Quote:
Originally Posted by lclund1946
Marky may be on to something as I believe the 7mm LRM is running some tight tolerances.
Doing my research prior with the 7 lrm I think the main culprit was inconstant thickness of the brass in the necks. From what I recall they had to be turned or people were getting pressure signs far too early.
I have found I had to do this with lapua brass as well. Not sure if it made it more accurate. But I think it helped with fliers and wild es
I would sooner see you post some actual figures like neck thickness, jump to lands, Velocity, Barrel length rather than just the bash the brass because you thought it was made by Hornady. A little research tells me that a moderate load with the 180 Berger Hybrid would be more like 71.2 grains if running 0.020" off the lands. Gunwerks claim 3075-3000 with 72 grains of H 1000 and the 180 Berger Hybrid seated 0.080' off in a 26" barrel. If you had measured case head expansion, as I outlined, and did a pressure ladder, over a chronograph, starting at about 70 grains you would not have destroyed the brass and likely found nice accuracy node at at about 3000 fps. The 7mm Sherman Short will do that with about 61 grains of RL 26 and run a 195 EOL to 2900 with 59 gains of RL 26. I never would have thought that possible when I designed the 28 EXTREME (7mm Magnum capacity) which is virtually the same as the 7mm LRM. There is a reason why the 6.5 PRC does what it does with less than 60 grains of powder.
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That’s where some of the problems are. With the 7lrm they had inconsistent brass from lot to lot. Early in the production run especially. The expectation is that it is made to spec. But in reality its a mass produced product that is relying on tolerances to a couple thou and when it’s less than a buck a piece. Chances that everything is perfect all the time is pretty low