Sherman Wildcats pressure limits?

[elkaholic]

I've stayed out of this because my name is on it, but......
With the 100's of Shermans out there and MOST people doing their own load developement, I would think there would be some real EVIDENCE of over pressuring vs everything else!!
In the case of the Saum, which has been proven in side by side tests, the SS is BETTER! It DOES NOT have less capacity, it's just considerably shorter and more efficient. Also, unless you throat the bageez out of a saum, it has LESS useable capacity than the SS.
If every design was equal, you wouldn't see people trending towards the ones that are now the most popular for competition.
I don't do load work up ANY differently for factory cartridges than I do my own and I stop with the same warning signs!
Just FYI, I think the Saum is a good case. I also think the SS is better. Just like many other wildcat designs have been better than the original and some have become factory chamberings.

 

[adam32]

Really??
The WSM runs 7,000psi more than the WM, BUT with heavy bullets it cannot match the velocity of the larger WM case............please explain why this is?

The WSM pushes lighter bullets faster for one reason.........case shape provides a more efficient burn in START PRESSURE with light bullets that it cannot do with heavies due to case capacity being lost due to how much bullet protrudes into the case.

Cheers.

A faster burning powder can be used is your answer, due to the smaller case. Nothing to do with the shape of the case.

And 7,000 psi is not just a little bit more, it's a good jump up.

 

[adam32]

I've stayed out of this because my name is on it, but......
With the 100's of Shermans out there and MOST people doing their own load developement, I would think there would be some real EVIDENCE of over pressuring vs everything else!!
In the case of the Saum, which has been proven in side by side tests, the SS is BETTER! It DOES NOT have less capacity, it's just considerably shorter and more efficient. Also, unless you throat the bageez out of a saum, it has LESS useable capacity than the SS.
If every design was equal, you wouldn't see people trending towards the ones that are now the most popular for competition.
I don't do load work up ANY differently for factory cartridges than I do my own and I stop with the same warning signs!
Just FYI, I think the Saum is a good case. I also think the SS is better. Just like many other wildcat designs have been better than the original and some have become factory chamberings.

I've never said it was bad or dangerously overpressure. Only that it's above SAAMI of the parent case.

 

[elkaholic]

I've never said it was bad or dangerously overpressure. Only that it's above SAAMI of the parent case.

I don't know that It is or isnt over saami and neither do you. I'm sure some people load it over pressure and some load the Saum over pressure. Loaded to equal pressure and equal length, the SS will EASILY out run it. PERIOD!

 

[adam32]

I don't know that It is or isnt over saami and neither do you. I'm sure some people load it over pressure and some load the Saum over pressure. Loaded to equal pressure and equal length, the SS will EASILY out run it. PERIOD!

How can you say that it will easily outrun the SAUM when loaded to equal pressure when just two sentences prior you said you don't know what pressure yours is running at?

 

[elkaholic]

How can you say that it will easily outrun the SAUM when loaded to equal pressure when just two sentences prior you said you don't know what pressure yours is running at?

I'm basing it on RESULTS from people who build them and have commpared them side by side. Some have already posted that, but I guess you missed it!
Im signing off of this thread now. You can take it up with all the others who disagree with you. I probably should have stayed out of it anyway.

 

[TG-5150]

My 7mm-08 A.I. can run a lot more muzzle velocity than SAAMI 7mm-08. Bet it's real similar to what you are trying to compare here. I'm gonna back out and see if one of theses Veteran reloader/cartridge gurus explains it.
FYI- there are a few wildcatters on this forum that are just as good as Ackley(looking around for lightning)or Gibbs or Newton or....
Wonder how much a test barrel and gauges would be? Does anyone know?

 

[MagnumManiac]

A faster burning powder can be used is your answer, due to the smaller case. Nothing to do with the shape of the case.

And 7,000 psi is not just a little bit more, it's a good jump up.

That is not the reason at all. A faster powder has a SHORTER burn under the curve, it's HOW the powder burns, which is why powders like RE17 were developed in the first place.

You need to do more research into pressure, time at start, time under the peak etc etc.

7,000psi is not a big jump, just switching from a standard primer to a magnum can have more swing than that.

TG-5150,
A piezo crystal for my pressure trace costs $30 each, inexpensive due to it's unlimited use on a barrel.
Have switched them to different barrels, but correct removal without damaging it or the barrel is quite time consuming but well worth it.

Cheers.

 

[RevJim]

Thanks for the replies, I am sure now that I was actually safe. Using new, fireformed cases, having that long throat, my old 35 WAI never gave me issues. Someday I'll have the old 35 WAI put back together! I just like the looks of that old round! I also will scratch that Sherman itch if I go all out on another wildcat! ha.

 

[adam32]

I'm basing it on RESULTS from people who build them and have commpared them side by side. Some have already posted that, but I guess you missed it!
Im signing off of this thread now. You can take it up with all the others who disagree with you. I probably should have stayed out of it anyway.

Okie dokie.

 

[adam32]

7,000psi is not a big jump, just switching from a standard primer to a magnum can have more swing than that.

Cheers.

A quick calc on QL shows a 7,000 psi increase on a SAUM case with a 140 Berger equals right at a 100 fps velocity increase with everything else staying equal...100 fps isn't a small jump...about the difference between a SAUM and SS isn't it?

 

[bigngreen]

How can you say that it will easily outrun the SAUM when loaded to equal pressure when just two sentences prior you said you don't know what pressure yours is running at?

None of use know exactly where the pressure were running is at all we can do is watch the case head on any case and run things accordingly, if I'm loading a SAUM an SS I'm loading them to the same level based on the case head which is going to be the same relative pressures, what that pressure is will be based on what pressure the case head moves at, maybe below Sammi maybe more, case design plays into regardless of what you think, you can always tell an SS because of the recoil change for the same velocity, the design changes the burn character. Also it's evident in the velocities at different barrel length that something has changed.
Even if I put a guage on the SS and a SAUM barrel and they are the same pressure they won't land on the same load for that pressure.

The other evidence for pressure having other components than peak pressure is that when you run a large ladder you do not see a linier velocity rise with the powder charge, we see places where the velocities almost flat line then make a big jump, then steady out then flat line and so on, if peak pressure and the amount of powder we the only two things going inotivelocity we would not see this.

There is no magic free velocity BUT if you don't and won't understand what goes into velocity other than simply peak pressure then that's will full ignorance and probably is a terminal case!

 

[bigngreen]

Common sense destroys the only peak pressure equals velocity argument, who hasn't loaded two powders to the same pressure and gotten different velocities, that alone tells us there is more than peak pressure to velocity.
How many times has anyone who reloads loaded a powder, pressures it out with low velocity and low load density then without thinking why just grabs the next slower burn rate and runs it up.

 

[WiscGunner]

A quick calc on QL shows a 7,000 psi increase on a SAUM case with a 140 Berger equals right at a 100 fps velocity increase with everything else staying equal...100 fps isn't a small jump...about the difference between a SAUM and SS isn't it?

I am no expert here but wouldn't you agree using the same lot # of brass for both the Saum and the SS make the brass alloy the pressure gauge? After all, that is what is being done with the same batch of quartz or ceramic or other material used in a particular piezo disc from one test barrel to the next. Or are you saying the brass doesn't test pressure in the same direction as the piezo disc?

Also if you have access to QL, could you run some numbers for common powders for us? Can you tell us, alternately to your proposed 7000psi increase, how much extra powder is needed to reach the same 100 fps increase?

BIGNGREEN or someone else with access to these cartridges... Once adam32 provides his QL data for necessary increase in powder capacity, can you provide the powder capacity (not H20) difference with the same powders between the 6.5 Saum and the 6.5SS with the same bullet loaded to the same COAL?

I would guess that the increased powder charge predicted by adam32's QL data will fall inline with the actual powder capacity of the cartridge. Then other factors like burn column, pressure and case shape case shape will be responsible for the remaining difference.

Until an actual pressure test is run, this is about as accurate data is possible to deduce and I suspect a pressure test will corroborate the results.