Any Ballisticians here? (Cartridge Pressure Discussion)

[6.5 forever]

Is there any correlation of a longer neck vs shorter neck on run out?

 

[Murray Brook]

I think it could be possible. If you look at the Hodgdon data for the standard 7/08 Rem they give 2650 ft/sec with a 175 gr bullet at a pressure of 58500 psi from a 24" barrel. Take this to 65000 psi and one could see 2710 ft/sec or there about with a 180 gr.. Now add the extra case capacity, the free bore and 28" barrel getting 2920 ft/sec seems like it may be possible. Is it worth the effort, probably not.

 

[jackieschmidt]

Stan Ware’s Radical No-Neck Wolfpup Wildcat​

View attachment 1435117

https://bulletin.accurateshooter.co...y-stan-wares-radical-no-neck-wolfpup-wildcat/

What Stan was going for was to make a legal case for HBR based on the BR case. At that time, case capacity had to be at least that of the 30-30. From what I heard, it shot quite well.
The minimum case capacity rule has since vanished.

 

[Kurz]

It demonstrates that his version with the shortened neck was perfectly capable of being accurate in the venue he chose. The point was to refute those who dislike the shortened neck feature.

 

[SKWERLZ]

It demonstrates that his version with the shortened neck was perfectly capable of being accurate in the venue he chose. The point was to refute those who dislike the shortened neck feature.

I don’t shoot in his venue and that short of neck would be nothing but a liability in my preferred venue.

 

[Kurz]

It's always good to be the exception...

 

[Dimner]

Stan Ware’s Radical No-Neck Wolfpup Wildcat​

View attachment 1435117

https://bulletin.accurateshooter.co...y-stan-wares-radical-no-neck-wolfpup-wildcat/

The bullet caster in me cringes to see a cartridge without a neck!

 

[Kurz]

Don't look.

 

[Pawnee Bill]

Novelty. The proof is in the targets.

 

[dgeesaman]

Getting around short action magnum speeds with a 308 length cartridge sounds spicy
I’m sure a long freebore and probably a powder like R26 help.

I’ll pass on a neck length like that.

 

[Gary in MD]

Big Ed !! LOL

 

[RegionRat]

Let's just pencil a few things out for perspective since they won't tell us their case volume or pressure.
If a 7-08 pushes a 175 to 2595 fps, that is 2617 ft*lbs
If the Moses is pushing a 180 to 2921, that is 3411 ft*lbs

3411/2617 => 30.3% more kinetic energy from an "improved" 7-08 case?!?

A 7-08 case has a capacity of roughly 52.2 gr.
A 280 Rem (which is a 30-06 necked to 7mm) has a capacity of 67.9 gr, and when the 280 Rem pushes a 175 to 2681 fps it generates only 2794 ft*lbs kinectic energy, which is roughly a 7% increase in kinetic energy over the 7-08 for a 15.2 grain case volume increase.

Even the 280 Ackley Improved is on the rough order of only 3247 ft*lbs.

No internal ballistics model pressure? No strain gage/pressure data provided? Claims a 30% KE improvement?
Hmmmm..... what could go wrong? YMMV

 

[chop house]

Hard to imagine what void this cartridge is intended to fill.

either the designers ego or billfold imho

 

[Dsrtibb]

There are some folks on Facebook preaching a wildcat called the “7mm Moses”. Claiming it can shoot at 7 Rem Mag and 7 PRC Speeds below at or below 65k PSI. It’s a 308 based case that looks to be fire-formed from a 7mm-08. Straight tapered body with a Weatherby styled shoulder.

Claim of 2921 FPS with 180 ELD-Ms out of a 28” barrel and at 3012 he blew out a primer.

I’m no ballistician, but these claims do not pass the sniff test with the pressures they claim. They have not done any testing with a pressure barrel as of yet and I don’t believe they will.

Thoughts? Over 65k PSI or not? Pic of the cartridge on the right.

I've seen this caliber in action from multiple guns with zero issues.

 

[jthor]

I've seen this caliber in action from multiple guns with zero issues.

Doesn’t mean it is not over pressure. The geometry of a cartridge helps with efficiency, as well as throat design and powder used. However, you can’t replace displacement entirely.

 

[Bullet Guy]

There are some folks on Facebook preaching a wildcat called the “7mm Moses”. Claiming it can shoot at 7 Rem Mag and 7 PRC Speeds below at or below 65k PSI. It’s a 308 based case that looks to be fire-formed from a 7mm-08. Straight tapered body with a Weatherby styled shoulder.

Claim of 2921 FPS with 180 ELD-Ms out of a 28” barrel and at 3012 he blew out a primer.

I’m no ballistician, but these claims do not pass the sniff test with the pressures they claim. They have not done any testing with a pressure barrel as of yet and I don’t believe they will.

Thoughts? Over 65k PSI or not? Pic of the cartridge on the right.

Just wanted to correct a couple of inaccuracies, and then ask a question to any members of the forum who might have, and are using pressure equipment.

First of all, there is a 0.010 taper between the base and the shoulder diameters, so the case is tapered.

Secondly, the shoulder is not curved like Weatherby. What you are showing looks like a hydroformed case that has not been fired yet in a Moses chamber. Additionally, the neck length is about 0.125” long.

Just to set the stage a bit, there have been several thousands of these cases and similar 223 cases made with the Moses modification from the parent cases without a single serious overpressure incident. Also several of the shooters using Moses cases have use them in local matches. From the velocity data I have seen, it appears to me that single digit SDs are easier to obtain with these cartridges than the parent cartridges. I am having a 308 Moses barrel made to verify for myself the velocity SD issue. The Moses modification of the 308Win case seems to add capacity for approximately 7 grains of ball powder. How well this added capacity improves velocity is not clear to me, but clearly there is no replacement for displacement.

Finally, does anyone have real pressure measurements that one can solidly attribute to primer flattening, primer cratering and/or expandion of the primer pocket that would lead to a loose primer? That would clearly be of interest to all handloaders. Speculation on this point is worthless without real verifiable pressure measurements. If one doesn’t know then say so. If you have data lets see a pressure curve. It does nobody any good to bash this case modification by promoting inaccure facts and speculation not based on verifiable facts and measurements.

 

[Bullet Guy]

Is there any correlation of a longer neck vs shorter neck on run out?

Personally, I don’t have enough experience with this case to comment intelligently. I can say that seating bullets in the unfired hydroformed case can be done using a 308Win micrometr seating die.

 

[Bullet Guy]

Doesn’t mean it is not over pressure. The geometry of a cartridge helps with efficiency, as well as throat design and powder used. However, you can’t replace displacement entirely.

As I mentioned before, it would be of great interest to have some quantitative pressure data that causes early pressure signs.

 

[Bullet Guy]

This is simply another outstanding case of the nonsense that is going on in our sport. With the preponderance of safe, laboratory cartridges already on the market why would anyone be interested in something like this? Hard to imagine what void this cartridge is intended to fill.

I had roughly the same questions. That is why I’m getting a barrel made in 8 twist to start experimenting with the 308 Moses.

 

[Bullet Guy]

The neck is a joke at best.

Low SDs (single digit) seem much easier to obtain with the Moses than the parent case Is it the neck? I don’t know. What little I have seen so far 0.002” of neck tension holds the bullet solidly when the shank/boat tail junction sits 0.005” above the neck/shoulder junction which translates to 0.120” of bearing surface grasped by the neck. I’ve tested this by measuring the run out before and after dropping the a dummy round at an oblique angle from 3 ft. I saw no change in run out.