ar-15 new build 7.62x40wt or 300blackout

[Plate plinker]

I have some lowers that need used. Any thoughts on these two choices. I read in the BLUE PRESS about the WT possibly making major power factor and thats of interest to me. I also would probably run a suppressor at some time in the future. Would make my own cases from 223 brass.

[kencha]

Two potential positives for the WT:
Easier to make major (300blk can do it, but it is more restricted in what components/powder will get you there)
More unusual (can be a plus and/or minus. I've done plenty of things just to be different, but it has drawbacks)

Everything else is pretty much a negative, as far as parts, components, mags, factory ammo, and their prices. For competition, a couple possible considerations are that it won't meet USPSA Heavy Metal requirements (but neither will the Blackout), and you'll need to be ready to deal with its trajectory on longer range shots (although it has the potential to be marginally better than the Blackout).

I doubt I've said anything you haven't already considered. I'd say it boils down to how important major power really is and whether or not the 7.62x40's uncommonness is worth the higher price to you personally. If you were really wanting one for use in competition, and you absolutely insist on running major but not heavy metal, and you have enough disposable income, I'd say to go for the x40.

[jmorris]

I have a 300blk. Supersonic it will beat out a 357 carbine, subsonic it is not a giant leap from a 45 acp.

The 6.5 creedmoor or 6.8 spc II would likely be the direction I would go next, super and I already have a 458 socom for subs.

[W.R.Buchanan]

After the SHOT show I am totally avoiding the 300 BLK. The word from the major Mfgs. was that it is a passing FAD.

I personally see no use for the round that can't be done better by the .308.

If you need to use up lowers I'd suggest a pistol caliber. Which could actually be fun and you wouldn't have to make the cases.

Randy

[762 shooter]

Another good thing if it is a passing fad is that a 5.56 is just a barrel away.

762

[pull the trigger]

Month old thread but I really want to build a 6x45. Just a barrel away from the 223. Same mags, bolt, brass. 100 grain pills. People that have them love em.

[dogmower]

agree with the 6x45. also, don't forget the 7.62x39. mags are relatively easy to come by, ammo is cheap, and in the ar, this is an accurate round with plenty of punch. I have a frankensteined ar with a 3x9 scope, nothing special, and I (as long as I do my part and the wind isn't blowing too hard) can hit the 10 inch gong at 550 yards all day long. not bragging (i'm not that good), but just saying this is an underappreciated cartridge for the ar.

[300blk]

For super use the 7.62x40 wt wins out,
blackout wins the day for sub(much better penetration than a 45 and better external ballistics.) and general parts availability. and is geared in powder selection toward shorter barrels.
7.62 x39 Has been a problem child in the ar series platform, but the new polyfomance wolf ammo sorted a bit of that out.

[LynC2]

For super use the 7.62x40 wt wins out,
blackout wins the day for sub(much better penetration than a 45 and better external ballistics.) and general parts availability. and is geared in powder selection toward shorter barrels.
7.62 x39 Has been a problem child in the ar series platform, but the new polyfomance wolf ammo sorted a bit of that out.

I agree, well over 100 fps extra velocity approaching an 200 fps advantage depending upon barrel and load. I am pleased with my 20" 7.62 WT and it does nicely with cast. I didn't care about shooting subsonic and didn't like the idea of that quick twist that the Black Out uses as it's not as cast friendly.

[yovinny]

7.62 x39 Has been a problem child in the ar series platform, but the new polyfomance wolf ammo sorted a bit of that out.

I thought the biggest problem for x39 in the AR was a magazine issue.
As in most x39 designed curved mags just dont work well going into the strait AR magwell.
Are you saying there is actually an ammo issue with x39 in the AR design, or just an issue with steel cased ammo ?

TIA
Cheers, YV

[dkf]

If all you plan to shoot is supersonic then I would go with the 7.62x40. If you want to shoot some subsonic then the .300blk is better suited. In case you did not know, White Oak Armament is now making 7.62x40 barrels.

[300blk]

The issue with steel case came with the thick lacquer that wolf used to use, the chamber would accumulate and stick brass cases and some times steel ripping rims off the brass in my experience. However, the newer wolf/ zinc/ brass washed and older copper washed norinco steel core seemed ok.

Steel cases have been reported to be rough on extractors but Ive never seen this personally.

That being said the reliability of the ar 7.62x39 mags left something to be desired.
Some companies have made ak mag lowers but I Have no experience with these other than looking at them in a shop.

[300blk]

I agree, well over 100 fps extra velocity approaching an 200 fps advantage depending upon barrel and load. I am pleased with my 20" 7.62 WT and it does nicely with cast. I didn't care about shooting subsonic and didn't like the idea of that quick twist that the Black Out uses as it's not as cast friendly.

A fast twist rate can be a problem, but outta my 9" 1:7 barrel I use the 155 lee gc'd and moving along at a fairly leisurely 1850 when worked up. accuracy started at about 2 moa and got down to about 1.5 with a little tweaking. (max distance tested with fixed 10 power scope at 200yds there is a bit of drop as you might imagine)
there are manufactures who make 1:10 super only barrels, but then I just would default to the 7.62x40.


the subs are another story of course.

its a great cheap to shoot cartridge, and was easier than most 30 cals (for me) to get accurate quickly due to smaller case capacity(better case fill)

It has its place, super with jacketed bullets it beats out the 7.62x39 with 16 inch barrel using similar weighted bullets by a little. But as I said, the place it shines is in shorter barrels.