BenchMark built custom 450 Ultra Magnum.

[high country]

I did a ton of research on brakes after my second shoulder surgery. What I found is at least 2 holes over caliber at at least 90* to the bore and a reasonably tight muzzle hole was the most efficient with regards to recoil and eating muzzle blast. Adding holes was a diminishing return....but effective. Muzzle clearance played a role also. I think you will be much better off.

[yorketransport]

The Muscle Brakes are good stuff. I have a 3 port on my 338/375 Ruger pistol and I'm having a 4 port put on the 375 RUM improved being built.   

If you haven't already, you may want to consider having top ports milled into the brake. The can make a pretty big differance in shooting comfort. Recoil can be fun, but being beat until you bleed gets old fast.

Andrew

[Biggerhammer]

The Muscle Brakes are good stuff. I have a 3 port on my 338/375 Ruger pistol and I'm having a 4 port put on the 375 RUM improved being built.   

If you haven't already, you may want to consider having top ports milled into the brake. The can make a pretty big differance in shooting comfort. Recoil can be fun, but being beat until you bleed gets old fast.

Andrew

Got it covered Andrew, just after I sent the barreled action out. I called and talked to Chris at Benchmark and he said theY would also add ports to the top of the brake.

I don't see how much you can really " Improve" a .375 RUM case considering it's shoulder angle already. Unless you are moving the shoulder forward and removing what little case tapper that is left. There wouldn't be but a small fraction of powder capacity gain.

[yorketransport]

Got it covered Andrew, just after I sent the barreled action out. I called and talked to Chris at Benchmark and he said theY would also add ports to the top of the brake.

I don't see how much you can really " Improve" a .375 RUM case considering it's shoulder angle already. Unless you are moving the shoulder forward and removing what little case tapper that is left. There wouldn't be but a small fraction of powder capacity gain.

That's pretty much what I did. Standard AI treatment with the 40 degree shoulder and minimal body taper, and then pushed the shoulder forward about .13". The increase in actual case volume will only be about 8gr. The biggest gain will be from extending the throat by .4" allowing me to seat the bullets (350gr Sierra MK) way out there so that they aren't taking up powder capacity. The rifle is going to be setup as a single shot, so OAL isn't an issue.

Honestly, it will be closer to a 375/404 improved since I'll probably use 404 Jeffry brass instead of RUM brass. The RUM brass needs to be necked up to 40 cal and then back down to 375 to create a false shoulder and fireformed. The 404 is just a neck down and fireform.

Andrew

[Biggerhammer]

The longer throat is great, I run 102 gr of IMR 7828 in my .375 RUM with a 260 Accubond and it flat crushes stuff at 3050fps but it's a compressed load because the bullet has to be seated so deep to fit in the mag box on a Rem700. The 350 Sierras should carry real well.

Check out buffaloarms.com , they have BELL .404 Jeffery cases, quality stuff for a buck a piece. They are cool, they have no headstamp. I picked up a bunch to use in my 450 Ultra , they are heavier than the Rem brass. The necks are so long and the brass so heavy I'm afraid of crashing my full length 450 die if I try using it to neck them up like I do with the .375 RUM brass. I'm waiting on a #41 shell holder from RCBS(Doesn't use the same shell holder as the RUM cases) then I think I'm going to fire form ten or so by using 18gr of Bullseye then some tissue packed on the powder, fill the case with cream of wheat, then a bit more tissue to hold it all in. Stuff it in and pull the trigger. bam!! Instant 450 ultra case. Load them up and see how they shoot compared to the Rem brass.

Here is a recovered 260gr Accubond that I took from a Eastern WA Mulie shot at 560 yards with a 375 RUM. He was faceing me head on down hill, I hit him center of the chest and found the bullet just under the hide near the pelvic bone.




My next build I'm having Benchmark do is a 6.5 Badger, a .338 RUM necked down to 6.5 with a 40 degree shoulder.

450 Ultra case left, 6.5 Badger "Go" gauge center and PTG 6.5 Badger reamer on the right.
No turn neck, 150 Free bore 1-30

[demontang]

Man wish i had the money to play with guns like that

[CAMPMEAT]

Who is your therapist ? Self torture comes to mind......
Beautiful " I want it gun ".

[yorketransport]

Check out buffaloarms.com , they have BELL .404 Jeffery cases, quality stuff for a buck a piece. They are cool, they have no headstamp. I picked up a bunch to use in my 450 Ultra , they are heavier than the Rem brass. The necks are so long and the brass so heavy I'm afraid of crashing my full length 450 die if I try using it to neck them up like I do with the .375 RUM brass. I'm waiting on a #41 shell holder from RCBS(Doesn't use the same shell holder as the RUM cases) then I think I'm going to fire form ten or so by using 18gr of Bullseye then some tissue packed on the powder, fill the case with cream of wheat, then a bit more tissue to hold it all in. Stuff it in and pull the trigger. bam!! Instant 450 ultra case. Load them up and see how they shoot compared to the Rem brass.

My next build I'm having Benchmark do is a 6.5 Badger, a .338 RUM necked down to 6.5 with a 40 degree shoulder.

450 Ultra case left, 6.5 Badger "Go" gauge center and PTG 6.5 Badger reamer on the right.
No turn neck, 150 Free bore 1-30

I have about 50 pieces of Norma 404 brass sitting around that I grabbed from the Bargain Cave at Cabelas a while back. They were marked down to $80 because they had been repacked, and I had a bunch of Cabelas points on the card which I cashed in. The way I see it, the brass was free.  I've tried necking down a few of them and it's much nicer than forming the RUM brass. Once the barrel shows up I'll get to fireforming with the same recipe you're using.

The 6.5 Badger sounds pretty cool as well. Are you going to have the barrel Nitrided or treated in any other way so that you get more than 300 rounds out of it before the throat is gone?

Man wish i had the money to play with guns like that

You may be surprised how reasonably you can build stuff like this. A custom reamer is only about $150, but often you can rent them for around $40. I do most of my builds on Savage actions, so all I need is somebody to thread and chamber the barrel, and I'll install it myself. The cost of rebarreling a Savage can be anywhere from $200-600, depending on who does the work and what barrel maker you use.

Granted, you can spend a lot of money in a hurry. Look at BiggerHammer's build. It's a high quality setup, built by the guys at Benchmark who really know their stuff. It's probably safe to say that it didn't come cheap, but it's a one of a kind gun. That alone can be worth a good chunk of money.

[demontang]

Yea I have a few builds like to do but just no money to do it. Ok I have a lot of builds I would like to do

[Hornseeker]

Holy Crow is right! Wow! That is a Beast of a Gun!

My daughter is going to be highly undergunned after elk with her 243 this year!!!!!         

[Biggerhammer]

UPS delivered my rifle back from Benchmark with the brake up grade, took it for a test drive today and the difference in recoil as compared to the original brake was reduced quite noticeably. As always Benchmark did a buetiful job on the installation and machining a extra top port and custom tension set screw.

[demontang]

  Wish I could take that kind of recoil my back wouldnt take it

[yorketransport]

The set scew is an interesting idea. This prevented them from needing to recut the muzzle threads to index the brake correct?

Andrew

[Biggerhammer]

Yes, so they didn't have to chop a inch off my barrel. But they did the brake perfect , so it indexes up perfect just touching. Then you set the screw.

[high country]

Is the new brake threaded larger than the old one? I am lost on the set screw.