OAL questions

[Lahunter76]

Ok, my COAL is 3.618 and with a compensator it's 2.890.

my chamber was supposed to be cut for 3.6 with a .225 freebore, which I believe is correct. And they used the same bullet and brass to measure and cut my throat/freebore

So freebore is just the space without rifling between the actual I believe point the bullet becomes full caliber(ogives I think) and the lands. So if my load is .018 longer I just minus that from the freebore and get the jump distance? So that a .207 freebore???

trying to make since of all this and if I am not stating my question correctly plz just ask me questions that you think would better help.
This weekend I will take my 14 rounds with 87gn of N570 out in my 30nos. The 87 shot the best so I have come Back and was able to duplicate all measurements and loaded them up to re test and get some good chrono data also and then stretch them out a lil if I can.

 

[QuietTexan]

You're describing the situation correctly, but you aren't actually measuring the point of interface between the meplat and rifling with the comparator, rather some point further out on the meplat. In theory there's a constant relationship between your measurement and where the bullet engages the lands, but the actual measurement itself doesn't mean anything.

This is an example of a tool that would have a meaningful measurement, in that it's cut more closely to an actual chamber versus the Hornady which is an oblong hole of varying size. My 30cal Hornady insert is undersized and not concentric with a minimum ID of .280" and maximum of ID .293" (as I suspect all of them are because they're so cheap).

Bullet - Modular Headspace Comparator Bullet Inserts — Short Action Customs, LLC

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