Question for velocity freak, 257 RUM IMP. Is it possible??

jtoews80 · Jan 15, 2008

Hey, I'm just stirring the pot here since I haven't really got the money to build a rifle with an extra barrel to fireform brass then change out for another with a 250 rnd life-expectancy, but sounds FAST eh????
:twisted:
Is it Possible to go this much over bore?

How fast could it go?

what could one expect from this rnd?

CC

JD338 · Jan 15, 2008

jtoews80

Thats almost insane! :lol:
You are right, not much for the life of the barrel. Maybe 500 rounds?
Maybe Pop can run quick load to get some numbers but I would guess you would get a 120 gr PT up to 3600 fps and the 100 gr to 3800 fps.

What a goat load, all the way from Michigan. :lol:

JD338

jtoews80 · Jan 15, 2008

Pop, if you've got a chance could you run Quickload and just see how nutz this rnd could get. I believe that the guys running 338 RUM IMP with a 50 degree shoulder are gaining about 10 grains, however to avoid the nasty case damage/shoulder collapse that usually occurs with severe shoulder angles on smaller diameter cases at sizing time, I wouldn't go more than 40. So, with the smaller projectile the case would still gain approx. 10 grains or so? This would leave a case volume of approx 114 or 115 grain.

Since this is merely a theoretical topic I believe that a 6.5mm projectile could yeild alot more favorable results due to slightly lower pressure & throat erosion with much better ballistics using more efficient 6.5mm bullets. Not to mention the much heavier selection of bullets without going right up to a 7mmRUM IMP.
Thanks, CC

jtoews80 · Jan 16, 2008

I contacted Hornady recenly concerning getting custom dies made for a wildcat cartridge. Custom dies for a wildcat case over 2.6 inch are 145 for FL dies and 76 for a form die to first build the conventional case than either fireform or use a new tool that hornady has that hydraulically forms the case to an improved shoulder(40degree). It is done by putting the parent case in a special locking shell holder, than run the case up into the die reshaping the neck to 25 or 26 caliber. lock the shell holder and there is a mandrel that is smaller than the bullet OD, (for obvious reason and to provide mechanical advantage) hit the mandrel with a hammer 4 or 5 times creating pressures of up to 20000PSI and forming new brass with almost as sharp a shoulder as fireformed stuff. COOL stuff!! The hydraulic kit is a bit more pricey @ 166, but saves on barrel life alot. By the looks of the prices I have been given between barrel, reamer, headspace gauge, dies & forming tool the tally will hit $1000. Add in the donor rifle and stock that will push the total to 1500, still needing glass. This isn't happening this year unless I sell a rifle I already have. That is if I build on a savage action to take advantage of the barrel nut and the ability to remove the barrel easily and recut the chamber an inch farther down the barrel until there is NO rifling left in the tube or it is too short to make a round of this type useful, probably around 24" or so(would start with a 30"). The idea of building a wildcat is not new, but I had no idea how simple getting the pieces togather would be.

I may not build this thing this year or ever, but now I know it can be done. Actually, the people at Pac-Nor pointed me pretty much right where I needed to go to get the reamer, headspace guage etc. and Hornady was quite helpful with the custom dies. I tried RCBS and Redding first, but was to late in the day to find anything out

Now the big question is? what rate of twist to go with on a 6.5 RUM IMP if I want to use 130-160grn bullets??

And even bigger, how to convince my wife I NEED this thing??? OK I'll tell her it will go with my new hunting boots

:lol:

Antelope_Sniper · Feb 8, 2008

I shoot the 120 gr Nosler BT out of my 7mm STW at 3800 fps. One of these great guns, perhaps in a weatherby Accumark might save you a whole lot of time and trouble.

jtoews80 · Feb 9, 2008

I may try a 7mm RUM and if it doesn't do the trick I'll have brass and an action to work with that is ready for the case size etc. From what I've seen for pricing I can have a 7mm RUM and a vanguard 257 wby for the same money, after custom reamer dies brass etc, so it's not really worth it.

kraky · Feb 9, 2008

Sometimes it isn't all about case capacity....here is a 300 wsm doing 4000 fps!!!
http://www.richardscustomrifles.com/fav ... rifles.htm

OU812 · Feb 11, 2008

You might give this a look see.

257 Allen Magnum

338 RUM - parent case

Ballistics: 130 gr. Bonded Core FBHP @ 3650 fps in 30" barrel; 156 gr. ULD RBBT @ 3350 fps in 30" barrel. This is the largest 25 cal on the market that I know of today. It far exceeds anything that the 257 STW or 257 Banshee can offer and with the 156 gr. ULD RBBT, it turns the 25 cal. into a legit 1000 yard deer chambering. It is one of the most extreme rounds in the Allen Magnum line. The 257 AM must only be used with ball powders to prevent powder bridging problems with the very large capacity and small bore diameter. Stick powders are simply dangerous to use. Cases must be fire-formed and annealed to prevent neck splitting. Accuracy wise, this round has proven very accurate out to 1000 yards and has taken coyote size targets out to 1200 yards with first shot kills in heavy sporter-weight rifles.