AR15.Com Archives
 3/07 PMag + single shot follower for .458 SOCOM
JimTh  [Team Member]
3/1/2008 1:38:20 PM
In my two trips to the range and limited time hunting with my .458, I found that the wide meplat JHP's would sometimes grab the feedramp and hang if I didn't let the bolt slam home with full force. I also found that the soft lead tip would sometimes become deformed if loaded repeatedly.
Upon seeing Bushmaster using a blue single shot follower in their .450 BM mag, I became interested. I believe Weldingrod posted pictures of one taken apart and this pushed me along a little further. Finally a couple weeks ago I ordered two of the followers from Bushmaster. Within a day or two I found out they are actually Fulton Armory parts and FA sells them cheaper. Oh well.
My goal was to combine a Magpul PMag with one of these followers for a lower cost, non-aluminum alternative to Bushmaster's $35 .450BM mag.
This post will document my progress to date and I will update it later after a range trip for live firing.
First, here's my modified follower alongside an unmodified one.

The "bill" on the front has to be severely reduced. I started off with a file but soon moved to 50 or so grit sandpaper. The sandpaper hogs material off in a hurry, then I used the fine file to return the plastic to an almost factory smoothness. I found that the PMag actually gets slightly smaller inside as you go up, so I kept having to remove material until it would slide freely.
Note that I also had to bevel the corners on the tab at the back. Otherwise it will bind in the mag.
Once I had it fitting, I installed the original follower and spring and loaded one round. Immediately I could see that the nose of the bullet was sitting higher than in a PMag with a standard follower. But, I knew that Bushmaster had also cut their feedlips back some. I suspected this was to allow the round to ride higher. The FA follower actually has some tilt to it, so it lifts the nose of the round up, where the regular follower does not.
So, I put my Dremel sanding drum in the drill press and used it to hit both feed lips at once. Turns out it's the perfect size, but it sands one side slightly faster than the other. I then used a file to round off the corners left by the sanding.
Here's a pic of an unmodified and my modified mag.

I quickly found that I need to make another small change. When I used a PMag to hunt last fall, I had filed down the front of the mag to act as sort of a feed ramp to start tilting the bullet up. Well, with that change done, the follower will move forward and not lock the bolt back. So, I modded a second mag and used the file to lightly bevel that nub that sticks out. Leave enough that it stops the follower, but round it enough that the case mouth won't hang on it.
Here are some pics of the results. In each pic, the unmodified mag is on the left, modified on the right.



You can see that the bullet nose rides quite a bit higher and typically clears the front of the mag. There is some front to back wobble in the PMag follower that creates some variance. Even with it wobbled forward, it's still higher than the factory follower.
So, how's it work? Well, I loaded 5 rounds in my modded mag and hand cycled them each through slowly. Yes, I rode the charging handle forward. Each one hit the feed ramp and slid right up into the chamber. Not a single hang on the feed ramp.
When time allows I will take the mag to the range for some live fire testing. For now, I'm calling this a success.
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Cold  [Moderator]
3/1/2008 2:15:12 PM

Originally Posted By JimTh:
In my two trips to the range and limited time hunting with my .458, I found that the wide meplat JHP's would sometimes grab the feedramp and hang if I didn't let the bolt slam home with full force. I also found that the soft lead tip would sometimes become deformed if loaded repeatedly.
Upon seeing Bushmaster using a blue single shot follower in their .450 BM mag, I became interested. I believe Weldingrod posted pictures of one taken apart and this pushed me along a little further. Finally a couple weeks ago I ordered two of the followers from Bushmaster. Within a day or two I found out they are actually Fulton Armory parts and FA sells them cheaper. Oh well.
My goal was to combine a Magpul PMag with one of these followers for a lower cost, non-aluminum alternative to Bushmaster's $35 .450BM mag.
This post will document my progress to date and I will update it later after a range trip for live firing.
First, here's my modified follower alongside an unmodified one.
home.insightbb.com/~jim-vicky/458follower.jpg
The "bill" on the front has to be severely reduced. I started off with a file but soon moved to 50 or so grit sandpaper. The sandpaper hogs material off in a hurry, then I used the fine file to return the plastic to an almost factory smoothness. I found that the PMag actually gets slightly smaller inside as you go up, so I kept having to remove material until it would slide freely.
Note that I also had to bevel the corners on the tab at the back. Otherwise it will bind in the mag.
Once I had it fitting, I installed the original follower and spring and loaded one round. Immediately I could see that the nose of the bullet was sitting higher than in a PMag with a standard follower. But, I knew that Bushmaster had also cut their feedlips back some. I suspected this was to allow the round to ride higher. The FA follower actually has some tilt to it, so it lifts the nose of the round up, where the regular follower does not.
So, I put my Dremel sanding drum in the drill press and used it to hit both feed lips at once. Turns out it's the perfect size, but it sands one side slightly faster than the other. I then used a file to round off the corners left by the sanding.
Here's a pic of an unmodified and my modified mag.
home.insightbb.com/~jim-vicky/458sxsu.jpg
I quickly found that I need to make another small change. When I used a PMag to hunt last fall, I had filed down the front of the mag to act as sort of a feed ramp to start tilting the bullet up. Well, with that change done, the follower will move forward and not lock the bolt back. So, I modded a second mag and used the file to lightly bevel that nub that sticks out. Leave enough that it stops the follower, but round it enough that the case mouth won't hang on it.
Here are some pics of the results. In each pic, the unmodified mag is on the left, modified on the right.
home.insightbb.com/~jim-vicky/458frontl.jpg
home.insightbb.com/~jim-vicky/458sxsflat.jpg
home.insightbb.com/~jim-vicky/458sxsl.jpg
You can see that the bullet nose rides quite a bit higher and typically clears the front of the mag. There is some front to back wobble in the PMag follower that creates some variance. Even with it wobbled forward, it's still higher than the factory follower.
So, how's it work? Well, I loaded 5 rounds in my modded mag and hand cycled them each through slowly. Yes, I rode the charging handle forward. Each one hit the feed ramp and slid right up into the chamber. Not a single hang on the feed ramp.
When time allows I will take the mag to the range for some live fire testing. For now, I'm calling this a success.


Thats great thinking! Keep us posted how it cycles! I bet it would great for the 50 B too.
JimTh  [Team Member]
3/1/2008 3:49:23 PM
Seems to me it would work for any of the big calibers with flat nosed bullets. If you wanted a slightly higher cap .450BM mag for instance.


Originally Posted By Cold:
Thats great thinking! Keep us posted how it cycles! I bet it would great for the 50 B too.