Tapered vs. straight-walled cartridges


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Oleg Volk
June 7, 2006, 03:25 PM
7.62x39 and 9x19 both use tapered cases. That makes extraction much easier than with straight-walled cases. I wonder why most other case designs use straight walls? Aside from the extreme cases like the old Lebel 8mm, seems that a slight taper won't make magazine design much harder, yet would improve some aspects of reliability...

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rbernie
June 7, 2006, 03:29 PM
Tapered cases hold less powder than a straight walled case.

DF357
June 7, 2006, 03:38 PM
A tapered case keeps the point of second round from hitting the primer in the first round.

Dave R
June 7, 2006, 03:46 PM
Are most cases straight-walled? .223 and .308 (and their military counterparts) are tapered. I believe all military rifle rounds in WWII were tapered, but I could be wrong. I also believe nearly all of the new cartridges after WWII are tapered.

.45acp is not, though...

nfl1990
June 7, 2006, 08:45 PM
I believe it has to do with pressure and barrel design, with a pistol round you have a shorter barrel so if the powder burns too slow you lose a lot of that energy the larger surface area allows it to burn faster, however the necked case would allow it to burn longer and (I think, although this advice is worth what you're paying) create higher pressures.

Oleg Volk
June 7, 2006, 08:50 PM
I don't mean straight vs. botttlenecked cases, I mean tapered designs within both categories.

Bwana John
June 7, 2006, 09:31 PM
I wonder why most other case designs use straight walls?
In looking thru my reloading manual there appears to be very few strait-walled cartridges, and most of these are revolver rounds.

I think revolver rounds need to be strait walled in order to not "back out" under recoil and tye up the cylnder. (like the ill-fated S&W .22 jet)

I imangine in the old days strait chambers were also much easyer to ream.

Even the 45 acp has some taper

Zrex
June 7, 2006, 09:53 PM
The .223 tapers about .020 from the widest part (not the rim) to the narrowest before it does the bottle neck thing. The .308 is about .016. Maybe testing proved that you don't need a whole lot of taper to benefit from the design?

Zrex
June 7, 2006, 09:57 PM
Here is the .223:

http://www.nazarian.no/images/wep/259_049.gif

here is the .308

http://www.nazarian.no/images/wep/266_124.gif

Lone_Gunman
June 7, 2006, 10:10 PM
A tapered case keeps the point of second round from hitting the primer in the first round.

I'm really sleepy right now, but I am not sure what that means.

Third_Rail
June 7, 2006, 10:10 PM
Maybe testing proved that you don't need a whole lot of taper to benefit from the design?

We have a winner! Even a very slight taper, on the order of a few thou an inch, will work to keep the case from sticking in the chamber. If there's going to be the possibility of a lot of crud, though, a faster taper helps more.

DF357
June 8, 2006, 05:00 PM
A tapered case keeps the point of second round from hitting the primer in the first round.

I'm really sleepy right now, but I am not sure what that means.


In a tube feed rifle, when you place one round behind the other, a tapered case lowers the point of the bullet to below center of the round in front of it. The 'nose' of the round will not touch off the primer in the preceding round.

C96
June 8, 2006, 05:06 PM
Taper is good for feeding and extraction, bad for pressure on bolt face and brass stretch.

Lone_Gunman
June 8, 2006, 06:19 PM
In a tube feed rifle, when you place one round behind the other, a tapered case lowers the point of the bullet to below center of the round in front of it. The 'nose' of the round will not touch off the primer in the preceding round.


What would be an example of a tube fed rifle that uses a tapered cartridge that would do this? Are you talking about lever actions? If so, I can't think of one that uses a cartridge with enough taper that it would matter.

Nashmack
June 8, 2006, 06:34 PM
'86 Lebel.

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