Proof 300 PRC CBTO to lands

[hburggunner]

I just measured 2.960" CBTO on a Proof 22" 300 PRC (prefit for Defiance Anti).

Hornady PH 212 ELD-X measures 2.930" CBTO, running .030 off the lands of this rifle. The PH 212 ELD-X did group very well and so did my handloads at the same CBTO (2.930"). I will go back and do a proper load development ladder soon.

I am curious if there are others with similar measurements or find that Proof chambers tend to be a tad short.

 

[hburggunner]

Update: case was once fired, but apparently I didn’t have my sizing die set just right. I did this again today, remeasuring to lands. I got a slightly longer measurement of 3.030”.

However after running additional testing I was not able to get a round to chamber at 2.999” or at 2.80”. Went to the press and set one cartridge at original length of 2.960” and that is confirmed as the max CBTO to the lands in this rifle. Chambers and bolt
closes snug.

Final measurement is 2.960” CBTO max to lands in this rifle.

Hornady factory is 2.930”. That’s .030 of a jump.