Discussion in 'Rifle Country' started by rbernie, Jan 13, 2019.
What will (and will not) work?
Most shorter magazine (20rd or less) will work unmodified. Straight 20rd works great for me. I did buy some 458 SOCOM followers from calegalmags.com and put those on some old NHMTG magazines. Found that makes loading the first round easier.
I have found 30rd magazines are a bit more finicky and sometimes will cause feeding issues when full.
The most important thing is be sure the feed lips have no sharp edges or corners. They dig into the side of the cartridges. I break the edges with a jeweller's file if needed and hit them real quick with a felt wheel and polishing compound.
My modified straight 20 next to a factory 450 BM magazine.
ETA: The rib down the front of PMAGS cause issue with many loads.
^^^^^ Good advice. Same holds true for the mags I use in my 458 SOCOM. Good idea to slick up the magazine feed lips and also 'scallop' the front of the mag.
The biggest problem I've found were the followers. Even the factory Bushmaster mags didn't get it right. The pics below will illustrate what part of the problem is. Some of the manufacturers use the same follower for both the 450 and 458. Both cartridge cases are not the same diameter, one has a taper and the other does not.
I found the Tromix followers to be shaped correctly to cradle the 450 cases. Photo below illustrates the difference, left is a Tromix...right is a Bushmaster. https://tromix.com/product/center-feed-followers-for-lancer-mags/
The best 450BM magazine is the one you make yourself. We use Lancer magazines, prefer the 10 round for hunting because they don't hang down below the lower receiver as far. We like the 20 round mags for the range. Take the magazine apart and snip off the plastic round limiting protrusion on the base plate. This will allow for an extra round to be inserted. Cup out the front of the magazine where the round will be pushed forward. Not doing so can cause the round to be pushed upward when feeding into the chamber. With that removed the round will make a smooth transition forward as the round is fed. We also like the Lancer semi clear mags and the ability to see how many rounds it's holding.
Those Lancer mags look real slick. And how did Bushmaster get the followers for their own cartridge wrong? Good call on Tromix's part. Great info.
The second photo down is a factory Bushmaster magazine, note how much space (or light) is under the cartridge. That's because the channel is too narrow (and tapered), cartridge doesn't get cradled properly like in the third photo down. The Tromix followers have a wider channel contour which allows the round to be fully supported front to rear.
I have never had an issue with the factory 450 Bushmaster magazine follower I have. Yes the follower does not have the correct radius but the 458 SOCOM follower I am using in my home built magazines only contacts the round on the two ridges molded into the follower and they work fine too. For that mater I have never had an issue using the 223 followers but I wanted dedicated 450 Magazine so I made my mods.
The scallop cut on the front of the magazine is not strictly needed, the nose of the round should hit the feed ramp before the round can hit the front edge of the magazine but it sure makes loading them easier and less likely to scratch up you rounds while loading.
mcb, we have three AR 450 Bushmasters between the boys and myself, two worked fine with the factory Bushmaster magazines, the third one constantly had feeding problems. All are the same manufacturer uppers, only difference was brands of lower receiver. Can't explain why the one jams and the others don't. When we went with the Lancer/Tromix units they all perform flawlessly.
I used regular old Colt 20 round mags with mine, didn’t change a thing.
I played with converting 10rd Magpul magazines but was not happy with the results. The 10rd magazine bodies are short enough you can easily use a good file to remove the rib from the inside front.
Left: Rib Removed, Right: Factory
I also filed the follower flat too though that was not strictly needed bit did makes it easier to insert with four rounds loaded under a close bolt.
Unfortunately with it being single stack and the rounds coming up in the center have a pretty good mechanical advantage over the feed lips and they spread badly in this case. It seems to function fine in the gun but when the magazine has even just one round in it the feed lips spread enough to make insertion difficult and it will not drop free.
To date I have used four different magazine in my 450 Bushmaster.
Left to Right: 10rd PMAG converted to 450 BM (hold 4 rds of 450BM), 5rd 450 Bushmaster Magazine made by DPMS*, 5rd 450 BM Bushmaster factory magazine**, Converted NHMTG 20rd magazine with calegalmags.com 458 SOCOM follower (holds 7rds of 450BM).
*I am assuming DPMS since that is on the floorplates. Wish I had more of this magazines. I only have two Not sure where it came from (I got it from a buddy that doesn't know where he got it from) but they are awesome. Nice and short, holds 5 rounds, with machined Delrin followers and have fed flawlessly for me. They were my hunting magazine this year.
** Not sure why Bushmaster put the dent in the corners near the bottom of the magazine body? This stops the follower early and thus the 5rd capacity. With that length of the magazine body it should hold 7rds like my converted 20rd magazine next to it.
I wondered about that also, appears to be a cheap way to limit the follower. Prevents follower removal for servicing.
In retrospect is for limiting capacity in states that have a 5rd limit when hunting. Ohio where I grew up was slug only and has a 3rd limit. That 3rd limit is now by the honor system now that they have allowed rifles with straight wall cartridges to be used also. I currently do all my hunting in Tennessee now and it has no magazine limit. I should have thought of that. You can get the follower out but its a real pain in the butt to work that follower past the stops.
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