.375 barrel contour

[Bravo 4]

Time to "upgrade" the .408 Cheytac to one of the large .375 chamberings. I am ordering a barrel early this coming week (Monday or Tuesday) and would like some opinions on length and contour.
What I have: BAT-M action, McMillan A5 stock, currently weighs about 25 pounds with 28" barrel (1.45" for 4", down to 1.1"@ muzzle, fluted), has the larger heavy pendulum style bipod and mount
What I want: 34-36", light as possible for hunting, T4 or T5 muzzle brake, change out the bipod (and mounting bracket) to a simple Harris or maybe Atlas.
I know this mostly spells heavy, but I have been reading for the past month on builders making these rifles well under 20 pounds with barrels in the 30-32" range.

If you have a rifle built off a Cheytac capable action, feel free to list what you have and it's weight, and if you would do anything different.
If you don't, list what you would do.

 

[royinidaho]

Bravo4, U asked for it.... Here goes.

Kirby Allen built my 375 Allen Mag 5 or 6 years ago.

I scarfed up the Bat M action and 30" 10 twist barrel from a LRH member in Florida.

Scrounged an Mc A5 from RBros.

With the big Pain Killer brake, 2 sets of NF alum rings and a 5-22x56 NXS the "Big Gurl" came in at 19 pounds.

The Idaho big game limit is 16 pounds, all up.

PacNor's flutes are puny. They wouldn't cut larger ones. Bad juju they said. She shoots a solid 1/2 MOA with 350 SMKs @ 3250 (very short case life) and half that with 395 Hammer Hunters @ 3125 +/-2 FPS. So no drinking with the barrel.

The barrel is 30" with 1.01" diameter at the base of the brake.

Weight reduction began with the A-5. Hawged the barrel channel to where anymore would certainly reduce strength. Plenty space for Idaho wind to blow through now.

Hawged out the butt stock to the same extreme.

Finally drilled as big a hole as I dared up the pistol grip.

Optics system was the next phase.

Got rid of the NXS for a Leuy MK-4 with the TS-29 reticle. (The TS-32 Wasn't available in the 20X version I had). the Ts-32 comes on most versions now. I now have a 20X w/the TS-32 on a 270 WSM. May I say I love that reticle.

Got rid of one set of NXS rings, the front one. Then machined away bars on the rail that weren't needed.

Then came the action.

Flipped that sucker over and viced it up in a mill and hawged out any metal I thought I could get away with.

She now comes in at 15.94 pounds on certified scales. She still maintains her accuracy.

Now for the important part-barrel considerations.

30" is two short and 10 twist is too slow.

As for twist and stability. CEB 350s and 377s won't stabilize beyond 800 yards. 1/2 MOA or better @ 800 but tumble with backstop missing shots at 1100.

The 395 HHs are got to go as far as a fella wants to shoot.

The longer 394 gr Hammer Hunter, longer with 0.040 higher projected bc may be a bit iffy in my rig.

Retumbo and 350 SMKs were the only thing recommended by Kirby back then. 3250 FPS was max with that powder with 4 shots brass life. @ 5 bucks a pop that was a downer for me.

Steve Davis sent me some Hammer Hunters and I thought I died and went to Heaven.

Kiwi Greg recommended RL-50 if I wanted velocity. I tried Retumbo, US-869, 50-BMG and RL-50.

RL-50 gets the nod! However . . .

147.5 grains of RL-50 produces 3125 FPS w/395 HHs with very satisfying case life. This is with the original Jamison brass which isn't the best for several reasons...

HBN treatment has been a big plus for me. So why not in the 375 AM?

The sad part of the story is with HBN no matter how much more RL-50 I stuff in I can't regain the HBN velocity loss. Therefore a 31" or longer barrel is most probably a must for maximum performance. Saying that I doubt extra bbl length would be needed with and unimproved 375 CT.

I emailed Shawn asking if a +P throat would help me out. He doubts it but is dying a study.

A bit faster powder and only a bit may help. It would have to be between 50-BMG and RL-50. Don't know if there is such a thing...

Experience with two barrels on my 270 AM, one 30" plenty heavy with Dan Lilja's 50 BMG flutes shot lights out. Not for very long though. About. 1000 shots.

The next barrel was 2" shorter, much lighter, with the same very large flutes. The shorter lighter second barrel produced the same velocity and accuracy as the longer heavier first barrel. I wouldn't be too concerned with barrel weight unless you were to take it to some dog towns. ;^)

If I were to do it again I'd do a 32" barrel, 8 or 9 twist (unless I wanted to shot 425 class Bullets) with no more than a Sendero contour with as large of flutes as the barrel maker would recommend.

Not well written but I think it gets the point across and just from one old fella's experience.

 

[alcesgigas]

Pretty impressive Roy. Did you try RL33 and VV n570? Then there's VV n2029 and the faster n2420 (not sure of the last numericals).

I'm fortunate in not having to deal with weight restrictions especially since I experienced the easy-carry nature of the bull pup LRKM at 21 pounds using a both-shoulder sling.

 

[Bravo 4]

Thanks for the response Roy. I planned on HBN coating the bullets as well, and I just got in an order of RL50. I have some 50BMG, 869, Rl25, RL33, and Retumbo I can try with different bullets and weights. Hammer, Chinchaga and CEB Lazers come to mind. Gonna go with an 8" twist as I don't plan on running the bullets in the 450 grain class, mostly 350ish. I had originally planned on a .338 but the .375s have really started to come about.

 

[Bravo 4]

Got my barrel in today; will finish at 36", .375 cal, wrought iron fluted.

 

[WildRose]

Interesting look to that fluting, can't wait to see the finished product.

 

[royinidaho]

Impressive!