I have a friend that has a 30-378 McMillan Rifle with a 30" inch barrel. The rate of twist is 1/10. The action is bedded and the barrel is free floated from the lug to the tip. He hand loads his ammo and is running a velocity of 3200-3300 fps. He is using a 180 grain bullet and cannot get better than a 3" group at a 100yrds. I suggested a 200 or a 225 grain bullet and backing down of the fps. I'm not sure of the powder but he said that he has the slowest burning powder he could find. He has 113 grains of powder with a slight compressed load.. My question for all those who are smarter than me is ..... What would you recommend he do with the situation...
30-378
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pretty low MV.
We'd need a lot more specific information to provide any kind of meaningful response, but if the groups are no better than 3" at 100 yards, there is something wrong with the gun or the shooter is simply afraid of the recoil.
Also, 3300fps for a 180gr bullet is about the right velocity, with 113 grains of H870. Even with a 30" barrel, 3200-3300fps is in the ballpark. The best you could get would be maybe another 100fps...even Weatherby's factory ammo only claims 3,400fps. Incidentally, there are only a few powders slow enough to be appropriate for this cartridge, the most common of which is H870. Check back with us if you can get the exact load recipe your friend is using.
Also, 3300fps for a 180gr bullet is about the right velocity, with 113 grains of H870. Even with a 30" barrel, 3200-3300fps is in the ballpark. The best you could get would be maybe another 100fps...even Weatherby's factory ammo only claims 3,400fps. Incidentally, there are only a few powders slow enough to be appropriate for this cartridge, the most common of which is H870. Check back with us if you can get the exact load recipe your friend is using.
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Sounds like the rifle is set up well and on face value, I'd lean towards recoil but could also be simply the rifle doesn't like the bullet/load. Anytime I get a new rifle, I shoot Sierra's Pro Hunters in it and if it doesn't shoot those, something is wrong.
I had a factory Accumark 30-378Wby and just alittle reloading experience with it. When I was looking for powder I settled on Retumbo on their front label they listed a max load of 113gr/Retumbo 180gr bullet @ 3460fps. I worked up to that max load got 3466fps even with a factory muzzle brake I got around 1" groups at 100yds.
One thing I'd be concern about with a 30" barrel is having it free-floated to the lug. Myself I'd want it bedded under the chamber area with that long of a barrel and I want to make sure it's pillar bedded. Also depending on what kind of rest your friend is using might want to see if that barrel touching the stock.
I set my OAL at factory spec for the 30-78Wby thats 3.648" and if your friend is trying to seat the bullet out further won't help as that rifle more than likely has the Wby freebore.
Well good luck
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