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Gents,
Owning a few rifles in straight wall pistol calibers, has me wondering how much, if any taper is really needed on non bottlenecked cases such as 38-55, and 444? What is the minimum?
Thanks
Juan
 

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Im assuming your talking a tappered crimp,Remember with tubed fed rifles you must have a sort of crimp there, due to the recoil may jar the bullet loose or push it back into the case, not good, this increases presures above safe levels. If your in a bolt, less likely to happen, but still can. A good Lee Factory crimp will work the best. If your talking about the case tapper, yes you need to have a tapper on the 444, this is what makes the 444 different than the 44 mag other than being longer, not sure about the other cart. Aim small hit small. RAMbo.
 

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Now I took it that he was asking about case taper...the difference in diameter from the base to the shoulder/mouth of a case, and I don't know how little there can be and still get the round to work right. The smallest amount (near zero) has been used on rimmed (no neck) revolver rounds, but they get their chambering power/control from your fingers. Some, like the .357maxi, aren't exactly low-pressure rounds (but aren't in the same ball park as some rilfe rounds).

I'd guess the taper is more important for any kind of mechanical repeater for it's effect on feeding...the more taper, the more likely a "straight" case is to self-load or work through a manual repeater smoothly.

Will make extraction easier...with a bit of taper, once the case moves rearward just a tiny bit, it has no contact with the chamber....with a real straight case, contact would maintain some contact through out the case's length.

All in all, "some" taper seems to be a feature of nearly every case...do think it's there for a reason.
 

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The taper has more to do with early cartridge design whereby gents were in transition from muzzle loading projectiles with a case of powder inserted in the breech. As time went by the bullet was "breach seated" first and the case of powder inserted behind it.
The gentle taper of top target rounds of the day i.e 32/40, 38/55 & 40/65 were to guide the breach seated projectile square into the rifling.
 

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For easy feeding in semi autos, taper is quite a good thing, as it may be for smoother feeding in bolts. In single shots, not needed. In fact, that is one of the tricks JDJ (SSK Ind.) uses on his handcannon rounds to reduce backthrust on the breech face of the Contender. Less body taper means more grip to the chamber by the case and less backthrust on the bolt face. That is one of his "secrets" to getting the kind of performance out of his JDJ line of rounds that he gets without causing excessive back thrust on the Contender's frame. With the Contender, the back thrust is the determining factor, not chamber pressure, and the straight walls of his cases reduces back thrust. On bolt guns, same thing applies but straight cases can make extraction and chambering a tad more difficult, especially on hot loads. On autoloaders, forget about it. Things need to be just a little looser because of the lack of chambering force compared to bolts or single shots. Any hang up at all and the arm will not go into full battery. This also applies to lever actions which certainly do not have the chambering leverage of bolts and single shots, but more than the semis. If you look at rounds like the .45-70, .458 Winny, and even the .444, you notice that there is really quite a bit of taper in their cases, even though they at first glance appear to be "straight."
 

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Worth mentioning that it would be better to take a look at chamber specs. (or chamber reamer specs.) rather than brass specs....in cases where the round actually doens't have much taper, they seem to build some into the chamber.
 

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Taper is just a law of Mechanics exaggerated... Think of a part that is pressed in... It will not require any other parts to hold it in.
Tapered parts are designed to come apart... More easily removed....

The pressure created in a modern rifle cartridge will lock a straight wall case in place.. Walls being perfectly parallel..
A minimum taper will allow it to come out of the chamber..

The rest like mentioned above are all benefits of the straighter wall dimensions.
 

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I think taper becomes more important as chamber pressure gets up there. Once one gets to 60 or 65 thousand psi the dirt and residue that naturally accumulate in the front of the chamber can definitely stick a straight case. However, not much taper is required to overcome this...a slight taper is every bit as good as a sharp one. Even the big RUM cases only taper .025 inches on cases 2.85 inches long. Removing that to get about a 4% increase in capacity and 40 fps more velocity is not worth it...You can get that just by loading to 61,700 psi instead of 60,000.
 

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I think Big Bore and Scout gave the reasons a cartridge case has taper.

The ones that really stick in my mind are the French 8mm Lebel and the .348 Win. One a bolt gun for military purposes and one for a lever gun. Each want quick and positive extraction of the fired case.

The Ackley Improved cases not only sharpen shoulder angle, but also blow out case taper to straighter dimensions.

The greater the taper, the greater the bolt face thrust.

I have a penchent for Ack. Imp. of standard rounds - some claim because I just want uncommon calibers, others for the increased velocity. Both are right - I just don't like tapered cases, thinking of wasted powder capacity.

Strangely, my fondest rifle was a pre-64 M70 in .300 H&H.
 

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