I got my first black rifle this month, a 16" 450 Bushmaster. I've been running the numbers in Quickload for several reloading options. I'm really surprised at how versatile this cartridge is.
230 grain FMJ ball at 2500 fps
250 grain factory loads at 2100 fps
320 grain RCBS 45-300-FN GC's at 1900 fps
415 grain RCBS 45-405-FN GC's at 1550 fps
I've been lubing and sizing 45-70 bullets to 0.457" and re-sizing them to 0.452" with no problems. Little Gun, H110, 4227, and 296 are the most suitable powders for full power loads.
I haven't had the time or energy to shoot up enough of the factory loads to get enough brass to work with yet and I'm surprised at how little felt recoil there is with a 250 grain bullet at 2100 fps. I shot a few 320's and 415's at full power and they were about the same as a Marlin 1895 45-70's loads in felt recoil at equal velocities but more of a push than a jab at my shoulder as the action absorbs some of the energy.
The FMJ full power loads will go through a telephone pole!
The .450 Bushmaster (parent cartridge is the 45 Professional) rifle/cartridge conversion, was developed by Tim LeGendre of LeMAG FIREARMS LLC., and licensed to Bushmaster Firearms International LLC., for production and distribution. LeGendre still retains ownership. The 450 Bushmaster is designed to be used in the standard M-16/AR-15 platform, using standard magazines.
Bushmaster asked Hornady to produce the 45 Professional ammunition for this project, Hornady agreed. Hornady wanted the 45 Professional shortened, to accommodate their Venerable 250gr., Pointed, SST bullet. Hornady asked Bushmaster for the change (1.771" to the now standard 1.700"), Bushmaster asked LeGendre to sign off on that change, and he did. Bushmaster eventually wanted a name change and LeGendre agreed, to what has now become the popular 450 BUSHMASTER.
Parent case is the 284 Winchester; Hornady's brass uses a small rifle primer for improved ignition characteristics. Groove diameter for the 450 Bushmaster is 0.450" and it shoots cast bullets well. Hornady ammo is loaded to 37-38K psi which is very conservative in comparison to the 45 Professionals working pressure of 60K psi. This cartridge headspaces on the case mouth like a 45 ACP does.
I'm using the RCBS 45-300-FN gas check bullet sized nose first with a gas check to 0.458" then lubed in the same die the normal way (lubrisizer) and resized nose first to 0.452". I'm shooting these 320 grain bullets at 2100 fps to develop over 3000 foot pounds of energy out of my 16" 450 Bushmaster Carbine. This load feels like shooting a 20 gage shotgun or a 12 gage with trap loads... surprisingly mild for that kind of energy.
IMO my 450 Bushmaster is one of the most versatile rifles I own with the ability to load it anywhere from mild to wild, and can easily handle any game in North America out to 200 yards. The 250 grain SST factory load routinely shoots 1" 100 yard groups from Bushmaster rifles. Hornady is making brass available now and introduced a new 300 grain SST bullet. By re-sizing 0.458" bullets to 0.452" including jacketed bullets the 450b can easily use bullets anywhere from 45 ACP 180 grain bullets to 405 grain 45-70 bullets... 230 grain FMJ's @ 2750 fps will go thru anything.
LeGendre's comments:
"Ok, let me be so bold as to think I might be able to offer some help and clear up some well meaning misconceptions concerning the 450 Bushmaster. First off, I have a strong background and experience with this cartridge. Fact-Hornady, does make some of their cartridges with their super powders. The 450 Bushmaster is not one of them. Fact-.451” SST Bullets are going to be hard to get for the near future, as all available bullets are going on loaded factory ammo, this is a hot seller. Ammo is available from Hornady direct or everywhere on the internet and can be shipped to you. Rifles are easy to find in the same mannor, shipping is different. Yes, SST muzzle loading bullets can be had, but this is an expensive option if you plan on shooting allot. Same for brass, but just get some 284WIN or 6.5/284 brass cut them to 1.700” -.003 and bingo, until others come on board, hint-Corbon, maybe. The FL resize can be done with a standard 284 fl-die and bullet seating and taper crimp with 45ACP dies, watch the bullet seater, the wrong one will leave marks on the bullet. Yes, if pistol bullets are used, designed to expand at range and 300fps, they won’t penetrate large game, so use bullets that will for crying out loud, this caliber has been around for 150 years, there are highly available bullets for every and any use, save the HP‘s for home defense, they wont penetrate anything but will leave a real mess if you shoot flesh. Fact-Hornady’s 250gr SST are designed for big game and magnum muzzle loader speeds, 2000-2200fps (Hornady’s 450b 2200fps+). Therefore, that bullet at much higher speeds, +500-700fps, would also under-penetrate big game because of over expansion. Fact-Hornady’s 450B loading, I believe, was held down so as not to over stress that bullet on Big Game. According to my strain gage test the Hornady loading is 38,000psi. The AR is stressed to well over 75,000psi. And the 460S&W factory “PISTOL” ammo is 60,000psi. Fact-200gr to 300gr bullets can be made to speeds of 500fps to 700fps faster than the 38,000psi loads and not exceed 60,000psi, all with our normal powders. Fact- the Barnes 200gr and 275gr bullet, that are made for the 460S&W, will expand and penetrate “EVERYTHING” at the same time and will fly at 2800fps and 55,000psi and a little more psi for the 275gr. If that isn’t good enough and more penetration is needed try the various 230gr FMJ’s at 3000fps. I like the 230gr FP-FMJ’s best of all, the FP disrupts more tissue than expanded bullets, fly straight through the body with no inter-body deflection off bones, which is all to common with expansion bullets and can result in non-recovered animals and best of all, the FP’s will kill “EVERYTHING”-“ANYWHERE”, with truly amazing aplomb. Just a little foot-up for ya all, just to get you started…"
The rifle comes with a 5 round magazine that's actually a 20 round 5.56 magazine with a single shot follower on top of the grey no-tilt 5.56 follower and a weird spring that limits the capacity to 5 rounds. My rifle will feed fine from the magazine with the single shot follower removed and will hold 7 rounds by replacing the spring with a regular 20 round magazine spring.
Regular 5.56 magazines will work OK, 20 round mags hold 7 rounds and 30 round mags will hold 10-12 rounds. Steel magazines with the no-tilt follower work best.
If your mags don't feed well add the single shot (blue) follower on top of the 5.56 follower.
LeGendre's comments about these pressures in the 450 Bushmaster:
"We normally load the 45 Pro to 60,000 psi with 230 ball or FMJ flat points my favorite. Yes, I know that the 458Socom and the 50Beo are loaded to the 35,000 psi area, but then again those great cartridges do not have the barrel thickness the 450b has in the chamber area. Here’s my example, a “Mountain Rifle”, bolt action weapon, chambered for the 284win case has a SAMMI spec in the area of 63,000 psi and has a barrel chamber diameter the same as the 450b. The other proof is Bushmaster told me that twice they loaded to these pressures and fired 6000 rds + each time with no ill effect and my friends and I load to these pressures and have done so for years, normally. So, why does Hornady load for 38,000 psi, as they have quoted? They tell me the Lawyers won or that they did not want to over stress their SST bullet, which is designed for magnum muzzle loader velocities of around 2000fps and would blow up on deer, like a varmint bullet would do, if you pushed them as we can actually do. My personal loads in the 450b, for the 250gr. bullet START at 2500fps and go up, but then who can afford those bullets, sold in twenty packs. I’ve tried the 200gr SST and compressed a load of 296 and achieved 2800fps, with only slightly flatting of the primers. If you need a pointed expanding bullet, Barnes makes excellent 200 & 275 grain varieties.
As for “Bolt Thrust” with these pressures (70,000psi +), Wayne State University’s Engineering Dept., in a published article, I forget which gun rag ran it now, actually ran “MEASURED” test, not calculated and found that at these increased pressures, the bolt thrust was just a little less that the .223 case and this because of a effect known as Bernoulli's Theorem, which basically tells us that necked cartridges have way more bolt thrust than straight cases and all the bolt thrust formulas are based on those necked cases, hence not at all accurate for the 450b. My Buddies and I have never seen a bolt failure and don’t ever expect to and we only use, what you might call, max loads, we don’t think they are but others might and we’ve never had a problem and together we have maybe a million rounds down range or certainly many, many, 100,000’s at least."
Like any other cartridge, some will load this one conservatively and some will push the limits. It's up to you to decide what feels right for your own comfort level and safety; however, you should shoot the rifle to experience the vastly different power pulse between a 223 upper and a 450b upper before making off the wall conclusions.
My personal experience with this cartridge in the AR platform has been similar to my experience with the 45 Colt... 320 - 350 grain bullets and enhanced performance levels can be achieved safely in modern firearms.
This information is presented simply as that, information. None of the load data presented by me in this thread exceeds Hornady's factory ammo specifications.
Finally had a chance to work some more with the Thumper and cast boolits. Got to thinking how much I liked Unique in my 45 Colt Blackhawk and Puma 92. Looked up some data for the 45/70 in the Lyman Cast Bullet Handbook and found loads with Unique. Started low and have so far worked up to 15.5 grs Unique. This isn't as much as the manual list for the 45/70 Ruger #1 loads but the 450 BM has less case capacity. This will not cycle the action (16inch BushMaster Arms 450BM) and will only occasionally eject the last round in the mag. To bad it won't cycle because I'm getting good initial results. Right at 1.5 inch at 50 yard with a red dot sight. Load seems real mild but I will probably switch to a slower powder to keep working up. Here's the load FYI.
Hornady case
Wolf small rifle primer
15.5 grs. Unique
Lee C452-300-rf, weighing 324grs checked and lubed
OAL 1.964
Average Velocity for only 5 shots, 1436 fps
ES 16 fps
SD 6 fps
With that kind of SD it's really tempting to work up to just cycle the action.
Stay safe,
Boomer
AR 15 450 Bushmaster (don't know where to put this)
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Originally Posted by Boomer Mikey
