Ever have one of those "Boomie" moments where you wonder about where the limits are for cartridge design? For instance, what the minimum case taper and maximum shoulder angle numbers are.

The Boomstick is a true asset to this URL, he gets a lot of us to thinking "What if..."?

I have reamers and dies for the answer, the 308 ZTSS.

Zero Taper, Square Shoulder, based on the 308 Winchester case.

Asked here, and answered around Tax Time of 2014.

Rich

I have lots of "Boomie" moments

I think a square shoulder is going to cause problems. You may find that it won't chamber easily and it may be hard on case growth. It should hold a lot more powder and if you maintain the same pressures you should get about 100 to 150 fps more velocity over the 308.

Excuse my ignorance, but I always thought some minimum taper was required to provide for reliable case extraction after firing. Am I nuts?

Case taper makes for better feeding.
There is zero taper in many auto pistols, shotguns and revolvers.

If the chamber is smooth and not over loaded no taper is needed for extraction.

The issue is when the design is for zero taper it is always possible for a manufacturing problem to cause a reverse taper and that is strictly a HUGE NO NO. So any design should include a little taper or the manufacturing process must absolutely not cause a reverse taper.

Sizing dies also wear faster at the open end if the case is straight since the radius of the open end is doing all the work.
A tapered die will distribute the wear over a larger surface.

quote:

Originally posted by SR4759:

The issue is when the design is for zero taper it is always possible for a manufacturing problem to cause a reverse taper and that is strictly a HUGE NO NO. .

And that is exactly what happened on a chamber of a S&W 22 revolver I bought a short time ago. roger

I had a customer bring me 2 1000 Yd. BR rifles in to have them bedded. One was chambered in a 30x378 Wby. with a 50 degree shoulder. The other was 338x378 Wby. with the 50 degree shoulder. I was always told that no more than 40 degrees or, the shoulders would collapse when fired. I asked the customer if he ever had this problem and he replied "No". When the job was finished I asked him to bring me a couple of cases for my collection. He did and both had severe "denting" all the way around the shoulder area. I just put them in the collection box and never said a word.

One would have thought that by now the debate about case taper and shoulder shape would have died a well deserved death . Handloader proved a few years ago that in the SAME barrel there was no ballistic difference between the 300 WSM and 300 H&H. You can't much more different case shapes !

Another case of BS hoopla is the claimed superiority of the 338 Lapua to the 338 RUM.
Its only superiority is that it is a strong tapered case designed to be used in full and semi-auto weapons. In a bolt action or strong single shot, the RUM will duplicate any Lapua ballistics and is far less expensive.

Insofar as exterior ballistics go, all that matter is how much powder gas is pushing what weight bullet down what length barrel.

For hunting dangerous game or people I would choose the strongest, best feeding cartridge every time .... the H&H and the Lapua. For punching paper and ringing gongs the RUM is cheaper and the WSM can be built on a more stable action.

A 300 RUM is faster than a 300 H&H only because it burns more powder in equal barrels. Case shape and shoulder don't mean anything.

In hot weather where a gun might get to
120 degrees it is best to have minimum amount of
taper, as the case can swell and the heat raise pressures
also and when fired hang up. A case with total taper
of both sides of only .001" per ..750" to 1.00" inch of case length not as sure extracting as cases like 458 Lott with .001" taper per .080 of case length.Ed

Agree that's why the wannabe sniper community has embraced the 338 Lapua not because they understand its design but because its "tactical kool".
The Lapua and RUM are ballistic twins, so those of us who shoot clean bolt actions or single shots are better off with the RUM as it is so much cheaper to shoot. Those with Semi/Full auto 338s or are in combat conditions are better off with the Lapua as it is a stronger case with plenty of body taper to ease extraction.

Different applications, different cases, same ballistics.