Iv'e done a search for this, but couldn't find what I wanted to know - sorry if it's been covered before! (GG) [img]/ubbthreads/images/graemlins/grin.gif[/img]
Iv'e been following Kirby's progress with the 7mm AM with interest and really fancy a 7mm Magnum to add to my collection - maybe not quite at the edge as Kirby's cartridge but somewhere near. [img]/ubbthreads/images/graemlins/shocked.gif[/img]
My question is this; if I commissioned a 7mm RUM or SAUM, would there be any benefit in speccing a tight necked chamber reamer or would I be wasting my time?
The basic rifle spec is something like this at present: Hansen action, Border 5R barrel, Macmillan A5 stock - (yes Pete, your'e doing it [img]/ubbthreads/images/graemlins/wink.gif[/img]) I intend to use 160 - 200 grain, match bullets or accubonds.
Most of my rifles have tight necks and I percieve there to be accuracy gains to be made here over the standard sloppy neck sizes - I've no past experience of Magnum cartriges and wonder if the same principle applies?
Most of the time the rifle would be used for range work, informal competition to 1000 yds and open hill stalking so I really want to extract "best" accuracy from my chosen cartridge.
As an aside, are there any muzzle brakes available, that offer similar performance to Holland but are cleaner looking? (slimmer design)
I am shooting a pair of 300 SAUMs, a Sendero and a Model 7. Brass fired from my Model 7 will not chamber in my Sendero even after it is full-length sized. There is about .003 difference in the neck with the once fired brass. Shooting the same loads in the rifles, I get about a 220 fps difference with a 4" difference in barrel length. I don't think you can pickup 55 fps per inch of barrel; half that would be more like it. I attribute it to the tighter chamber.
It may be voodoo in my head, but its the only thing that makes sense to me.
FWIW if you do the SAUM, buy up some extra brass. On a different site, a guy posted that RP will not be making it beyond 2006. I have no idea if its true, but better safe than sorry.
Location: The rifle range, or archery range or behind the computer in Alaska
Re: Tight Necked RUM / SAUM
I think you would be right about getting more preassure with the tight chambers. I shoot a 300 RUM with a "tight" neck (.333") and a very tight chamber and if I follow the reloading manuals it WILL sieze my bolt in place. [img]/ubbthreads/images/graemlins/blush.gif[/img] I use about 10 grains less than published. I also use and get good velocity with H50BMG which isnt normaly used for the 300 RUM (too slow).
All in all, I like my tight neck in this caliber. Longer brass life, always have perfectly straight brass after resizing, better accuracy ect...
Long range shooting is a process that ends with a result. Once you start to focus on the result (how bad your last shot was, how big the group is going to be, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.
Ian, the 7mm AM really appeals to me, but I wasn't aware that anyone other than Kirby had the reamer or that Pacific Tool would sell that reamer profile - it would be a very strong option for me if a reamer and dies were available.
The kudos would be nice, but it isn't really a concern - I just want to have a hard hitting, fast shootin, damn accurate smokepole! [img]/ubbthreads/images/graemlins/laugh.gif[/img]