Win94 BB 375 cast loads

I've got a Win94 Big Bore in 375 Win that I've been trying to get some loads worked up. For Brass, I fireformed with Grits and Unique some Fed 30-30 cases, then trimmed the mouths to square them up. I have a box of Hunters Supply 260s that I loaded out to 2.550"(2.570" would cycle, so I backed it off just a little) It's still not touching the lands, but I can't really seat them out farther. I tried RL7 at 31 and 32 gns. 31gns gave 1822fps and a decent group, 32 gns went all over the place.
http://www.lsstuff.com/pics/fireform/375-260hs-01.jpg
This was shot off the bench at 75yds with my old eyes and a Peep sight.
The first shot went way low and left. I'll have to shoot it some more and see if it consistantly puts the first shot that far out. Most of the others looked pretty good, but I did have 2 outliers to the right that I was wondering if maybe a gascheck came off or something??
Any thoughts on where to go from here?
TIA
Glenn.

My first thought is what diameter are the bullets? That second group MIGHT be all over the place due to leading the barrel with the first group, dunno just questions. Were the two to the right early or late in the firing order? Can you repeat the first group with the same load? Did you try 31.5 grains? How does that work? What diameter is the case mouth after resizing before you load the bullets? My 38-55 was resizing(swaging) the lead bullets down after I carefully sized them causing me all kinds of headaches until I figured that out. Good luck. I shot one of my biggest whitetail with a .375 in a Marlin. Tom

Interested as I will be loading some 375Win for a friend's Marlin.

Were the boolits used gas checked? With the info given I might try a little less than 31 grs of Rel 7, along with some others.

Depending upon how you go with this rifle you might give the guy out at Bear Creek Supply a call (209-874-4322). He makes and sells poly coated boolits and has a 250 grain FP available in .377,.378 and .379 for .38-55 and is supposed to be bringing out one just for the .375. His rates and delivery times are good, too. GF

I need to get off my duff and load some too!!

I bought a LEE mold in the spring and cast a couple
Hundred to try. I powder Coated them but did not size as they are .379 aft PC and I wanna try them before making them any Smaller.

Mine are Marlins with micro groove.

Cw

I had Win 375 back when 1st out but never loaded for it. 4 yrs ago got a Marlin 375 for Ohio deer. Brass was hard to come by so I blew out Win 30/30 brass. I had a Lyman 375248 250gr FN mould , plain base - no GC.
Cast 50:50 lead wheel weights. Sized & Lubed .377". First 20 I loaded with 10.5gr Unique at approx 1300fps.
Shooting at 60yds / scope I was getting 1.5" X 5 shot groups. Wasn't sure what 30/30 cases would take so that was more of a 38/55 load but no leading. Then I cast up a 3:1 WW to lead and loaded them with IMR-3031 at 27.5grs= 1550fps. It got me down to 1" at 60yds and about 1.25" at 100yds. I did come up to 27.5 gr of 3031 from 25.0 gr at .5 gr at a time. I was still worried about 30/30 brass strength and didn't go beyond that. Still had no leading problem. I really didn't like the Marlin that much and traded it off for a Ruger #3 in 375Win. At same time I was able to get new 375win brass and scraped the project. I'm now running Speer 235gr spitzers in Ruger/ scope and getting about the same at 100ys but much better groups at long range. I didn't have the fuzz to shoot full power loads with jacketed bullets out of the 30/30cases. I've seen a couple articles that warns against full power in the 30/30 case. I did notice that Win and Fed brass formed much nicer than Rem brass when blowing out with meal.

Had one years ago (375 BB winchester) it was a top eject model and likely the best made model 94 I have seen.
used a 3/8 expander rod on PMC 30/30 brass - loaded 36 grains RL7 under a 225 grain CBE cast gascheck.
brass held up ok (I actually disected a couple to look at)
sold it cuz I wanted to shoot blackpowder - ended up with a 38/55 commemmorative.

Good morning
We have a couple around the house (Marlin & Winchester) when up north there. Barrels measure at .376 - .377 groove diameter so depending on desired velocity we size .001 - .0015 over groove.
A gas check design will help you get those groups tighter but cast or sized diameter is very important. Cast slugs are the piston and if your's are undersized do not expect your rifle to be able to perform well.
Mike in Peru

Quote:

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Originally Posted by missionary5155

Good morning
We have a couple around the house (Marlin & Winchester) when up north there. Barrels measure at .376 - .377 groove diameter so depending on desired velocity we size .001 - .0015 over groove.
A gas check design will help you get those groups tighter but cast or sized diameter is very important. Cast slugs are the piston and if your's are undersized do not expect your rifle to be able to perform well.
Mike in Peru

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Hornady gas checks and a LEE 379 size die worked for mine

Agreed, diameter on that piece is real important.
1981 or 2 I traded off the big bore after giving it a brief work out.
Should have kept it.

I got a few 375 take off barrels and used 2 of them on rolling blocks to make 38-55's . I am able to use starline 38-55 brass without any issues. so far I have only shot 2F BP loads ,.