It has been a while since I posted. I have read the extensive posts on this caliber but not a lot about this rifle. Still struggling with this rifle. It has a 1-15 inch twist and has a groove diameter (slugged and chamber cast of .376) and have installed Lee Shaver rear peep and front globe. Have been using two cast bullets (30 to 1), the common Lyman 249 gr plain base and a custom from B and D at 296 gr. tapered. Both sized a .377.
I have an original Ballard #9, all original including sights, and have been shooting consistent one and a half inch group at 100 yards. Twist is 1-19, .387" groove and .382
bore ( chamber cast). The bullet is a custom Barnett at 310 grains with 18.5 of 4198 for a chrony of 1292 fps average velocity.
Here is the problem, unlike the original Ballard, I can not get the modern repro Winchester to get under 3 inches. I am using 2400 16gr, 4198 20gr and 4227 17gr with the Lyman and B and D. These 3 combos work the best of many tried! Have not tried Unique as shown in various manuals ie Lyman #47.
Any suggestions would be appreciated. I believe the bullets are both good for weight and fit, it is the powder and velocity that seems to me to be the problem. Thanks in advance.