I recommend you use a starting load of 57.0 grain since that is the starting load shown in my old reloading book. You wanna be cautious about using TOO SMALL a powder charge with any SLOW-BURNING rifle powder. While IMR4350 USUALLY doesn't cause problems due to low loadings, it CAN happen, even with IMR4350.
My data is older than yours
but IMR4350 hasnt changed enough (if any) to be concerned about it.
My old reloading manual (circa 1970) shows a starting load for the 7X61mm Sharpe & Hart cartridge using a 150 grain bullet and IMR4350 to be 57.0 grains which should yield 2860 fps with a maximum load (63.0 grains-a compressed load) yielding 3140 fps.
My book also indicates an accuracy Load as being 57.0 grains of IMR4350 which is, of course, the "starting load".
HOWEVER
there was a warning concerning the free-bore of the barrel indicating that the test rifle was free-bored. It goes on to say that if your rifle is NOT free-bored, then you MUST reduce your loads by a full 5% and even then, maximum loads should be approached with extreme caution.
For the traditional (for a 7mm) 139 grain bullet, the same book indicates that IMR4350 is probably the best powder with a starting load of 58.0 grains of IMR4350 which yields 2950 fps (this load is also the accuracy load for a 139 grain bullet) and a maximum load of 64.0 grains (a compressed load) yields 3260 fps, the highest velocity of any powder tested by more than 60 fps.
I noted that IMR4350 is shown as being the powder found to be the most accurate with every bullet weight tested (using starting loads in each bullet weight) including the 120 grain, 139 grain, 150 grain, 165 grain and the 175 grain bullets. The same powder at maximum loads also yielded the highest muzzle velocity of any powder listed in each of the bullet weights tested.
It was also noted that these loads used Norma brass and Remington 9½ primers in a Shultz & Larsen 65DL with a 24 barrel using a 1:10 twist.
I hope this helps you
:wink:
Strength & Honor
Ron T.
