Cutaway Image of 300 AAC Blackout

[golfindia]

I guess you guys load your subs shorter than I do..

Looks like FOG is close to AAC recommended OAL.....

https://www.google.com/url?q=http://www ... OqRxpMIR-w

[BoomerVF14]

Wow, I'm ashamed to confess I never knew that - thanks for the link GI.

All of Hodgdon Online's OALs are 2.26 and that's where I started with my 208gr A-Maxes. Not surprisingly I decreased to 2.20" on my own because I noticed at 2.26 the ogive runs along the rib of the PMag, just like AAC says. And OBTW, I had huge cycling problems. Got better after swapping my H2 for a carbine buffer, but I still can't achieve BHO.

Now it's back to the drawing board (i.e. reloading bench)...

Any experts out there with insight on why there's such a disparity in published OALs?

[golfindia]

The OALs listed in manuals are nearly all "max" lengths. In many other cartridges, loading longer than the listed "max" equals danger. The mfgs aren't going to get into OAL minutia, usually, because everyone has different guns, mags, etc. I think AAC made the BLK chamber with a long throat to make room for long 220g bullets.

Loading "off the lands" like a bolt gun bench rester sort of breaks down in a 300blk auto loader. In my experience, loading longer only means you use more powder to achieve the same speed, and it's no more or less accurate because the bullets are still a long way from the lands, regardless. And you also may have to grind out mag ribs so you don't get pigeon toed rounds with a full mag. I just don't bother.

[SuedePflow]

I just measured some factory Remington 220gr stuff and they are all in the 2.210"-2.220" range.

I used to target 2.265" but sometimes had issues with the rounds nosing into the mag. Reducing it to 2.245" has given me 100% reliability with unmodified gen 2 Pmags.


Golfindia - thanks for the link above. Some excellent into in there.