The belted case is to headspace on the belt. Necksizing after first shot notwithstanding.

I was looking at my reloading manuals. The “rimless” rim diameter is .532. The belt diameter is .532.

So, why did the belt appear necessary to head space when the “rimless” rim was the same diameter? Could not the rim have been used instead of the belt given each are the same diameter?

Easy of feeding out of a magazine. Belts are wider and stack up easier. Rims are narrow, get hung up on each other and require a slanted mag box or rotary design.

Jeremy

well, i will try not to get long winded here.

the "rim" diameter is NOMINALLY .532 (measure them, they aint.. neither are the belts) .. but there's nothing to stop the case on the rimless .. (yes, i know there are rounds that kidna sorta headspace on the mouth .. not in scope)

headspace is a datum point .. and should be a place that there is mechanical interference at "0.00" .. the shoulder/belt/rim (not rimless) when properly on the bolt, should touch the chamber at the datum at "0.00" .. most chambers should be 0.003 "'longer" to account for "Stuff"

it's FAR better to do most belted carts off the SHOULDER as a datum, and this is exactly what a 9,3x64 does .. as it's really just a belted case with the belt and rim turned to .511 .. which is NOMINALLY the diameter of the case just before the belt

in short, it's about the DATUM line, not the shoulder (the datum is usually about the middle of the shoulder - but could be neck line or point of shoulder). ..

i didn't succeed in not going long, so here it is in a nutshell

there isn't an interference free way of head spacing off the "rimless" part without having the belt in the way

quote:

Originally posted by LHeym500:
Could not the rim have been used instead of the belt given each are the same diameter?

The short answer is yes.

The longer answer is that the belt was conceived/perceived as providing extra strength to the head, which it does only marginally, if at all. Mostly, it was put there as a matter of appearance.

It is ironic that many of the early belted cartridges had "rimmed" counterparts for break-open rifles which were identical to the belted versions in all other respects. There was no belt and the rims were somewhat larger in diameter and thickness than the rim of the belted case. Check out the .375 H&H Flanged for example.

Farbedo said it correctly; it was just for feeding from bolt
actions. Period. Didn't want to use a rim because it is harder to make them stack and feed from box mags, although not impossible.
But why didn't they just use the shoulder to headspace off of? (No long discussion of exactly where the "point of contact" is; it doesn't matter).
Because, look at the early, large bore cartridges; they were either straight, or had long tapers to them. Look at the very first belted case; the 400/375; it has a tiny little shoulder and is actually fairly straight, meaning not tapered. It needed the belt to headspace on, and to feed. Or like the 300 and 375 H&H; no real shoulder to use. And also remember they were loading cordite, and smooth feeding was a consideration. None of these things we use for cartridge nowadays. Look at the RUMS, for example; they are .532 all the way down; using the shoulder.
Hence, the belt.
But, to answer your question, could they have just used a rim for headspacing; Sure. but thereby introducing other issues for bolt actions by dong so.

DPCD you forgot more of this stuff than I can know, but I am not asking about a “rimmed case”. The belt and diameter of the rim of a “rimless” belted case are the same diameter.

Thus, in my mind the belt was not necessary on the 375 based cartridges, the rimless “rim” would have worked the same as the belt. This s because the diameters of the belt and the “rimless” rimmed belt case are the same are the same.

Look at the 375 Ruger case, the rimless rim and the casehead are the same size as the belt on a belted case. The case just does not step down after the belt. Of course, the 375 Ruger based cartridges are headspaceimg on the shoulder.

I know “rims” were forgoed due to feeding, but a “rimless” Case has a rim. That “rimless” rim is the same diameter as the belt. So, on the early belted cartridges with shoulders too step, why not leave off the belt and just use the “rimless” rim which was the same size as the belt.

Jefferso: Could you not have left the belt off and headspaced on the “rimless” case since it was .532 in diameter like the belt if the belt would have been forgone?

I apologize if I am not making myself clear. I know why the “rimmed” rim was done away for feeding in the magazine. Thus, we are told we need a ridge to headspace on with early HH cases with narrow shoulders. However, it looks like the belt was not needed for headspacing at all, the “rimless” rim of the 375 based cartridges is the same diameter as the belt. Same diameter means same surface area.

Now if you were using a .473 diameter rim, then I can see the necessity of the belt. All belted cases or Althea’s common ones use a .532 “rimless” rim. Technically, I do not think they are even rimless, because no place on the cartridge is the rim smaller in diameter excerpt at the shoulder.

Are you really asking why the rim is the same diameter as the belt?

The rim could be smaller, but it would rebate it relative to the belt. The belt limits how high the cartridge rises at the feed rail, so the rim would then be lower than optimal. Like any rebated case. Lowering that rim can create feeding issues. Keep in mind the actions being used at the time as well. The .425 WR wasn't well loved for that reason.

But with no shoulder to use for headspace in their design, something had to be used and they wanted to feed vertically out of a straight mag box.

Not sure if I helped or not.

Jeremy

I understand your question now, and farbe said it; a Rimless case does not have a Rim at all; Rim meaning something that is larger than the major case diameter; they could not have used just even the small .532 oversized rim because of the bolt action magazine thing and they could not use a rim the same diameter as the case head, to headspace on the shoulder because those early case designs do not have enough shoulder to do so. Rimless cases don't have rims; they have extractor grooves. That little ring of brass is just a result of the groove; don't call it a rim. Rims have to be larger than the case head. Clear as mud and I just made all that up. The other reason not to use a thin rim in a bolt action is that then you have to cut an extractor groove on the barrel; something rimless and belted cased Mausers don't need to do; just more drama, and fitting. Also, we are talking about British cartridge designs; Mauser and other European designs, have sufficient shoulders. Think Cordite and you will have the idea. And the British for obtuse designs.

Gentlemen, I think I am following. I just do not understand why he “rimless” belted case has a rim diameter the same size as the belt.

Should not the “rimless” rim be smaller in diameter than the belt. I always assumed it was smaller in diameter than the “rimless” rim, but looking at reloading manuals I realized the belted rim is the same size as the belt. Hence, my post.

The “rimless” rim of the belted case is the same diameter of the belt. The “rimless” rim is larger than the case body.

Farbedo has it on the head. Why have the rim diameter the same size as the belt?

The short answer is so the case is not rebated for feeding, but why headspace on a .532 inch diameter belt when a .532 rim is right behind the belt? Or better stated why not take the belt off the case and just use the same diameter rim?

That is what got me head scratching. I always assumed the “rimless” rim was smaller than the belt in diameter. If the belt diameter was larger than rim diameter, the belt would be necessary to my mind, However, it is not. They are the same.

Forgive me for being dense.

This is why dpcd builds rifles, and I just shoot them.

quote:

Originally posted by dpcd:
Look at the RUMS, for example; they are .532 all the way down; using the shoulder.

Sorry Tom, they are nominally .550 "all the way down", with a rebated rim to .532 .. i kinda sorta designed a whole series of rounds around them...

quote:

Originally posted by LHeym500:
The “rimless” rim of the belted case is the same diameter of the belt. The “rimless” rim is larger than the case body.

yes, they do... and the case would be equally "valid" if the .532 went from the belt to the rim .. but now we are talking about web strength, which is an ENTIRELY different conversation - but, functionally, the belt is just the rim "jerked up" a bit

Sorry, bad example; I apologize for that faux pas; I was just trying to give an example of a large modern case with no belt. A very amateur mistake, for which I am mortified, and one which I will endeavor not to repeat.
For the OP, I explained why the belt cannot be removed and leave just the small rim. (Definitely not there for radial brass strength.) It would work, but would create more problems than it would solve.

I have been reading and thinking. I think I got it. Because the “rimless” rim, even though it is the same diameter as the belt, it is not continues with the case because the extractor grove in front of the rim on a rimless case steps down. This creates an area to small for the rimless case to headspace, so the belt. Issues with narrow shoulder not withstanding.

There are issues with web strength trying to headspace on a rimless rim.

The .532 rim being the same size as the belt helped with alignment/feeding from the vertical box. The “rimless” rim if made smaller than the belt would have been rebated making feeding on a bench made scale hit and miss.

Have I got it?

The belt, the rim, and the case head on belted cases are all .532 inches. At least, that is what the Hornady, Nolser, and Barnes reloading manuals say. The “rimless” rim/base on the belted case is not smaller.

one COULD do the following.. but just because you could doesn't mean you should ... and the measurements aren't EXACT, but let's pretend it's close enough

the body diameter of an HH case is ~.511 or .510 nominal AT but above the belt ...

people can (i have) make 9,3x64 cases by turning off the belt, making a straight section of .510 all the way back, recut the groove, and other tweaks .. that's still rimless

it would be POSSIBLE to do these same things, but leaving the rim at 0.532 .. making it semi-rimless ....

the 475 linebaugh (made from 45-70 cases, originally) is a turned rim at about .540 .. that's a thicker than normal sheet of paper wider than .532 on both sides...

you COULD make (hmmm, now you've got me thinking of yet another useless wildcat) make a "rim" from an HH case, that would be fully functional ...

one of the stand out problems would be, for me, is that rim THICKNESS in this case isn't a super critical measurement, and we have a history of the belts not be made with tight tolerances .. so it would be a crap shoot for head spacing... and we ALL know how EASY it is (not) to get flanged cases to feed in a "normal" bolt gun

which brings as back to my original point that one CAN use a neck datum on MOST belted cases...


let's backup and talk about an assumed knowledge..
functionally the rim(flange) or belt serve EXACTLY the same purpose - to headspace off .. though the rim additional usually serves as an aid in extraction, something that the belt usually isn't used for.. i can't think of an exception to that, but i could think of how it would work...


let's spin this .. and take a 2 1/2 410 shotshell (flanged) and a 458 winmag ... (well, i would start with a lott case, for top "Wad" but you get the point)

both are 2.5" long
410 is .535 rim, 458 is .532 belt
other than folding the top, you could put 410 loads DIRECTLY into a belted case, and (assuming correct barrel) the results would be along the same line (not identical, but you get the point) ..

but the 410 extractor system wouldn't work on the belt.. it would have to work on the rim...

anyway, that was a more or less useless thought experiment ...

but a short "rimmed" former HH case, straight case, necked to .458, in a wheel gun. ...

nah man.. i need to go have a lay down and forget that....

dang it!! a 45 LC that uses .458 bullets ... (stop jeffe, that's just a waste of time.. you KNOW it is.. ) ... but it's intriguing

Lheym; sorry to say, you are way overthinking the geometry of a belted case. Not trying to slam you at all..
Bottom line is that, yes,if you removed the belt and left the .532 rim, it would work very well in a chamber cut for it. Strength is not the issue. Function through a bolt action magazine, is. And if it has a shoulder of any size, you don't need the belt or rim at all, for headspace purposes, read the good analysis that Jeff wrote. Come over and we will lathe turn off some belts, AND rims, and shoot away. On most any magnum you can name.
If you want to talk about it, PM me.

The first 30 cases I had for my 9.3X64 were made by turning the belts off .338 Win Mag cases. They work great.

Completely unrelated thought, sorry.

Jeremy

No it is quite germane; reinforces the fact that at the belt is not there for strength.

One thing to keep in mind when one considers the origin of the belted rimless:
Back in the day, Brit sporting rifles tended to have rather “generous” chamber and shoulder dimensions in order to accept various makers ammo (no SAAMI or CIP standardization back then) as well as ensuring chambering with dirty or deformed ammo out in the boondocks of India or Africa.
This worked OK with rimmed cartridges in typical single shots or double rifles.

But what to do to achieve safe headspace in a sporting magazine rifle without using rimmed ammo that has the attendant design/engineering issues feeding from a magazine.
Ah Hah......Why not a belt....safe headspace, mostly smooth feeding in a straight stack magazine, and still workable with sloppy chambers!
- Mike

I'm with Stonecreek, The belt on the 375hh was a appearance thing. The belt also brings some additional expansion/resizing issues along with it.
(Note: I only use once fired belted cases on hunt. On Belted cases that have been fired several times I check and resize as needed with the Larry Willis collet resizing die. www.larrywillis.com)

B&M Rifles and Cartridges did extensive testing on straight walled rimless cartridges headspacing on the rim and mouth and just on the rim. Both works perfectly.

quote:

Originally posted by dpcd:
No it is quite germane; reinforces the fact that at the belt is not there for strength.

Good point. If you cross section a case, it is mostly solid at the head where the belt would be regardless whether it is a belted case or not.

One of the better examples of a belt being needed is the .458 Win Mag. You could headspace it on the case mouth like a 45ACP (and others), but would not be able to crimp a bullet.

Crimping on that cartridge is required to make it work well.

Using a rimmed version would make it difficult to adapt a wide variety of actions to it.

The belt, like it or not, makes this cartridge possible, and was key to making it popular, IMO.

Jeremy

[QUOTE]Originally posted by dpcd:
Lheym; sorry to say, you are way overthinking the geometry of a belted case. Not trying to slam you at all..
Bottom line is that, yes,if you removed the belt and left the .532 rim, it would work very well in a chamber cut for it. Strength is not the issue. Function through a bolt action magazine, is. And if it has a shoulder of any size, you don't need the belt or rim at all, for headspace purposes, read the good analysis that Jeff wrote. Come over and we will lathe turn off some belts, AND rims, and shoot away. On most any magnum you can name.
If you want to talk about it, PM me.[/QUOTE

Geometry and engineering are not my areas. I just saw it, and thought well, that is interesting, why if they are the same size.

I take nothing as a slam. I draw the line at cussing each other. Obviously, does not apply here. You put a bow in it for me very nice.

Redstone, I submit has added to the discussion.

Thank you all.

you need the rim diameter to not be rebated or the bolt face would slip pat it and try to feed off the belt causing a big jam at the end of the rails.

so the full size rim behind the belt is there to catch the bolt face.

Yes, Red made very valid comments.
Note that we do have successful rebated rim cartridges, where the actual rim is smaller than the case body.
Also, the belt is/was not there just for appearance; it was there for a purpose, as discussed above. Belts, per se, do not introduce any problems in and of themselves; any issues with case stretching and separation are due to over generous chamber and brass tolerances. Both of which can be overcome by ignoring the belt and headspacing off the shoulder. As discussed elsewhere ad nauseum on AR.

Muddy watering..

KISSm both the belted magnum and the rimmed cases should be headspaced on the shoulder, to do less the belted case and rimmed cases will separate sooner than not, its over working the brass...there is just too much variation in headspace due to inaccuracy of the belt and rim..Keep it simple use the shoulder to headspace either one in sporting rounds..I found this to be true even in the double rifles, but due to a lesser degree as the pressures were much milder, Your brass will last much longer even though you will probably have to full length resize on occasion as the necks streatch.

To the best of my recollection, the belt was put on not only to accommodate bolt gun mags, but to accommodate using those cartridges in double rifles. H&H apparently didn't like headspacing off the shoulder for a double, and almost nobody reloaded them back in the day, the 375 was designed to extract easily, with almost no shoulder, because they didn't want to build it to headspace that way. It was their solution to having to have a rimmed and a rimless cartridg. It was also easier to manage for their sub-contractors in the trade as well, as they had a line of cartridges in mind. I forget where I read that, but, it was a long time ago. Look at the line of cartridges they built with the belted case. That was their line of thought apparently, so it was said, as I remember it.

The trouble with belted cases in double rifles is the extractors are prone to hop the belt and tie up the rifle in some cases..Its argueable as many doubles were made in .458, 375 and seemed to work...But I wouldn't even consider it. The double was made for rimmed cases of yesteryear for the most part, and proved their worth as such...A number of double rifle makers tried pimping the .416 Rem, 458 and 375 and eventually dropped them because of the number of returns for repair...old lesson learned..

209; no, the belt was not invented for double rifles; there was no need for it as all double rifle cartridges had typical rims, including the 375 Flanged Magnum.
There was no need to invent the belt for double rifles.
They were added to double rifles as an afterthought, and as Ray said, it is not ideal for them. Remember the first belted cartridge was a 375-400, designed only for bolt actions.

I had always read that belts were there for ease of headspacing with gently tapered cartridges of the day. They also eliminate the rim over rim stacking issue for magazine fed rifles while preserving the safety and gas seal efficiency of the rimmed round. They are an effective gas seal forcing gas to make two 90 degree turns to escape vs rimless(rebated rim) which is straight out. Feeding is not quite as smooth as rimless but has proven reliable over the last 90 years or so.

Well I'm gonna throw in my $.02 worth.
The early belted cartridges were used for all the reasons mentioned.
As years went by these long tapered belted cases got wildcatted. Mostly by blowing out the shoulder to minimize taper.
At this point the belt became moot It didn't really serve any purpose. They could have easily turned the belt and rim to make a rimless case. They left it there mostly because the parent cases had them.
Then along a few years later someone said we have a bolt head with a .532 rim size. Why don't we just make a rimless case with a .532 rim. This would increase case capacity.
So they did.
This is why there are cases rimless and belted that use a .532 bolt head size.
Leo

Actually, the belt came about because of (2) early cases that NEEDED to have a belt (the 300 H&H and the 375 H&H). They needed to have a belt because their shoulder had a very shallow angle, and that caused misfires. Rifle cases need to have a surface to provide a firm forward stop to prevent forward movement. Adding the belt solved this problem. Otherwise the firing pin strike would be absorbed and cause misfires.

No other belted case (except a few rare wildcats) ever needed to have a belt. Way back in history, the marketing guys figured the H&H calibers were so wildly successful, that they’d never be able to sell any magnum rifle if it didn’t have a belt. So, any time you see a belted magnum . . . . that’s the story. Because of its location, the belt doesn’t add any strength to a case, not even a little bit.

I designed (and patented) the Belted Magnum Collet Resizing Die (now used by almost 7,000 shooters). It solved a problem that plagued handloaders for decades.

I also designed (and patented) the Digital Headspace Gauge that lets a handloader measure chamber clearance at the shoulder. That is especially important for those that reload belted calibers. Hope this info helps somebody.

Innovations, Thanks for sorting out the history on the start of the belt.

I have your belted Magnum Collet Resizing Die and it does the job perfectly. I also got one for my Ph in Africa. It is an important tool for a handloader/hunter with belted cartridges. Brian