quote:

Originally posted by 500grains:

Now, what about the rebated rim on the Rum cartridges? It seems that the solution so that problem is to base the cartridge design on the 404 Jeffery case instead.

Dan,

I do, and I am sure Jeff does to, get your point on the rebated rim. It is not the most desireable solution on a case.

However, this ARcartridge is supposed to be some sort of a Volkswagen, meaning a gun for everybody. A .470 on a standard CRF action, with available, cheep brass.

Praise those who can afford custom rifles in wildcats and classics, but for some, such a rifle is beyond dreaming.

What Jeffe has come up with here is to me a grand idea. Maybe not for You, but he will make many people happy.

Regards,

Bent.

Bent,
You are correct, it's aimed at being a volks round.

General thesis
there is some point where rebated rims are bad for feeding, just like the twist and yaw questions. The 500 jeffe is obviously on the "bad" end, and the 376 steyr is obviously on the "doesn't matter" side. At least from my experience building them.

To clear this up for the non-gunsmith wondering "why are they discussing this?" The rebated rim issue is when, in the course of feeding, the rearmost case head doesn't or loses contact with the boltface, slids down (overriding) and causes the bullet nose to initially jump UP then DOWN when the bolt hits the extractor angled edge (porposing). Even in the worst offenders (425 WR and 500 Jeffe) proper gunsmithing CAN relieve this (this is a high skill level in these two rounds)


if ANY designed rebate is "bad", then how much worse is UNPLANNED rebate?

Take your digital calipers, and a 404 case, and a 375 HH ( two of the greatest rounds ever) . and their case spec has NO rebate...

now measure them...

Pretty disturbing


Second point.
If a fella wanted to spend $50 more for the bolt face, he could make these cases from 404 cases. and pay three times for brass..

for .020 "...

or, if the amount of rebate on the 375 HH is acceptable, then its a question of about .010 ..

BTW the big weatherby cases are .035 or MORE rebated


third point.
No gunsmith (none) complains on the rebated rim causing RUM feeding problems. the PROBLEMS have been the last .365 of the feeding rails and the follower.. and if one replaces the follower, the problem is generally solved.


<from lots of rebates to little then none>
500jeffe, 460 weatherby, 284 winchester, RUM, HH magunums, 404 jeffe, 376 steyr, 416 rigby (zero)

So, I've built or gunsmithing all these beasts.. of which, only the 500 jeffe was a nightmare to get to feed.

The trick to making any round feed is to have constant contact with the bolt face, plus enough to not worry about it slipping off. if I had a 8x57 mauser that .01 made a difference if it slipped off out not, I would rework it.

jeffe

i guess the plywood pahyderm shoot might help end atleast part of this runnign discussion...

seemed to have nicer discourse a year ago.

Who here will be the first to build a 1:10 twist 585 or 600? Not to be an ass. I just really wonder want kind of sense an "across the boasrd", 1:10 twist rate makes for .458 cal on up. (AND UP HAS GOTTEN UP TO DAMN NEAR 1" AS OF LATE!)Where is the thresh hold? I would never build a 7X57 with a 1:10 twist. I would want to shoot bullets heavier than 120-140 grain weight. I am really just wondering what I should do for my long awaited 500 Dark Continent.............

Wildcatter,
the needs for twist, for stability, is MORE pronouced in smaller calibers, the oft mentioned 223 and, of course, the 244 rem.. opps, change the twist and call it the 6mm rem.. which, btw, was then saami'ed at the faster twist.

for example, a 1x18 tiwst in a .300 mag, trying to shoot 220gr bullets would result in groupings of keyholed shots!!

but, a 1x18 in a .585 results in a perfectly accurate rifle, and that's a far faster twist than the 577 NE was built around.

jeffe