30 BLK OUT/350 LEGEND

[Duce]

I've read the 350 Legend, in an AR, needs a prioritize magazine. In my search for one I've found there are magazines specifically for 300 Blk Out. I always thought a standard 5.56 would work. Thoughts? <><Duce

 

[nucular]

Mags made specifically for 300 BO work a lot better. Especially with long heavy subs.

 

[tcecil88]

5.56 mags do work, but mags for .300 BLK definitely work better. I used 5.56 mags for a couple years, but now I use Magpul and Lancer .300 BLK mags with good results.

 

[Mgderf]

The only difference is the follower.
If you can find a .350 Legend specific follower you can change out a 5.56 mag follower and be done.

 

[ed1838]

I have had some trouble with front edge of mag catching the brass causing feeding issues. Just rounded it out a little and that took care of that problem. Next problem I have had is sharp edge on ejector, lightly rounded it. Mine works great now.

 

[Fixer]

I have run both my 300 Blackouts with standard 5.56 mags with no issues. Typically run 190gr subs and a mix of supers. The only problem I have had was a few C Products magazines with weak springs. Had failure to feed on the last few rounds. Picked up some new springs and problem solved.

 

[Mgderf]

I have run both my 300 Blackouts with standard 5.56 mags with no issues. Typically run 190gr subs and a mix of supers. The only problem I have had was a few C Products magazines with weak springs. Had failure to feed on the last few rounds. Picked up some new springs and problem solved.

Interesting.
I have used a lot of CProducts mags and I've never experienced an issue with weak springs, or any other problem really.
I've had really good luck with CProducts mags.

 

[Fixer]

Interesting.
I have used a lot of CProducts mags and I've never experienced an issue with weak springs, or any other problem really.
I've had really good luck with CProducts mags.

I have a couple of their Duramag magazines and have not had any problems. I have had the mags for a while but they haven't been loaded the whole time. The subs i was running are a little slow. I tuned them at about 1050-1080fps in my 10.5" barrel, but they run about 850fps in my 7.5" barrel. Might just be the difference. They do run ok with the new springs though. Just an interesting quirk I happened to find. I am planning on speeding them up just a bit for that gun. I just got the chance to run them thru the chrono this last weekend.

 

[Kirk Freeman]

I've read the 350 Legend, in an AR, needs a prioritize magazine. In my search for one I've found there are magazines specifically for 300 Blk Out. I always thought a standard 5.56 would work. Thoughts? <><Duce

Yes, .300BO magazines reduce hiccups. I have Magpul and Lancer. Mark them with white 3 on them. The Bubbas just think I am a NASCAR fan.

May get some D&H mags soon too.

 

[JAL]

.300 AAC Blackout Magazines:
Standard Magpul PMags have had problems feeding .300 Blackout. Consequently Magpul makes .300 Blackout specific magazines for this cartridge. My Hexmag have had no problems with them and other users have had the same success. I put the 5.56 in Magpul and .300 BO in Hexmag with an additional band around the Hexmag to prevent confusion and loading a .300 BO into a 5.56 firearm. I can verify that some Magpul PMags made for 5.56 (versus PMag made for .300 BO) do not play well with some .300 BO ammunition.

.300 AAC Blackout Gas System Cycling:
Proper gas system operation must support the .300 BO cartridges being used, and silencer use:

• supersonic vs. subsonic ammunition
• use with or without a silencer

Most problematic combination with under-gassing is subsonic heavy projectile without a silencer. May require tweaking buffer weight, and the gas system must be efficiently operating.

.350 Legend Magazines:
This cartridge requires magazines made specifically for it, and it's proven finicky with magazines and upper/barrel chamber combinations. A follower change won't "fix" a magazine made for 5.56/.223, or for .300 Blackout for use with this caliber. This cartridge has straight walls all the way to the projectile. It headspaces on the cartridge case lip which means it cannot be crimped (just like a 9mm Parabellum). 5.56 magazines have reinforcing ribs that stand too proud for the cartridge to feed properly. Various videos on YouTube show individuals grinding ribs completely out of PMags which makes them flimsy. The best magazines for this cartridge are reportedly metal ones made by DuraMag. Some users have reported success with CMMG's magazines. Lancer has a 15-round polymer that has some users reporting success. Ruger's magazines for its AR platform .350 Legend are made for them by DuraMag.

.350 Legend Feed Issues:
Feed problems aren't always magazine, if one properly designed for it is being used. Feed issues have been encountered with numerous inexpensive uppers at the feed ramp interface between the upper receiver and barrel extension catching the cartridge case lip. Those doing a DIY upper build should check this immediately after mating the barrel to the upper receiver before proceeding. Inefficient gas systems combined with buffers & springs have also caused feed issues with the BCG not having sufficient momentum to push the cartridge into the chamber properly. I'm loathe to denigrate a manufacturer but I've seen quite a few complaints online about Bear Creek Arsenal rifles and uppers having feed problems. Suffice it that this cartridge is finicky due to its shape and the shape of some of the projectiles used in it. All the action related components in the firearm have to play well together, not just the magazine.

 

[STFU]

All I have ever used in my 300BLK AR is Gen3 5.56 PMAGs.
Knock on wood, but I run both subs and supers (yep, sometimes in the same mag) and I have never had feeding issues.

The only 5.56 I have is FDE, so...FDE PMAGs.
The 300BLK is black, so...Black PMAGs.
No color confusion issues either. lol

Can't speak to the 350L...yet. It's on my list for a new upper.