Work backwards 0.1 grain at a time until the bolt scars remove themselves, sounds like you are right there just slight tweak if you like the velocityHere's the story:
I started load development with a 245 Berger in a 300 Norma Improved (35º shoulder). This rifle is built on a BAT HR with a 27", 1:8 twist Rock Creek barrel. Shot a pressure ladder with RL33 and the round barely seated to fit in a CIP length Lapua magazine (I believe cartridge OAL is around 3.710" or so). This puts the boattail barely above the neck-shoulder junction and the bullet .025" off the lands in this chamber. Anyway, I ran it up to 94.8 grains of RL33, carefully watching for pressure signs and had none. I then shot a ladder at 700 yards and found two nodes - one from 90.8 to 92 grains, and the other from 94-94.8.
To test both nodes, I loaded up rounds in the middle of both nodes and shot for groups at 185 yards. The loads with 91.5 grains averaged around an inch to slightly over an inch (mostly horizontal dispersion), but the loads at 94.4 shot bugholes. Seeing this, I decided to pursue the 94.4 grain load and took it out to confirm zero and get velocities.
This load averaged 2999 fps over a Magnetospeed with an SD of 8.7 (good enough for me). I removed the Magnetospeed from the end of the barrel and went to finalize a zero, which is when the issue occurred. After not seeing any pressure signs at all with about 20 of these loads thru my gun, I got very faint ejector marks (only visible in bright sunlight) and the slightest hint of stiff bolt lift. Considering this is Lapua brass, the fact that there are ejector marks makes me think this load is too hot to continue shooting.
I'm reluctant to give up a fast and extremely accurate load, but safety is #1 in my book and I don't want to cause damage to my gun and especially to anyone that might be shooting it. So, where should I go from here? Should I try to tighten up the horizontal in the low node and play with that a bit? I'm thinking simply dropping down to 94 or 94.1 grains to try to run the high node wouldn't make that big of a difference in pressure.
Or, maybe I should send the gun to Shawn Carlock to have him work his +P magic on it and hit that node without any worries...
1x fire formed. After firing the cases the 2nd time, it didn’t appear that the shoulder was any sharper, but I suppose it wasn’t visible to my eyes and I’d need to measure h2o capacity. I’ll drop the load down to that 91gr node and see what happens out of caution. Maybe tweak seating depthsIs this virgin or fire formed brass?
Barrel was a little fouled, that RL33 is dirrrrrty compared to some other powders I’ve used (H1000, H4831, etc). Would it be possible for a carbon ring to build up that quickly?Was your barrel beginning to foul? Maybe try cleaning it after the 20 rounds and see if that helps.
Doesn't have to be a carbon ring, for powder and copper fouling can increase pressures. Especially in a new barrel that is just beginning breakin.Barrel was a little fouled, that RL33 is dirrrrrty compared to some other powders I’ve used (H1000, H4831, etc). Would it be possible for a carbon ring to build up that quickly?
I'm not really a fan of rl powders slower than rl25 in the 7'mms for this reason. I haven't really gotten my 7stw or 7rum to settle down well with either rl33 or rl50 and I think some of it is fouling. I'm running either rl25 or retumbo in my 7stw at present and h50bmg in my 7rum (short throat). The 30 cal. rifles I own treat the slower rl powders a good bit differently then the 7's. They (30's) don't seem to foul out even at a couple boxes through them between cleanings.RL33 is pretty dirty, my experience in the 28N shows to need a good cleaning every 20 to 30 rounds and with a new barrel, my opinion, you probably need a good cleaning. Not sure if you have a borescope to check the barrel or throat for a carbon ring, if you do not have one, get a Teslong borescope that can be used on your phone or with your PC. It is a very good scope for about 50.00 on Amazon.
Yup... hear ya on availability. I'm pulling teeth getting more 200 eld-x 30 cal into the house at present without paying gb prices. I gave my pills away as I hadn't found a load, then was putzing with my Pops 300win and ran a few 200's pushing with v565 through my old browning. Cloverleaf at 100 at mag. length.. O.K., now where to find more pills to explore this option... I've got a back order in but I suspect it'll be a spell. Usually I'm sitting on hundreds of a certain pill but the screamer group comes up with a bullet I'm out of with a powder I only have a couple of # of.When I received my 28N in 2016, Retumbo and H1000 was like finding hen's teeth. I did use H1000, had some from a year before, but running 195gr Berger's was not all that well for Velocity, but plenty of RL33 around during that time.
Yes. The carbon ring can build quickly. The 28 nosler is the same way, and I clean my 28 every 30 rounds.Barrel was a little fouled, that RL33 is dirrrrrty compared to some other powders I’ve used (H1000, H4831, etc). Would it be possible for a carbon ring to build up that quickly?