I'm really not sure. I had sized five 300 gr shockwave bullets to .451" to try out of my .45 cal GM LRH barrel. While at home I dumped a load of 80 gr of Goex FFFg down the bore, a .45 cal felt pad and one of the bullets. (I did this at home to make sure i wouldn't have a problem at the range) I was only going to shoot at 50 yards to get an idea how these shot. First shot hit about 3" high and 1" right which I contributed to a different bullet. I then went to load the second shot and realized I forgot my felt patches.- grrrr.
I figured what the heck I'm here. Loaded the second shot and fired. Height perfect but right the same 1". Third shot touching the 2nd. Hmmm promising even without the felt wad. It was looking like rain so I was in a hurry and wasn't swabbing between shots. Fourth shot really hard to get down the bore but finally got it down on the powder. Fired and it hit 3" low and still 1" right. I took a min and swabbed the bore with a spit patch and loaded #5. This shot was touching #4!
What a crazy group. I'm not sure if its even worth the effort to size some more and try them or just stick with the paper patched or .451" lead conicals.
Edit: I want to add that this rifle is a very good shooting rifle. Its just that I never had a group like this in my almost 60 years of shooting black powder. It seems odd that if you throw out the first shot you would have 2 touching in one area of the target and 2 more touching about 2-3" from the other 2. Peep sight was solid. I'm sure fouling played a roll in this but it still seems odd.

Try to be more careful with your shooting regimen the next time you decide to try out a barrel with some new bullets.
Good powder and bullets are expensive, so try not to waste any shots.
Remember, if it were meant to be easy then it wouldn't be any fun!

thats what I get for being in a hurry to try and beat the rain.

Aw Bronko, there's no such thing as a wasted outing when it involves shooting. You always learn something. In this case, you learned to not forget the components you planned to shoot. 😁

I think a second try with those bullets is warranted, with two changes - (1) wipe between shots, and (2) repeat a five shot string with the 80 grain load and add a five shot string with 90 grains.

And now that I think about it, looking back to my younger and stupider years I'm pretty sure I had a few wasted outings. But they had nothing to do with shooting and a lot to do with being wasted.

[QUOTE=And now that I think about it, looking back to my younger and stupider years I'm pretty sure I had a few wasted outings. But they had nothing to do with shooting and a lot to do with being wasted.[/QUOTE]

LOL...Sir you are just not right in the head! I guess that's why I like you. We have lot in common.

Clem, if you have a .452 sizing die try sizing some with it and see how it does also.

They already are at .452. I can try but I don't want to get it stuck half way down. I could try some .45 cal sub base w as ds if I can find any.
I had that happen to a .45 Seneca years ago. I had to use a mallet to get the PRB seated on the powder!

Oh, I thought they were sized to .451? If you really did size them to .452 try .451 if you have the die.

MMP only offers the sub bases in 50cal You can buy .463x.060 polywads or just cut the petals off of a 45cal sabot.

Yeah thanks GM. I had already dropped them a line and they told me they only have them in .50...