So if this has as much sholder as the 411 Hawk, then would it be workable? How much minimum body taper is acceptable? It has .016 right now. maybe cutting it back to .01" to increase the sholder. What sholder angle does the Z-hat cartriges use?

I like the idea of the inexpensive RUM brass.
Thoughts?

seems like a good idea....

this looks allott like a 475 a&m, less belt... and FAR FAR FAR wiser than a 475 capstick


jeffe

why dont you like the capstick?

what will a 475 ultra do with a 500 gr. pill? 2500 fps?

BS,
the capstick is a cute little round, with no real gain over the 458 lott, and runs at high pressure to get "book"

if a rum had enough shoulder to headspace on (i don't know) it would be
1: larger case capacity
2: lower pressure at same vel vs capstick
3: higher possible vel, at same pressure

It won't do 2500, as that's more 470mbogo space (416 rigby, improved and necked up) than 404 jeffery (basic parent cacse of rums)

jeffe

why does the capstick get so much creedence here...is it becouse the "right people" own one

why?

because it's a quick and easy 470 based gun.. anything that can take a 375 HH can take the capstick

jeffe

its kinda what the lott is to the win mag i guess...is the 475 cal gaining in popularity? i hope so...beter and more bullets for the 480 ruger 475 linebaugh 470 mbogo(kaboom!)

I currently have a 70 Capstick, a 470 Mbogo and a 475 A&M. If I could only have one it would be the Mbogo and I wouldn't hesitate one second on that decision either. Low pressure to get a 550 gr bullet to go 2500 fps and brass everywhere. I love my A&M but because of the platform it's on not the case.

The capstick is nice but really dosen't offer too much over the lott except for frontal area. This does count for something but Still all in all the mbogo is the best choice in the 475 class of bolt rifles.

JMO

You gotta take the Lottheads with a grain of salt. The Capstick is just plain better than the Lott, after all they use the same case, but the Capstick has more capacity since it is both longer and shoots a shorter 500 gr bullet with the same COL. For this you get more energy with a bigger diameter bullet at the same recoil level.

quote:

Originally posted by Sabot:
You gotta take the Lottheads with a grain of salt. The Capstick is just plain better than the Lott, after all they use the same case, but the Capstick has more capacity since it is both longer and shoots a shorter 500 gr bullet with the same COL. For this you get more energy with a bigger diameter bullet at the same recoil level.

I'll buy all that except the same recoil comment, increase velocity with the same weight bullet, and recoil increases. I'd also expect that the nearly straight 470 Capstick would be even more of a bugger to get flawless feeding from a staggered mag than the Lott, which isn't the easiest round to make for perfect feeding either.

Ok, lets look at a 475 RUM. If it's .540" at the casehead, and you run the case tp .530" dia at the shoulder, and we assume 0.0125" walls for a .500" neck dia, then we have 0.015" for the shoulder. If 0.015" is good enough for a belt to headspace off, I figure it's enough for a shoulder, but, at what shoulder angle? My preference would be a steeper shoulder, say 40-45 deg, which would then require a form die for setting the shoulder back, which would make for some ultra critical brass forming and fire forming.

If you're going to all the expense and trouble of building something that uses larger dia brass than the belted basic case, I just can't see going to the ultra mag case when the 416 rigby case aka 470 Mbogo totally alleviates all the issues of 404 case, and drops pressure. It's as simple as getting a 416 Rigby and swapping barrels.

I would never talk anyone out of the Mbogo, but for the record, isn't the Ultra brass more like .550" at the casehead? And so we could say .540" at the shoulder, etc., etc.

bb,
**jeffe was wrong on casehead diameter***


so, paul is right.. the only thing that the rum would be better at is if itwas shortened to 2.65" and would then fit in a standard action, with a .475 bulllet

which is the 470 trollbane

jeffe

I've gotten conflicing dimensions on ultra mag brass, it is supposed to have been 404 brass that was rebated to a belted mag rim, which would mean 0.540" casehead, 0.532" rim. I've also heard that in actuality the um case has a 0.550" casehead.

Either way, you can produce an itty bitty shoulder, enough to headspace on with a fireformed wildcat, but not enough for a production round, or enough to keep you from inadvertantly moving the shoulder around when forming/sizing.

I'm more keen on simplicity, and having more than enough when it comes to big guns, so the 470 Mbogo is the best answer for a beltless case bigger than a 470 Capstick and having a sufficient shoulder.

Jeffe, you have actual RUM bras you're measuring? If so, that's pretty sad. Isn't the SAAMI tolerance .008" over spec? If spec is .550", one could conceivably have a chamber that is .558" and brass that is .018" smaller!
My Norma 404 brass is .542" or so. I've considered using the RUM, but figured it would be to tight in my fairly tight chamber, but maybe I should get some and measure for myself....

Just looked at the 10th Ed. CotW. It shows .550" base dia. for the 375 RUM.

I do not have any RUM brass, myself, to confirm this.

Hog Killer

375 rum

Yes. That is indeed the spec. We need some real brass, though, to see what it really is.
Jeffery "spec" is something like .545", but Norma's at least comes out to .542" - nothing to write home about. But a .010" difference would do nothing to help accuracy....
The WSM is spec'ed at .555" and from what I hear the brass runs pretty close to that.
[BTW, if the RUM is indeed .540" and the rest looks like that pic above, it will be SO easy to form my 358-404 'cat from that.

I have a rum case, and it is indeed .550" at the head. It was necked up to 416 as a dummy of what a 416 Howell would look like when I thought about building a 416 Howell.

BTW, the 416 Howell reamer, Ken's original, that I had was a floating pilot, and might work as a body reamer for the 470, though I think there is too much body taper. I also don't think I'd have much luck buying it back from the smith I traded it to, but it might be worth looking into.

the # on the far right is wrong...sorry

If it helps, the Lazzeroni brass is .577 at the base and .557 at the shoulder. In spite of the cost, I would choose that for a 475 to make certain that it would headspace well. IMHO, too much is made of brass cost when talking big bores that shoot at modest pressures. Just use it 10 to 12 times and the cost seems OK.