Here's an update. I had another thread going trying to figure out my fouling issue.
https://www.longrangehunting.com/threads/copper-fouling-location-in-barrel.278407/post-2280097
No resolution. It's a heavy fouler with Hornady and Speer cup and core bullets.
I think I've found this barrel and Speer HC shoots best when loaded with copper. I initially did a seating depth test to start and it seemed to like being 0.020 off, but also had a nasty flier in that group and quite a few in the others. The fouling was heavy, after 20, so I figured it was likely that. I then tried a 20 round test on a clean barrel to find best charge. Lots of fliers, decided to try a different bullet.
I thought I heard Hornady jackets were harder than speer, so decided to give the Hornady 165gr BTSP a try. The fouling was much worse and got nowhere trying to develop a load because I'm just not going to clean a barrel every 5 rounds.
Tried some Tubbs TMS bullets. Visibly, it smoothed out the awful reamer marks in the throat quite a bit, but there was no significant change in fouling or groups with the Hornady 165gr after.
So I went back to the Speer. I loaded 30 of the best seating depth hot cor load today, rather than try to continue development on a clean barrel and chase my tail, to see if it got better as fouling increased. After 30 shots, the lands are coated nearly solid with copper for the last half of the barrel. Not in the grooves though, like the interlock did. Near the muzzle, it may look a little less gloopy than it did before the TMS bullet treatment.
30 rounds
Virgin Peterson brass
56.5gr h4350
Cci200
Speer hc 180gr ~0.020" off lands
2861 fps avg
9 SD
20 ES
There were a several fliers 1.5" away in the first 20 rounds and then the last 10 were acceptable. I used a new rear rest that took some time to get the stability during trigger break figured out, so I had some definite misses in the first 15 shots that screw with my overall results. But, given the last 10 shots, this will do for hunting. I'm going to just do a light clean on the bore and chamber with hoppes and see how far it will go before copper buildup becomes a problem.
I think this cartridge has a great potential. My '06 would take this same load to about 2850 fps, but it used 58.8gr of h4350 as opposed to 56.5gr this one uses. I can get this cartridge and bullet to at least 58.5gr without any pressure signs so it has to be pushing 2925 or 2950 with that charge. I unfortunately didn't have my Chrono that day so I don't know for sure. That's on a 22.5-23" barrel and with a very poor shooter!
I'm sure if some of you guys took on this cartridge, you could really make it shine.
I need to get with a good smith and have a reamer designed for myself.