300 BO AR and MP 311-410

[popper]

No, the problem with the short bullets is they don't always feed right and get pulled forward in the mag by the one above it or the BCG. Rims need to NOT have any rough spots. They get pushed to the front of the mag, bolt hits them and nose jams in the feed ramp. Don't load more than 4 in the mag so spring pressure isn't so great helps, I still get a jam once in a while. Try those 110gr half jackets - lots of jams. Always bang the mag on something hard to seat the cases against the back of the mag helps too. A proper solution would be a mag with smaller internal dimensions.

[Drew P]

I had problems with mag pull mags in 300bo, so, that’s likely your problem. But, one little piece of gold I picked up along the way is that you need to seat the bullet so that the rib in the magazine contacts the bullet at the point which measures .250”. After heeding this my cycling got waaaay better.

Also worth pondering: a sheet metal mag will always have more internal volume than a plastic mag. Volume matters when you are trying to stuff cartridges with bullets 4x the size of the designed parameter into the mags designed for 223.

[tayous1]

What problem are they intended to solve? I don’t see any claims.

Not buying a whole new magazine but buying a follower that you can replace an 223 follower?

To me getting a a few of these followers are cheaper then buying one 300 blk magazine unless I'm missing something?

[imashooter2]

The followers aren’t a problem. The magazine body is the problem. Specifically the ribs in the front of the 5.56 magazines pinching the cartridge stack IF the bullet body is too large where it contacts them.

[Drew P]

The followers aren’t a problem. The magazine body is the problem. Specifically the ribs in the front of the 5.56 magazines pinching the cartridge stack IF the bullet body is too large where it contacts them.

Correct. Try a c products mag. And seat them as I outlined. You’ll be shooting pretty

[tayous1]

Correct. Try a c products mag. And seat them as I outlined. You’ll be shooting pretty

Any C products mags or is there one I should buy? I'm sure I have a few laying around the house just have to find them

[imashooter2]

My opinion again… If you’re going to buy magazines, buying dedicated 300 BLK units will make your life easier. Otherwise try the ARFCOM instructions with what you already have.

[tayous1]

My opinion again… If you’re going to buy magazines, buying dedicated 300 BLK units will make your life easier. Otherwise try the ARFCOM instructions with what you already have.

What ones?

[imashooter2]

I like Lancer because they have translucent smoke bodies that differentiate them from my 5.56 magazines. Magpul have different texture on them, but are opaque black plastic, same as the 5.56 magazines. Just make sure you are buying the dedicated BLK part numbers. Companies like to advertise standard 5.56 magazines as “5.56, .223, 300 BLK.”

There are Midway links in one of my posts above, but if you shop you may be able to find them cheaper.

[Drew P]

Any C products mags or is there one I should buy? I'm sure I have a few laying around the house just have to find them

I would just say any metal mags that are not magpul, but if you really start to look at the situation with a critical eye you will be able to identify the reasons why some mags don’t work, while at home just loading and looking. I’ve had good luck with all my c prod

[Rapier]

I use the 230g in my BO, as well, however, in the end, switched to the 6mm Mongoose, to push 80g FBSP bullets up to 3k, so they do not go flying all over the farm. The last yote I dropped, did not have through and through penetration, bullet entered and exploded DRT. I doubt you can ever get what you want in velocity out of the BO case. I am building a 24 GPC at the moment to get about 3,200.

[sukivel]

So an update to my original post...

After looking at several mags, load data, and seating depths I tried several things, and it appears I have rectified my problem.

The first thing is I was way under powder charge. The only published data I could find was for a 16" barrel, and mine is 8.5". I was initially attempting to stay at roughly 1700ish fps so I was loading slightly below starting powder charge and the lighter 130 gr cast bullets were battling to get the bolt back all the way. But again that data is for a 16" barrel. That's my hypothesis anyhow.

Second, I was seating the bullet to the crimp groove, which is very short for the 300 BO, and the new round was not smoothly feeding fast enough and allowing the bolt to close on it. Also to add 1 grain of powder ( which is still under a starting load), I needed to seat the bullet out further for it not to compress.

Third, I have been using 30 rnd Pmags for all of my other 300 BO loads and they all function great, but I noticed I had been using a 20 rnd Pmag to function test these instead, and for some reason I found through testing some other rounds that the 20 rnd mag experienced some problems.

After adjusting those three things I have gotten this little MP 311-410 to cycle a half mag through, but I want to function test a little more. The funny thing is, after firing half a mag of these and then the other half a mag of my NOE 232 gr subs, I really don't like those loud little suckers coming out that close to my face! They seem "hot" compared to my 232 subs. I was also down on my range and found that with my Sierra 110 JHP zero on the rifle, I was able to still hit my 10" plates out to 100 yds with the dot on center target. My main reason for the cast 130 gr HP was for 100 yd predator defense, and apparently I can get there with the subs, which are funner to shoot, so...

I'm still like these little hollow point boolits though...

[popper]

The ribs in the 223 pmags only contact the shoulder of lower rnds, no the top 2. Will cause lower rnds to bind but not a feeding problem. The front of 223 mags can be a problem. They were designed for a small pointy well feeding bullet. Even lancer mags were designed for a normal COAL. Pistol gas and 15gr 4227 is enough pressure to cycle and get 1400 fps. 18 gr for 1700 fps and pressure is high at port. Most all will give muzzle flash as powder is slow.