500 B&M & 458 B&M EX
Currently, I don't recall exactly when I decided to proceed with an in between cartridge, between 500 MDM and 50 B&M, but based on the same RUM case. This case is 2.5 inches, and resembles a shortened 500 MDM.
But for what purpose you ask? 500 MDM and 50 B&M have proven themselves over and over in the field, and both these .500s have desirable traits in the field, so how could it be possible to improve on either? In all reality the new 500 B&M cannot improve on either 500 MDM or 50 B&M within their respected domains. It only offers an interesting project, with some attributes that might be desirable in some cases.
At 2.5 inches, the 500 B&M does in fact give some higher performance than the 50 B&M, but of course not as much as the 500 MDM, so it does indeed fall in between. As a stand alone cartridge it has proven to be as good and valuable as the other .500 caliber B&Ms. The difference is in the action. For this cartridge I use the longer Winchester M70 RUM action, same exact action that the 500 MDM is designed for. At 2.5 inches one can load the various .500 caliber, long nose projection Raptors, and add the Talon Tips. These loaded rounds, fit, feed and function from the magazine. The Talon Tips added to these bullets buys one an additional 100-125 fps IMPACT at 50 yards, a very distinct advantage over either the 50 B&M or 500 MDM. While the 500 MDM might start out a bit faster than the 500 B&M does, by the time they reach 50 yards that gap has narrowed, simply because of the added Talon Tip increasing the BC. Naturally the 500 B&M is an increase over the 50 B&M.
The 500 B&M that I built uses the larger Winchester RUM action, but the same barrel contour as the 50 B&M, and I did go with 18 inches of barrel as well. This makes the 500 B&M just slightly longer than the 50 B&M, and about the same weight, maybe a few oz more.
I did not, and do not consider these two cartridges standard B&M cartridges, with their own menu pages. More of a speciality cartridge, and something for me to explore.
I wanted a special stick of wood for this gun, naturally Wes at Accurate Innovations handled this for me. He picked an excellent stick of Bastogne out of his back room for me. This stock had to have special dimensions, since it was neither a 500 MDM or 50 B&M, but a mix of both.
I also elected for a matte black GunKote finish, and standard B&M specs such as the NECG Barrel Band front sight and matching rear adjustable, standard on all B&M rifles.
I also elected for an upgrade in checkering as well.
The rifle really turned out very pleasing, it handles great, shoots great, and its performance is very pleasing. The cartridge proved rather easy to load for, and like its bigger brother, the 500 MDM, it favors many of the same powders, such as IMR 8208, H-4895, V-N530. It also performed very well with H-322, X-Terminator and the current version of RL 10X.
This cartridge starts to get very serious with 450 gr bullets. With V-N530 and H-4895 it can safely run 450 #13 Solids over 2400 fps, and that matching 410 Raptor at over 2500 fps. Adding a Talon Tip to this 410 Raptor makes it a serious bullet capable of taking on buffalo with ease. The penetration of the 450 #13 Solid is very capable of handling the largest of beasts, elephant and hippo, buffalo from any angle.
The heavier combination 500 #13 Solid and Matching 450 Raptor comes in respectfully at 2250 fps and 2350 fps. During this time I also had CEB make some 525 gr #13 Solids, the 500 B&M can run those to over 2150 fps. I have good solid data below, feel free to download.
In June of 2014 I took the 500 B&M to Zimbabwe. This Safari was my son Mark David's first Safari in Zimbabwe, so I did hardly no shooting. It was more my job to back Mark David, but his shooting was superb with his own 475 B&M Super Short and I never fired a round in that role.
I had loaded the 410 Safari Raptor at 2500 fps and backed with the matching 450 #13 Solid at 2400 fps. One morning we came across a herd of buffalo near the village and decided to take a large cow with the 500 B&M. The first shot, 410 Raptor, hit the buffalo left point of the shoulder quartering to me. The hit was absolutely devastating, nearly knocking it off its feet.
The only thing the animal could do was turn around 180 degrees facing the other direction, dead broadside to me, as it started to go down I had committed to a second shot with the 450 #13 Solid. I did not know it at that moment, but there was a 8-10 inch diameter tree that got between me, and the front shoulders of that buffalo. The bullet hit with such force that it knocked a huge section of the bark completely off the entrance side, continued dead straight through the tree, striking the buffalo square on the right shoulder, and then proceeded to completely penetrate the animal exiting the left shoulder, all dead straight line penetration! I was totally amazed at this level of performance with both bullets, the 410 Raptor and of course the 450 #13 Solid. We recovered the "Blunt Trauma" remaining bullet from the 410 Raptor after over 3 feet of penetration, including busting bone on the left point of the shoulder.
Currently there are only two 500 B&M rifles built, mine, and good friend, and B&M enthusiast Russ Green has the other. At some point Russ changed out his 500 B&M with a lesser caliber and I ended up with the 500 B&M barrel. I decided to have a second gun built, and once again wanted a very special stock for it. Just so happened that Wes had an extraordinary Myrtle blank on hand. It turned out to be one of the finest, if not the finest rifle I ever owned. I have since become a very big fan of the 500 B&M, even over the 50 or the 500 MDM. There are some advantages to this, one is brass, brass can be made from any 300 RUM brass, including the superior Norma brass. A very big advantage over the 500 MDM that requires 375 RUM, of which none has been available for years now.
As for the 458 B&M EX...... The EX can be "Extra".. HEH or "EXPRESS" or anything else you want it to be. I had to come up with something to separate it from the 458 B&M. One day I was forming 500 MDM brass, and bored. With too much thinking and being bored, I decided to do a 2.5 inch 458 version to match the 500 B&M. At the time of this decision, I was very pleased with the performance of the 500, so why not do a 458 as well.
This rifle is in the works as I write this. Circumstances left me with a spare English AI Stock, a very nice one. This stock was built for a 500 MDM, and I have decided to use it on the 458 B&M EX. For the rifle to work with this stock I had to go with a 500 MDM barrel contour, which is slightly heavier than the 500 B&M or standard B&M contour. This will add about 6 oz to the rifle overall. If any other 458 B&M EX rifles are built, they would be built on the smaller contour barrel. This rifle will sport a 20 inch barrel, with all the standard B&M features. Once rifle and dies are completed I will go to work on load data at that time. Stay tuned, this should be an interesting 458 caliber cartridge and rifle.
I received the 458 B&M EX a couple of months ago, and have been busy and at least have some load data started.
The rifle turned out very nice, maybe about a 1/2 lb on the heavy side because of the heavier contour barrel. With its 20 inch barrel is is giving 458 Lott velocities or slightly better with 450 gr Bullets. With the incredible performance of the 450s, there is just no reason in the world to work with anything heavier. At this point we are running 450 #13 Solids at 2440 fps and under maximum pressures. Work just started with the matching 420 Raptor.
I will keep this updated as I get data completed.
After the initial 2015 test work was completed, I basically became bored, and moved on to work on other projects, leaving the 458 B&M EX. Until 2020, when I decided to get many of the big bore rifles up and running, with loaded ammo on the shelf. This is when I really became more interested, and more enthusiastic about the 458 B&M EX. I had a lot of left over bullets on the shelf, that would not be used in anything else, such as the 480 #13 Solids and 425 Lehigh brass HP's. I put these two to work for Shelf Ammo in the 458 B&M EX. Incredible results running the 480s at 2370 fps and the 425 Lehighs at over 2500 fps, both to POI at 50 yards. And, once again, 458 B&M EX brass can be made from any 300 RUM, including Norma, which gave even better results by around 40-50 fps.