Does anybody have the dimensions for this cartridge? It's a necked up 375 Rem Ultra Mag to accept 416 bullets. Curious how close it is to the 416 Dakota for interchangeability of brass and ammo purposes.

Thanks!

Never heard of it.

But in my 416 Dakota, RUM brass wouldn't work. The area in front of the rim was just enough bigger to not fit, and wouldn't resize down. Hornady 404 brass would work.

That was with Redding dies and a chamber cut with a Manson reamer, IIRC.

Strange you should mention this. I was just thinking about the Dakota and maybe digging the barreled action out of the safe and giving it another go!

Details on your build setup? Whose action? Always enjoy learning about similar caliber setups!

It be pretty near a Rigby.

Mine is a Winchester Model 70 action paired to a 25" Lilja Pre'64 375 contour barrel. Williams bottom metal and a barrel band sling swivel.

Unfortunately, while I was gathering the parts, dies and reamer/guages Dakota quietly discontinued the cartridge! I think I got the last three boxes of brass Midway ever had and Dakota sold all their brass to a custom reloader. So while I was waiting on someone to make up some properly headspaced brass, it got shoved to the back of the safe and other projects called. I have 416 Remingtons and Rigby so it wasn't a real priority!

Hornady claimed 2600fps was possible for a 400 grain bullet and Ross Seyfried claimed H4350 was "the" powder for it, but I think he stopped at 2500-ish fps. Personally, I was looking for a 350 grain TSX at or near 2600. Which it should do, since the 375 RUM will drive a 350 TSX at 2500 and change.

Interesting cartridges mentioned. The type of stuff that quickens a wildcatter’s pulse rate and launches an immediate need for a new rifle and associated paraphernalia.

However, a well loaded 404 Jeffery, with RL-17 - which I prefer over H-4350 in this class of cartridge because it can result in higher load densities and velocities - will produce 2524 fps chronograph velocity @ 15 ft, with a monolithic solid in a 24” barrel. I use one less grain than that in my hunting load for 2491 fps. Easy extraction and good case life.

Using practice loads with 375 RUM cases formed in one pass through the FL die - laid in a supply when they were fairly easily available - works well. Advantage is the relative ease of available reloading supplies and equipment for the 404 J, as well as Hornady and custom reloading outfits’ loads, albeit at a pretty penny, for the well heeled non-reloader are also out there

If justification as a ‘wildcat’ is needed, this is not the original 404 J - 400 gr bullet @ 2150 fps - which effectively killed thousands of elephants but the modern rebirth of the cartridge. There is that!

I am actually in the process of building a 416/375 RUM right now...just waiting on my dies from Redding so I can load up some dummy rounds to send to my smith. Main driver for my project is that I am a lefty and things get more expensive/less available when you move up from a standard 3.6" action to something built for Rigby length. So I have a LH Model 70 CRF action that was in 300 Win Mag that will get rechambered, and rear bridge opened up.

Building with the 350gr Barnes TSX/TTSX in mind...I know 2700fps and some change is reachable with RL17 so it should be a fun project.

I'm getting 2715 FPS TSX in my 416 Remington with 93 grains of 2000MR. You should be able to do better than that

Sort of getting back to the roots of the RUM line. except of a 416 instead of the original 404 (0.423”) Jeffery case.

Now, this seems like a finishing reamer away from a shortened-neck 404J case conversion for a Win M-70 416 Rem Mag. Not even the need to open up the bolt face in all likelihood.

Wildcatter rifle loony type of stuff!

Looking at case dimensions, I don't believe a 416 Remington can be reamed to 416-375 unfortunately.

As an update on this project, I've acquired 180 pieces of 416 Dakota brass, reloading dies, and a 300 RUM Montana 1999 action that nobody seems to want. If that 1999 action doesn't sell soon, it's going to get rebarreled. Looking at some load data posted a while back from JE customs, it looks like 2850 with a 350 grain is possible. With a sharp pointy CEB or similar, that should be quite the hammer.

I'm interested in your 416 Dakota brass at a reasonable price.

I built a .404J on a .300 RUM action. Liked it, but ultimately traded it.

The fatter RUM based round needs a RUM action, or a RUM mag with some action tuning for those rounds in a std 3.6” mag action.

Worked with good bud’s .416 Rem on a M-70 action. To me those are easier to get to feed smoothly and if building another, would probably go .416 Rem.

Plenty of power for cape buff or about anything.

Bullet selection may be more important than the specific round. Of course, rounds in the same class.

DF