.300 AAC Blackout… I Don’t Get It

[Paul]

That is a comparison between the AK system and the AR system. My comparison is between 300 BLK and 7.62 x 39. I doubt whether a 0.003 difference in diameter makes any real world difference. If both calibres were available in the same platform I do not think any one would be able to differentiate between firing 300 BLK and 7.62 x 39 from the same platform. The 7.62 x 39 has a larger case volume as far as I know, so performance wise it would beat the 300 BLK when loaded to achieve maximum velocity with a given bullet weight. COR BON at one stage had a 7.62 x 39 load firing a 150 grain bullet at 2300 + fps. I have Yugoslavian 120 grain soft-points that average 2400 fps from my rifle. I am not aware of a 300 BLK load that can equal this, although there might be such a load available.

Your base of assumptions is wrong. The 7.62X39 bullet is ballistically inferior to the true .30 cal AND the greater case cvolume of the 7.62x39 does NOT equate to more vooma, just more recoil. THAT is the secret sauce with the 300 Black! It is ballistically superior to the 7.62x39 in every loading (by 15%... Travis Haley estimates 17%, see ).

[atunguyd]

AND the greater case cvolume of the 7.62x39 does NOT equate to more vooma, just more recoil.

Can you elaborate on the above? It doesn't makes sense to me that increasing case volume (and hence powder charge) while keeping all else equal will only result in extra recoil and not much else.


Take for example the 338 lapua vs 338 winmag both using a 250gr boolit.
The lapua fires said projectile around the 3000fps mark while the winmag comes in at 2600 thereabouts. The only difference in this example is the case volume difference.

[FNBROWNING]

My question relates to cost of loading, Nosler custom competition 223 bullets are very occasionally available in 1000 round boxes at reasonable prices. These are very good grade target bullets and my last batch of 70 or 80 odd grain (not sure offhand ) cost 2-40 per bullet. The 52 grain ones have been known to go for as little as 1-30 but with the rand where it is who knows what these will now cost. As Paul sais on could use FMJBT but I am not sure what kind of accuracy one would get from them given that they are I think military bullets. Paul has a point on case life and fractionally less powder which may enter into the equation. Of course you also have to factor in the much higher initial case costs either your time converting or buying brand new cases.

[M43]

I am aware that there are loads for the 7.62 x 39 that push a 150 grain bullet at over 2250 to 2300 fps. In fact I know that there are people on this forum who reload for it and duplicate or improve on that performance. I've done it myself, but I much prefer a 145 grain bullet at 1800 fps as it has almost no recoil. I have had a look at some of the published load data for 300 BLK and 1800 fps with a 150 grain bullet seems to be about the top end of what a 300 BLK is capable of (with 150 grain bullets). So I remain unconvinced of the superiority of the 300 BLK over the 7.62 x 39. Perhaps someone has load data for the 300 BLK that shows different figures?

[LoopSoosStroop]

So I remain unconvinced of the superiority of the 300 BLK over the 7.62 x 39.

I agree with you, ballistics with the same powders and bullet weights will be close to identical, and the recoil issue is more dependent on platform than cartridge design. But in practical terms in SA it has many advantages compared to 7.62x39.

1. Bullet availability, finding cheap .311 bullets is a pain. That is the reason Ruger put .308 barrels on their 7.62x39 Mini30's and why Lee supplies the 7.62x39 dies with both a .308 and .311 expander plug. Much higher availability of cast bullet designs as well.
2. Brass availability. Finding and keeping 7.62x39 boxer primed re-loadable brass is a chore and very expensive. If you make your own .300 BLK brass it can be cheap.

That said, I would love a 7.62x39 SKS. Love the history of the caliber.

[Paul]

So I remain unconvinced of the superiority of the 300 BLK over the 7.62 x 39. Perhaps someone has load data for the 300 BLK that shows different figures?

Ja... locally that's a function of our local propellant availability. S265 gives us very little case capacity to play with.

Hobbes has published some great data on this forum, and I believe he is going to experiment with MP200 and small pistol primers.

[Lian]

compatibility is still the biggest "pro" factor in the 300BLK platform.

223 brass (reamed ofcourse)
308 bullets
AR15 flatform
AR15 mags

just because it's currently a pretty expensive round, doesnt suddenly make it "bad".
it's the perfect SBR/CQB calibre, imho. perfect for the 7.5 / 10" barrel 223 crowd.

[Kayback]

I'd love a ~10" AR15 in 300BLK but don't have the capex.

Oh well. I want a Cirrus SR-22 as well.

[Pirate]

The article in the OP makes the critical error of comparing the calibres using energy, rather than momentum. The author's arguments would very probably be floating dead in the water if he used the latter.

Re 300BLK vs 7.61x39 (when firing similar weight bullets) I doubt if there would be any significant external- or terminal ballistic differences out to about 150m (no, I've not checked this...) but it does seem as if the 300 achieves the "same thing" somewhat more efficiently.

Practically being able to use .308 vs .311 bullets (from a reloading perspective) is of course very nice.

What's the 300BLK throat look like? could one use 200gr/220gr RN bullets for subsonic loads?

Oh well. I want a Cirrus SR-22 as well.

S-O-O-O last century. Go check out the Pipistrel Pantera....

:- P

[Paul]

What's the 300BLK throat look like? could one use 200gr/220gr RN bullets for subsonic loads?

That's its party trick!