375 ultra mag

[biff's reloading]

For any case capacity, theres an ideal bore size for the intended use. Find the capacity of your case in grain of water, and divide It by bore area in inches. This gives you an "index" to compare to. A 3006 has capacity of 68gr. Bore area (pi x r2) is .0745". 68/.0745= 913. 300wsm is 1025. Theres a sweet spot around 1000. Cartridges in this range tend to be excellent all around guns. Not super mags, but better terminal performance than many of the lower scaled rifles like the 308win(750). The 300rum is a fantastic Round, but relatively Inefficient Use of 100+ gr of powder. Its output in ft-lbs per grain of powder is pretty low. Neck that case up to 375 and you have a real winner in terms of efficiency and Terminal effect. 375rum is right on the money at 1050 on this Scale. Right next to lots of the most loved Cartridges for their ability to punch above their weight class. 270win, 22-250, 300wsm, 338wm, 260rem, and 280ai etc. Its a 270win times 2. It really doesn't get much better than that. Take most any 270 load data and double it, and you have 375rum data. 130gr load in a 270 is half of a 260gr load in 375rum, and they fly the same speed with about the same ballistics...but the 375 is also able to cleanly take double the animal size.

once you start doing the math and ignoring the opinions of people, you realize what your rifle is actually capable of, and what it's not. Compare this bore ratio to other "favorites" in whatever class of cartridge you are looking to run with. the cheytac is revered for it's long range ability. It's at 1150 or so. So is 338lapua and edge. Any cartridge near 1100 can be built to run with those guns. A bit over, like 7mm magnums Or 300rum are good too, but a bit under doesn't lose much speed and you get a few hundred more rounds of barrel life in the trade. The 375rum is just on the heels of a 408ct in terms of bore ratio (ability to toss lead), and with these new high bc bullets designed for bigger case 375's, it's got real elr reach equal to and beyond many established long range cartridges... and it does it in a rifle package that can be purchased affordably and easily carried anywhere. It's in a special overlapping gray area between average hunting cartridges and elr cartridges like the ct and I can only imagine more n more guys will be building them as these new bullets release.

Its funny to think of a 375rum as a general purpose hunting rifle, but that's really what it is. It's just "more" of it per shot. I shoot everything From woodchucks on up with mine. Theres not many critters on earth you'd need much more gun for.

 

[Taylorbok]

For any case capacity, theres an ideal bore size for the intended use. Find the capacity of your case in grain of water, and divide It by bore area in inches. This gives you an "index" to compare to. A 3006 has capacity of 68gr. Bore area (pi x r2) is .0745". 68/.0745= 913. 300wsm is 1025. Theres a sweet spot around 1000. Cartridges in this range tend to be excellent all around guns.

Its funny to think of a 375rum as a general purpose hunting rifle, but that's really what it is. It's just "more" of it per shot. And I prefer "Most"

I've never seen this over bore calculation before. I like it.

I think we have different ideas of a general purpose hunting rifle.
390gr projectiles going north of 2800 is gonna make for a sweet ELR rig on the cheap. Just gotta burn up this barrel and these bullets so I can justify it.

 

[biff's reloading]

I've never seen this over bore calculation before. I like it.

I think we have different ideas of a general purpose hunting rifle.
390gr projectiles going north of 2800 is gonna make for a sweet ELR rig on the cheap. Just gotta burn up this barrel and these bullets so I can justify it.

I definitely don't mean to be shooting Atips at 75 yard whitetail. but 270gr speer or 260ab do a great job of it. With a 10 twist, it can do both.

 

[Chase723]

I definitely don't mean to be shooting Atips at 75 yard whitetail. but 270gr speer or 260ab do a great job of it. With a 10 twist, it can do both.

But you could…and it would be emphatic! Lol. All kidding aside, what I really love about this thing is that it provides a pretty incredible level of performance without a lot of the muzzle blast, concussion, recoil and cost that is found in something like a 33 or 37XC. My buddies have 33XCs, 37XCs, 375 Cheytacs, and 460 Steyrs and I wouldn't even shoot one of them unless I was shooting 1000 yards or more because the blast/concussion. This is very tolerable in all regards, albeit in a 27lb platform.

 

[Earnhardt]

I have a 300 rum, a 338 Edge, and a 375 RUM
With "average loads", what do you think the barrel life is with the 375 RUM?

 

[Chase723]

No idea. This is my first 375. The 300 RUM and 338 Edge seem to be 1000-1500 rounds. My guess is similar. Maybe slightly more due to it being relatively underbore, but probably depends on how hard you push it.

 

[biff's reloading]

I have a 300 rum, a 338 Edge, and a 375 RUM
With "average loads", what do you think the barrel life is with the 375 RUM?

Depends on what you need it to do and if u shoot it one by one or 5 shot strings. For me, itll last a lifetime. At least 2000 rounds I'd guess if you cared for it. It might get finicky at less than that but unless it's a dedicated elr rig, I dont mind a 1/2moa "flyer" because I cant hold a group less than that at extended range in a hunting gun anyway.

I'd expect The same life from a 375 as any other cartridge in the 1000-1100 range on that bore ratio index. Lots of guys over 2k on 300wsm or 260rem's. The internal dynamics are the same. Alk things equal, itd last longer than a 300win, and shorter than a 30-06. That's a lot

 

[Chase723]

It's in a special overlapping gray area between average hunting cartridges and elr cartridges like the ct and I can only imagine more n more guys will be building them as these new bullets release.

Its funny to think of a 375rum as a general purpose hunting rifle, but that's really what it is. It's just "more" of it per shot. I shoot everything From woodchucks on up with mine. Theres not many critters on earth you'd need much more gun for.

My experience with my current setup shooting the 390s has me seriously considering building an actual hunting rifle in 375 RUM. My pressure testing with RL 16 makes me think you could actually load to mag length and run a full house load…I'm really interested to see how it would do in a 20-22" barrel suppressed. My guess is just over 2600fps which would still be supersonic to 1800 yards at sea level…that's a lot of performance. My only concern in something weighing 12-14lbs would be recoil but honestly with the right stock and recoil pad it probably would be pretty tolerable…might not be what you would want to shoot all day at the range but for hunting it'd probably be fine.

 

[Chase723]

Final follow-up until I take it out to 1000+. I think the load will be 105.3gr N570 at 40 Thou off. 2820fps. Not sure if my barrel sped up a little or what but 105.5 started out like pictures but then the groups spread horizontal (I tested 106.2 as well but it had more vertical) so I dropped down to 105.3 and it seems to be back to shooting a cluster. Shot 3 confirmatory groups today and 2 of them were 1/3-1/2 MOA at 525. Absolutely drilled it at 300. I think I'm going to leave well enough alone and stretch it out.

 

[Earnhardt]

Chase, which bullet in the plate pic?
Thanks

 

[Chase723]

Chase, which bullet in the plate pic?
Thanks

390gr A-Tip

 

[Taylorbok]

I ordered a .375 barrel 9 twist. I don't know if I can talk my self out of the AI version

 

[biff's reloading]

My experience with my current setup shooting the 390s has me seriously considering building an actual hunting rifle in 375 RUM. My pressure testing with RL 16 makes me think you could actually load to mag length and run a full house load…I'm really interested to see how it would do in a 20-22" barrel suppressed. My guess is just over 2600fps which would still be supersonic to 1800 yards at sea level…that's a lot of performance. My only concern in something weighing 12-14lbs would be recoil but honestly with the right stock and recoil pad it probably would be pretty tolerable…might not be what you would want to shoot all day at the range but for hunting it'd probably be fine.

Mine is 10.5 in the hunting stock. 350smk at 2900 recoils like an average 9 or 10lb 300wm unbraked, if that. Dont even need to think about it when taking an offhand shot and I never feel a thing with a deer in the scope.

Stock is a factory 110V that had been in a flood. I kilned, stripped, inletted and devcon bedded, and refinished. crappy pics. Sorry. Took me 3 months to find the correct savage buttpad.

 

[Marine sniper]

Mine is 10.5 in the hunting stock. 350smk at 2900 recoils like an average 9 or 10lb 300wm unbraked, if that. Dont even need to think about it when taking an offhand shot and I never feel a thing with a deer in the scope.

Stock is a factory 110V that had been in a flood. I kilned, stripped, inletted and devcon bedded, and refinished. crappy pics. Sorry. Took me 3 months to find the correct savage buttplate

Nice rifle;
I am currently building a 375 Lapau AI; was hoping for 2900 fps with a 350 Sierra or Cutting edge with a 26 in tube, looks like I should be able to it.

6500 Ft lbs, awesome.