Has anybody run 300 AAC Blackout Go and No-Go gauges on your 300 Whipser and 300/221s

[Quarterbore]

I have a few 300 Whispers and 300/221 Fireball builds including a 11-inch Contender, a 10-inch AR-15 pistol, a 16-inch AR-15 Carbine, and a 20-inch rem 700 LTR Clone. Now that the 300 AAC Blackout has hit primetime I am seeing ammo at prices I can afford to just buy and shoot so I am thinking that I should get the gauges and see if my chambers are good to go with the 300 AAC Blackout:


http://www.midwayusa.com/product/196...ckout-762x35mm

http://www.midwayusa.com/product/643...ckout-762x35mm

I figure if they are tight, I could find a gunsmith and have these guns chambers opened up a little bit to make them compliant too.

So, has anybody tested your older guns? Has anybody else consider opening the chamber a little to use the 300 AAC Blackout instead of the 300 Whisper ammo of days past?

[sha-ul]

I don't know if those would check the throat, which I think may be the biggest difference.

[Quarterbore]

Good point... Perhaps I just need to buy a box of ammo and look at fired casing for signs of pressure? I think the ARs will have loose chambers anyways but the bolt gun and contender are likely pretty tight.

I guess I could work up some loads too and look for pressure signs but if I were doing that I might just as well reload 300/221s as usual. Just about $11/box of 20 makes the 300 AAC Blackout a tempting buy.

[sha-ul]

Would the factory 125 grn have more jump than the factory 220 grn?

Once before I suggested a headspace gauge with a movable insert that could be used to measure the throat clearance, I don't know if it would be possible to make one that would do that, or not.

[Alleycat]

Originally Posted by Quarterbore

Good point... Perhaps I just need to buy a box of ammo and look at fired casing for signs of pressure? I think the ARs will have loose chambers anyways but the bolt gun and contender are likely pretty tight.

I guess I could work up some loads too and look for pressure signs but if I were doing that I might just as well reload 300/221s as usual. Just about $11/box of 20 makes the 300 AAC Blackout a tempting buy.

[sha-ul]

Alleycat, any issues with that? I was worried with the video title of Kaboom.

[Alleycat]

LOL!!! My titles are kind of an inside joke with some of my friends. A true 300 Whisper has a longer throat than the Blackout. The 300 fireball / 300-221 and all the other names you can think of have a shorter throat. It may not be the case with early Whisper. It is my understanding that the very early ones had a tighter neck area and required the use of 221 cases. I have no Idea about the throat on those chambers. I had zero pressure issues with the Blackout in my Whisper. I do have a selectable gas block. The actual load was less than my standard load with 125s. I believe it was 18.5ish grains of h110. (Quoting from memory) The Blackout chamber is two thousandths larger in the shoulder and one thousandths larger in the neck. The unfired cases are the exact same spec as Hornady 300 Whisper brass. The big problem with firing a Blackout in a Whisper, is knowing your gas port size and your chamber. Did someone sell you a 300 fireball and call it a Whisper? I would determine your maximum OAL with the Blackout bullet in question and compare it with the factory load. I may be able to get 100 or so Accutip bullets and load them to max OAL and see the difference. I would not fire my hot Whisper loads in my Blackout. My Blackout has a larger gas port so that I can use VV N110 with subsonic ammo. If you know your gun, It’s not a big deal.

[tp555]

The shoulder of the 300 blk is .004" wider than the 30/221. The original ptg 30/221 is .006" wider. I have all 3 reamers. Big deal is the throat of the 300 blk is deeper. Measured about .100 deeper using 220 grain noses. So use a throat reamer for a touch more depth and your good to go.

[mstarling]

tp555,

So are you saying that your "match" 300/221 with the long throat is likely to chamber 300 BLK ammo?

Mike

[tp555]

That was the purpose of the long throat.Yes.