Well, I guess this gives you bragging rights to the "only .223 rolling block" so congratulations. I agree with others, in that it's a head scratcher in terms of "why bother" and "just buy a high wall". But, you made it and that counts for something, so good luck with that.

craigster wrote on Jul 2^nd, 2019 at 10:30am:


I wouldn't even consider a Tippman action. They're ugly, and much more money than the plentiful military actions I find for Rolling Block builds. That hammer on a Tippman looks long enough to spear fish with!

Interesting solution to firing pin blow by. Is this your work or is it part of the Tippmann action? Perhaps it's part of the "stepped button" solution you mention.

As for the button, I'm still scratching my head as to why that worked but setting the barrel back didn't.

Dave Higginbotham, who did my rolling block, told me how he handled the stack up of clearance in the parts. I can't remember all the details, but I do recall he used strong elastic bands to pull the breech tightly rearward as one step.

You stated earlier that you're a mechanical engineer.  Use some of that training to ask yourself a question, that it is very apparent that you are not considering, from your discussion above.

How does the 39,000 psi internal cartridge pressure relate to the 60,500 psi strength of the barrel, and the 52ksi of the action.  For bonus points, what does 52ksi strength of the action as stated by the manufacturer mean?  Is that the yield strength of the action steel?  The block steel? the pivot pins?  Or is that a safe cartridge internal pressure?  If so, for what size of cartridge?

I'm not saying that the action isn't strong enough for the cartridge, I'm just asking how are you comparing three entirely different numbers that don't directly measure any related things.  You would have to do the appropriate calculations with measurements from the action in question and the specific cartridge to relate those three numbers in any meaningful way.  Cartridge PSI is not barrel hoop stress is not action tensile strength.  Those numbers cannot in any way be directly compared.  Only by calculating what forces the cartridge PSI puts on the barrel and action can you compare what those material strengths have to do with the safety of the cartridge.

As far as the gas venting, firing pin blowback or blowout is only one potential gas vent problem, and probably the least one.  How will your rolling block handle gas leakage from a case separation?  or an overload case rupture?  Leakage that vents gas into the gap between the breechblock and barrel end.  That's what vents into the shooters face.   

Yes, you have managed to get this to hold together even after using a workaround to deal with a gross headspace error by the gunsmith and/or problem with the action design.  Yes, you can download the cartridge pressure to keep it working with your workarounds.  It still is not a very good idea to do!  The next owner could very well put a factory cartridge in it, and be right back to higher pressure than even your adaptations will work for.  And your adaptation "button" made the resulting gas leak even worse for the shooter.

Quote:


Dave Higginbotham had one of his No.1 size actions in .33 WCF which he loaded to full factory performance. Honestly, I don't think even NATO spec .223 would stress the action more than that. He also fired factory 7 mm in an old action. That one flew apart one day.

The ones that amaze me are the WW-I Remingtons made up for the French and Russian service cartridges. Yikes!

Regardless, my .30-40-220 scares me somewhat.

With your button fix, what sort of case life do you get?

SSDAVE;
I am  a mechanical engineer with metallurgy experience, this has little to do with the complexity of a firearm explosion in a chamber. 
In the practical world of stress analysis the process is the use of tested or stated material properties such as tensile and yield strength. In this case the lower value of Yield strength is used to calculate a conservative number. 
Max stress using yield strength as a limit
 
Formula S=P*R2sq+R1sq)/(R2sq-R1sq)
P= cartridge pressure, stated at 39000
R2=Barrel radius at chamber
R1= Chamber radius (largest)
So plug in the numbers and get 47,000psi
So the barrel material yields is 60,500 as tested by ASTM, by observation the result is less than the tested value
Given that I personally haven't tested the individual pieces, I have to rely on published values for the pieces. 
In the case rupture , it has already happened early on when the breech rolled back under firing conditions. The breech face as part of the roller is only parallel (theoretically) at the "closed position, as the breech roller rotates around it's pivot pin the (thousands, maybe micro inches the parallel becomes an angle , opening the chamber, and this is certainly where rearward gas travels and then perpendicular out the breech. 
Accuracy and build up of tolerances in the RB do not help this, But this is not unique to this cartridge .223. It is the same for any center fire from the beginning of RB's
I guess I am amazed at the response from those stating the technical details that haven't done the same level of engineering to state that this is not a good idea. 
Skepticism is good if you don't know the details, I welcome that. Proof in technical terms would help. Please provide what you feel is the right way to establish a level of safety
The stepped button head apparently takes up the slight headspace (and it is headspace) non parallel of the breech face.
I guess I could make the roller given the manufactured location of the breech roller pins and the relative position to the back of the barrel and chamber to eliminate the steep. 
The step appears to work, don't understand the "makes it worse for the shooter" comment. This could be said for all RB's in that case.

RB Maker wrote on Jul 4^th, 2019 at 7:46am:


It does not make it worse for every Rolling Block. But it will likely make it worse for every Rolling block chambered in a very high pressure cartridge.
One reason to keep Rolling Block style actions in conservative calibers is to lessen the odds of a mishap ever happening. So allowing for the chance of gases in a shooter's face by staying with more traditional calibers and lower pressures.

craigd wrote on Jul 4^th, 2019 at 2:02pm:


Opening up the gap by another .003" will allow more particles/gas to exit.  Instead of gap headspacing a rolling block to allow for misalignment, I make a threaded plug that goes in the action threads, with a center bored hole.  I use a flat headed lap that has a shaft that is a nice fit in the center hole, and lap the breech block face square to the action threads.  The threaded plug can be screwed in a bit at a time to put thrust on the block as it is lapped, so that you take up all the slop in the mechanism, and you don't have to do a workaround like a button behind the case.  If the block is far off of square, use the lap to mark it, and then mill it first, and then lap it for the final fit.