Belted vs. rimless??

[travis0127]

Is the belted round (say a 7mm wby mag) really less accurate than a rimless version (say a 7mm Dakota). I mean, given the same bullet, and (imagine) the same rifle to be fired out of (except the bolt/chamber, etc.), is the belted round a disadvantage?

I picked up the 5th edition hornady books, and they mention that Dakota's whole philosophy seems to be "belted sucks". Is this a realistic view point? Hornady mentions such things as:

superior bore alignment
improved functioning through magazines
increased powder capacity
more consistent powder burning rate

I obviously pulled this straight out of the book (pg. 301)

The speeds are the same, so what is the powder capacity/burning rate all about?

Bore alignment??

Why is rimless better? Just because of where it headspaces? How does this truly affect accuracy?

Thanks in advance for your comments.

 

[Jeff, CA]

Let me take a hack at this.

1. Superior bore alignment - there is some truth to this. Since a belted cartridge is designed to headspace on the belt, there will generally be more clearance at the shoulder. A rimless case will headspace on the shoulder. The "cone-in-cone" effect tends to give more positive centering of bullet & bore than the belted, with its loose fit at the shoulder. Note that if you handload, you can adjust your sizing die so it doesn't set back the shoulder of your belted case. It will then headspace on the shoulder, giving you the centering effect of a rimless case. Problem solved.

Increased powder capacity - It's hard to make a blanket statement like this, because there's so much variety in case sizes and shapes. A belted 7mm STW has more capacity than a rimless 7mm Dakota. So? This statement is only meaningful if everything else is equal; the increased capacity comes from the (slightly) larger case diameter.

Powder burning - I don't know too much about this, but it seems to be a rule that a short and fat case is more efficient and consistent than a long and skinny one. Benchresters, back me up on this?

You're talking about big game cartridges, too, not super-accurate benchrest cartridges. Any difference in inherent accuracy is probably so small as to be unnoticeable in field shooting conditions.

As a side note, the belt was first used on the .300 H&H. H&H originally loaded it with cordite, which was manufactured in long strings. They had to leave the shoulder & neck unformed (full diameter) in order to get the cordite strings into the case. They could only form so much shoulder with the cordite already in place, hence the shallow shoulder. The shallow angle wasn't enough to hold headspace reliably, so they added the belt. It isn't stronger than a rimless case, contrary to popular belief.

[This message has been edited by Jeff, CA (edited August 03, 2000).]

 

[Mike Irwin]

The BIGGEST problem with a belted case from the reloader's standpoint is that it can be very difficult to get the case resized adequately just in front of the belt. This can cause chambering problems in some guns with tight chambers.

I don't care much for the concept of a belted cartridge. As Jeff says, it provides a theoretical advantage, but I'm not so certain that there really are any advantages at all.

------------------
Beware the man with the S&W .357 Mag.
Chances are he knows how to use it.

 

[Paul B.]

To belt? Or not to belt. That is the question. Whether to tolerate the proper fit of a beltless cartridge, or the iniquities of belts that are supposed to headspace properly, but DON"T! Measure the belts on new unfired magnum rounds sometime and you'll see my point.
Is there a need for a belt on say, a .300 Weatherby? Of course not. Not on most of the magnum cartridges available today. Maybe the .375 H&H and .300 H&H, yes due to the slight shoulders, but certainly not on the rest.
If my research is correct, the first belted cartridge was the .400/.375 Belted Nitro Express (H&H), a round developed by Holland & Holland in 1905 to compete with the 9.5 Mannlicher-Schoennaur round. Power is in the same range as the .358 Winchester. The next belted cartridge in the H&H lineup was the world famous .375 H&H in 1912, followed by the .300 Super (.300 H&H Magnum) a few years later. These three cartridges need a belt to insure proper headspacing. The more modern sharper shouldered magnums do not.
BTW, After firing my first shot from a magnum round, I resize it so that from now on, it headspaces on the shoulder. Brass lasts a lot longer, and accuracy seems to be improved somewhat. Works for me.
Paul B.