Need advice on load development with new Peterson brass

[Bassnbow]

For background, I'm loading for a 280AI with 26" barrel. Relatively new rifle (about 300 rounds fired) with ok results. I have been loading with monos so far because I live in the communist state. I had found a couple of rounds that have shot pretty well (143 HH with H4350 - 3/4") (152 Maximus Cutting Edge with H4831sc - 5/8") and (144 Barnes LRX RL23 - 3/4"). All have been showing promise, but with lack of components what they are, I haven't really been able to fine tune any of them.

I've been using Nosler brass, because that's what I could get. I was recently able to finally get 100 new Peterson cases. The Peterson brass looked very good and consistent case-to-case. All I did prier to loading was size necks with a 21st Century expander die. I knew from posts here that the Peterson brass was likely going to increase pressure, especially when new, so I backed off all my loads by 3 grains thinking I would work back up. I made 5-3 round groups, each .5 grain difference, for my first range trip. None of the groups were within a grain of max load, as my original groups were not at max. The only set of groups I was able to shoot was the 143 HH with the H4350. I did get all of those shot without any signs of pressure with similar velocities as my previous loads (2900-3065). All the other sets of groups I had made, 1 with 143 HH and 3 with 152 Cutting edge, showed signs of pressure immediately with first round fired (heavy bolt lift and deep extractor mark). The 3 sets of groups with Cutting Edge were with 3 different powders (h4831, RL-23 and RL-26) Obviously I stopped there and did not shoot the remainder of loaded rounds. I was very surprised there were signs of pressure 3-4 grains below max loads with the Peterson brass.

My plan is now to use the same approach and start again at 3 grains less than where I found pressure, but in several of the powders that is lower than the minimum book load. I know that the brass will stabilize as it gets fire formed, but how many firings is that going to take? With components as hard to come by as there are, I'm likely to be out of bullets and low on powder before I have settled on a final load. Should I just load all the new brass with extra bullets I do not intend on ever shooting at a low powder load to fire form brass before I even start to develop a load? Am I wasting my time with load development before brass has been fired multiple times? I'm also guessing I would be wasting my time with a string test until they have been fire formed? I really havent had this issue in the past with other calibers, but I also really haven't made a brass switch that was this different, any suggestions would really help, I really don't want to burn through all my components.

Thx in advance, Pat

 

[74honker]

Surely someone with more experience will chime in here but here's mine with Peterson. I run it in a 7RM. It's great brass for many reasons imo. Very consistent. I already had a "pet" load for my gun with RP. At first like you I had some learning curve with Peterson. I first I tried my normal load to just to try and it was ugly, no pressure or anything, just wide spreads in velocity and my group was crap. I then downloaded 1 grain, better group but velocity was off. I took the 1x fired and tried again with my normal load and the group improved and I actually gained some speed over my normal. Tried it again and group bugholed as it used to with some extra velocity to boot with zero pressure signs. I now have 3x fire on them and velocity has settled back to single digit SDs and groups right back where they were with the RP. I do full length resize and also did so before the first firing when they were new. I think there may be a possibility of you may may have downloaded too far with dropping 3-4 grains. I have had issues with that in other calibers before while working up loads. It can do the same wierd stuff to brass as overpressure can.

 

[Bassnbow]

Thanks for your input, I figured it would take a few firings. You could be correct about going too low and having issues with that, but not comfortable trying any higher than I did with pressure signs I had. Maybe someone else will chime in with recommendations!

 

[waveslayer]

Easiest is tune Quick Load to your current data. Then measure case capacity with the new brass, and reduce or add based upon that. Do a quick OCW test around what QL says. You will be golden, then measure case capacity after 1 firing .

I do this for other calibers and it's worked perfectly. For example in my 6.5 SAUM Remington Brass uses 58.7 gr of H1000, Hornady Brass uses 58.4 gr of H1000 because case volume is less

 

[lancetkenyon]

What were your velocities?

 

[Bassnbow]

The velocity with the 152 cutting edge and RL26 was very high at 3240, but the others were about where to be expected, around 2900-3000

 

[Seabeeken]

My 280AI with Nosler brass liked Reloder 22 and H-4831SC with the Barnes bullets. Nosler brass is made by Norma and is good quality. I'd back off to a safe book load and work back up to the velocity that shot well.

 

[Lefty7mmstw]

If it's showing pressure, it's showing pressure. I've got a short throated 7rum I basically run 7stw loads through, and I have to run a rather bulky powder to keep the load density up. She pressures up early with the short throat.
If your new brass has less capacity, it is similar to going UP in charge weight, so a 3 grain drop may have just gotten you back to parity with fired brass. If you were warm already, it still may not be quite enough; couple that with not all brass being the same hardness, and I could see where you can still see pressure signs.