300 BO AR and MP 311-410

[sukivel]

I'm trying to load the MP 311-410 HP pc'd for my 300 BO AR-15. I am having cycling issues with this lighter weight bullet. I have worked up to max with IMR-4227 and the round fires and ejects but the bolt closes on the next round being fed and jams it up.

I have several other Hodgdon and IMR powders, but should I look to a faster or slower burning powder?

Any other tips or suggestions? I really want this cast boolit to work! I load an NOE 230 grain boolit with 4227 and it works great, but I need a lighter, and flatter, HP for quick action coyote/bobcats around the farm.

[John McCorkle]

What is the barrel details...ie... barrel length and gas system length?

Absolutely should be able to get a good working load but this can be more complex if you have something with a very heavy buffer and very short dwell time

In short though alot of folks have good success with that bullet in 300 blk so take heart, it's been done many many times before

Sent from my moto g power (2021) using Tapatalk

[imashooter2]

Sounds more like a magazine problem to me. What magazines are you using? If you single load one, does the bolt lock back?

[sukivel]

What is the barrel details...ie... barrel length and gas system length?

Absolutely should be able to get a good working load but this can be more complex if you have something with a very heavy buffer and very short dwell time

In short though alot of folks have good success with that bullet in 300 blk so take heart, it's been done many many times before

Sent from my moto g power (2021) using Tapatalk

8.5" barrel

1:8 twist

FWIW...My JHP Sierra 110 grain loads, Lee 155 gr cast loads, and 150 gr RN loads all work flawlessly.

[sukivel]

Sounds more like a magazine problem to me. What magazines are you using? If you single load one, does the bolt lock back?

I use Magpul magazines and have not once had an issue with any other load. Yes the bolt locks back when single fed.

[imashooter2]

If the bolt locks back when single fed, you have a magazine problem. If they are standard .223 magazines, then the forward ribs often cause feeding issues based on where they contact the boolits, either pinching the cartridge stack or pushing the boolit nose off the feed ramps as they strip. The easy solution is to either file them down a bit or buy dedicated 300 BLK magazines that already have the ribs cast lower.

[imashooter2]

Also, is the nose “pointy” enough to use the feed ramps in the barrel extension? I have no luck with round nose or flat nose projectiles. They all jam on the locking lugs.

[sukivel]

If the bolt locks back when single fed, you have a magazine problem. If they are standard .223 magazines, then the forward ribs often cause feeding issues based on where they contact the boolits, either pinching the cartridge stack or pushing the boolit nose off the feed ramps as they strip. The easy solution is to either file them down a bit or buy dedicated 300 BLK magazines that already have the ribs cast lower.

After you fire the last round, or single feed with the mag in, the bolt stays open. It's supposed to do that. I/we must be describing something differently. It is a standard magazine, but with ALL of my other 300 BO loads, everything functions perfect. 110 gr, 155 gr, up to 232 gr all function great.

[sukivel]

Also, is the nose “pointy” enough to use the feed ramps in the barrel extension? I have no luck with round nose or flat nose projectiles. They all jam on the locking lugs.

Yeah it is pointy, except the hollow point. My 150 gr RN JSP loads feed great, that's why I'm perplexed.

I'm starting to remember why I enjoy single shot rifles more...

[imashooter2]

After you fire the last round, or single feed with the mag in, the bolt stays open. It's supposed to do that. I/we must be describing something differently. It is a standard magazine, but with ALL of my other 300 BO loads, everything functions perfect. 110 gr, 155 gr, up to 232 gr all function great.

If the bolt locks back, it indicates you have plenty of gas and bolt travel and so it isn’t the powder or bullet weight that is the problem.

This isn’t all your other loads. This one is a problem. The behavior of the rifle strongly indicates it is a magazine problem with this particular boolit. Most magazine problems with the BLK have to do with the forward rib on .223 magazines. It contacts .30 caliber bullets differently than .22 caliber.

When you fill the magazine, do the cartridges stack smoothly down the sides, or does the rib pinch the column towards the center off the sides of the magazine box? If it does, then this causes the cartridge stack to bind and the next cartridge may not be in position to strip in the very short time allowed by the bolt travel.

When a cartridge strips off the top of the stack, does it travel forward straight and hit the feed ramps or is it pushed towards the center and jam on the locking lugs?

These are the most common failures with 300 BLK in .223 magazines. Good luck!

[tayous1]

I have the same mold and found that unless the OAL? I had to make mine I believe 2.100 OAL to make it feed it worked but looked odd. I was not even able to push the Boolite down up to the lube ring but I used H110 and it cycles in my 18 inch and 7.5 inch barrel with no problem.

[tayous1]

If the bolt locks back, it indicates you have plenty of gas and bolt travel and so it isn’t the powder or bullet weight that is the problem.

This isn’t all your other loads. This one is a problem. The behavior of the rifle strongly indicates it is a magazine problem with this particular boolit. Most magazine problems with the BLK have to do with the forward rib on .223 magazines. It contacts .30 caliber bullets differently than .22 caliber.

When you fill the magazine, do the cartridges stack smoothly down the sides, or does the rib pinch the column towards the center off the sides of the magazine box? If it does, then this causes the cartridge stack to bind and the next cartridge may not be in position to strip in the very short time allowed by the bolt travel.

When a cartridge strips off the top of the stack, does it travel forward straight and hit the feed ramps or is it pushed towards the center and jam on the locking lugs?

These are the most common failures with 300 BLK in .223 magazines. Good luck!

How do you take care of this problem?

[imashooter2]

You can fool with the seating depth to vary where the boolit ogive contacts the rib to allow the cartridges to stack straight and against the sides of the magazine box if that is the problem. The rib pushing the boolits to the center to jam in the lugs is harder to solve with seating depth, but sometimes it can be done.

Easiest is to buy purpose made 300 BLK magazines that have the rib cast lower to allow for the larger diameter boolits to ride correctly. You can also disassemble and file down the ribs of Magpul .223 magazines for the same effect.

[tayous1]

You can fool with the seating depth to vary where the boolit ogive contacts the rib to allow the cartridges to stack straight and against the sides of the magazine box if that is the problem. The rib pushing the boolits to the center to jam in the lugs is harder to solve with seating depth, but sometimes it can be done.

Easiest is to buy purpose made 300 BLK magazines that have the rib cast lower to allow for the larger diameter boolits to ride correctly. You can also disassemble and file down the ribs of Magpul .223 magazines for the same effect.

Are there rib casts that you can buy to replace the 223 ones? I have notice when I try to load the 230gr on a magazine I can't get 30 rounds in them and the magazine will hang up.

[imashooter2]

No, but there are dedicated 300 BLK magazines with the lower ribs from the factory. Magpul and Lancer make good ones. I like translucent smoke Lancer’s to set them apart from my Magpul .223 magazines.

Magpul dedicated 30s or 20s, $15.15 each:
https://www.midwayusa.com/product/1018507080?pid=977210

Lancer's, $5 more:
https://www.midwayusa.com/product/1022346310?pid=985277

I didn’t shop, just looked at Midway. You might find better deals.

[Bashby]

Read the third post in this thread.
https://www.ar15.com/forums/armory/3...ead/42-385765/

It explains how to determine what OAL will feed properly

[tayous1]

Read the third post in this thread.
https://www.ar15.com/forums/armory/3...ead/42-385765/

It explains how to determine what OAL will feed properly

That's good information! Use to like going there a lot had since 2001 but they now uphold rules to people who are members.

[tayous1]

I'm using a 7.5 inch barrel. Bought some followers that where made for 300blk I will rate them when I get them if they work with the shorter OAL.

[tayous1]

I have nothing to do with these company! Just saw a solution to a problem!

https://muddy-river-customs-llc.mysh...39570674188440

[imashooter2]

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