375 ultra mag

What optic are you running? I have tried the following and just do not like any of these so far.

Schmidt Bender 5-25x56mm
NF ATACR 7-35
Leupold 5HD 5-25x56mm

Issues with eyebox and the SB for the price very disappointed with shooting past 1,000y

Any ideas?

I use a March 2.5-25x40 Tactical. Outstanding scope. Light, insanely clear, tough and tracks perfect. No regrets. My next rifle will have the same only in 52mm obj.. In my experience with any high(20x+) vari-power scope you can run into some eye box issues. Not that's there's anything wrong, just that scopes can get pretty finicky on the high end. I find it just takes a little practice to figure out the scope you choose. Some are better than others or they just don't suit your shooting style. You'll find one that works. I'd consider putting March on your list. I've had no trouble with eye box or anything else at any distance with March.
 
I can't wait to have this build done, what are you seeing with the hammers? 2900 or so? I'm going to develop a load with the for my hunting load and use the SMK's for my target rounds.


In my rifle with a 27" Benchmark, it only takes 96.7gr of RL26 to hit 2810fps, which is My elk hunting load. There's tons of room left there for more, even with the relatively fast for case size, RL26 magic dust. What a wonderful powder!! very versatile.

If I used Retumbo, RL33 and N570, I'm sure 2900+ would be a walk in the park. especially with the longer barrels You all are looking at. RL33 I believe will be the ticket. You can get some crazy velocity out of that stuff. It's stable to. I used to shoot 99gr of Retumbo with the 350gr SMK at 2815fps. There were no high pressure signs and could have gone further. Very accurate (6"groups avg at 900yards). I've never been one to chase speed. I always want my brass to last as long as possible so I tend to hang around 2750-2850fps. Nice and easy on brass, accurate, hits elk with authority and with my rifle scope combo, I can get it out to 1500yds before it goes subsonic at those speeds.
 
I agree. I own March. It was always on my list.

The 10-60x56mm was a huge disappointment in glass quality at 1200y that acquisition hurt. I was told by my DM to get the NF ATACR 7-35mm. I did and went back to the 5-25x56mm Leupold HD. Better at high end, far enough power. You need clarity more than power and the March high power at 1500y was so disappointing and the only reason I did not look again at March. The lower powered March optics are killer.

Truth be told the best 2 mile optic I ran on my 338s were the Schmidt-Bender hands down over Kahles 5-25 x.

The clarity of March lower power rival top end NightForce any day.

To choose an optic for this monster 375 RUM AI one has to realize these qualities of the build:

1. The 375 RUM AI is NO 1 mile let alone 2 mile weapon. Far too anemic despite CEB and Hammer bullets. I built it for being a sledge hammer inside of 600 yards.

2. If I wanted a 1500- 3700 yard .375 caliber weapon I would have chambered this build in a 37XC or 375 CT. 375 RUM and RUM AI simply is limited despite the performance of accuracy and velocity I am seeing in my 29" 1:9.4" twist barrel.

3. This is an M24 Contour 29" barrel so this not a Safari Grade big game short barrel so low power safari optics are not a good fit for wide field of view or eyebox needs.

4. This rifle has a Manners T4-A stock built for more mobile Safari and fixed stand or ELR shooting & hunting only.

So looking at this lower power March is indeed an option with larger objective.
 
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In my rifle with a 27" Benchmark, it only takes 96.7gr of RL26 to hit 2810fps, which is My elk hunting load. There's tons of room left there for more, even with the relatively fast for case size, RL26 magic dust. What a wonderful powder!! very versatile.

If I used Retumbo, RL33 and N570, I'm sure 2900+ would be a walk in the park. especially with the longer barrels You all are looking at. RL33 I believe will be the ticket. You can get some crazy velocity out of that stuff. It's stable to. I used to shoot 99gr of Retumbo with the 350gr SMK at 2815fps. There were no high pressure signs and could have gone further. Very accurate (6"groups avg at 900yards). I've never been one to chase speed. I always want my brass to last as long as possible so I tend to hang around 2750-2850fps. Nice and easy on brass, accurate, hits elk with authority and with my rifle scope combo, I can get it out to 1500yds before it goes subsonic at those speeds.

Well said. If you chase speed go up in cartridge 37XC or 375 CT
 
I agree. I own March. It was always on my list.

The 10-60x56mm was a huge disappointment in glass quality at 1200y that acquisition hurt. I was told by my DM to get the NF ATACR 7-35mm. I did and went back to the 5-25x56mm Leupold HD. Better at high end, far enough power. You need clarity more than power and the March high power at 1500y was so disappointing and the only reason I did not look again at March. The lower powered March optics are killer.

Truth be told the best 2 mile optic I ran on my 338s were the Schmidt-Bender hands down over Kahles 5-25 x.

The clarity of March lower power rival top end NightForce any day.

To choose an optic for this monster 375 RUM AI one has to realize these qualities of the build:

1. The 375 RUM AI is NO 1 mile let alone 2 mile weapon. Far too anemic despite CEB and Hammer bullets. I built it for being a sledge hammer inside of 600 yards.

2. If I wanted a 1500- 3700 yard .375 caliber weapon I would have chambered this build in a 37XC or 375 CT. 375 RUM and RUM AI simply is limited despite the performance of accuracy and velocity I am seeing in my 29" 1:9.4" twist barrel.

3. This is an M24 Contour 29" barrel so this not a Safari Grade big game short barrel so low power safari optics are not a good fit for wide field of view or eyebox needs.

4. This rifle has a Manners T4-A stock built for more mobile Safari and fixed stand or ELR shooting & hunting only.

So looking at this lower power March is indeed an option with larger objective.

Yeah, when you get into strictly and 1-2 mile Rig, I'd be looking beyond any of these scopes. The march 10-60 was and is a 1000yd benchrest scope. A very good one and very popular. Out to 2 miles, I have no double you'll lack some clarity. Enter the March Genesis..
https://marchscopes.com/column/king-of-2-miles-in-france-2019/
 
Agreed. It's been a wonderful barrel.

I have built hundreds of rifles in just the last year as a professional builder. To me $ for $ no other barrel is better than Benchmark.

If you have a personal preference I will not ever bash your choice but I literally have owed all other brands and can nearly 100% assured you I tried all brands.

The Benchmark was the first barrel that I built for my own personal 338s and 375s and from receipt of the barrel to installing on custom actions to Rem 700 factory actions the accuracy was mindblowing. Putting 3 rounds down range from a brand new barrel and having that massive 350 SMK group in a cloverleaf at 200y convinced me.

From that point on no other barrels go on my builds.

We will put ANY barrel of choice a customer chooses I just let them know I wont guarantee subMOA with anything but Benchmark.

We do all brands of barrels. Over .308 caliber I am turned off on Proof Research Barrels however.
 
Corey, what is different about your 375? My sammi chamber and throat was hot hot at 101gr mrp with 285gr grand slam and just over 3k. 105gr with a 350 would be disastrous I'm afraid. Bertram brass, fed primer. (116gr mrp is a full case). I'm cutting my throat to .400 to address this, but looking for any bright ideas. I'd love to just send the barrel for "+p", but doing my own work is how I justify all this shop equipment to the boss ;) I may have to send him one just to find out what the heck it really is... im sure its not magic, just a long leade
 
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Bigreen could you give a explanation of bad heat treated barrels. Examples, please. I was told a couple of years ago they got some bad steel.
 

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