I'm working on some mid weight bullet loads in my 45-70 BFR. When I started working with the 400gr Speer, I had to put an "extra high" front sight on so that I could zero the gun at 50 yds. I am happy with my load with this bullet, so I moved up the the 440gr CP LFNGC and. Now, I need drop down to a "high" front sight to bring the point of impact up with the heavier load.

This is were I get confused. My understanding is that heavier bullets impact higher due to the longer hang time in the barrel during recoil. Is this wrong? If it's true, why is the heavier load hitting lower? Does it have something to do with cast-vs-jacketed bullets?

I suppose I could just deal with the sights the way they are. With the sights set as the are now I have the following:

300gr Hornady HP/ 60.0gr Varget- 100yd zero
400gr Speer FP/ 44.0gr IMR4198- 50yd zero
440gr CP LFNGC/ 45.0gr IMR4198- 25yd zero

Any insight would be helpful. Right now I'm stumped.

Andrew

generally speaking, heavier higher; lighter lower. This is exactly why one must shoot particular loads. As to your situation, I don't have a solution at the moment. I'm tired and need to study on it a bit.

What I see is too slow of a powder for the 300 gr. I bet there is a lot of unburned Varget falling out of the empties. You are actually getting more velocity with the heavier bullets. I would try the Varget with the heavy bullets.
I have had problems with both 4198's and pressure excursions with cast boolits. With jacketed I had a few shots jump from 1550 fps to over 1800 fps. I quit using it.
My favorite loads right now are; 317 gr WLN and 31 gr's of 4759, ( This boolit when zeroed at 100 is a shade high at 50, 4" low at 150, 16" low at 200 and 26 FEET low at 500.) 330 gr WLN and 31.5 gr's of 4759 and the Hornady 300 gr with 32.5 gr's of 4759. The Hornady has done 9/16" at 50 yd's and all the bullets have done an inch at 100 yd's for me.
I am just starting to work with heavier boolits and had good accuracy with Varget even though it is a slow powder. Reloader 7 has shot great. I have 5744 loaded, yet to shoot them and am going to work with 4759 and 322 also.
I have tried all kinds of powder, 4227 sucks for accuracy. 4198 scares me.
3031 shot some great groups with the 317 gr cast but was very slow with a lot of unburned powder, even more then Varget, 4895 was the same. Even my 10" barrel can't burn all the slow powders. Powder choice is critical.

I've used 322 with 400 grain Speers, but that was in a 14" Contender. Shot great. I'm on the road, had just gotten to Austin when I replied last night. Don't have the load data handy.

The "rule" only applies if the velocity of the bullet (in the barrel) is slower.
Peter.

I think there are at least a couple of factors:

1. If the bullet is slower, there is more time for recoil to make it hit higher.

2. If the bullet is a lot slower, a point will come at which it will hit lower despite recoil. Also, lower velocity implies less recoil which at some point will also factor into a lower point of impact.

Whatever you do to effect recoil will change the point of impact. Barrel time is only one factor. Even a powder change will effect recoil even if the velocity remains the same. A case full of slow powder recoils more then half a case of faster powder.
There isn't anyway I know to predict were the boolit will hit, reason for adjustable sights!

I think it's time to just break down and buy chronograph. I suppose that would make this all much easier. I have a feeling that it's a combination of a lower velocity load with the 300 grain bullet, and a higher velocity with the 440gr. I know that the 300gr bullet and Varget don't make for a top end load. On the other hand, 45gr of 4198 is a pretty heavy charge for a 440gr bullet. I came up with this load while trying to match 500 S&W ballistics with the 45-70.

As for powders, Varget has proven to be the most accurate powder with the 300gr bullets and the worst with the heavy slugs in my gun. IMR 4198 has given me exceptional results with bullets over 400gr and not so great with the lighter bullets.

Anytime I have bought any short barrel gun for a large case, finding the right powder and charge has been a challenge. Even the 10" 30-30 I had drove me nuts.
I love the big 45-70 and have shot some tight groups to 500 meters with it but it is real fussy with powder for every change of boolit. I have had the gun for a while and killed a bunch of deer with it but every day I feel I still don't know how to load for it. Every time I look at another weight boolit, I scratch my head. At least I have my fall back to loads when season opens.
There is a total lack of information for this revolver and even Handloader has never done a thing with the BFR's. We have to play a guessing game with them.
Friends come to shoot and I love to put up cans at 100 yd's and peel them off one after the other from the bench. But my .475 BFR does the same and is soooo much easier to work with. I haven't found a boolit from 400 gr's up that doesn't shoot and it only takes one powder.