I was test firing a new rifle at the range Wednesday. Mod 70 ss classic with a Danny Pedersen ss CR barrel in a slave stock.
I was fire forming the .375WBY brass from .375 H&H ammo using a 300 grain bullet. From the bench at 50 yards 5 shots grouped into 1.01" with 4 shots into .775".
Two questions: #1,can I expect the same or better accuracy when I reload the fire formed cases? #2,any suggested primer and powder loads for a 300 grain bullet?
Thanks,
Dave Wesbrook

In my experience the first loads in unformed brass for an improved chamber shoot about as well as the formed brass on subsequent firings. (At least this is true in hunting-style rifles; perhaps not for super-precision bench rifles.)

Per example, I use resized .30-06 brass in my .280. Since the .280 shoulder is a tad forward of that of the '06 this leaves a very small "false shoulder" at the base of the neck, making an odd looking divot in the othewise smooth shoulder slope. The first loading groups under 1/2 moa at 300 yards. I've had similar experiences with .22 Hornets in a K-Hornet chamber and, close to your issue at hand, regular .375's in a .375 AI (40 degree).

I wouldn't expect your accuracy to change much on the second firing -- assuming that your loading technique for the formed brass doesn't cock the neck or in some other manner degrade the concentricity of the round as compared to those loaded in unformed brass.

quote:

In my experience the first loads in unformed brass for an improved chamber shoot about as well as the formed brass on subsequent firings

I didn't have my 375 Wby long enough to really get it broke in. One of those offers you couldn't refuse. H414 was showing promise.

Mine is very accurate after fireforming.
My favourite load with Woodleigh 300gr PPSN is 89gr of 760 in reformed 375 H+H Remington brass and WLRM primers, found no difference in POI with Fed215 primers either. This load averaged 2790fps in my 24" barrel. A charge of 90gr averaged 2830fps, but primers were cratering although bolt lift was fine, temp on the day would have been in the high 90's, not a good load for hot weather.
I too have a Win Model 70 Classic Stainless.

Cheers.

Dave

From my experience (rechambered from H&H in a Brno) the fire forming load I used gave great accuracy at 100 yards. That didn't mean the same load was equally accurate after fire forming. I think you are asking if your experience means that the rifle is a shooter? I'd say yes, but you will still have to do the work to find preferred powder/bullet combos.

To be specific, I used 73 grains IMR 4350, Fed 215 primers and 300 grain Hornady RN solids. My notes (11/25/98) show 4 shots went into 7/8". After fire forming 47 the work began. Over time the Brno showed a preference for the 4831's.

Cheers!

Dave, I have a 375 H&H Ackley Improved, which is essentially the same as the 375 Weatherby. IMO the 375 H&H Ackley Improved/375 Weatherby is the ideal Africa gun - it will do everything and with ample power; and should you get separated from you ammo, you can shoot standard 375 H&H in it with little loss in performance.

These are my favorite loads (26" barrel). They are MAX so work-up to them...Most have been to Africa and worked perfectly.

250 grs. TTSX 88.5 grs URP 3088 fps

250 grs. TTSX 88.0 grs Re17 3140 fps

300 gr. TBBC 85.5 grs. Re17 2876 fps

300 gr. North Fork CPS 87 grs. Vv550 2910 fps.

300 gr. North Fork SS 90 grs. Ram Hunter 2884 fps.

300 gr. GSC-HV 85 grs. Re17 2907 fps