300 blackout magazine

[inter1]

Maybe some one can shed some knowledge.i just got a 300 Blackout ,have not shot it, AR 15 platform, the lower made by Olympic arms,planning to run handloads only,have tryed several brands of magazines they all lock in fine empty or with 1 cartridge in it,once i put the 2nd or more they do not lock anymore in to the lower.Any idea as to the cause of that,never had the problem before shooting the 223 same magazines same lower.I am aware of the rib problem ,but it relate more to feeding ,my problem seem to me of a different nature.
Anyone has any idea how to solve this?

 

[yugorpk]

Don't load over 2.25" OAL.

 

[rbernie]

Is the bolt closed or open when you try to lock in the magazine?

 

[waffentomas]

If the bolt is closed the magazine probably just needs a good bang on the bottom of it to seat it. This is a good thing, as it means your magazine spring is not weak. You can rough the thing up a bit, it's plastic and steel, not porcelain and crystal.

 

[Lennyjoe]

First I heard of it. My blackout has a Spikes Tactical lower and everything from P-mags to basic GI mags feed it just fine.

 

[cfullgraf]

I load all my 300 BLK ammunition so that the ogive of the bullet clears the rib inside a 223 Remington magazine. If not, the rounds down in the magazine do not lie straight against the sides of the magazine.

This means, with some bullets, the cartridge over all length is quite a bit shorter than the maximum length the magazine can hold.

I cannot say that I have experienced the OP's 300 BLK problem with anything less than a full magazine with the bolt closed, but I could see if the rounds are not properly seated in the magazine, they could increase the resistance to move the magazine follower.

But, also, I'd expect that the OP would also have difficulty loading the magazine as well.

So, maybe I am no help here.

 

[Tirod]

First, the AR is loaded with the bolt back - military standard practice. Never closed. The magazine should always lock in place with little effort.

If loading with a full mag against a closed bolt, you have to compress the stack of rounds against the maximum spring pressure it is already exerting, which takes some force. About the same as getting the last round in. It's also why there is some room, about a half cartridge, left in the stack, to allow closed bolt loading because the bolt has to hand down just enough to push the base of the cartridge forward to load it. That's the reason you don't load against a closed bolt in AR's. It's awkward, creates the risk of dropping the magazine, and simply isn't necessary in the first place.

Any other difficulty loading the mag with more than two rounds is most likely due to a magazine or ammo issue, and they are the top to problems it has.