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7MMRUM loads
Mark T
Member Posts: 140 ✭✭✭
Hey guys, just brought home a NIB 700XCR 7mmRUM. Couldn't wait to work some loads and shoot. All the shop had was IMR7828 so I used that, I wanted RL25, but the Nosler book liked 7828 and the others (Hor.,Lyman) like the 25. Anyhow with 162gr BTSP the max listed was just a shade over 82gr in the Hor book, however the Lyman listed up to 85gr with the same bullet and primer. The Nosler book list the 160gr with 85gr as well, they list a federal primer. Why the differance? I loaded 82gr with a WLRM primer same as the Hor and Lyman book. Shot very well, 3060fps no signs of access press. Are the companies test equipment that much different? Or is it the size of the round itself, it takes larger amounts of powder to realize a small increase in velocity and pressure? Just pondering this, must be why I love loading and shooting!!
Comments
Regarding the 7mm RUM I can not give you any specifics from personal expertise. The design of the cases is now, with great characteristics. I've not worked that one.
Regarding the 700 XCR, it'll no doubt punch your ticket. No fuss, no muss, low maintainence, etc. Expect that you'll be happy with it.
Just a couple of notions for you, without specifics if you're willing.
Generally, when regarding the primers the entity outlining or listing the particular loading, is just outlining the specifics of what they used. It need not be the only, or the best, but what they used for their application, and one of the many actual variables.
And yes primers definitely affect the speed of ignition, the pressure in the chamber, etc.
With Your question: "it takes larger amounts of powder to realize a small increase in velocity and pressure? Regarding velocity increasing powder for lesser and lesser increases in velocity ... Yes, that is very real. And at times the accuracy goes down the toilet too.
((I picture it like driving my P/U ... gets to a point that the fuel useage does not normally justify the increase in velocity. If I were attempting to out-run that Tsunami ... I wouldn't care about the fuel useage, nor about burning the valves. If I want have the use the truck much longer ... without trashing engine , use my over stretched $$$ more sanely, etc. I get where I'm wanting to go with less hassle.))
On the second part of your question ... regarding pressure ... I'll just stress sensible caution ... from my readings and experience the pressure can seem OK, and the slightest variable can be the "tip-point" ... the straw and the camel, etc. I do know, that it can be sane now and push a little and be insane.
Like you know, come in deliberately a bit lower and if the need or want be there, work-up very gradually.
the best to you
I have those you have mentioned, but have not worked them up as yet. I'm putting my hopes on the .338 RUM for my needs and wants. My brother, is betting on the .375 RUM for his dream machine.
I am proceeding with the .338 in a couple of directions ... have been getting things together for a bit. (Need to get moving more but have allowed some of life's foilbles to slow me some.)
Personally, I have little real loading data on the 7mm RUM. I've a gap or derth of info. here regarding it, unlike the 300, 338 and 375 RUMs.
There are a number of folks here and on the AtE forum that have sufficient experience and knowlege with the RUMs to be invalualable sources for you.
From what I have been picking-up, from all the way around ... great recoil brake is paramount to realize and appreciate the potential of any of the RUMs. I'm planning that in spades, because I want to shoot a lot, enjoy it and learn the rigs and the loads well.
((For what is worth ... when I was studying the numbers in my different manuals, noted quickly that some seemed to load up much hotter ... sometimes starting quite high and going higher still. I have started out very modestly each time working up ... just as the folks' feedback here states.))
If you hav e not as yet done so ... I'd encourage you to do some site searches here on this forum and on the AtE forum ... I believe there might be things from earlier, that might help you some. If not specificly ... generally regarding RUMs. It's helped me quite a lot.
best of luck in your search.