Finally got a .450 BM upper and magazines.

[MCMXI]

I ordered this .450 BM upper and extra magazines from Bushmaster about 14 months ago and finally received them today. I have a bunch of brass, 260gr bonded bullets, powder and primers and plan on working up a load to use on pigs and possibly deer. I have a BM lower with a Geissele trigger and a Leupold Mark 4 1.5-5x scope for this upper so it should be a good package. I'd like to put a suppressor on it eventually but I may need to have one custom built. I don't think the TiRANT .45 I'm waiting on will be able to handle the .450 BM.

 

[horsemen61]

that's awesome id love to see it all put togather

 

[MCMXI]

Thanks ... I'll need to do some research to figure out the ideal buffer weight to use with a collapsible stock.

 

[LeonCarr]

That will be a stomper of a rifle once you get it all together.

Really nice setup.

Just my .02,
LeonCarr

 

[MichaelK]

Aaaaaaah, I wanted that one!

 

[brian923]

Ive always wanted to play with this caliber. Looks awesome!

 

[Txhillbilly]

1858,Welcome to the world of Big Bore AR's.
I've been shooting a 458 SOCOM for several years,and it's the absolutely funnest AR in the world to shoot.
Out to 200 yards,they are very accurate,and are a sledge hammer on wild hogs,deer.

 

[MCMXI]

Txhillbilly, thanks. I shot a .458 SOCOM a few years ago and liked the results and consider the .458 SOCOM to be a great big bore AR cartridge too. I might have gone the SOCOM route if not for the fact that I got a great price on the .450 BM since I worked for Remington when I ordered it. I also have a truck load of brass and bullets for the .450 BM. I think this will be my last AR. I finally have the four that I "need" to cover just about any situation whether it's competition, self defense or hunting. I like the platform but not so much so that I want to acquire more.

 

[MCMXI]

I got around to assembling the .450BM this weekend. The lower is a BM that I bought about 8 years ago. The rifle has a Geissele SSA trigger, K&N anti-walk pins, a VLTOR EMOD stock, PRi BM latch, LaRue scope mount (SPR-E LT139) and a Leupold Mark 4 1.5-5x20mm M2 (SPR) scope. The rifle weighs 9.0lb with an empty 5-round magazine (shown). I found some .450BM dies in stock on Amazon that were cheaper than the out of stock dies at Midway. I'm not sure if I'll keep the aluminum forend or upgrade to an Omega rail from Daniel Defense to save weight. I do plan on ordering a roller cam pin from POF though and will need to figure out a good sling for hunting. I'm looking forward to sending some rounds downrange and have three boxes of Remington 260gr AccuTip to play with before I start to work up a load.

 

[MCMXI]

I noticed something today that I find a bit odd. The "gas block" forward of the hand guard isn't connected to the gas tube. The actual gas block is hidden by the aluminum tube. I have to wonder why it's there at all. If it had a provision to mount a front sight it would make more sense. Maybe it's plugged and there to seal a port in the barrel but that would be odd too.

 

[horsemen61]

Looks nice

 

[MCMXI]

Thanks .... any thoughts on the gas block?

 

[horsemen61]

Yeah I am not sure on that one maybe has to do with the fact that 450 is a bigger round no clue

 

[MCMXI]

I called Bushmaster today and the CS agent I spoke with had no clue as to why there are two gas blocks on the barrel. I sent an email to BM with a photo to see if they can provide a reasonable explanation but at this point I think I'll remove the set screws and slide the gas block forward to see if there's a port underneath. If there isn't I'll remove the gas block completely and may or may not replace it with a gas block with an integral Picatinny rail so that I can add TROY BUIS that I have sitting around.

 

[Arizona_Mike]

Your TiRant should be fine with subsonic loads (the pressure at the end of the barrel will be substantially less than .45 ACP with standard barrel length and that is a 10mm and full-auto rated silencer. The key is to find a thread adapter that will work with an available AAC TiRant 45 Piston.

Don't even think of using the TiRant with a supersonic load!!!

Mike

 

[MCMXI]

I assume the threads at the muzzle are 5/8-24 but don't know that for sure. I can check if I pull off the muzzle brake this weekend. I contacted a number of suppressor manufactures and AWC has the T.H.O.R. PSR model with a brake that would work well for super sonic use. They would make it work for a .458 caliber bullet so I could possibly use it on my Guide Gun but it's an expensive suppressor. Another option is to have a guy in Arkansas make one but he uses an all aluminum core and I'd rather have Ti or at least a stainless steel blast baffle. His suppressor would be a lot cheaper though.

 

[788Ham]

Mmmm, nice bacon slayer. That rifle ought to really put the smack down on them, like DRT ! Congrats !

 

[MCMXI]

788Ham, thanks. I finally got to shoot the .450 BM today and it's awesome! Recoil is midway between an AR-15 in 5.56mm and an AR-308 in 308 Win. The rifle ran great although we only shot 13 rounds between snow flurries, but enough to get the scope dialed in. I installed a new gas key (staked) and roller cam pin from POF on Friday. I decided to use an H1 buffer and Tubb spring and ejection is perfect with empty cases landing just a few feet away. The action is very smooth and rounds feed really well, so well in fact that I wondered if I'd get a click rather than a bang after pressing the bolt release. When I ran a .45 bore snake through the barrel prior to shooting I was impressed by the barrel finish. It looks to be chromed and appears to be polished to a mirror finish.

I removed the forward gas block and still have no idea why it's there. There are two dimples machined on the underside of the barrel where the redundant gas block was located. The threads on the muzzle are 24 TPI and probably 3/4" based on the O.D.

Overall this is one heck of an AR and I'm looking forward to better weather and working up some loads.

 

[MCMXI]

One final update, according to Machinery's Handbook and my measurements, the muzzle brake thread is 11/16-24 UNEF (not sure if it's 2A or 3A) so not an easy task to find a muzzle brake or flash hider to use with/without a suppressor. It's probably a good thing it's not 5/8-24 or else someone could/would thread on a .308 caliber flash hider!!

 

[wally]

The key is to find a thread adapter that will work with an available AAC TiRant 45 Piston.

Most also recommend a "spacer" to replace the spring when using a fixed barrel and a recoil boosted can.

Might also be able to buy a spare piston and have it bored out and threaded to match.

 

[MCMXI]

I installed a Daniel Defense 12" modular float rail and DD low profile gas block this week along with a VLTOR SASE-2 Enhanced Receiver End Plate for a single point sling option. The DD rail is considerably more svelt (feels really good), lighter, extremely rigid and way more functional compared to the DPMS forend. It weighs 11.75 oz which includes the barrel nut. I have two extra Picatinny rail sections that can be mounted if required (uses slots) and also have a set of TROY BUIS I could mount but I don't expect the Mark 4 scope to fail. I'll be shooting some Hornady 250gr SXT Flex Tip ammunition this weekend to see how well it shoots. I've read nothing but good things about that ammunition so I'm hoping for good results.

 

[Float Pilot]

That is how you turn an AR into a REAL home defense firearm.

 

[MCMXI]

That is how you turn an AR into a REAL home defense firearm.

It's a beast for sure and runs really well. Talk about a reliable rifle. I've had zero issues in the first 50 rounds and barrel simply doesn't heat up much at all.

I added TROY BUIS on Saturday which are mostly aluminum so don't add any significant weight and offer the advantage of somewhat usable sights in the event of a scope failure. The front post is way to thick for precision shooting at 100 yards since it's about as wide as an 18" target at that range. I'm going to look into a thinner front post. The Hornady 250gr FTX ammunition seems to shoot quite well. My friend shot the target shown below at 100 yards yesterday under quite difficult conditions with the sun quite low in the sky and directly in our faces. The POA was a dot 4" below the dot near the group. The scope is zeroed for Remington 265gr AccuTip ammunition so Hornady's FTX load shoots 4" high at 100 yards with virtually no windage correction required. We were shooting off a makeshift rest with the 1.5-5x scope set on 5x but even so, I'm fairly sure this rifle is capable of sub moa accuracy at 100 yards. All in all this rifle is AWESOME!!