Greetings all!

Anyone own a 500SW Mag revolver? I am seeking some help from any other willing to assist. I'd like to make this a reality and I believe it shouldn't be too hard to pull off, but I would like to obtain some dimensions on the revolver without bringing my caliper to the gunshop.

(Ok, I posted, and 80% of my thread is not here...? Strange.

I'll have to edit and repost all that was lost later now.)

The short and sweet version is that I am seeking the minimal web material thickness tangent to the cylinder outside each 500 chamber.

The 500SW case is 0.530" OD at base, the wildcat I'm attempting to convert to is 0.640" case base diameter.

If anyone has a 500SW revolver and could caliper or mic the web thickness minimum at the chamber, that would be a huge help to start from.

Thanks again, and happy holidays everyone!

Hi. I have the .500 and a caliper. I'll be happy to try to tell you what you need to know, but I'm not savvy enough to figure out what to measure. If you would describe it another way, I might understand. Thanks.

Think I figured it out. I measured each bore hole in the cylinder, at the rear of the cylinder, at its minimal thickness point. I get .109", 110, 112, 112, 113. This is a new cyl that S&W installed for me which has about 30 rounds through it, so if you take an average of my readings, that might put you in the ballpark. Sorry I couldn't take better measurements.

Important correction -- I measured front cyl thickness, not rear. Perhaps S&W could give you exact measurements.

Interesting idea. What brass would you for the parent case.

Because they don't make a .58?

Mine measures .112 at the chamber rear web. Smith is not going to give you any data like that.
So, if your case measures .640, you need a chamber at least .005 larger, which gives you a chamber ID of .645, which is (your .500 chamber is .536 ID) .104 larger, divided by two, is an increase of .052, minus the .112 cylinder wall, leaves .060 thick cylinder wall. Enough for black powder or more if you feel lucky. You will also have to machine the rim clearance, in the cylinder rachet. Make sure the rim increase is not larger than the cylinder OD, or it won't rotate. I don't know what the barrel threads are, but that has to be considered.

If you can find a copy of 'The Custom Revolver' by Hamilton Bowen.
Chapter 9,,there is an article , a very detailed one where he shows how he built a .577 cal revolver on a Ruger RedHawk.

Kind of what you are seeking to do.
A wildcat 58cal round, reloading, custom projectile/mold, brass ect.

http://bowenclassicarms.com/th...m_revolver_book.html

It's an NFA 'Destructive Device' (handgun w/a bore over .50 inch).
So you need to apply for and be granted permission (BATF) for the build before you start,,& pay the $200 mfgr tax of course.

That's all the initial help I could have asked for, thanks guys! I didn't expect much room to work with on the cylinder.

Ok onto some specifics--or rather just some of my ideas--so you can imagine what I'm trying to do.

The case I would be using is the 505 Gibbs (as most know this is the 408 CTac parent case). I came across a lot of the brass for another project. That project involved shortening the brass to about 1.55" before bottlenecking it to a 30 cal. Once I trimmed one down, I stuck a Remington Accutip 385gr projectile from a 12GA sabot, the projectile being 0.580" OD, and it fit snug. I carried it around in my pocket for a few days, pulling it out often, imagining what I would chamber it in. I thought about doing an AR10 build w piston upper, then recently I thought, "A 585 revolver; HMMM!"

Now, here I am.

Are you planning on using half or full moon clips.

I don't know what is going on here, I write a post, but when I click "Post Now", I end up with the majority of my post not there. Is there some kind of character limit on posts? I don't understand it, that's what just happened again on my previous post.

I'll re-write what I had tried posting in a separate place this time, then copy and paste, as I can't retrieve what's lost after submitting the post if I use the browser back button.

I have found if your internet service is interrupted during the sending part they get lost.

Since this will be a smokeless, not BP cartridge, and the brass has been proof tested well beyond 60kPSi with zero extraction problems, 0.060" is not very promising as far as a chamber support thickness at minimal web, for this proposed cartridge. That brings up a good point in question; any smiths or engineers around here know how to calculate what the minimal wall thickness should be, based on the chamber diameter/cylinder material/pressure safety margin? I assume the calculation would be treated simply as a tube's burst pressure based on material, with the tube thickness being minimal cylinder web thickness. At least that would seemingly be a conservative approach to the problem.

As far as the book mentioned about the Ruger in .577, that sounds interesting and I will have to see what I can dig up. Was that gun built using a smokeless cartridge and/or did the cartridge have a name?

As far as getting the tax stamp for >0.50 cal in a pistol, I'm aware of the many sporting-exempt big-bore cartridges chambered in rifles. Is such exemption still possible in a pistol (those who know)?

The next step is looking at the frame clearance above/below the cylinder on the 500SW to determine a maximum allowable cylinder diameter, with respect to swing-in/out path of the cylinder (which probably doesn't effect the allowable diameter very much, but I am imagining that being the only other factor pertaining to maximum cylinder diameter beyond the static frame-to-cylinder clearance). Can anyone possibly check on that dimension? Seems to be the next logical step to check before progressing toward the barrel.

As far as half-moon or full-moon clips being asked about; I hadn't put any thought into that just yet, other than realizing clips will be needed, of course (it's a rimless case). Can one explain the possible importance of one or the other, in such my scenario?

Really appreciate the help here.

Edit:

I found the book mentioned above, sold out hard copies, I'll have to purchase the Kindle version they have for $10. I'm checking out the preview now. Thanks for heads up!

Also a photo; L->R: 40SW, 1.5" .585 (505 Gibbs case), 5.56*45mm

quote:

As far as half-moon or full-moon clips being asked about; I hadn't put any thought into that just yet, other than realizing clips will be needed, of course (it's a rimless case). Can one explain the possible importance of one or the other, in such my scenario?

They allow the extractor star to engage and extract the casing from the cylinder.

The can also help with head space.

I see you are using a rimless case; no one makes a moon clip, so I do not know how you are going to manage that. This is a sporting cartridge, so it is not a DD. We make 577 Nitro rifles every day.
Brass is not proof tested; that has no bearing on your revolver.
How much cylinder wall thickness do you need? It depends on the pressure you intend to generate, but if you are looking at the 500 S&W pressure; forget that too. You will rupture the cylinder. For such a large bullet, you don't need high pressure, and it will be hard to generate anyway.
Realize that we can't "develop loads" in a revolver, like we do in a rifle. The safety margin is far lower, and once the high pressure signs show up in a revolver, it might be too late.
I have built a few 500 Linebaughs; one guy ruptured a cylinder trying to do just that. Don't be that guy.
I have that Bowen book; I'll look and see if he has any load data. He used Minie bullets in his.

Only RIFLES with bore diameter over .50 inch can be graced by the BATF as being acceptible for Sporting Purposes and be exempt from the NFA Destructive Device classification.

Handguns are not taken into that Sporting EXEMPTION consideration re: over .50" bore dia.

So if you still want to build one,,which you can,,you first have to apply to BATF on the proper form, pay the NFA mfg tax ($200), wait for the OK and Tax STamp issuance,,and then you can procede.

(Shotguns are already exempt in the law of course)

IF you make a Rifle chambered for a NEW cartridge with a bullet/bore diameter over .50",,the BATF has to grant that NFA exemption for Sporting Use for that specific over .50" bore dia cartridge to make it legal and exempt from the D/D NFA classification.
It's a written request for an NFA D/D Sporting Exemption of the cartridge (for use in a rifle) you have in mind (supposedly before you go ahead and chamber/build the combination .)


You can not just make up a wildcat boomer, chamber it in a nice looking sporter and call it a sporting rifle and cartridge and consider it Exempt from NFA.

Look it up if you don't believe it.
BATF-NFA Handbook
or call the BATF Tech Div.

Yeah I read all their rules....

DPCD,

I had asked about moon clips because someone had brought up the question earlier in the thread. I wasn't exactly sure about that, the full or half moon, I had only assumed they were used for rimless cases. TBH I have not studied the ejector star on a rimless case revolver, definitely not an expert but rather a noob in the revolver dept. So I am definitely listening to everything being said here, and I appreciate it. As far as brass not being "proof" tested, pardon the improper terminology usage. The brass was custom made in a large batch by Bertram, then tested for internal deformation in a pressure barrel setup at high PSI to check the draw tooling die and internal radius left inside the brass base from the draw process to see if the brass was going to hold up well at higher pressures and if the brass was formed well. Apparently another case batch had a base with too small of an internal radius left by the draw rod, and as such it wasn't holding up well at higher pressures. This brass is a totally different design, though, and held up well in testing at 80kpsi. I am aware of the process by which pressure acts on a vessel, or a given projectile diameter. Yes, it's far easier to generate high forces on a projectile of larger diameter due to the area square as radius increases. I'm not attempting to teach you this of course, but rather letting you or others know I am not a 14 kid with a big bore pipe dream. I do work with big bores on a regular basis, however that work is done in bolt rifles, I've never ventured into revolver wildcatting, and your info is logical--the cylinder walls on revolvers are no where close to chamber thicknesses on heavy rifle bbls. So, when you ask about how much pressure I intend to run, I currently don't have an answer, as I'm here basically attempting to figure that problem out first and what pressures might be obtainable--with an adequate safety margin.

What if we talk about cylinder materials, as well? I can access yield strengths of all metals of course, but is there a "proven" type of metal which would make most sense as a cylinder material as used in a revolver? What I mean is, one that doesn't include cons that would outweigh the benefits for use as a cylinder material.

The frame looks very close to the cylinder on the 500. That seems to be possibly the biggest problem currently. First there would need to be room for a larger diameter cylinder. Does frame modification (relief) even sound plausible? I wonder how much the frame itself could be relieved before approaching an unsafe condition, so that the cylinder could be well-strengthened. I do perform most of my own machine work, but am not an engineer. I could possibly build a model in Autodesk Inventor of the revolver frame, then run stress simulations (but I'm reserving that idea before getting ahead of myself here).

Thanks

2152hq,

I'm with you, but the project plausibility seems to preclude the idea of registering the build, if you catch my drift. If it sounds plausible, then I'll proceed accordingly.

Just use black powder then your pressure should well be within the limits.

you send a case drawing and letter to the ATF wanting a sporting designation for the cart.. and then you might need to send in the gun to verify (we had to do this on the .550s) it's a sporting round and gun ...

takes about 8 months per letter,

not doing so results in an atf raid