.300BLK 10RD pistol magazines?

Not today RCMP not today

Hahaha well s#!t.... I didn't notice this question was from yet another one post wonder.

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Judging by the replies, .300BLK uppers on a multi caliber stamped lower receiver do not require a stamped .300BLK magazine for me to legally run a a 5.56 pistol stamped magazine with 10rds of .300BLK in it. Is this the case? Anyone brave enough to answer this for me with accusing me of being a government agent? LOL.

Yes, you are correct.

The problem you note in your first post (magazine reliability) is a real problem, with the commonly available metal pistol magazines. You may not alter a 10 round LAR mag to “more reliably” feed 300 BLk. That would be manufacturing a prohibited device, which carries a minimum sentence of 3 years.....

In short, if the magazine needs to be altered in anyway to operate correctly, it’s not the right magazine for the job.
 
From the Lancer website for 300Blk magazines.

These magazines have been specifically designed and optimized to alleviate the stacking and feeding issues commonly experienced when running 200+ grain subsonic 300BLK cartridges in standard .223/5.56 magazines. If you are shooting lightweight supersonic 300BLK ammunition (<150gr), we recommend using a standard .223/5.56 magazine.
 
I did load some 110-125 grain noslers before . No feed issues with those . But those were pointed ballistic tips . If your trying to load say 30 carbine bullets you could have feed probs .
I did have problems feeding various hunting bullets till I got 300blk mags .


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That's good news. From my research, I think .300BLK cartridge feeding issues in magazines are caused primarily with heavier weight bullets. Can you confirm if reliability is significantly improved with 110gr and 125 grainers? Are you aware of any specific .300BLK mags for pistol use that have a legal round limit of 10 up here in Canada?

No but i would like some also . I dont have an AR platform I have a Ruger american , I find it looks kinda goofy with 30-5rnd P-mags
 
I plan on building a .300BLK AR upper and was curious if there were any stamped .300BLK 10rd pistol mags in Canada for a legal 10rd limit, I could not find anything after some searching. I don't think the XCR pistol with a .300BLK upper, if there ever was one imported into Canada, had a 10RD pistol mag like for the 5.56. I'm pretty sure it would have just used the regular 5.56 mag. There may already be stamped .300BLK pistol mags already available for purchase in Canada, but I cannot find them.

I have noticed a recent trend moving towards manufacturers designing mags specifically for .300BLK to increase feeding reliability; must be increasing in popularity or manufacturer's wouldn't be investing funds to create these which is a good sign that .300BLK could become more inexpensive down the road. I wonder if there are any U.S. based manufacturers that are stamping there .300BLK mags for pistol use like Robinson Arms has done with their 5.56 mags for the XCR. Ruger just came out with their new .300BLK AR platform pistol; the pistol is using magazines marked .300BLK, maybe its stamped for pistol use?

I think I already know the answer, but what are the legalities of inserting .300BLk cartridges into a stamped 10rd 5.56 AR platform pistol mag and using it in a 5.56 or multi caliber stamped lower receiver with a .300BLK upper?

Nothing you've said makes any sense. Better do some more research.
300BLK and 223 use the same magazines, there is no difference at all even though you can get them with a 300BLK stamp on them.

There is no trend recently, this has been going on for years.

I hope you already know the answer to your last statement because I can't understand where you're getting these ideas, who's been filling your head with fragments of information that make you think the magazine has to be marked the same as the cartridge you are using.

Short answer, buy yourself some 223 pistol magazines and use them for your 300 Blackout. All of the magazines you use in your 300BLK will be 223 magazines regardless of what is stamped on the side.


Why do you want a 300 Blackout? Will this be a restricted firearm or non restricted? Not trying to say there is something wrong with the cartridge, I have two rifles chambered in 300BLK and have owned others. What I'm getting at is that if this will be a restricted rifle for use at the range only there is really no reason to be shooting 300BLK over 223. 223 is a better cartridge for target shooting and general plinking due to the cost per round and the flatter trajectory. 300BLK shines away from the range and in the hands of a handloader where you can take advantage of the versatility of the cartridge. The factory offerings for ammo are not as plentiful and cost more than 223.

That's good news. From my research, I think .300BLK cartridge feeding issues in magazines are caused primarily with heavier weight bullets. Can you confirm if reliability is significantly improved with 110gr and 125 grainers? Are you aware of any specific .300BLK mags for pistol use that have a legal round limit of 10 up here in Canada?


I've run everything from 110 grain through 208 grain projectiles through 4 different semi auto 300BLK rifles over the last 5 years and have never had any feeding issues with Pmags or metal STANAG magazines. As far as I'm concerned any specialized 300BLK magazine is a marketing gimmick to make you pay an extra $10 for a stamp that says 300BLK instead of 223.

Just use 223 mags and worry about feeding issues later if you have them, not worth worrying about before you've even built the rifle or fired a single shot.
Legally you can use any magazine that fits in the rifle regardless of any markings or stamps on it as long as you don't have to modify it to make it function.
 
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There is much controversy regarding the Beowulf mags. They are unaltered, and you can use them with 5.56. I applied the same logic to using .300BLK in a magazine intended to be used with 5.56. Both magazines are unaltered, correct?

The controversy is that 99% of Beowulf mags are 223/5.56 magazines with a new stamp and the rivet in a lower location. A true Beowulf magazine should have a single stack follower and not be able to hold 223 cartridges any more. They are modified by the manufacturer instead of the customer, no difference in their eyes.

Your comments about the 300BLK, the magazines are the same and hold the same number of either cartridge without modification so as long as it only holds 5 or is stamped pistol and holds no more than 10 you're safe.
 
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