Alot like my 243SRC. Necked down and blown out 25-06.
Im pushing a 105gr to 3400fps and a 75gr HP to 3800fps. You did it right with a 1:8 twist. Mine has a 1:10 Hart barrel that is 30" long, I really wish it had a 1:8. If I ever build one (traded into this one) I would do a 28" with a 1:8. I love the round its a killer round for sure.
Shoulder angle is a good question. I would guess 30-35 but Im not sure, I didnt design the round and I can seem to find specs on it.
Before I started with the 105's I was using Hornady 75gr HP's pushed by 56.5gr of H4831sc for about 3800fps, it just flattens critters. My brother took an antelope with it a couple years ago at 445 yards and it looked like someone pulled a rug out from under her.
The 105's I am using (I think data not infront of me) 53.0gr of H4831sc for just under 3400fps. This is probably going to be the first rifle and load I hit a 1 mile target with. I have a friend hitting 1 mile with a 6 Dasher and 105's and 115's so I think I can do it with the extra 600fps I am getting.
Do you have to trim your cases? If I recall correctly, he may have taken the 243 SRC chambering and lengthend the neck to allow for less trimming of the neck. I don't have to trim necks with mine. I think the 243 SRC is 30 degree give or take a few degrees.
I also could have done a 243 SRC because he has the reamer, but I can't recall exactly what the advantage of my chamber is. Ballistics wise, they must be identical.
I do trim my cases just to true them up basically. I think my trim to lenght is 2.460", once its all to lenght I debur the flash hole. After I fireform I neck size than turn the necks, again just to true them up. I just formed up some brass on 30-06 LC 69 brass, orginally I used FC 270 brass but I was new to this wild of a wildcat and was over sizing and causing to much headspace. After I got that figured out I had pretty good luck with 270 brass except for the only getting 3 loadings out of it. I switched to Winchester 25-06 brass and got 5 loads out of the last batch before primer pockets got loose to loose. Hopefully I get several loadings out of the LC brass.
I think we are shooting ballistically identical rounds (in the same lenght barre), there might be slight differences in the case though. I love mine its a killer round.....55gr NBT at 4500fps send pdogs to low earth orbit.
Just wanted to post a little update. I haven't shot this rifle in quite some time, so I took it out the other day and shot at 600. The link below is a video clip of the adventure. Not my best day out, but OK for not shooting in several months, gotta brush some rust off!