It’s good you understand the terminal ballistics between bullet types, especially in this High Performance Cartridge. You are miles ahead of some so called experts. There was a highly regarded genius on another board who used a 50b, which primarily uses bullets designed for the 50AE, on a deer this year and posted his shocking pictures, with a pathetic story, that was picked up by PETA, who for a time used him as their Poster-Boy. Needless to say he horribly blew up (nearly off) the shoulder. The deer got away and was later dispatched by another with a 7mm Mag. Our hero thought the bullet just fell out, he had no understanding of what actually happened. A pistol bullet designed to expand on soft targets at range and say maybe 300fps, will blow up into thousands of little specks on big game at 1800fps+, with no penetration into the boiler room. To be sure the same thing can happen with the 450b, so choose bullets that will accomplish your mission properly. The opposite can also happen, bullets that are designed for thick skinned big heavy game and rifle velocities, will not expand at all on thin skinned deer, and are inappropriate for home defense, it is not wise to use some types .458 bullets that will take out elephants or Planes Buffalo on deer or other targets that may need an expanded bullet or no penetration at all. Which is why I say the 450 Bushmaster is the most versatile, AR-Big Bore on the market. Use pistol bullets when zero penetration is needed, like 180gr-230gr hollow points, which will not penetrate a common house wall reliably, sure don’t want to kill the neighbor’s dog now. Choose fmj’s when penetration is needed and Flat Point FMJ’s when penetration and tissue disruption is most desirable. As a note here, the FP’s disrupts more tissue than an expanded bullet does after it expands and the FMJ-FP penetrates any animal on this planet, killing elephants, Cape Buffalo or deer with equal ease. Keep in mind that 230gr fmj round ball bullets work well in big game too. Think of it this way, though that bullet won’t really expand, 45 cal is already bigger than a 30 cal gets after it expands, so shoot’em if ya got’em! If bigger heavier bullets are desirable, then buy them, they are available or get a Lee lube-sizer die set-up (about $30) and shrink down .458 bullets, we’re only taking them down .003” per side, two and a half times less than a standard human hair. I’ll take a soft lead lubed .458 bullet and use it to lube the die for every 5-10 jacketed bullets or use some Cast Performance .458/500gr bullets to lube that die and then you’ll have some really heavy bullets for plinking in your 450b, not necessary but fun and maybe quite useful. I often use 350gr .458 Hornady bullets, for fun, and do not experience any jacket separation at all in our hydro test or on the reported Buffalo that have been killed with this set up. In other words, it is possible to use .458 bullets in a .451 barrel, but 451-452 bullets in a .458 just does not work well, if hitting the target is the goal.
I can fill volumes with things I’ve been told and I do not know about the 454C problems you discuss (a call Causal might be helpful), but with no forcing cone on an AR and now millions of rounds of fmj’s through the 450b, I’d have less the zero worries about using the fmj’s in the 450b, in fact I recommend them for many applications. However, as stated above, using them in a 458 SOCOM will not work so well, bullet wobble down the barrel is the problem here.
Trim length is 1.700” plus .000”, minus .003”
Concerning your proposed 240gr/1680 starting load, Slash’s last load was 45gr of 296/H110- (their data is interchangeable) with a 240gr bullet, as I remember, as 1680 is going to lower the pressures for the same charge and extending the OAL to 2.250” will also drop the pressures and as 296 and 1680 have the same specific gravity, I’d start at 45gr of 1680 and work up, looking for pressure signs all along and stopping when necessary. But here’s a novel idea. I always like to know the max amount of powder the case is going to take when a compressed load is used, when developing a new load. I sacrifice a single case by drilling a 3/16 hole through the primer pocket. Then seat the desired bullet to the OAL of your dreams. Now, fill the cartridge through the new flash hole, make the powder flush with the base. Plugging the flash hole with your thumb and holding the bullet with your fore finger and pointing the case down, tap the cartridge with a kitchen spoon, many times. When you remove your thumb you’ll see the powder level has gone down. Refill again and repeat the process many times. The last time make sure the powder is again level with the base, now weigh this charge, this represents a slightly compressed load and should be the max the case can hold, with your chosen bullet. With some powders this will be of course way to much powder, but with the slower powders you may well get to this number in your developmental process. I hope I painted the correct picture here. I do this all the time, and as I’m not standing next to you, all bets are off, be careful. But here’s the goal, I wouldn’t by a Corvette to drive 25MPH, if there is performance to get I want it, but of course driving 200MPH has it’s dangers and so does handloading, be careful. One other warning, all powders, but most assuredly ball powders do have high pressure problems if undercharged…t
Now, the 450b is directly based off the .284win., and thus, turning or reaming should not be an issue, but what to do in the mean time? First, assuming you have full length resized and then trimmed to the factory standard of 1.700” (plus nothing, minus .003” and use the order given – resize and then trim), load a dummy cartridge and try the “THUNKING” test. Pointing the barrel down “drop” your reload into the chamber, it better have a decided Thunking sound when the mouth of the cartridge hits the end of the chamber. If it does not, take safety precautions and again full length resize and re-crimp, the reloaded cartridge; it’ll go “THUNK” now! Second don’t worry about squeezing the bullet a little in the resized loaded case; the bullet is a little over sized and the barrels are ever so slightly undersized and the dies (assuming they were made right) will not over crimp the bullet, so as to let the mouth of the case go pass the end of the chamber (remember we have the same set of problems with the 45 ACP). With that in mind put on a heavy tapper crimp, “NEVER any kind of roll crimp”, into the case, enough so the bullet is visibly dented, again don’t worry about denting the bullet, in fact you want to see a slight dent (you wouldn’t have to do this if you had the bullet sealing gum that Lake City uses, but normally we don’t, so not to worry). This will not affect accuracy at all and will assure proper bullet pull, and will stop any bullet travel, in the case, that can occur in the shooting/cycling process and still yield minute of angle accuracy and better.
Now, what to do about over pressure signs? It is very normal for under pressured cases to kick the primer out first, before the case releases, thus a flat or detached primer. It is my opinion; you may be very much under pressured. Randal gave numbers that say 35,000 to 37,000 psi are dangerous pressures (based on the program Quick Load), nothing could be further from the truth (no offence Randal, also none of the bolt thrust formulas are accurate either, more on that latter). 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.
My recommendations? Assuming you will take proper safety precautions and use great skill, use WW296 for the lighter 200 grain Barnes, which is a pointed-hollow point bullet and AA1680 for the Barnes 275 gainers, which is also a pointed-hollow point. But consider the Hornady 230 FMJFP, which the Flat Point will disrupt more tissue than an expanded bullet does. The flat point doesn’t really expand and will penetrate straight through an animal, as opposed to going squirrely, as is the case with many expanded bullets, on occasion, even to turning 90 degrees in side of flesh, been there, done that. Your loaded length of 2.1” is way short too, load the 230’s to 2.2” (but not much more, you still have to hang onto the bullet) or longer and the pointed bullets to 2.250”, max is 2.260″, but you do need some clearance in the magazine. AA1680 & 230’s will increase your speeds and lower your pressures and still yield 2800fps, which is more than enough for any animal on this planet, if FMJ’s are used. In fact this combo has twice been to the Cameroon’s and has dispatched Cape Buffalo and Elephant, with reported ease. Keep in mind that this is with a version that is .070” longer, the 45 Professional. The standard 230gr hollow pointers are cheap and because of these highly increased speeds just explode on anything, making them good for home defense.