Thanks for sharing the specifics of the new 7 LRM reamer throating. The suggested .025" jump is shorter than what Kiwi Nate suggested for the 7mm LRM in his article on the 7mm Practical: "To avoid finicky performance, its best to have some freebore with this design, approximately .250". The case capacity is just a little too much to do otherwise." Any way you slice it the freebore is far shorter than the 7 RUM! This is very useful knowledge.
I have been using a PT&G reamer for a 7mm/375. (full length shoulder and short neck) I recently installed an old barrel on my LA Ruger that has a lengthened mag box. Box is still too short yielding a .210" jump to rifling! I shot this package just to see how the jump would work. It didn't. Thankfully the rechambered 284 win barrel was something that I won't be using and can be thrown away. It WAS funny to use a 21" barrel for the test. Pet loads of H-1000 and 180 berger hybrid yielded 2900 and change. I didn't see the fireball but I'd bet there was some significant flame in front of the barrel and it was LOUD.
I have concluded that I will send my reamer back to PT&G to shorten the throat length so I can kiss the rifling with max OAL to fit Ruger's magazine then seat bullet an additional .025" or so. I will also buy a throating reamer so I can lengthen the throat for other rifles with longer magazines.
I have a worn out Lilja barrel that is currently a 257. It is a beauty #5 fluted SS 28" long. I am going to have Dan Pederson re-bore and re-rifle it for 7mm. This way I can get some value out of this expensive barrel. Am going to use a faster twist as I would like to try the upcoming 195 Berger.
Looking forward to more updates from you or tdean on your results.
i got me a dial indicator on vice grips and did not move off zero when loosened guard screw, of course you have to make sure its balanced so gravity doesn't pull it out see pic, note i did this test after i dremeled out where it was hitting action, i know there was stress because i could feel it when i loosened screw with my hand on foreend, cant feel it now
Tried some retumbo yesterday in the previously mentioned 7mm/375 with 180 hybrids. Got same accuracy as the best load with 74 gr of H-1000 and gained 90 fps for 3030 fps from 26" barrel. Did not work up to max load but am close.
Some US 869 is coming in Friday. Will give it a try next along with refining the retumbo load sometime next week.
Just in case any readers didn't read the earlier posts, while the 7mm/375 is similar it is not a 7mm LRM. Case is larger so don't duplicate the above load data in a 7 LRM.