You mentioned youre .1 off the lands. Have you already tried seating depths closer to the lands? Maybe .01 or .02?
It is not possible on this barrel to get that close. It has long throat and bullet to the lands means almost no bullet in the neck. My other 204 is not nearly as bad but it doesn't like shallow seating either. At .175 the old 204 shoots under .2 but that limits my case capacity. At .100 they both shoot much better than at .050 or less.
80-100 fps... OK I hear ya. 3700 is still pretty fast. What weight bullet?
H 335 is a flaked powder. You can fit a bunch of it in a .223, I bet it will compact nicely in your 204. Might fix the velocity thing.
Varget is small pellets, it doesn't pack quite as nice, but it works all season. It's our AR powder. We go through pounds of it every year.
40 grain Vmax and 39 grain Sierra BK.
I tried to stick with temp stable powders and of course powders I could actually find on the shelf. LOL. I use this rifle during winter hunting in temps from 0 to 40 degrees so I guess it was just a peace of mind sort of thing.
So far I have not really run out of room before I ran into pressure issues. Ejector marks and bolt lift.
My thinking was to help reduce pressure by adding volume in the case.
Assuming its a new barrel, i thought maybe the throat lead in could be causing more resistance than your 22" gun and a smaller jump could help increase volume and possibly allow more powder while smoothing the curve.
Only other idea i have is to try a colder primer, or maybe a thinner case. If that isnt possible or doesn't work id revert back to bullet bumpers idea of different powder.
I would find it difficult to start changing things with a load that shoots in the .2's
Accuracy is not the issue for sure. I am fine with that. I do know something else is wrong though for a 26" barrel to be slower than a 22". So I am on a mission to increase my knowledge and experience. This is my first rifle build so I naturally figured I might have an issue with HS. Last night I was messing with my cases and checking necks, lengths etc. What I noticed is that some fired cases would hold a bullet tight and others would not, hmmmm, that is odd. I went to grab the cases used in the other 204 and noticed they were gone. Quizing my son it was discovered he cleaned them and unknowingly mixed all the brass together. DOH. So I have mixed brass.
I am going to start over with annealing all of it, body size, shoulder bump, trim, etc.
Yuck for sure. It is OK, he thought he was helping and I didn't tell him what I was doing.
I have some 1x fired Hornady brass from the new barrel that I will sort out and use for the next test. My hope is that my issue was with mixed brass and the chamber will handle more powder for a similar charge weight and get the increased speed and accuracy I expected. If this holds true I can fire a similar charge weight and get about 100 fps faster velocity via the barrel length.
I have another 26" 204 varmint contour barrel I want to put on my original 204 with the 22". If all works out like I hope I will sell the new set up, rebarrel the old, and have gained the experience of building a savage.