New Build

Talk about the AR15 style rifles chambered in 450 Bushmaster.

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New Build

Postby Gary8907 » Sat Apr 21, 2018 2:40 am

I'm new to this forum and I hope that everyone will forgive my newcomer questions, but I'm not very good at doing forum searches so I'm sure that the answers that I seek are here somewhere but ....... My objective is to build a .450 Bushmaster rifle for my grand-son based on the AR-15 platform. I want to build the rifle from individual parts, so I have absolutely no interest in buying a complete upper receiver, therefore I'm looking for advice on what stripped upper receivers have the best track record, in the opinions of the forum members ? Along that same line what bolt/bolt carrier manufactures get the highest ratings, and of course what barrels receive the highest marks ? I have several stripped lower receivers, plus parts, in my inventory (New Frontier, Aero Precision, Seekins etc.) so unless I'm missing something, on compatibility, I think i have the lower covered. Thanks for your consideration and I'm looking forward to any, and all, comments.
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Re: New Build

Postby Bmt85 » Sat Apr 21, 2018 8:02 am

Any standard lower will work. As to mags, I prefer 450B specific mags, but I do have some converted 5.56 mags. Any big bore AR mags will also work. The most expensive is going to be the 450B specific and other big bore mags, while the 5.56 mag will be the cheapest. If you go the route of 5.56 mags, be careful of polymer mags. Some work, some won't. You also have to watch the feed lips on the polymer mags.

As to uppers, Any upper that will work for other big bore AR's (458 Socom, 50 Beowulf, etc) will work for the 450B. Most of the time it's a standard upper with the ejection port opened up. You can also do it yourself, there's info on the site. After that you have side chargers. Every side charger should work because they open the ports up pretty big on them, at least everyone I have seen. I have a Bushmaster factory upper, which is a standard upper opened up, I have a standard upper that I opened up using a dremel (not perfect, but turned out pretty good, honestly), and 2 side chargers used in my 450B's. They all work, and I have no preference either way.

There are several barrel makers out there, and this is where personal opinions really come into play. A few that have been used numerous times with good reviews are Tromix, Gryphon, and Satern. I have 2 Blackhole Weaponry barrels, and so far I'm liking them, still need to experiment though. Other options are GLFA, Windham, Faxon, and a few others I'm forgetting. It honestly depends on what you are trying to do; what length, profile, gas length, threaded or not, material used, etc.

Also when getting a barrel, some will come with a bolt, or it will be an option. If it's an option, I would opt for it. If the barrel doesn't come with one, you have a few options out there. Also any standard BCG will work, just swap the bolts.

There is a lot of information on this forum about builds and parts, so take your time and start reading.
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