I feel as though this is the same situation with my rifle I was right on the cusp of velocity and once the barrel fully broke in and the brass formed it speed up and opened right up and so so I am going reload a few rounds -3 grains below what I was at and reload another few at -2 grains from what I was at and then go from thereI had a 7UM, in Rem. Sendaro, factory gun, which just loved Swift Scirocco 150 gr. at 3542 fps. Going above that, it opened right up, as did another rig I loaded the same load for. Around 96 gr. of R-25 did the trick.
When I first worked up the load I was at and around 3100 fps with a 26 inch barrel, that load shot well
Necking down, if he did that, does thicken necks.The first thing that came to mind was your brass necks are getting thicker, causing excessive pressure.
7RM virgin brass has a way shorter headspace than fired brass. Meaning you use a lot of energy during the burn to form the brass. Usually something like (using a .420 headspace comparitor), virgin will be 2.107, and fired will be around 2.121".
Now, the 2nd firing, if you bumped shoulders back correctly, will be taking that wasted energy and putting it behind the bullet, instead of blowing out the case.
Also, if you now have 100+ rounds down the barrel, your barrel is breaking in, smoothing out, and speeding up.
Drop powder charge by about 1.5-2gr, and your velocity should come back down to the original speeds.
^^^Yep!^^^This is why you should have load developed with fire formed brass.
Changing seating may or may not affect MV. Depends on land relationship and load density. What does seating of .03 or .05 mean?
Going up in velocity does not decrease stability.
You just need to start over
I’m shooting 150 grain ttsx and I wish I could shoot 185 but I only have a 1:9 twist barrelif you pull powder and chrono back up to just under that 3100 at the same seating , i bet you end up right where you wanna be
also 185 barnes ttx may be ready to clean it back to metal ??
Seating deeper increased speed by raising pressure and made it worse. Pressure equates to speed. Back off and do a ladder test to get back to your 3100 sweet spot and then see if the groups tighten back up again. Go back to your .030 jump.Well I went ahead and seated the bullets from .30 to .50 to give them some more jump and it made things worse. The group at a 100 yards opened up and also velocity increased. Doesn’t make any sense to me but it’s clearly not the right answer or bandaid to get me by. I very well could have created a flinch since I haven’t shot much this year with the shortage of ammo and supplies.
185 shots down the tube , could be ready to clean bore down to bare metalI’m shooting 150 grain ttsx and I wish I could shoot 185 but I only have a 1:9 twist barrel
I clean it back to metal after every season is over.185 shots down the tube , could be ready to clean bore down to bare metal