New to the forum , saw a 2017 post on questions of converting a Rem Rolling Block to a .223 caliber
Before hand I apologize to all for the concept and I didn’t know all the “issues” ahead
First let me say I have been non professional smith guns for a long time and maybe to my discredit a mechinal engineer with metallurgy background
That said and certainly to the RB purists this is probably sacrilegious 
I did create a working RB in .223
Used a Tippmann Armory receiver, a Green Mountain /5” barrel machined to a tapered octagonal shape
First issue was to modify the bottom center extractor for the rimless .223 case
Tippmann sends a .357 extractor but it is too short, so welded to length and filed to fit
Next bigger issue is the tolerance of the rolling block mechanism just does not lend it’s self to a short high tapper case as proved in the actual firing
The chamber was head spaced to go no go gauges and round chambers ok
But on firing the vet slight clearance of the breech roller to the hammer roller is just enough to cause the shell move back a very few thousands and caused case separation
The only way I solved this was to make a stepped button on the breech face that had a .003 step pressing on the case head
This solved the case rapture
Also had to make this button any way as the original firing pin was way to big and repaired the primers
Made a smaller go and hole in the button to match
So far this has worked have 100 plus rounds thru it
Materials for the barrel and receiver are rated to 52,000 psi
Will see if long term use holds but definitely a good plunger a shoots a 1.5” group at 100 yd

I'm an engineer also, and this reminds me of something someone told me a long time ago.  "A smart man can calculate and logically talk himself into doing something very stupid".   

The rolling block action is not suited for a high pressure round.  It showed you that by the case stretch, and you did a work-around that made it even less safe; fixing a symptom, but leaving the original problem in place.  The biggest problem with a rolling block action and higher pressure is that it has no provision for handling gas leaks safely.  It vents right into your face.  Your "button"  made that gap even worse.  It did stop the immediate problem of case separation, but if you have a case separation or primer rupture, it will vent even more easily into the shooters eyes.

There's hundreds of different .223 rifle models out there.  Why would a person have to pick one of the most unsuitable actions to make one on?  If it's just to have a single shot classic .223, Browning and Winchester Miroku high walls are plentiful and easy to find.  I have one and it's an excellent shooter, better than any rolling block would ever be, and this is from a real rolling block lover.

I remember a rolling block chambered in 6 PPC for sale at Etna Green years ago, some people just like to play with fire.  Ledball

It's not what the rifle in question is made of but the design itself. stackable tolerances between the hammer,breech block and both the hammer and breech block pins come into play. Yes the hammer locks the breech block in place upon firing, but at those pressures for which that action was never designed for, sooner or later something will fail. And as ssdave pointed out that action has no gas handling capabilities at all. Everything comes back to the shooter.Frank

I think I can picture what a stepped button looks like. If the action can close and function with a .003" button, maybe the headspace wasn't measured correctly in the first place? I'm not a fan of the .223 idea, but once a solution was needed to try, why not set the barrel back? I'd worry about the gas handling like others have mentioned. Could be interesting to see a slow motion video of what the action does on firing.

RB Maker wrote on Jun 27^th, 2019 at 6:43am:


I don't see the logic here? Nothing about this combination could be considered as "taking the conservative approach"? It's anything but conservative.
Just doing something like this doesn't make sense, and it flies in the face of everything written concerning Rolling Block actions and what is acceptable. An old saying comes to mind for me. "Just because you can, doesn't mean you should do it."
And I sure hope that nobody else is encouraged to do the same, just based on you doing so.

The ability and capability and suitability of an action to handle a cartridge is a lot more than a "can handle xxx psi pressure" question.

Just to start, what cartridge was the 52,000 psi for?  At Least Pedersoli had a pressure for each cartridge size.

Pressure is one factor, case diameter is the other major one.  Barrel/action ring bursting pressure and breech thrust use both factors.  Case shape matters to a lesser extent.

But, the absolute pressure handling capability combined with case size isn't really relevant, when the weak point is the brass case and primer.  Only if the action is designed to overcome limitations in the brass case can the action strength be the controlling factor.

In the case of the rolling block, the lack of rigidity in the breech block headspace dimension makes it susceptible to brass weakness.  And, it has no gas blocking/diverting capabilities to overcome that weakness.  Drilling a hole into the firing pin cavity can help avoid blowing the firing pin back into your brain, but it  doesn't divert any of the leaking gasses from your face and eyes.  That's the major weakness of the rolling block.

I too have anecdotal evidence that a person can survive firing a rolling block with an unsuitable chambering.  I would be willing to bet that I've owned and shot more rolling blocks than 99% of the people that read this.  I've seen several in .22 hornert, .223, .308, .30-06 and similar.  I've owned two rifles that were spectacurally mis-chambered.   

One was a 1905 smokeless action chambered in 7mm STW.  I bought it from the widow of the owner that commissioned it, he died before he picked it up from the gunsmith that built it.  I presume that the gunsmith fired at least one cartridge through it before delivering it.

I also owned a Pedersoli rolling block (one of the early, soft Navy Arms ones with brass triggerguard) that was chambered in .50 Alaskan.  I got detailed loading information from the original owner that built it, that showed about 120 rounds had been sot through it.  All of them heavy, smokeless loads.  Most were in the 50,000 psi range, (not CUP, PSI).  The last 10 were in the 65,000 psi range.  He said that recoil was too much, so he decided to sell it there.   

I did not shoot either; I sold the pedersoli with good information on safe, usable loads, and rebarreled the 7 STW to 7mm mauser.  But, both of them existed as monuments to the fact that a lucky owner can shoot unsuitable chamberings without damage.

Quote:


Welcome.

It's an interesting project you have. Would setting the barrel back a few thousandths have worked as well, or were other parts of the finished rifle (such as sights) already in place?

You mentioned head separations. Did you film these to see how extensive is the gas blow back towards the face? My .30-40 rolling block scares me a bit, thinking about the consequences of a separation. I'm not getting significant stretching, though, and I do keep the pressures under 35 ksi.

While the 62 ksi of the .223 (European spec ammo) is daunting, there are a number of .22 Hornet rolling blocks out there, and those carry a 49 ksi spec (SAAMI) in relatively fragile brass. Uberti sells a No.2 clone in that.

It's certainly not a cartridge I'd have chosen for a No.1, but cheap factory ammo has its appeal. Do keep those safety glasses on.

How was the workmanship on the Tippmann action?

   Karl