Decided to go with the 7.62x40 WT...

[pdx_blackout]

I'm pretty sure the failures to feed are a result of 2 different issues.
- the large subsonic rounds sitting wide and putting pressure on the sides of the mag
- hand loads being loaded to max coal.

I've shot about 800 rounds of 15 different types of factory bullets all 110-125 grain and have never had a failure to feed.

Maybe the issue is your mag and not the ammo?

Also, how is your failure to feed occurring? It could even be a gas adjustment issue

I didn't test the rounds through a gun, but the feed rib on the M2 mags hits the ogive of the bullets (120 grain Rem UMC) so they don't seat properly in the mag. It gets worse the more you load in. Common issue that can be solved by filing down the feed rib... or by buying different mags. I have 15 or so M2 mags so I just filed a few down. And they still work with 223 as well after modifying.

[A-Game]

I thought it was funny reading an article a few years ago of Bill Wilson singing the praises of 300 Blackout and hunting with it.

So what does the 7.62x40 do that 300 Blackout can't? I'd like specifics please and thank you.

[NeVs24]

I'm pretty sure the failures to feed are a result of 2 different issues.
- the large subsonic rounds sitting wide and putting pressure on the sides of the mag
- hand loads being loaded to max coal.

I've shot about 800 rounds of 15 different types of factory bullets all 110-125 grain and have never had a failure to feed.

Maybe the issue is your mag and not the ammo?

Also, how is your failure to feed occurring? It could even be a gas adjustment issue

I didn't test the rounds through a gun, but the feed rib on the M2 mags hits the ogive of the bullets (120 grain Rem UMC) so they don't seat properly in the mag. It gets worse the more you load in. Common issue that can be solved by filing down the feed rib... or by buying different mags. I have 15 or so M2 mags so I just filed a few down. And they still work with 223 as well after modifying.

I'd still have to disagree with having to modify the mag for factory load supersonics.

And since you already have so many modified ar15 mags it would not require you to have dedicated mags like you mentioned.

[pdx_blackout]

I'd still have to disagree with having to modify the mag for factory load supersonics.

And since you already have so many modified ar15 mags it would not require you to have dedicated mags like you mentioned.

Well agree to disagree then. It's certainly an issue with certain rounds that have a more blunt ogive profile and with seating them out further to maximize case capacity. The M2 mags have the largest rib, which is what I have. Supposedly the M3 doesn't have the issue.

[pdx_blackout]

I thought it was funny reading an article a few years ago of Bill Wilson singing the praises of 300 Blackout and hunting with it.

So what does the 7.62x40 do that 300 Blackout can't? I'd like specifics please and thank you.

Around 5-10% higher muzzle velocity (depending on bullet/charge) due to higher case capacity, maybe 50-75 yards further effective range, and a chamber and rifling that's designed more around lighter supersonic rounds as opposed to a do-everything barrel. The difference is small, but I figured since I'm starting from scratch with this build, I might as well use the cartridge that was designed around my use case and maximizes the 223 case's ability to push a 30 cal bullet at supersonic speeds.

[rebel]

I just have to say something. Not dogging your choice as that's what makes the world go round.......but....... I own 4 Blackouts, 2 of which are AR's. I have run supers and subs, flat nose, round nose, pointy nose from 100 gr to 265 gr. I have US GI mags, Lancer, P mags, Troy and one Wilson Lancer mag. I have never modified a damn one of them for feed issues. The P Mags I have replaced with Lancers or Troys over time. So saying that without actually shooting it is kinda like saying new Chevy trucks suck when all you have driven are Toyota Camry's. In any case, enjoy your rifle.

[pdx_blackout]

I just have to say something. Not dogging your choice as that's what makes the world go round.......but....... I own 4 Blackouts, 2 of which are AR's. I have run supers and subs, flat nose, round nose, pointy nose from 100 gr to 265 gr. I have US GI mags, Lancer, P mags, Troy and one Wilson Lancer mag. I have never modified a damn one of them for feed issues. The P Mags I have replaced with Lancers or Troys over time. So saying that without actually shooting it is kinda like saying new Chevy trucks suck when all you have driven are Toyota Camry's. In any case, enjoy your rifle.

Fair enough and thanks for the input. I believe you. I could see the rounds in the mag looking a bit cross-eyed in my M2 mags from the feed rib hitting the ogive so I filed a couple down and now the rounds lay in there nicely like 223 rounds do. Probably would have cycled fine regardless.

[dellet]

I just have to say something. Not dogging your choice as that's what makes the world go round.......but....... I own 4 Blackouts, 2 of which are AR's. I have run supers and subs, flat nose, round nose, pointy nose from 100 gr to 265 gr. I have US GI mags, Lancer, P mags, Troy and one Wilson Lancer mag. I have never modified a damn one of them for feed issues. The P Mags I have replaced with Lancers or Troys over time. So saying that without actually shooting it is kinda like saying new Chevy trucks suck when all you have driven are Toyota Camry's. In any case, enjoy your rifle.

Fair enough and thanks for the input. I believe you. I could see the rounds in the mag looking a bit cross-eyed in my M2 mags from the feed rib hitting the ogive so I filed a couple down and now the rounds lay in there nicely like 223 rounds do. Probably would have cycled fine regardless.

Since that bullet was designed to run in a standard GI magazine, at that length, in an AR chambered in 300 Blackout. I would say if there was an issue feeding, it was not due to the bullet design or length it was loaded to.

So has Wilson finally come out with a magazine you can load to capacity, or are they still recommending that you load 2-3 less than full?

That was always a problem in states where you were limited to 5 round mags.

[pdx_blackout]

Since that bullet was designed to run in a standard GI magazine, at that length, in an AR chambered in 300 Blackout. I would say if there was an issue feeding, it was not due to the bullet design or length it was loaded to.

So has Wilson finally come out with a magazine you can load to capacity, or are they still recommending that you load 2-3 less than full?

That was always a problem in states where you were limited to 5 round mags.

The GI mag doesn't have the large rib that the Magpul M2 pmags have. I'm sure the rib was added to the M2 mag to help with feeding before the 300 BLK became popular, which explains why the M3 doesn't have it.

And not sure about capacity with the WT. I can see how if the rib is hitting the bullet ogive it would make the round stack taller, reducing capacity. But with the case width/taper being identical to 223, it should load to a full 30 rounds in a modified M2 pmag as long as the rib isn't interfering with the bullets.

[dellet]

Since that bullet was designed to run in a standard GI magazine, at that length, in an AR chambered in 300 Blackout. I would say if there was an issue feeding, it was not due to the bullet design or length it was loaded to.

So has Wilson finally come out with a magazine you can load to capacity, or are they still recommending that you load 2-3 less than full?

That was always a problem in states where you were limited to 5 round mags.

The GI mag doesn't have the large rib that the Magpul M2 pmags have. I'm sure the rib was added to the M2 mag to help with feeding before the 300 BLK became popular, which explains why the M3 doesn't have it.

And not sure about capacity with the WT. I can see how if the rib is hitting the bullet ogive it would make the round stack taller, reducing capacity. But with the case width/taper being identical to 223, it should load to a full 30 rounds in a modified M2 pmag as long as the rib isn't interfering with the bullets.

This is why I said earlier and you have confirmed again, that you are buying hype. You have no actual experience and are trying tell people that have 10's if not 100's of thousands of rounds down range, that they don't know what they are talking about.

You made the right choice from a maximum velocity stand point. At some point, after gaining some experience, I suggest you re-visit this thread. Then you'll realize that the people that told you, the only advantage was 100 fps or so were right. But you'll also need actual, not virtual, experience with both cartridges.

No one is attacking your choice, only your facts as you see them.