300BlkTalk

smustian wrote:Anything I have tried from 110-130 grain have all fed fine with sanded ribs.

How far down inside the mag do you take the rib out?

About 1.5 inches.

357MagAR wrote:

rlandry6 wrote:Magpul manufactures 300 BLK specific mags but only in the 30 round version. What limited information I have found says the standard AR15 mags are only an issue with the larger bullets and work fine with the smaller bullets, the problem being the rib in the magazine hits the larger bullet and causes it to shift in the mag.
Anyone have any direct experience with this? It would be nice to use 10 rounders, especially for bench shooting where the longer ones may interfere.

D&H recently came out with 300 BLK specific magazines in 10, 20, and 30 round versions.

I've been using some 10 and 20 round versions off the bench (30's are a little too long) and they have worked with zero problems so far.

For giggles I purchased the Magpul 30 and all three sizes of the D&H. They work well. I only had an issue with the 20 round D&H as it wouldn't lock in. I've sent it back for a replacement.

You can also get 20 rd Magpuls for bench work, I run them as the standard mag in my BO pistol.

i handload 225 gr bthp bullets to COL 2.25" and they would shift in an unmodified 5.56 mag. It will still feed and cycle OK, I had trouble filling all 20 rounds in a 20 round mag (which works fine for shooting off the bench) I could see the seam on the mag start to separate slightly as I loaded more rounds into the mag. magpul 300 blk mags work fine and can hold 30 rounds without issue. I wonder if these 300 blk mags will work OK for 5.56, if so then I'll stock on these instead (too bad they dont make ones with window).

I also handload 125 gr ballistic tips to COL 2.10" and these seemed to work fine in a 5.56 mag without mod. I'll have to load more to find out for sure.

Other than having a red follower, can you see or determine if there is anything different from their standard 5.56 magazines? My assumption about the P-Mag is the plastic ribs are thicker because of the plastic construction and this is why Magpul had to modify them for 300BLK ammo.

I'm looking for mags for my 300blk, so you have given me some good info, and unfortunately I'm in communist CO and can't have a magazine over 15 rounds.

B y r o n wrote:Other than having a red follower, can you see or determine if there is anything different from their standard 5.56 magazines? My assumption about the P-Mag is the plastic ribs are thicker because of the plastic construction and this is why Magpul had to modify them for 300BLK ammo.

Thats correct. The standard mags should work fine with the smaller bullets.

A Boy Named Sue wrote:Lancer is making 300 BLK specific mags. Why... I have no idea, since the regular L5AWM's work fine with everything. I'm guessing marketing. But they have discontinued colors, I know the ODG ones are no more.

According to Lancer, who I like, they increased the rib clearance for increased reliability.

If you’re looking for a 15 round low profile mag, E-Lander makes one.
I just picked up a RAR .300bo that takes AR mags and while it runs all my mags just fine, I wanted some low profile mags so I tried an E-Lander 10 & 15 round mag. Not .300bo specific but I’ve had good luck with E-Landers running .300bo in my ARs.
D&H does make a 10 round .300bo mag but I had one on backorder for a month and still have not gotten it yet.
I just picked up a 20 round .300bo Lancer, never had any issues with the 5.56 Lancers running .300bo. Runs great.