300 BLK with P-Mags

[HokieCasey]

No with 300 blackout, OAL is an issue as that portion of the mag is intended to ride on the case neck of 223/556 rounds. Depending on the bullet you want the circumference of the bullet at that point to be roughly the same diameter of a 223/556 case neck. If not you could end up with feed issues out of some magazines or deal with that slight canting.

To me what it means in this case is oal is in spec but due to variability some are loaded slightly longer resulting in the described problem.

When I reload 300 blackout I work up a load using that reference point as my limiting factor, instead of max spec OAL.

 

[HT4]

The OAL length should only be an issue if the rounds hit the front of the magwell (loading anyways).

It is only the ones with the longer OAL that interfere with the nubs. When it hits the nubs, the round tips up and out of the mag... not enough to pop totally out, but enough that I need to tap the back of the mag after loading every 2 rounds or it will jam. I've got so many P-Mags that I really don't care to buy something else... so I will probably just use a dremel sanding drum to take about half of the nubs off.

I'm just surprised that more people have not run into this issue...

No with 300 blackout, OAL is an issue as that portion of the mag is intended to ride on the case neck of 223/556 rounds. Depending on the bullet you want the circumference of the bullet at that point to be roughly the same diameter of a 223/556 case neck. If not you could end up with feed issues out of some magazines or deal with that slight canting.

To me what it means in this case is oal is in spec but due to variability some are loaded slightly longer resulting in the described problem.

When I reload 300 blackout I work up a load using that reference point as my limiting factor, instead of max spec OAL.

You understand exactly what the issue is. It's a little hard to describe without the pictures. Do you function problems arising out of this issue? I went through my first 60 rounds without issue, but that really doesn't mean anything.

 

[HokieCasey]

I have not noticed any feed issues using factory loads even with a little bit of push in, to date about 200 rounds through 2 builds. But I have had to 'tap' the mag during loading to get them all shifted to the rear of the mag. Now granted I have only used 20 round mags due to concerns about overall mag weight for a thirty and how well the spring will keep up with 220 grain subs.

I suspect you would have mag loading issues as brad suggested if it was too far off, or have the tip hit that center nose rib on the pmags, and then have resulting feed issues.


And I have not had issues with reloads, but I use a seater (forester) that indexs off of that point on the bullet.

 

[MindOOB]

Here is an actual picture of my mags... it gives a better view of the interference and also shows the vast difference in overall length that may be contributing to the issue.

That totally makes me want a 300 BLK upper now.. Darn you

 

[huesmann]

Here is an actual picture of my mags... it gives a better view of the interference and also shows the vast difference in overall length that may be contributing to the issue.

I can see from the pic how the nubs may be just barely tipping your bullet sideways. If those were .223s, the nubs wouln't interfere at all, but with the wider .300 bullet there could be contact. What is the purpose of the nubs--just stiffeners for the wall of the mag? If so, just filing them down near the lip of the mag should solve your problem.

 

[HT4]

I can see from the pic how the nubs may be just barely tipping your bullet sideways. If those were .223s, the nubs wouln't interfere at all, but with the wider .300 bullet there could be contact. What is the purpose of the nubs--just stiffeners for the wall of the mag? If so, just filing them down near the lip of the mag should solve your problem.

Not sure what they are for... I suspect that the nubs aid in 5.56 feeding by ensuring that the rounds are in position as they approach the feed lips. In any case, I am going to sand the nubs down about half way (with an angle to match the 220gr loads) on a couple of the mags down and label them as 300BLK. If it helps, I'll do a few more.

 

[11Bravo]

Where have you guys been buying your 300AAC ammo? While the uppers themselves seem to be near mainstream, the ammo itself still seems to be elusive and pricey.

http://www.bulkammo.com/bulk-300-aac-blackout-ammo-300aacblackout115grctfbrem-200

 

[HT4]

http://www.bulkammo.com/bulk-300-aac-blackout-ammo-300aacblackout115grctfbrem-200

If you are going to order online, that's too expensive.

http://palmettostatearmory.com/inde...ton-300-aac-blackout-115gr-ctfb-l300aac2.html

 

[clandestine]

It is only the ones with the longer OAL that interfere with the nubs. When it hits the nubs, the round tips up and out of the mag... not enough to pop totally out, but enough that I need to tap the back of the mag after loading every 2 rounds or it will jam. I've got so many P-Mags that I really don't care to buy something else... so I will probably just use a dremel sanding drum to take about half of the nubs off.

I'm just surprised that more people have not run into this issue...



You understand exactly what the issue is. It's a little hard to describe without the pictures. Do you function problems arising out of this issue? I went through my first 60 rounds without issue, but that really doesn't mean anything.

Most rounds shouldnt contact the internal ribs, but if some loads do then you are correct, you just file down the nubs so no contact is made.

Without the nubs it may cause reliability issues with 5.56 rounds. I have seen doublefeeds increase when those nubs are removed and 5.56 is used.

Once modified consider them .300 BLK only.

Emags dont hane as many hiccups as pmags do either with .300blk.

 

[HT4]

Most rounds shouldnt contact the internal ribs, but if some loads do then you are correct, you just file down the nubs so no contact is made.

Without the nubs it may cause reliability issues with 5.56 rounds. I have seen doublefeeds increase when those nubs are removed and 5.56 is used.

Once modified consider them .300 BLK only.

Emags dont hane as many hiccups as pmags do either with .300blk.

Thanks. I actually made up a stencil last night to spray paint 300BLK on the edges of two I will modify so I don't mix them up. Assuming that works out, I'll do a few more. If not, I will try a different type of mag... or just dig out my old GI spec AL mags.

 

[DarthZed]

How many rounds of .300 can you load in an 30 round AR mag? Just curious, trying to decide if I want to get a Blackout upper for one of the lowers on the group buys.

 

[Kingjamez]

How many rounds of .300 can you load in an 30 round AR mag? Just curious, trying to decide if I want to get a Blackout upper for one of the lowers on the group buys.

30 rounds 300BLK in a 30 round AR mag.

-Jim

 

[11Bravo]

If you are going to order online, that's too expensive.

http://palmettostatearmory.com/inde...ton-300-aac-blackout-115gr-ctfb-l300aac2.html

You Sir, Are the shit. Thats the cheapest I have seen it so far. Thank you!

 

[HokieCasey]

How many rounds of .300 can you load in an 30 round AR mag? Just curious, trying to decide if I want to get a Blackout upper for one of the lowers on the group buys.

300blk is one for one in size for 556. My comment was on the comparitive weight of 220 grain subs vs 62 grain 855

 

[11Bravo]

Most rounds shouldnt contact the internal ribs, but if some loads do then you are correct, you just file down the nubs so no contact is made.

Without the nubs it may cause reliability issues with 5.56 rounds. I have seen doublefeeds increase when those nubs are removed and 5.56 is used.

Once modified consider them .300 BLK only.

Emags dont hane as many hiccups as pmags do either with .300blk.

Could it be a mag issue with the batch of mags he currently has? I feed .300 BLK through my windowed Pmags without issue and they feed the 5.56 green tip lake city all the same all day. Anyone else having this problem with their mags with the .300?

 

[BradMacc82]

So far, in it's limited firing, I've had no issue with 300BLK in Pmags or standard GI mags, 110, 125, and 220gr rounds.

 

[clandestine]

Could it be a mag issue with the batch of mags he currently has? I feed .300 BLK through my windowed Pmags without issue and they feed the 5.56 green tip lake city all the same all day. Anyone else having this problem with their mags with the .300?

PMags are generally very consistent, but it could be the mags. In my experience the sporadic issues are generally the weapons fault and not the mags when it comes to this specifi issue. Ramps and Gassing effects the reliability of the .300 in a major way, much more so than 5.56.