450Bushmaster.net

Hello members,
Newbie from Michigan here with some questions. I am wanting to build a Bushy upper. I have a Mega Arms upper/lower billet from a previous 5.56 build. Has anyone built a 450 upper with a MEGA Billet Side Charge Upper? I am wanting to purchase a Mega side charge billet upper (https://www.rainierarms.com/upper-mega- ... ing-upper/) as I know it will mate up with my existing Mega lower. It looks like the port would be large enough from a side charge upper, saving me from modifying the ejection port. I also have other questions, like barrel length (was thinking 18"), gas port location (was thinking mid length), adjustable gas blocks, which BCG to use, and do I need a barrel with threaded end for a brake or a target crown? I will be using this for hunting southern Michigan. Max shot 200 yards. I will be reloading for this rifle as I already have reloading equipment for many other rounds. Thanks for any input.

Don't have actual dimensions, but the opening on the Mega side charger looks to be much bigger than a standard ejection port, so it shouldn't be a problem. I am a HUGE Mega fan, unfortunately they were bought out by Zev. Well, they say merger, but looking around online at Mega parts availability, a lot is already phased out. I was looking at there standard billet uppers the other day, and only a couple places still have any. So, I have 2 billet uppers (that I didn't plan on buying right now!) that are currently being shipped to me. If you want anything Mega, get it NOW!

As to barrel, length is a personal preference, and you do gain a little bit going over 16" (about 100fps difference between 16" and 20" barrels from same manufacturer). A midlength gas system is a good all around choice for 16"-20" barrels. If you want to run a muzzle brake or comp, then get a threaded barrel, if not, then get a target crown. If the barrel your looking at only offers threads, and you don't want a brake, then either run a thread protector, or take it somewhere to have the threads cut off and recrowned. I will say this though, I recently went on an Elk hunt (cow cull tag) with my 18" Tromix wearing a Ross 4 port comp, NOT fun when in a ground blind with no hearing protection! I stuck that muzzle as far out the window as possible, and I still didn't get my hearing back to normal for over a week. The Ross brake is very effective, and very nice, when wearing hearing protection.

You can run an adjustable gas block or you can add weight to the system, if it's needed. I went with adding weight (Slash's XH buffer) and haven't had an issue, but either way should work.

A standard bolt carrier and 450 bolt is all that's needed.

Forgot something. If your taking 200yd shots for hunting, you have a few options for bullets. My suggestion would be the 275 TSX. You don’t need that much weight for deer, but it has an opening velocity of 1200fps. Even in a light load, it will still open at 200yds. Some of the newer bullets should work, but haven’t been really tested.

Thanks for the reply. I did not know Mega was bought out/merger. I have a couple AR's built on their platform, and I really like their parts. I think I will purchase their side charge upper. I now need to find a quality BCG. What are the thoughts of the Eisenach side charge Bolt Carrier? (https://eisenacharms.com/collections/ar ... lt-carrier) I know there are others, but I'm just starting to look.

welcome aboard!!

It will work fine, I had a barrel on mine just for function test a couple years ago, plenty of room for cases to kick out. If you need exact measurements I can do that tonight.

18" barrel a good choice, there are some good barrels out there, bud has a Gryphon that's a bug holer, just stupid accurate with everything we've tried. He's running a standard gas block, dumps cases 4:00 and 3' out. He's also using a Ruger brake which works good, not quite as good as a 3 port Ross thou.

Thanks for the replies. I currently hunt with the savage 220 slug gun, which is a very nice setup. I have ventured into the AR field quite a few years back and built quite a few. I had a friend at work remind me that the 450B was legal for deer, and now I have that itch!! I think my friend did that on purpose, as we all know what its like to get that ITCH. The good news is, I reload for the 454 Casull and have a stockpile of Hornady XTP bullets ready to reload, just need some brass and dies. I may have to get some 275g TSX Bmt85 mentioned.
Another question though, can I still run the charging handle even though is is a side charger, or does it not matter to fill the hole at the top rear of the receiver?

Yeah well aware of what it’s like to have BRD (Black Rifle Diesease)!
Eisenach bcg should work and I’ve heard good things about them. I personally would go with that or a Young’s.
You shouldn’t have to use a charging handle, but it might help if you get a lot of gas in the face. Don’t know if you will or not.

Well I pulled the trigger( sorry for the pun, couldn't resist) on a the parts for my first 450B upper.
Mega Arms side charge Billet upper, this will match the existing lower of my custom Grendel build.
Mega arms 12.6" wedgelock matching handgaurd.
Tromix 18" barrel and bolt,1:24 twist, mid gas system, thread protector until I research brakes, if I even need one.
Basic gas block, I have adjustable blocks on my other builds, but not sure if I need it on the 450B.
Eisenach side charge bolt carrier.
I have an older Vortex Scope I will be installing for now.
I'm excited to get the parts and assemble this newest addition to my collection.
I bought a 5 round factory magazine as this will be used for hunting S Michigan.
I bought 2 boxes of factory Hornady ammo that I plan on breaking it in with.
I also bought some dies, powder, and bullets to reload this round, and I will be in the reloads section gathering much of the excellent knowledge there.
Are there any suggestion for me, as this is my first venture into the 450 world?

msd4141 wrote:Well I pulled the trigger( sorry for the pun, couldn't resist) on a the parts for my first 450B upper.
Mega Arms side charge Billet upper, this will match the existing lower of my custom Grendel build.
Mega arms 12.6" wedgelock matching handgaurd.
Tromix 18" barrel and bolt,1:24 twist, mid gas system, thread protector until I research brakes, if I even need one.
Basic gas block, I have adjustable blocks on my other builds, but not sure if I need it on the 450B.
Eisenach side charge bolt carrier.
I have an older Vortex Scope I will be installing for now.
I'm excited to get the parts and assemble this newest addition to my collection.
I bought a 5 round factory magazine as this will be used for hunting S Michigan.
I bought 2 boxes of factory Hornady ammo that I plan on breaking it in with.
I also bought some dies, powder, and bullets to reload this round, and I will be in the reloads section gathering much of the excellent knowledge there.
Are there any suggestion for me, as this is my first venture into the 450 world?

Nice build component list. Just an observation unrelated to your choices. After the obligatory 223 build, my first serious AR rig was the 450b. The next was a 24" ER Shaw barreled, Grendel. Tossing a 123gr Hornady AMAX bullet, the Grendel recoil is on par with a 450b squib load.

Off Topic: My Grendel is the most accurate AR upper I have. It will put 5 of my 123gr AMAX pet load shots at 100 yds, into a single 450b bullet hole. Loves Lapua brass.

Hoot

My first AR build was a mix of parts, because back in 2010 parts were hard to come by. That was a JP 223 barrel in a VLTOR upper. I then put together a Mega Arms matched upper/lower billet with a JP 6.5 grendel barrel. I have not had much time with that gun as of yet. I used an adjustable gas block, and I was having issues with the cases getting stuck in battery. I was also seeing some signs of pressure, even though it was factory Hornady 123 Amax. I opened the gas a bit more and it does cycle, but I think I need to put more rounds through it to smooth things out. I'm hoping that it will be a decent shooter.