Shot my 450 Bushmaster for the first time today.  It was raining on and off with very strong wind gusts today, probably 20-30 MPH, though they were mostly at my back.  I was using a 2.5 fixed power Leupold FX2 scope.  I replaced the Bushy trigger with a RRA 2-stage before shooting.

I shot two 5-shot groups with Hornaday 250 grain SST ammo at 100 Yards.  One group went 1.55", one went 1.69".

The accuracy is good enough I wish I would have put on a higher power optic so I could get a better idea what the gun is capable of.... my 41 year old eyes, a gloomy, rainy day, and 2.5 power magnification just weren't getting it done.  I may try again later with a 14 power just to find out.

The generous feed ramp cut was well done, and appears to have been done with a mill or some other machine tool.  The extractor appears to be a purpose built, unmodified  part.  It engages the cartridge rim to an equal depth for the entire length of the engagement surface.

The buffer tube spring doesn't feel noticeably heavy compared to a .223 spring - so it may be the same(?).  In any case all brass was thrown pretty uniformly about 6 foot to my right.

A modified 20 round magazine is used - it holds 5 rounds.  A single stack style follower is placed in the mag on top of an anti-tilt follower.  It appears the forward top corners of the feed lips have been cut back rearward about 3/16" - it looks like this was done by a milling operation before the mag was coated.  Otherwise the feedlips look unmodified - ie they don't appear to have been bent at all.  The quality of the work looks good.  The mag is pretty easy to load.

Function was great.  The brass came out without being chewed up on the rim, or anywhere else.

The thing thumps pretty good!  I was also shooting a .308 SOCOM 16 side by side with it today and the 450 felt to have twice the shoulder thump of the SOCOM.

Gong hits are definitive.

This is a really nice gun and I had a great time shooting it... I am seriously considering trading off a .223 or two to get another 450.  Time and round count will tell if there are any glitches, but so far it appears to me Bushmaster did a first class job with this project.

At the request of another forum member, I took apart the BM mag to check out the inside.

The blue single stack follower is placed on top of a standard Magpul no-tilt follower.  No adhesive is used.  I see no modifications to the Magpul part.

The spring inside the mag is odd... it is about 6" tall when out of the mag body.  The upper portion 4 3/8" looks normal.  The bottom 1 5/8" inch or so of the spring is about 26 wraps of coil bound wire - ie the the coils are touching and don't have any space between them to allow compression.  The obvious effect is that this serves as a magazine plug to limit capacity to 5 rounds.  I don't know how the spring rate compares to a normal 5.56 spring.

I just replaced the BM spring with a normal C Products 20 round mag spring and now the mag holds 7 rounds easily.  I don't know how the spring rates compare, but just by pushing up and down on the follower with my finger they feel about the same to me.

You got an old 30rounder? Put the blue follower in it and see how a 30rnd mag works.

Are you going to try to do some long range testing? I'm curious to here what kind of range it has.

Good review and thanks for the follow up!

I tried some 30 rounders with both GI and no-tilt followers and standard feed lips... they will hold 11 but it wouldn't be practical.

The curve of the 30's fouls things up.  The cartridge only has about .020" taper from the rear to front of the loaded case.  So as the 30 is filled, the rounds start to go nose up at the top of the mag, with no real uupward pressure at the base of the top cartridge.

It looks to me that 7 rounds will likely be the max practical in any AR mag, and a 20 can do that.  Though it seems to look good, I need to do some testing to verify good function with the C-Products spring and 7 rounds in the BM mag.

A C Products stainless straight 20 with their "modified" (cut-down) Magpul follower, the BM blue follower on top, and a little file & stone work to the feed lips to match the BM design might be  the ultimate set-up for a 7 round magazine.

I took apart a Cproducts 6.5Grendel mag, a 5rdr I think it was, and it had that same wierd spring setup, with about 1.5" of coiled spring, and then the rest normal spring.  It is wierd for sure, and seems to add un-needed weight.  I am sure there is some sort of reason for it I guess??  I can't rmember what people said when this was discussed previously.  ANywyas, so the 45Bushwacker has a single shot follower on top of a magpul antitilt follower and is not glued or anything?  Does the Magpul still have the raised section on the ttop, or is that ground flat?

The magpul looks unmodified.... just a standard 556 follower including the raised section on top.  The bottom of the blue follower appears to have been made specificly to set properly on top of a standard unmodified follower.  No glue.

Fox  - If everything works out I will probably shoot groups at 200 yards with a 14x scope on Saturday.

 is there any added advantages to the 20" barrel over the 16" barrel?  

congrates on your purchase.  i am really contumplateing this round for a build, in the next couple years.( money kinda tight.)

Thanks

Bushmaster told me they measured 2144 FPS in the 16" barrel and 2214 in the 20"..... so about 70 FPS or ~ 3% difference.

thank you.  looks like i  might be going the way of the 16".  i ve always like the look of the shorter barrel, and if its only that much differenace, i would never know the differnace.  thanks again, brian

I got a chance to try the rifle with more magnification (14 power) and at longer distance today.  The extra magnification was a huge help over the 2.5 power I used before, plus the weather was much better.

Wind was still, overcast, and temp was cold - above freezing, but cold.

100 yards
5 shots
1.125"

200 yards
5 shots
2.50"

again:

200 yards
5 shots
2.50"

.... and 3 for 3 gong hits at 100 standing with sling

Figure why not some pics:

Decent groups, hope I see the same(or better).

I just recieved my 16" 450 upper this past wed, ordered it with a lowprofile gasblock and rifle length FF tube. Added a Nikon Omega scope. I already put it on the bushy lower wMagpul PRS. Waiting on ammo now(tomorrow), should make a very versatile brush gun.

Weldingrod,

Thanks for the report.  Looks like the BM accuracy potential is gonna be perfect for the likely ranges for the rifle.  What I am gonna be real interested in is whether or not anyone will be able to duplicate factory ammo performance with handloads.  I have been kinda wondering whether or not Hornady is using the same technology as their leverRevolution ammo, namely powders not available to handloaders, for a little extra giddy-up.

If you have the chance, you might look at the Leupold 1.5-4 scope for your 450.  I use one on my 458 Socom, and I really like it.  It seems about the right size, and 4 power is usually plenty for 200 yard shots.

And good luck with the magazines.  I am not sure whether or not you will be hunting with your 450, and if you have mag restrictions, but I had to get creative with a couple of different versions of 556 mags for my 458 to keep things 5-round legal in Colorado.

Craig

very kewl....

now kill something with it...

Just for kicks I tried a standard 30rnd mag(with front of mag mod'd for 458) and it worked fine without the blue follower.

Here are some pics of the BM magazine and follower.

The mag with the orange follower is an aluminum C Products curved 20.  The mag with blue follower is the aluminum 450 BM magazine (also a curved "20").

You will notice the front of the feed lips on the BM mag have been cut back rearward.  Kind of looks like an end mill cut with the cutter being run crosswise across the top of the magazine - though I think that area could have been sheared out prior to forming the mag body. The opening between the lips measures in the ballpark with my other 223 mags... I don't think this dimension was altered.

You can see the blue follower is designed to sit on top of a standard follower.

You can also see how the coil bound spring functions as a 5 round magazine plug.

Just got mine the other day, now I have to make some time and go shot it.  Great review and info.... I put a magpul ranger floor plate in my 20 round 450 mag and now it only holds 4.  Oh well I like the ranger floor plate and if I haven't hit the animal I was aiming at with the first 4 probably not going to hit it with the last one either!

Heres some photos of mine. Not that great of photos though...
http://i27.photobucket.com/albums/c175/sigeq/450%20thumper/IMG_2442.jpg
http://i27.photobucket.com/albums/c175/sigeq/450%20thumper/IMG_2440.jpg