Things we need to know for a 450 Bushmaster Build

[leroy]

Dear folks:__________
I want to do a custom 16 inch 450 bushmaster upper to add to my ar15 stuff. Are there any unusual items or quirks that i need to know about before ordering parts? Some of the following items come to mind:
1. Upper reciever. Who to order from, what brand, any mods needed?
2. Stock type. Will a good multiposition like Magpul or Viltor work? Which one do you like best? Should i just use an ace skeleton?
3. What are your preferences on muzzle brakes? Does it need one; or just a flash suppressor?
4. Thoughts on best mags. I like the 20 round ar length.
Feel free to opine and give advise.
Thanks in advance.
Kind regards,
LEROY

[wildcatter]

Welcome, welcome, Leroy, good to have ya-all.

What you are asking is allot like someone suggesting what kind of woman you need. All suggestions are quite subjective and you should get lots of replys here.. You seem to have a handle on the problem already and some of your thoughts are really good. I can tell you've been shopping.. Some thoughts.. Building a weapon like Johnny Cash's Car song, .."one piece at a time", certainly is one way to do it, but something to consider is, usually doing it like that ends costing you way more and you won't actually be shooting for some time.. I like to start out with a whole weapon or upper and go from there. Of course you'll be hard pressed to better the Bushmaster Platform. After all, there is a reason why the CMP uses them for National Match Shooting and it looks like Bushmaster might be winning the new USGI Contracts, just rumor, no fact.. I just love the IZZY brake, from an over all stand-point, it's mechanically the best. The bottom of it is not open to the air, so as not to kick up dirt, if you are shooting prone and the remaining gases are expelled to the sides and up, making it very effective.. there are so many options these days that it'll keep your head spinning. So let's here it guys, do ya like blonds or brunettes??..

[MudBug]

Dear folks:__________
I want to do a custom 16 inch 450 bushmaster upper to add to my ar15 stuff. Are there any unusual items or quirks that i need to know about before ordering parts? Some of the following items come to mind:
1. Upper reciever. Who to order from, what brand, any mods needed?
2. Stock type. Will a good multiposition like Magpul or Viltor work? Which one do you like best? Should i just use an ace skeleton?
3. What are your preferences on muzzle brakes? Does it need one; or just a flash suppressor?
4. Thoughts on best mags. I like the 20 round ar length.
Feel free to opine and give advise.
Thanks in advance.
Kind regards,
LEROY

1.) I would just go with a stock complete upper at first, they are amazingly accurate.

2.) The VLTOR E-Mod is a great stock that has a decent recoil pad built in, that's what I originally used before I switched to a Cav Arms polymer lower. I've never used an Ace stock but people here seem to like them.

3.) I think the only real choices for a brake right now is the stock brake that comes on the upper, and maybe some of them made for the 458 Socom. There is a new combo brake/flash hider being made for the 458s that looks interesting but it hasn't been released yet.

4.) You mag choices are really limited to either the BM style mag, (buy from BM or roll your own BM style mag by buying the blue sled style followers from Fulton Armory and installing them in your own 20 round straight body mag.) which hold 5 rounds, or the Sig 556 mags which will hold 12 rounds but more reliably function with 10 rounds.

Some here have managed to make the Blue sled followers work in standard GI 30 round mags, but my first attempts haven't worked so well.

[2zero6]

+1 on the Vltor Emod stock and the Sig 556 mags. I have been using a Duostock but when I get some extra play $$ I will be getting an Emod stock. I Got a couple of the sinclair aluminum mag followers to use in G.I. 20 rounders but the blue plastic ones are cheaper and work just as well, except I havent been able to get the aluminum ones to run as well as the blue ones in the G.I. 30 rounders.

http://www.sinclairintl.com/product/5693/AR-15-Magazines-Followers


http://www.bushmaster.com/products.asp?cat=16

[talonxracer]

As far as the muzzle brake/flash hider goes the only commercially available unit that will fit the Bushmaster barrel's threading is the "izzy" brake from Bushmaster that comes on the barrel. You can take most any comp/hider and re-thread and open it up for the 450 round though, that is what I did.

[leroy]

Many thanks to all who have took the time to post. I really appreciate it. Does anyone know if the ejection port of the upper needs to be opened up? I seem to have read or imagined that somewhere. Let me know what you think.
Kind regards,
LEROY

[2zero6]

Many thanks to all who have took the time to post. I really appreciate it. Does anyone know if the ejection port of the upper needs to be opened up? I seem to have read or imagined that somewhere. Let me know what you think.
Kind regards,
LEROY

You are not imagining you read it, IIRC.

http://www.nrapublications.org/si/bigbite.html

The .450 Bushmaster cartridge is quite a bit fatter than the .223 Rem. and requires a widened ejection port. The feeding ramp on the .450 Bushmaster rifle is also enlarged to ensure reliable function.

Speacial thanks to YoteAddict for all his hardwork,clear photo's, and knowledge in the following information

threads on AR15.com :
http://www.ar15.com/forums/topic.html?b=3&f=121&t=386749

Here's an image of the upper receiver whose ejection port is widened. The forward half of the ejection top is wider than the aft half of the ejection port top. The standard dust cover is provided and even with the widened ejection port, the dust cover operates as expected.

http://www.ar15.com/forums/topic.html?b=3&f=121&t=398944

Originally Posted By AR-lifer52: First problem, they sent me a .960 gas block and the barrel requires a .750 gas block. You would think they would have assembled at least one barrel and should have known what size gas block!!! I had a Larue .750 gas block on hand so I used my own and returned the larger gas block for credit. The barrel assembly went together without a problem and fit nicely into my MGI upper. Dry cycled a round only to find the ejection port was to small to allow the 450 Bushy round to eject. Called MGI and explained the problem. I was told to send the upper back to have the ejection port opened and I should have it back in a couple of weeks. Again, you think they would have known the ejection port was too small if they had ever assembled one of these and attemted to test fire the assembly??? I have access to a milling machine so I opted to open the ejection port myself, which I did

[leroy]

Thanks Zero. That is just what i need to know.
Kind regards,
LEROY

ps --- Any thoughts on the best upper reviever for the 450; or does it matter?

[MudBug]

Thanks Zero. That is just what i need to know.
Kind regards,
LEROY

ps --- Any thoughts on the best upper reviever for the 450; or does it matter?

Just going on the fact that a normal upper will not work without modification I would have to go with a Bushmaster upper made for the 450b.

[YoteAddict]

threads on AR15.com :
http://www.ar15.com/forums/topic.html?b=3&f=121&t=386749

Here's an image of the upper receiver whose ejection port is widened. The forward half of the ejection top is wider than the aft half of the ejection port top. The standard dust cover is provided and even with the widened ejection port, the dust cover operates as expected.

It sure feels good to be 'quoted' not having to quote myself. Thanks for the post...