The AR World is Nonsensical: Here’s My Latest Contribution.

[rickyrick]

Ordered a 20” .450 Bushmaster upper by Radical from Primary Arms along with a carry handle sight by AeroPrecision and a Troy Battlesight HK style fixed front sight (non-flip)
I thought the upper came with a magazine, but I guess they don’t on the ones sold through PA. I have one coming from Bushmaster. I guess I could hand-feed some cartridges in it until the magazine arrives.
According to my research, this cartridge can be temperamental in feeding from a magazine, so I am anticipating having to do some tweaking in the future.
I have temporarily orphaned my 24” bull barreled upper for this project (a previous nonsensical project)
It’s the first complete upper that I have purchased, so fingers crossed. I’ve always assembled them myself.
Anyway here is the beast, looks ok so far. No fancy finish or anything. Made in Texas, so that’s a bonus… maybe lol.
I will probably use the carry handle on a different gun later on, after I get any kinks out. Hopefully I can fire it this weekend, but I may be preparing for the arctic plunge heading this way.




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[44caliberkid]

I love the Panzer muzzle brake, one reason I bought a Radical upper in 458 SoCom. I use ASC mags for the 450 Bushmaster and they work fine. Go ahead and try a 5.56 mag, because I think the only difference is the follower. I bought some 450 followers to convert regular AR magazines, but it’s been 5 or 6 years and I don’t remember if I used them or not.

[rickyrick]

Thanks for the tips, this is my first foray into big bore or single stack AR calibers.
I will probably order some followers soon.

I weighed choosing one of the bottle neck cartridges as a project, I’m really not going to be shooting long ranges in the near future. If I do, I have non-AR .308 rifles.

I landed on .450BM because of factory ammunition availability for now.

[9x19]

When I had one, I used the USGI 20 round mags with a replacement follower as well, and they worked just fine, no feeding issues.

[44 AMP]

I do like the "Panzer" style muzzle brake.

[rickyrick]

I do like the "Panzer" style muzzle brake.

But, does it need it? The cartridge doesn’t look that BIG.
Panzer Thing is making me flinch by just looking at it.

Signed,
Feeling Apprehensive

[44 AMP]

Panzer Thing is making me flinch by just looking at it.

Really? it ought to be having the opposite effect.

IT adds a few ounces of steel, and reduces felt recoil. Plus, I think it looks cool, reminds me of the brake on the production model Panther tank (Pz V)

Since its already there, I wouldn't bother removing it, it doesn't hurt anything and might even help.

Remember the round fires a 250gr slug in the 2200fps range. That is neck and neck with a factory loaded .358 Win and only a couple hundred fps slower than a .35 Whelen or .350Rem Mag with the same bullet weight.

The bigger bore (.45) will change the feel of the recoil, and so will the straight line AR stock. Overall, I'd be glad to have a brake, and not so happy without one.

Interesting tidbit, the panzer style muzzle brakes were not installed for recoil reduction. They do that, some, but that was an added benefit, not the primary purpose. Their main benefit, on the tanks and anti-tank guns was redirecting some of the muzzle blast to the sides and not raising as much of a dust cloud directly in front of the muzzle. This allowed the gunner to get back on target a little faster. Same reason you find birdcage type flash hiders "clocked" with a solid bottom, so as to raise less dust and debris when fired close to the ground (prone).

[rickyrick]

Really? it ought to be having the opposite effect.

I was being a bit tongue in cheek there due to the aggressive look of it.

I learned about muzzle blast kicking up dust back when I was killing coyotes with a Mini14 from the prone position.
I ended up installing a brake without ports in the bottom for that very reason. (At least I thought I installed it)
Funny thing, unnoticed to me, the roll pin hole for the brake was in the wrong position for the rifle and I ended up launching it into muzzle brake Valhalla two years later

Hopefully I can get out and fire the upper tomorrow, will certainly try it this weekend if only to test the functionality of it.

I do like the brake, won’t be removing it. Shooting it should be fun, it’s completely new to me.

[44caliberkid]

Originally Posted by rickyrick

But, does it need it? The cartridge doesn’t look that BIG.
Panzer Thing is making me flinch by just looking at it.

Signed,
Feeling Apprehensive

“Need” has nothing to do with it. I just think it looks cool, and badass. I pick a lot of my AR accessories just for aesthetic reasons.

[davidsog]

arctic plunge

We used to just call it "Winter". Nice rifle.

[rickyrick]

“Need” has nothing to do with it. I just think it looks cool, and badass. I pick a lot of my AR accessories just for aesthetic reasons

Roger that, was mostly joking around, I like how it looks too.

We used to just call it "Winter". Nice rifle.

I live on a creek in the forest that drains into a bayou… 7 degrees is cold to us lol. Busy packing the well house with hay hoping it doesn’t freeze

[rickyrick]

Well just got finished test firing and it’s a short stroker.
Will try again with a carbine lower before doing anything else.

The recoil isn’t bad at all, probably due to the Panzer thingy, haha.
Let family members have a go at it, even though it was basically a single shot. My 5’1” wife didn’t complain either, but the A2 stock was awkward for her.
The concussion was pretty impressive though

[44 AMP]

You might consider one of the collapsable multi position buttstocks for the wife's use. Just be sure to get one that doesn't have a "cheese grater" buttplate. Something rubber coated without sharp metal edges would be best.

Even a home made rubber pad, slipped on or glued on will turn something that "bites" into something much more comfortable.

Good Luck with the short stroking issue. Could be the gun isn't correctly "balanced" between gas amount and recoil system, or it could be its not set up right for the ammo you are using.

[rickyrick]

I’ll try a carbine lower, I have several.

I prefer rifle buttstocks but I found that they don’t always cooperate with some calibers and gas lengths.
It’s not the end-all if I need to use carbine stocks and buffer set ups.
I have a few buffers of various weights and I also have tungsten weights. I suspect a standard buffer will do the trick, if that’s what fixes it. Of course I’m gonna give the gas block a look over too.

[9x19]

I used a carbine H1 buffer in mine, but it was a shorter barrel, with a carbine length gas tube.

[stagpanther]

I put a panzer brake on my 458 socom build--mostly cause it was one of the few I could find. You can order lancer single stack followers from Tromix. My 458 socom reminds me of shooting a moderate 45-70.

[rickyrick]

The recoil wasn’t bad at all, I’d dare say that it might be on par with my 10.5” 6.8spc, of course it’s considerably lighter than the 450 and it has no brake, just a 6” flash can pinned and welded. I’ll do a side by side one day and see.
Either way, the 450 recoil wasn’t near to what I was anticipating. I guess the panzer brake did it’s job.

[44caliberkid]

I think the cartridge was developed using a carbine buffer and spring. My 450 build was also short stroking and I traced it down to an unusually stiff recoil spring, not sure where it came from as I have a couple drawers of AR parts and most are not in original packaging. Once I installed the standard carbine buffer and spring it worked fine.

[rickyrick]

I was thinking that might be the case, seems like most ARs run carbine buffers and springs theses days. Of course, that’s just the view from my corner of the room.

[rickyrick]

It is still short-stroking with a carbine lower and standard buffer, however it is cycling a little better. Will feed 2-3 rounds on its own but fails to pick up new rounds often.
Also will not completely lock the bolt open on empty mag. It will catch the bolt carrier but not the bolt.
I also took an empty buffer with me with no better result.

My next step will be to pull the gas block and check for alignment, but may end up drilling the gas port. Drilling the port seems to be the winning solution with these rifle length 450BM uppers.

[44 AMP]

If you wind up drilling the port in the barrel, I'd suggest getting an adjustable gas block to go with that. It's not impossible that opening up the barrel port could result in the gun being overgassed and an adjustable gas block should be able to compensate for that, if that condition does occur.

Good Luck!

[stagpanther]

This drilling the port thing--It's more than just putting a hole in the barrel. I've sent more than a few back to the manufacturer that were not done or finished well. Just sayin.

The recoil wasn’t bad at all, I’d dare say that it might be on par with my 10.5” 6.8spc, of course it’s considerably lighter than the 450 and it has no brake, just a 6” flash can pinned and welded. I’ll do a side by side one day and see.
Either way, the 450 recoil wasn’t near to what I was anticipating. I guess the panzer brake did it’s job.

What kind of load are you using in your bushmaster? I've never had any issues with my 458 socom--which is similar-- but when I fire it it always gives a very respectable thump and I always think to myself "yup, this is about as far as I want to go in an AR15."

[rickyrick]

I’m just running factory loads: Hornaday and Winchester 250gr.
I was expecting more recoil than it actually has.

Drilling will be my last option, however when I order things I take a gamble, I’m relegated to solving this one myself. I would probably send it back, but none of the carriers will pick up at my home in the forest and I’m never off work in time to get to one of the shipping places.

[rickyrick]

I took the gas block off and found no signs of leaks or misalignment. Measured the gas port and it came in at a whopping .109-.110”.

I checked everything over, read various internet sources and determined that it is not unusual to have a port of .120” on a 450 bushmaster with a rifle length gas system.

I went ahead and opened the port to .120” which is the maximum because that’s the ID of the gas tube.

Test fired today and it cycled properly at first for the most part, with a couple of hiccups in the first few magazines, but would feed rounds and lock back when empty.
After that, it would run through magazines just fine probably just needs more break-in.

Interestingly, it didn’t like to chamber rounds completely by using the bolt release, but chambered them just fine by slingshotting the charging handle. That’s something I could live with because I tend to be a slingshotter anyway.

Seems to have a touch more recoil now.

I guess I’m gonna have to get set up to reload for this one, and decide on an optic. It’s pretty fun to shoot.

[stagpanther]

Interestingly, it didn’t like to chamber rounds completely by using the bolt release, but chambered them just fine by slingshotting the charging handle.

I've had that happen a couple of times with AR 10 builds, sooner or later things went downhill--light pin strikes, not able to go into battery fully, double-stacking etc. By slingshotting, I assume you mean you need to fully retract the charging handle and let go to get the carrier to successfully chamber a cartridge from the magazine? Since your set-up is new, you might be able to see signs of uneven wear on the carrier and lugs.

My guess is that you have something that might be interfering with how the bolt/carrier rides in the upper; perhaps something to do with the magazine and how it interfaces with the lower. Might be something as simple as how the cartridges are stacking in the magazine; a bit of bulge or tilt by the follower. I know the bushmaster isn't identical to the 458 socom but I chose the lancer magazine and tromix single-stack follower right from the get-go though I did read someplace that the bushmaster can be more prone to feed issues than the socom (one of the reasons I chose the socom over the bushmaster when I did my build). I'm traveling at the moment and it's been a long time since I looked inside my 458 socom--I seem to recall that the barrel extension was ramped in such a way to facilitate straight-on presentation of the cartridge that you might have from a single-stacked magazine; IIRC it doesn't have a lug at the 6 o'clock position. My less than 2 cents.