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.

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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

Has anyone other than OP used a Tippman action ?

Hi KWK
The case separations were not at the head, they were about .3" from the head. I tried to move the barrel back to accommodate the slight movement of the breech block as it tightens up on the hammer roller, this did not work consistently as the hammer roller would hang on the breech roller.
The stepped button in the face of the breech roller did the task of keeping the breech roller tight against the head of the cartridge as it fired and keeps the cartridge in place. 
Wouldn't shoot the 62 psi stuff or 5.56, just too much energy. and certainly not for original materials, don't do it.
Solved the direct gas path concern as the firing pin is a two piece unit with the forward pin a button headed piece and a vent hole in the breech block to redirect a cap rupture.

KWK , the chamber was measured with go-no-go's and is accurate to these, the breech block would close and allow the hammer roller to rotate. 
I am not sure exactly why but the button seems to keep the cartridge in battery longer as the hammer roller rotates and tightens up the breech roller, there is a slight difference of the hammer roller radius from the start of the breech cut out to the radius just below the hammer stem.
This seems to be just enough lock up to prevent the rearward movement of the case. 
Again , this is not a set of ideal conditions for a highly tapered case and a"loose" action.
Just as a point of reference for the responses that this is dangerous for various reasons, ALL firearm mods are Dangerous.
If you do the engineering and material analysis before, some of this can be mitigated to a "Safer" level. 
The .223 using Varget and a 69 gr bullet is capable of 39,000 psi according to Hodgen in a test barrel. The 4140 chrome moly steel of the barrel is identified by  ASTM in the annealed state as 60500 psi, the receiver is stated as 52ksi.
The question of primer puncture and venting was addressed by the two piece fp and a vent hole added to the bottom side of the breech roller. There is no direct path thru the breech roller.
It seems that all center fire cartridges have the same possibility of rupture in the RB actions, new or old and the emphasis has been on this particular configuration as being more "dangerous" and stupid.
I get the discussion for the originals and I would not recommend it either but not for the unfounded reasons stated. 
A less tapered cartridge with a rim is ideal for a RB action. 
I just had to stretch the accepted norm which didn't make sense from stated beliefs. Experience counts.

Tippmann first conceived of its rolling block as an air gun using prefilled cartridges (which for all the extra work does add considerable realism).  Just out of curiosity, does anyone know or care to guess as to why the hammer spur is so long as to be ugly?

Bill Lawrence

I have a buddy who recently bought a rolling block converted to 348 Winchester ; he asked me if I had any loose ammo he could try. I said yes I have some but politely declined to give him any.

This might be of interest for this discussion. It is a study of pressures produced from Norma factory 8x58R ammo loaded for both the model 67 rolling blocks and 89 Krag rifles.

In short Norma loads for the converted rolling blocks was around 25,000 psi, maxing out around 28,000. The rifles were refitted, but exact specs were not given.

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

It seems if it was only headspace, it might be addressed either through the original chambering, or sizing of the cases if reloading. I'd think the metallurgy could contain the relatively small diameter case size, but doesn't account for the play in the action and changing headspace/breech face angle when firing. Possibly, at around 40K psi, neck sizing and indexing the cases when chambering could help the ammo fit the situation. 

I don't think that all centerfire cartridges have the same risk of case failures in the rolling block, because likely lower pressures flex the action to a lesser degree, if all else is equal with the condition of the actions and way the whole packages were put together. Yes, I can understand traditional cartridges would have greater surface area at the head, but that wouldn't necessarily mean higher back thrust against the block. Interesting discussion, I'd try not to take personal. Maybe, keep an eye out for changes in the brass and action the more it's fired. Have a great Fourth.

Why lap it, just use a guided counter bore. You can still use the threaded guild to put pressure on the BB.

While the 223 pressures are a bit high, chamber for 222 and use that data, that should be ok, bringing thrust pressure, in line with the larger BP cases. Hoop and thread strength aren't a issue, with modern steel barrels. After all they were made in 30/40 and 7mm Mauser. The 30/40, gives a little more breech thrust than the 223 and so does the 7mm.

I would feel safer with a RB, made from alloy steel and would use that, over the original ones, made from a close relative of mild steel.

I posted about venting the FP, at least a few years ago. It's not hard to do when making a bushed BB. I didn't get any flax at that time.

For myself, I have more issues about milling the receivers rings octagon and CCHing. 

The '03 is much more prone to catastrophic case failure than a RB and doesn't handle gas well, either. Low numbers can and have blown up, altogether at lower pressures. I think many more people have been harmed with the '03 than RB's.

Frank

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Now that brings back a conversation I had with Higginbotham nearly 20 years ago. I think he did mention using a stub of a barrel, although it seems that was to center mark the end of the firing pin hole on the breech face. Regardless, your technique makes eminently good sense.

Thanks Frank
Was really looking for some other experience in caliber/chamber pressure info. Seems you have been down this road a while ago.
Along with ssdave this is good info. 
And Bill, I did mark the barrel with .223 only

Milling the receiver rings to octagon is no different than Remington did originally IF the receiver ring is the late version with the larger receiver ring. 
I wont use an earlier smaller receiver ring milled to octagon for anything but a .22RF myself. It just leaves far too little metal to make me feel comfortable for any CF cartridge I'd want to use in a Rolling Block.

Are those pressures for 7x57 and 8x50 the pressures used for loading them back in the early 1900's when Rollers were chambered for them? Or are those modern pressure ratings? 
I've been told that those cartridges were not loaded to the same levels then as they were later. And I've seen a large number of #5 actions chambered in 7x57 that were loose from shooting that ammo. It's pretty common to see headspace issues in original 7x57 Rollers.

The Lebel number appears to be the old CIP crusher indicated psi, likely for the later Balle N machine gun rounds. The rolling blocks were likely for Balle D or maybe even for surplus Balle M. I have seen a claim the WW-I rounds ran 41 ksi, which given the case diameter, would have been a quite high load on the breech.

I've read the "7 mm" was not quite the Mauser but an approximation made by Remington and not loaded to Mauser pressures in the ammo Remington supplied for them. 

I'm not sure where the "published .223 max pressure of 39kpsi" comes from. Hodgdon has data close to the 55 ksi (piezo) SAAMI limit, and the CIP rating is 62 ksi which is likely the NATO limit.

The "max stress capable of the breech roller is 52,000 psi" is likely taken off the Tippmann site and looks suspiciously like the typical SAAMI max for CUP pressure ratings, for 52 ksi is rather low for a modern gun steel. 

I did some back of the envelope stress calculations once. I recall thinking the maximum stress is in ring surrounding the breech pin, but it's been a while.

KWK
The 39.000 psi came from Hodgen for Varget max loads, granted not Rem factory, so I ran the stress numbers on the 55 kpsi:
The Tippman steel is identified as 52 kpsi
Breech Roller max force = 6071 lbf
Sigma for the breech roller at minimum cross section = 12065 psi
Sf= 4.31
Shear load in same= 6780 psi
Sf= 3.83
Double shear in the roller pins= 27500 psi
Sf= 1.42
Made a model in Solidworks and loaded as above and the model stress analysis agrees with the calculations, the max stress is located at a a change in geometry where the pivot pin flanges meet the larger breech roller block, which is where you would expect. However this is a concentrated spot and not a broad area of stress, could be rationalized that the high stress is "spread" to the larger mass surrounding it. Typically in modeling these kind of stresses are considered very low in critical analysis. 
The calibers the RB used certainly have varied over their life span, don't doubt the lower charges for the same caliber. The Brownell video implied that a lot of RB's were "abused" with loads that were not recommended but used anyway in time of war. Just goes to the mystic of the RB holding up to the overpowered loads. May have been detrimental to the RB action in many forms but seems they held together on a larger scale'
This has been informative for me to gain the insight of those experienced and knowledgeable of the RB.
The .223 RB has been performing really well and groups at 50 with iron sights has been less than 1" and I don't shoot that well. Tried a 16" gong plate at 300 yds and rang it 3 out of 4 times, quit after that , Quigley moment, and probably couldn't repeat that on a bet!
Cheers

marlinguy, the failure is in the pin flanges on the roller, sigma = F/A, with 15,558 lbf applied to the face of the breech roller the flanges fail in tensile failure, pins will fail before this happens. This would be a catastrophic failure. One would have to load a super hot double load to get this kind of force. 
However, the failure mode for a block like this is probable fatigue failure, repeated firing of excessive pressure rounds would do this, a crack would start and propagate. Probably one flange would fail, and block would become to loose to function. Material properties of the breech rollers and pins would have to be tested to verify the real values of tensile strengths for old guns. 
This is were the caution of "old" guns and experience is invaluable.

The flange is the projections below the breech block which has the pivot hole for the pin
Tippmann has distinct flanges  separated by a .25” gap between them, for the bottom located extractor
Originals have either, side extractor seem to be solid

Those "flanges" never fail. They do get "beat" from the breech thrust pushing them back against the hammer. But I've never heard of one failing. As KWK mentioned, the blocks fail at that same point I mentioned before. The internal corner that's the thinnest point adjacent to the pin. Being a squared internal corner, and the thinnest part, it's also the weakest point in the design.
Anyone whose spent much time with old Rolling Blocks has seen numerous breech blocks with excessive wear on the "flanges" as you call them. But I've never seen or heard of them failing there.

KWK wrote on Jul 10^th, 2019 at 1:22pm:


I don't think so. He described them as "projections" and said they had a 1/4" gap for those with the firing pin retainer. Sounds like the "flanges" are what I called the tails that are shaped to ride on the curve of the hammer and set the headspace. 
I'm talking about the internal 90 degree angle where the block pivots on the block pin. That internal 90 is the weakest point, and where they crack. Those tails or flanges just get beat up from rearward thrust, and gradually get excess headspace. But never heard of them failing?

I think you and I are on board and agreement with the weak spot, and where they break or crack. That's exactly where I was referring to. It's not uncommon to see parts with internal 90 degree machining fail at those areas, even when there aren't extreme pressures thrust upon them. Another example of this is the internal 90 on the hammer of a Ballard. They are often found cracked in this area, and there's virtually almost no stress on this point other than the fall of the hammer. 
Any of these situations could be reduced immensely by simply rounding that internal 90 degree cut. In the case of the Ballard hammer it's not a real issue. I found this on a #4 Perfection I bought 3 decades ago, and talked with Dave Casey at Ballard Rifle Co. back then about it. He said to leave it alone and not worry about it. So it's worked well for the last 3 decades and still cracked at that point. I own several others with the same crack, and don't worry about them either. But they're not under pressure like a Rolling Block breech block is.

Ok pics this time

Have herd it for years and have had comparisons with outside vendors ( use to work for L-3 Flight Simulation) and it is comparable with other high grade analysis packages
Recent changes by Dassult have added plastic flow, hydro flow analysis and a simulation capability that allows dynamics and variable constraints to be applied
Heard, expensive, SW is 4-5 k for a single seat with most of the bells and whistles 
No question on the stress riser locations and where to expect proemThe thing that may not be real clear in a cad analysis is the “explosive” load magnitude in such a short duration event, more like sudden impact loads the real escalate the high stress issues

Cheers

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Okay, I'm a little dated (in more ways than one). Again, no surprise that Dassault has improved their product.

As for the dynamics, I believe LS-DYNA was one of the first successful packages to handle that. Varmint Al uses it to analyze loads under cartridge firing, which is pretty spiffy.

Quote:


Again, based on the failures marlinguy and I have read about, a catastrophic failure is nearly always in the breech block at the stress riser at the corner, not the pins. In cases where failure is limited to yielding, it's possible that occurs elsewhere; perhaps he's seen a few such.

What alloys Remington used in each part I can't say, and this could affect the results.

Bill
The chance of both pins failing in double sheet is theoretically possible but very unlikely
What happens in structural failures is that one member may start bending or yielding to its limit then typically the surrounding structure starts receiving the stress and spreading it over a larger area
Let’s say for conversation sake both pins sheared off at both blocks
The hammer roller kinda drops down into the receiver, the breech roller depends on the hammer roller location
If the hammer is down in the firing position, the breech roller has to go down into the receiver as well 
Not sure how these position would look at the moment the pins fail
Don’t think they would exit the receiver as both rollers are somewhat shaded from a direct exit path
I would think the breech roller pin is more likely to bend causing the breech block face to open up and potentially releas pressure at a perpendicular direction to the shooters face
Would not want either scenario 
To bust the pins in a catastrophic mode pressures would have to be well above 85 kpsi  not sure  a load can get ther

Seeing the picture of the Tipmann block, it looks more apt to fail than an original with the wide cut through it. That @1/4" wide cut removes a lot of strength in the area most prone to failure. Leaving two "ears" that the pin pivots on makes it even more likely for those ears to fail under higher pressures.