Okay, I may be on the wrong forum for this information but I think I need to let people know what Hornady is telling me and then ask how come I see people exceeding this max load by 4 and 4 gr in off the shelf rifle and then ask what am I to believe so here we go. I am trying to work up a load for my 308 Winchester TAC-12 20" BBL 1 in 10 bolt action that matches the stock 178 GR ELD-X ammo from the factory at 2,600 FPS using IMR-4064 and here is what I am being told.
ANSWER - Thank you for your inquiry. The load data found in the manual listed for 4064 is correct. The ammunition velocity that we can achieve is also correct. We do not use the same propellants that are available to hand loaders. Our blends of propellants give us higher velocity without increasing peak chamber pressures. If you tried to obtain the same velocity with canister type propellants you would be way over the SAAMI maximum set limits. The bearing surface of varying bullets have a lot to do with pressures. A bullet of similar weight having more bearing surface in the lands will drag more causing higher pressures. The service rifle data used was an M1A. When dealing with that type of action, one has to look at propellants that will not harm internal parts as well as making sure the dwell time of the action is correct. that way you wont have issues with extraction and feeding. The data that is found in the loading manual is correct in accordance to our specs.
Thank you, TK
Hornady SnapSafe Tech Team
So, with that being said why do I see people shooting 42 - 44 and more grains and not having any problems and claiming they are getting the 2,600 FPS and good groups. As you can see according to this photo 30 GR of IMR-4064 is only going to give ~ 2,400 FPS which is 200 FPS under factory making a big difference in POI at all distances especially when using the Kestrel calculator. Just searching for information, advice and experience.
