Re: Barrel wear with 7mmRUM
I would agree with Goodgroupers general comments but would also like to state that there are powders on the market that will dramatically increase barrel life with a large cased, small bore magnum round.
The first thing to do is get rid of stick powders. I know they are supposed to be the best for varying temps and such but Ramshot has new powders on the market that will produce extremely similiar velocity and temp change resistance and are in Ball powder form.
I would recommend Ramshot Magnum which is very similiar in burn rate to RL-25 and Retumbo, the two best powders I have found for this case size and bore size.
I have been testing Ball powders in my Allen Mags and have been totally amazed at the difference in barrel temp compared to stick powders.
My 257 and 6.5mm Allen Mags simply must be used with AA8700 powder as there is no other suitable commercial powder that will work safely for these two extreme rounds, luckily, this powder works like it was made for these two rounds.
Compared to the 257 STW which has 17 gr less powder capacity and is 200 fps slower then the 257 Allen Mag. Using a top charge of Retumbo under a 115 gr bullet in the STW, after 5 shots you can not touch the barrel. This is a 3600 fps load in a 30" barrel using Retumbo.
The 257 Allen using nearly 20 grains more powder and acheiving 200 fps more velocity can be shot in 10 shot strings and the barrel is only warm to the touch. IT is definately warm but not so much that it is uncomfortable to hold the barrel indefinately.
So why are ball powders not used more often, well, they have gotten a reputation as being very dirty burning which is not a result of using them in the wrong situation such as a 7mm Rem Mag loaded with a 160 gr bullet with a full case of H-870. The case capacity of the Rem Mag is not large enough to get chamber pressures up in the 60,000 psi range where the ball powders burn the cleanest.
They also are thought to be very inconsistant in velocity change with temp changes. This is true with the older Ball powders but the new ones from Ramshot are basically the same as the Hodgdon Extreme Powders in this respect.
The main benefits of them are significantly lower burn temps, and they are dramatically less abrasive to the throat of the rifle as the powder is forced through this area when fired.
Now I am not saying the 7mm RUM will provide 2000 rounds of barrel life but I will say that the 257 STW will hit 1000 to 1200 rounds with 3/4 moa groups or under. I am betting the 257 Allen Mag will provide 1200 to 1400 round barrel life with the 3 groove Lilja barrels as long as they are not abused.
The main problem is the use of the standard 6 groove rifling with these high intensity rounds. A factory 3 groove barrel would be much better but then the factories do not want the rifles to last a long time, they want you to buy a new one in 3 years!!!
I am also nto talking about competitive accuracy either, I am talking big game hunting accuracy even for hunting out to 800 yards or so.
Comp shooters need higher levels of accuracy and as such barrels will be fitted more often on their rifles.
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