Interesting. I am having a 6mm-280AI being built presently. I see that there is people that are ahead of me. I am using a Rem 700 action, a Bartlein Barrel Metal Grade, 400MOEDBB heavy Palma, twist rate of 7-1 cut to 30". Looking and have Hammer 100gr bullets and Berger bullets on hand. Order out 500 Peterson 280AI brass, and have others in different case sizing presently. I generally use H powders, and mostly H4350, I trying to get my hands on H4831, H1000, and Varget. I generally stay away from Reloaders, and IMR powders, and few other do to extreme temperature variances. I generally use fed 210 primers with powders loads up to and including 75.5grs of powder, but these are in 300 mag area.Looking for any information or experiences on powder bridging within a cartridge and pressure spikes. We ve built 2-3 6mm-280 AI s and in testing found Retumbo to be a little quick burning ( pressure signs before we hit anticipated velocities) and then moved to R33 and US869. Our velocities were higher without pressure signs at 80 degree temperature range. (3400 FPS range with 27-30” barrels)
Fast forward and we ve seen high pressure with same R33 loading at 40 degrees. Same batch of loads. Chose R33 over 869 as thought it would be less temperature sensitive, and logic would anticipate LESS pressure in colder temps.
So in trying to figure out what’s happening came upon the powder bridging notion and read an old post on this forum that I think Fiftydriver wrote saying that stick powders in small caliber overbore cases can cause powder/bridging and erratic pressures and that ball powders are less prone to such.
Have any of you experienced such and was there a viable solution? R33 is a large kernel stick powder and I can see where this makes theoretical sense. We re burning 64-65 grs in the case behind 108-110 gr bullets.
Interested in any experiences. Thx
Any info that you are willing to share would be welcome.