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Loading the 45-70, one grain at a time.....
Posted by Murphy on Jul 29 2005
Grizz,
You have a good plan with that guide gun. The Ashley rail and sights are a very good setup. Firelapping works doesn't it? I think all the Marlins benefit from it and it's really a must for good cast bullet accuracy with new barrels. Do you have the XS sights also? Does WWG give you both aperatures for the ghost ring? I think you have a full load there with that bullet, it will smack you around a little. Buy a Past shoulder pad if you shoot from the bench, I would never use one of those cradles that hold the gun butt. Sure it catches the recoil but it is harder on the gun and it will not shoot to the same place as it will off your shoulder. The 3-4" group, considering the low power scope and your mention of the recoil, is probably pretty good. The rifle and the load are likely capable of half that group. I take the news of all the super groups with a grain or two of salt. I know it happens but alot of what we see/hear about are a one time thing. I will tell you I have never shot a Marlin lever gun well. They kick the crap out of me (the stock shape, the length, etc), they don't lie well on the bench and the triggers are generally not like a good bolt gun. If I could consistantly shoot that rifle and that load and that 2X scope into 4 inches at 100 yards, I'd go huntin'. Maybe others out there who shoot a guide gun more than I have a different story.
Now to the loading question, my field. Some people use .1 or .2 grain steps to check a load, it accomplishes nothing. The velocity variation is less than the standard deviation (SD). You won't know what is happening. The rule (My rule) is one percent of the powder charge. For a 223 a .2 or .3 grain variation can make a difference. For the 45-70 I would use .5 grain steps or more and if you have a chronograph, or can borrow one, you can see what's happening. You would check that powder/bullet/primer/case combo in .5 grain steps from about 48 to 52 grains and look for equal increases in velocity for each step. Probably be about 20 fps per .5 grain increase. If the velocity increases are less than the SD, increase to 1 grain steps until you see the drop. When velocity drops to say 15 fps increase, go back to the last load and accuracy test that. Then we can go .5 grain steps either side of that. There is a reason for this but it would take a lot of space, you'll have to wait for the book. Anyway, 1% is usually ideal and of course it varies from caliber to caliber and gun to gun. I use 1 grain steps in 30-06, 300 mags, 338 and 375 and get great results. Good luck and good shootin'.
Murphy
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