BlackJack bullet. What's to dislike about a 131 gr. bullet doing a solid 3200FPS out of a 25-06AI?

 

[Tommie]

Having the bullet heel at the neck/shoulder junction is usually considered optimal. I understand your interest in being able to chase the lands as the throat wears, but how many rounds per year are you anticipating to shoot?

 

[JRanum]

Make sure your dummy round is short enough so you can eject a loaded round. Sounds silly but in my Kimber 280AI I can actually run my OAL long enough to load gun and function in magazine but the action port is slightly smaller and ejecting a loaded round the tip can hang up and stop everything. Only rifle I've ever seen do it.

 

[Todd Morley]

Similarly, I am building a 280 AI, intending to load Berger 168-grain VLD Hunter bullets. The SAAMI standard specifies 0.179" of throat length. With that, a VLD barely has enough shank in the case's neck when the ogive touches the lands. Won't be able to load to the lands when the throat erodes. Has anyone chambered to SAAMI-standard 280 AI, but with a zero or shortened throat? (And is there a common throat profile for 168-grain VLDs in a 280 AI?)