.375 Mark X & plainbase bullets

[NuJudge]

My Dad gave me a Lyman 375248, about 250 grain, flat nose, plain base, 4 grooves. Anybody have suggestions for the 375248 in this rifle (or any other .375 H&H), or should I just invest in a 375449?

The rifle shoots exceedingly well with jacketed bullet, full charge loads, but they get somewhat . . . tiresome.

CDD

[6pt-sika]

I have a Mark X Whitworth in 375 as well but I've never shot cast in it . How ever the two molds you speak of are both good in my 38-55's .
I have another Lyman mold #378674 that is a 335 grain semi spitzer design . And some of my friends have used it in their 375 's with decent success.

[Buckshot]

..............What twist doe it have? I have a 375 Whelen AI with a 12" twist. With the 264gr FNGC Lyman about 1600 fps is tops and then they start flying all over. It has a Universal 4X scope with fairly heavy crosshairs. I had some NEI cast slugs that weighed 328 grs and 352 grs and they did much better. As I didn't have the mould all I had to work with were the few sent to me.

I had the 352's going just over 2100 fps and the 328's doing 2240 fps. They'd put 3 into 3.5" at 100 yards. The lighter Lymans just sprayed at that range. As I said, I didn't have very many of the big ones. They hurt :-)!

Jacketed slugs (270 & 300gr Hornady's & Sierra's) would place 3 in an inch and a half at 100 yards.

................Buckshot

[6pt-sika]

I got my 375 when Nosler still made the 260 grain Ballistic Tip . And a little while later they quit making the BT and went to the Accubond in that weight . Anyway I had already worked up a load with the rifle using the BT . So I had my dealer scour his distributers and got me about 7 boxes (350 bullets) , that should keep me running for awhile. Mine also likes the Nosler 260 grain Partition , so if I run out of BT's I'll just shoot the Partitions .
I never shot anything heavier then 260's in my 375 . If I want a heavier bullet I'll just unlimber the 416 REM MAG (this was also a Mark X Whitworth in 375 at one time ) :drinks:

[Bass Ackward]

A pretty standard recipe with any over bore case design is to fill the case with something like H870 until you have just enough room for about .7cc of some plastic shotgun buffer that will compress to keep things from mixing. Should get you in the 2100-2200 fps second area with a PB design. Ball park maybe 3" or less depending on how hard you want your bullets.

[felix]

12 twist might be a little much for 2100 fps at 3 inches. Just cut the same powder (H870 or equiv), and increase the PSB until accuracy comes into view. ... felix

[45 2.1]

That is not a real high speed design, but is wonderfull when cast of wheel weights, lubed with LEE liquid alox as cast and loaded in front of IMR 4227. It makes a great plinker, target load or small game load which will shoot bug holes.

[Larry Gibson]

My Dad gave me a Lyman 375248, about 250 grain, flat nose, plain base, 4 grooves. Anybody have suggestions for the 375248 in this rifle (or any other .375 H&H), or should I just invest in a 375449?

The rifle shoots exceedingly well with jacketed bullet, full charge loads, but they get somewhat . . . tiresome.

CDD

The PB 375248 makes for a fine plinking and small game bullet in the .375 H&H. Some may find it ok for deer at close range also. Years ago a friend had a MX and we worked up a load with H4227 as 45.2.1 suggests. Sorry I don't have the load.

A few years back when I picked up my M70 three six bits (1-12" twist) I also found a single cavity 375449 GC mould and find it is a very good choice for the .375. Over 36 gr of 5744 it runs 1850 fps with consitant 2 MOA accuracy. Over 48 gr of 4895 and a 1.5 gr dacron filler it runs 2175 fps with sub 2 MOA accuracy. Both loads are easy to shoot and make good practice loads or deer loads.

But back to the 375248; I have shot them on my M70. I went with two loads out of older Lyman manuals. 14 gr of Unique (no wad or filler) which gave very good accuracy at 50 yards running 1300 fps. The ones I was shooting were cast of WWs and air cooled so they wre somewhat soft. With 20 gr of 4759 they were just over 1500 fps but accuracy was poor. At 19 gr of 4759 they ran 1470 fps and shot 2 MOA at 100 yards.

I've thought of getting a PB mold for the .375 but haven't needed one. For small game I use a round ball (.376 cast - RCBS mould) or the .375 Hornady or Speer RBs lightly lubed with LLA. Over 4 gr of Bullseye the run 893 fps and shoot into 1 1/2" at 50 yards. Great for hare, ptarmigan or grouse and of course plinking.

Larry Gibson

[NuJudge]

I tried it both lubed with Beeswax/Alox in a .379 Lyman 45 size die, and dipped in thinned Lee Liquid Alox. Both worked decently. I think I'll go with machine lubing for quantity loading, as there was just a little leading at the start of the rifling with the dip lube. With the Lyman 45 lube size machine, I set it to fill all the bullet grooves except the front one. I did not see a deposit on the muzzle of bullet lube, but so long as there is no leading I don't care.

Christopher Dingell