RIMLESS .284 Winchester HPT?


#1

Does anyone know the why of the 284 Winchester HPT cartridges without the rim?

Ray


#2

Ray, I can’t answer for this specific cartridge, but I have seen a number of proof loads without rims or grooves. I have rimless/grooveless proof loads in 9mmP. I suspect it was a way to ensure these proof loads didn’t get mixed with normal ammo, but why was this only used occasionally unless there was something special (like extremely high pressure) about these proof loads.


#3

I can’t vouch for this, but many years ago I believe I read that the rebated case design failed under proof pressures, so Winchester eliminated the extractor groove for this loading in the .284. Might have been in a Tillinghast or Dunn catalog of the 1970s?

.


#4

[quote=“Iconoclast”]I can’t vouch for this, but many years ago I believe I read that the rebated case design failed under proof pressures, so Winchester eliminated the extractor groove for this loading in the .284. Might have been in a Tillinghast or Dunn catalog of the 1970s?

.[/quote]

Teak

I’m not questioning that, but if true doesn’t it seem a bit odd? HPT cartridges are intended to test or proof the barrel and/or receiver but if the case itself fails there are some major flaws somewhere in the program.

I’m wondering if the rimless cartridges are intended to be fired in a special test apparatus rather than a conventional receiver/barrel? But even so, it would seem to me that a standard case would work just as well since all that is missing is the extractor groove.

Still wondering.

Ray


#5

BTT


#6

Maybe the best ones to answer this question are our French friends. They have made these, as Lew said, in at least 9mm, and they are called “Auto Frattage” (I may have spelled that wrong, so forgive my bad French if I did - it mighe be “Frettage”). I don’t know the exact translation of that, but it may be a clue to their use. I suspect that Ray was on the right track - that these are fired in test barrels in some sort of fixture, rather than used for the normal proof-testing of rifles before they are sold.


#7

IIRC these are used to proof barrels during manufacturing. This is done after the chamber is cut, but before the extractor cut is made so there is no need for an extractor groove.

However, a normal proof round can also be used for the same purpose, so this still does not answerer the question as to why they are made without a rim. Perhaps the factory can save a few pennies or a bit of wear and tear on there tools?


#8

John,

Barrels are sometimes tested and stressed by either hydraulic pressure or by firing a high pressure round. The bore is expanded beyond its elastic limit but the outer layers are not. The barrel therefore remains under stress, the outer layers compressing the inner layers. This high pressure “stretch” is done before the barrel is mated to its action, hence no extractor available and no extractor groove required. These auto-frettage rounds would never be fired in a finished firearm and differ from a normal proof round. I knew that this was done on the larger guns (4 inch to 8 inch) but have never seen auto frettage rounds for rifle calibres before.

gravelbelly


#9

gravel

I always thought that pressure stressing of artillery barrels was only done to more or less bind the liner to the barrel or, in the case of built up barrels, to bind all of the hoops together resulting in a strain in compression. This is usually done by heat

I have not heard of such a thing being done in one-piece barrels. Not that it hasn’t however.

How exactly are the rimless HPT cartridges different from the conventional ones? Higher pressure? Why wouldn’t a conventional cartridge work?

Ray


#10

These “Auto-Frettage” (self-compression) cartridges were made for .30-40 Krag and .30-06 up to about 1911 to stress unfinished barrels… After that standard HPT cartridges were used. Why were they once used and why did they stop.

As for the .284 Win., I have them with SUPER-X and SUPER SPEED headstamps. The .284 is the only modern rifle case type I have seen in this headless proof. That leads me to agree with the idea it had something to do with the rebated rim. But, I also have a .284 Proof WITH an extracter groove and SUPER SPEED headstamp. They must have 2 different functions. And of course, the question remains, why aren’t the headless type made in all case types?


#11

If I am understanding this correctly, it seems I was half correct in my assumption; that is, they are fired in some sort of testing fixture, but they are not test barrels but the actual barrels that are fitted to a firearm. Regarding only used in “big calibers,” the only one I have ever had is the French 9mm Para in my own collection.

Thanks, guys, for confirming my second spelling as correct - the “frattage” didn’t look right when I typed it, but I wasn’t sure, therefore my second “frettage” spelling. I also thank Ron for the translation. I can banter my way around in Spanish and Italian, and talk cartridge talk in German, but French will forever remain a mystery to me.


#12

Once again I confess my ignorance of frettage as it relates to small arms, but from the descriptions given it seems to me to be more of a stress relieving or normalizing rather than pressure inducing such as is used in large caliber artillery barrels. Today, stress relieving is accomplished (when necessary) using modern techniques such as cryogenics. Even so there are arguements on both sides inasmuch as today’s barrel steels are darn near perfect and many believe such things are a waste of time.

I’d like to learn more about frettage. Anyone know of any links to information.

Ray


#13

Teak

I’m not questioning that, but if true doesn’t it seem a bit odd? HPT cartridges are intended to test or proof the barrel and/or receiver but if the case itself fails there are some major flaws somewhere in the program.

I’m wondering if the rimless cartridges are intended to be fired in a special test apparatus rather than a conventional receiver/barrel? But even so, it would seem to me that a standard case would work just as well since all that is missing is the extractor groove.

Still wondering.

Ray[/quote]

@ Ray -

The tests subject both the brass and the firearm to substantially higher pressure than will occur under normal operating conditions (I realize you know this!). My personal premise for accepting the explanation I was given is that the .284 is a modern round with a fairly high chamber pressure as compared to the .425 WR or similar types. I would note that one can see a similar evolution in the rebated base .499 LWR - the original production has a wider and deeper extraction groove than the second series. As a side note, it would be interesting to to know the configuration of that proof round, although I expect the difference has more to do with reliable extraction than with chamber pressure.

While I don’t have any proof per se (no pun intended), the theory I posed originally certainly has some remaining credence by logic and inference.

To whit:

(1) A HPT with the standard head configuration does exist (I had one in my old “general” collection), but I’ve seen but a few over the years, in contrast to the dozens of the rimless / grooveless types. This is consistent with both of the proposed scenarios.

(2) The .284 was the only rebated base round Winchester ever produced (AFAIK). I believe the extractor groove would thus have less metal in the walls than the more common rimless, belted and rimmed types. Again, consistent with both arguments.

(3) Winchester has made all sorts of rifles in all sorts of chamberings. I’ve yet to see any other rimless / grooveless commercial American HPT rounds (and darn few military ones). But these .284 proofs are common enough in the market to assert they are not especially scarce.

(4) If this were something Winchester were to do in the course of the normal manufacturing process, surely other types would be known, especially where the .284 was not a commercial success and was only available for a short time. But, again, I’ve never seen nor heard of such a thing of commercial American origin except the .284.

Now, it occurs to me that the truth of the matter may actually be a synthesis of these two ideas, i.e.: Winchester started by using a “normal” proof case design but encountered case failure problems, so began using the rimless / grooveless type, either earlier in the process or with a change in the test fixtures.

.


#14

Teak

All that you said makes perfect sense. Lacking examples for US Commercial cartridges other than the 284W seems to point to the rebated rim as the reason.

But I still have a hard time believing that a normal HPT case would fail even with the rebated rim. Most HPT cartridges are loaded to about 1 1/2 times normal pressure (75,000 CUP) but I believe that laboratory tests have confirmed that a modern brass case will withstand even more pressure (as much as 100,000 CUP) which is more than some actions will hold.

Maybe we will never know the “why” of those 284 HPT cartridges. I doubt if anyone in the industry would give us an answer (lawyers and such) but I suppose as collectors we should be thankful for them, for whatever reason.

Ray


#15

To satisfy my own Yankee curiosity, I retired to my garage laboratory and sliced open three cases to see what the insides would tell us.

The first was an R-P 7mm REM MAG, then a WW 284 WIN, and finally, what many consider to be one of the weaker cases out there, an R-P BASIC (308W).

As you can see by the photo, it certainly appears that the rebated 284 case is lacking nothing when it comes to case head strength.

I realize that three cases does not a legitimate test make and the only thing I learned for sure was that I need a new hack saw blade.

But now, does anyone have a spare grooveless 284W HPT case that the would sacrifice for the cause?

Ray


#16

[quote=“Ray Meketa”]gravel

I always thought that pressure stressing of artillery barrels was only done to more or less bind the liner to the barrel or, in the case of built up barrels, to bind all of the hoops together resulting in a strain in compression. This is usually done by heat

I have not heard of such a thing being done in one-piece barrels. Not that it hasn’t however.

How exactly are the rimless HPT cartridges different from the conventional ones? Higher pressure? Why wouldn’t a conventional cartridge work?

Ray[/quote]

Ray,

From what I remember of my Royal Navy ordnance training (long ago), auto-frettage was a way of strengthening barrels. Earlier barrels were either hooped, where steel hoops were heated and allowed to shrink onto the barrel tube, or wire wound where the wire was applied both hot and under tension. Both of these methods resulted in a composite barel where the outer layers applied a compressive force on the inner tube. Later, when single piece barrel tubes were perfected, the barrel tube was subjected to very high pressure to stretch the inner layers and thereby allow the outer layers to apply the compressive force.

As an example, taking a bore of 7.62mm and an outside diameter of (say) 20mm which was expanded by pressure by 0.1mm. The circumference of the bore would increase by 0.1 x pi (3.142) mm which is 0.3142mm or a little over 4%. The outer diameter would also be increased by 0.1mm and this circumference would increase by the same amount, 0.3142 which is only 1.57%. So it is possible to stretch the inner layers to beyond their elastic limit, so they stay there, whilst stretching the outer layers within their elastic limit so that they try to revent to their original dimensions.

This process was applied to 40mm Bofors barrels, by hydraulic pressure, before final machining and rifling. I have not previously heard of this process being applied to small arms calibres. Perhaps it is because the process was applied to partly finished barrels that the extractor grooves were omitted, just a guess.

I hope that the above crude description makes some sense to you all.

gravelbelly