308 ZTSS; coming in the spring...

[Idaho Sharpshooter]

I have always wondered (or maybe my mind just wanders) how little case taper and how sharp a shoulder angle one could get away with.

This spring I intend to find out.

For many years I wrote for Precision Shooting Magazine ("Just a Rockchuck Shooter from Idaho").

I got to thinking seriously about the turn of the Millenium. Taking the 308W as a basis, I got Dave Manson to cut me a set of chambering reamers (rough and finish) to make a 308 ZTSS. He went to bat for me at Hornady and convinced Lonnie Hummel to make the dies.

ZTSS stands for Zero Taper, Square Shoulder. I talked with Seeley Masker, and Dave Tooley about it. They agreed, at the Super Shoot, that it might, just might work. Harley-Davidsons and hunting Africa got in the way, and paying off a new house did too. All that is done, and I retired 5 years ago.

So, the project begins. It will revolve around a Savage RB/LP single shot action, no barrel nut, a 1.25" cylindrical barrel, and a newly found source for those old fat laminated stocks like the 4x4 seen here in other threads.

Rich

[tomme boy]

Sounds great. Savage website used to have a tech article on the 3 screw actions for tuning the torque of the bolts and accuracy. Don't know if you ever saw it or not, but it makes for good reading in the winter.

[220swiftfn]

Not to belittle experimentation, but if the round is truely "square shouldered", I forsee a problem with telescoping cases (the neck will get pushed back into the body.)


Dan

[Nrut]

Interesting..
I am wondering what advantages that you see your ZTSS cartridge might offer over conventional tapered cases..

[felix]

Rich, sounds like a fun project. Square cases tend to reflect waves more profusely which provide a hotter ignition, depending upon the case-body length from the primer, and, of course, the primer's intensity itself. Study here is needed, pertaining to which primer type and to which powder type (ball versus stick, same approx speed), i.e., small grains break up wave fronts mo'better than more openly spaced sticks. I have noticed that sharper cases, in general, tend to increase powder speed, so expect that to some extent. For boolits, I have concluded the more tapered cases provide easier accuracy procurement, a.la., 22-250 style. It would be nice to compare exactly the same capacity cases in each style. Would need to compare the ZTSS with TCTS, Tapered Case, Tapered Shoulder (30-06 truncated to ZTSS capacity). ... felix

[reed1911]

How square of a shoulder are we talking about here? 90 degree, 80 degree?

[308w]

Idaho Sharpshooter, I hated it when PS closed its doors. That was one fine gunzine! If you are one of the contributors here is a kudos to a job well done, wish it could have lasted longer, I miss that magazine. PS good luck with your ZTSS, keep us posted on your results, Thanks, Joey S aka 308

[felix]

Yes, prolly correct as included angle. It seems the best compromise is around 60 degrees (during these latter condom BR days) to smooth out the acceleration curve's top section somewhat. The curve has to be peaky enough to assure complete powder burn commensurate with contemporary barrel vibes. Keep in mind BR cases are just large enough to propel a 270-300 BC bullet 3250-3350 fps with current powder technology. ... felix

[runfiverun]

i'll confirm the powder speed being bumped to a faster rate.
the minimum tapered bodied 7x57 Ackley shouldered rifle I had built will give me higher velocities than my standard 7x57 Ackley grain for grain of powder.
it should give slightly slower velocity's due to it's larger case capacity.
it will also give me almost 100 fps higher velocity's than the wifes standard 7x57 with one more grain of powder.
it also doesn't show higher pressures the same way a normal case does [so be careful there]