SAAMI Throat Freebore

[65Whelen]

I'm looking at the Grendel C.I.P. rev. 15-05-19. Just want to make sure I'm reading it right. The L3 = 38.86mm/1.5299 is the case demension. So, the G = 7.32mm/.288 would be the throat or freebore cut into the chamber. Correct?

http://www.65grendel.com/forum/showthread.php?8080-Official-SAAMI-and-CIP-6.5-Grendel-Drawings

[Drillboss]

65 Whelen, I believe that dimension, which is 1.818" from the bolt face, is the end of the 1.5 degree throat taper and is where the rifling lands are at their full diameter of 0.256".

[JASmith]

Yes, the CIP drawings even more difficult to read than SAAMI!

Drillboss has it right.

The dimension you mention is about where the rifling ends and the bore dia (F=6.50 mm) starts.

The length of the throat proper should be equal to the sum of the difference between G and (h + s). The step down from neck diameter to the start of the freebore is half of the 90 degreee angle specified for a1.

SAAMI lists the point as a reference dimension, meaning that it results from stacking the definitive dimensions.

[sneaky one]

Whats your thinking there 6.5 Whelon ? What are you making dude?

[65Whelen]

I've got three Grendel barrels(AA, Sabre & Rock Creek). Going to do some chamber casts just out a curiosity. We've had so much discussion about throat/freebore I need to look at more than a print. I want something to put a Mic on.

[sneaky one]

Hmmm, that chamber casting will be a tell all between the 3. Great idea. Coming to st paul anytime soon? Redhawks!

[65Whelen]

Sneaky, another true hockey fan, it's Redwings. Unfortunately no hockey in St. Paul this year.

We'll see how the other two chambers stack up against the AA barrel. It should be to SAAMI Spec.

[rickOshay]

Hey 65Whelen - what velocities do you get with each gun using the same load or commercial ammo. Is there a significant difference?

[65Whelen]

RickO,
It'd be apples to oranges, cause they're all different lengths(14.5, 16 & 18 inch). Still it'd be an interesting exercise. If I get chance I'll post the results.