Author Topic: New Stub project (Read 1439 times)

trotterlg · « **on:** December 06, 2008, 06:08:02 PM »

I am going for something different this time. I have two barrels done, just the finish on them left to do. With the demise of the versapack I am going to do a little science experment with a 12 gauge stub and a 20 Cal barrel. How about a 5mm Remington Magnum RF for a center fire handi rifle, best thing is that it could be used on either a SB1 or SB2 frame, and it is the hottest rimfire out there. I got the Stub and a 25 inch 20 cal barrel, so all I have to do is figure out the easiest way to make up an offset barrel with a non offset 12 gauge stub. Larry

NFG · « **Reply #1 on:** December 06, 2008, 07:01:18 PM »

Make a hammer with a switch firing platform ala T/C??? Then a mount double firing pin in a steel cage and drill/tap it into the NEF Frame...Think it would be MUCH easier to use a RF frame tho"...no messing about with changing hammers or firing pins.

I have a question for you...do you think a 12ga stub barrel would work? I want a longer rifled barrel than is available from NEF and can get a 30" one from PacNor for about $300. Been thinking of doing a fine threaded stub frame...28-32 TPI or just doing slightly less than an interference fit, 0.001" gap, and silver solder or epoxy.

What do you think???

The load pressure would be around 25 KPSI...basically a 12GAFH using either the 3.85" 50BMG modified cases, 3.5" Cheddite shotgun cases or the 3.5" from RMC.

Rough calculations indicate a 2.5 to 3X safety margin at 25 KPSI.

I have a NEF SB2-980 heavy rifled coming in early next week and will do some muzzle brake games with it.

Thanks

Luck with your project.

trotterlg · « **Reply #2 on:** December 06, 2008, 07:23:04 PM »

I take it you are thiking about a rifled slug barrel. If I were going that way I think I would spend a few bucks and start with a 10 gauge barrel and frame, in the end the cost of the 10 gauge would not be that much compared to what you will have in it when finished and you will have a little extra safety factor built in. When you are cutting fine threads, just a little flex in your boring bar will give you fits when you try to do long threads, this is why I only thread the rear 1/2 to 5/8 inch for the lock ring, 20 tpi is about as fine as I want to work with, this gives a double depth of thread of about .055 inch. Big stuff like your project is kind of outside of my comfort zone. I like to stay with either small cal or low pressure rounds, I still have all my finges and both eyes, have fun but be safe. Larry

Airsporter · « **Reply #3 on:** December 07, 2008, 12:28:10 AM »

Maybe mount the barrel between centers and offset the tailstock. Guess it depends on how much metal you have on the 5mm barrel.

Guy Pike · « **Reply #4 on:** December 07, 2008, 03:54:44 AM »

If you can build a rifle that shoots the new 5mm accurately I want one! Neither of my 591s likes it but shoot the original stuff like a laser!

Graybeard · « **Reply #5 on:** December 07, 2008, 04:30:26 AM »

Since the original Remington ammo is long gone or what's left sells at absolutely ridiculous prices and the new supplier is rather expensive and the future of it uncertain and I've even heard it's not all that accurate why not go centerfire with it.

There is an outfit who has been converting the old Remington rifles to centerfire for years. They offer dies, brass, even bullets and loading data for the round as a centerfire not rimfire. Why not take advantage of that and make it a center fire 5mm Remington?

NFG · « **Reply #6 on:** December 07, 2008, 06:08:29 AM »

Thanks, Larry...You're certainly right about the threading bit...not matter how tight I lock things down or keep the overlaps as close as I can or indicate things in, I can't get a nice tight fit at one end or the other with 3" long threads...beside my lathe not being all that precision or precise.

Have you ever fit a 10 ga barrel to an SB2 frame? I don't have ANY measurements for the 10 ga frame or barrels or how much they differ...

Do you or does anyone have those measurements or a source where I can go to find them???

Thanks

Luck on your projects.

quickdtoo · « **Reply #7 on:** December 07, 2008, 06:11:56 AM »

10ga barrel swells are 1.2XX" in diameter, the frame has the same outside dimensions and an SB2 rifle frame, the side walls are just thinner to allow for the ~.100" larger barrel.

Tim

trotterlg · « **Reply #8 on:** December 07, 2008, 06:17:08 AM »

I picked the offset stub because I haven't made one up before, also there are no more of the offset RF barrels from H&R so if you want one you have to build it. The 5mm RF was chosen because it is different, I'm sure it will a one of a kind. Also some areas are RF only to hunt, this would be a good alternative to a 22 Mag for Coyotes. The same methods could be applied to make a 22 LR, Mag or 17 HMR barrel. Larry

mrbgt · « **Reply #9 on:** December 07, 2008, 06:26:37 AM »

2 companies (aguila is 1 ) are making the 5mm rimfire again , but who knows for how long, if it doesn't take off . i like the centerfire option as well

NFG · « **Reply #10 on:** December 07, 2008, 06:46:20 AM »

Thanks Tim...I've eyeballed the SB2 frame once with a piece of 1.20" barrel laid in the groove and I thought it would fit using some judicious grinding here and there, but just kept the info stuck back in my mind.

Is the 10 ga barrel made of 1137 or 4140 steel?

...

Using a 10 ga barrel as the stub would give roughly 0.170 walls to work with at least.

I think this project could get a bit pricey also....10 ga barrel plus CM PacNor plus chamber reamer........maybe need to look for a different solution.

I might just settle for a barrel extention/muzzle brake combo on the USH.... hahahahahaa....groan.

Thanks

Luck on your projects.

Thanks

quickdtoo · « **Reply #11 on:** December 07, 2008, 06:59:34 AM »

I didn't ask specifically about the 10ga barrel, but was told that shotgun and rimfire barrels are 1137, rifle barrels are 4140. I only asked about one shotgun barrel specifically(IIRC

) which was the 45/410 Survivor which is also 1137.

Tim

NFG · « **Reply #12 on:** December 07, 2008, 07:30:39 AM »

Thanks again...Tim

I would suspect that at the pressures I will be running, if I do this project, the thickness combination of 1137 in the shotgun barrel and 4140 in the PacNor barrel would have at least a 3X safety margin and probably much more. Recoil with the heavy 3 oz slugs is the limiting factor anyway...I will reach my recoil limit long before I hit any pressure limits.

I will be doing the extension on the USH first anyway...maybe a 100 f/s increase will be all I can stand.....Hahahahaha groan.

Luck on your projects.

PHATINJUN · « **Reply #13 on:** December 08, 2008, 05:29:25 AM »

Cheaper Than Dirt has the Centurion 5mm on sale for $13.97 a box .That is as cheap as I have seen it since it came back on the market I think they got the shelves all filled now so the price is gonna come down. The 1st 1000 rouns I bought cost almost $16 per box almost a yr ago. It shoots great out of my Remington once I put a good scope on it. I've never seen anyone else make the 5mm other than the original Rem stuff. Kurt

mike@nds · « **Reply #14 on:** December 09, 2008, 02:29:58 AM »

Personally, for rimfire, I would start with a smaller diameter chamber such as a .410 or .22 hornet barrel stub. And plunge mill my hole off center to locate for rimfire ignition.

Then tap the stub, and turn the barrel threads in a conventional manner.

trotterlg · « **Reply #15 on:** December 09, 2008, 03:43:28 AM »

This is good, everyone is thinking about how to solve the problem. I hadn't thought about a milling solution. I do know how I will do it, I'll take lots of pictures when I get started. Larry

NFG · « **Reply #16 on:** December 09, 2008, 07:40:34 AM »

I think Mike hit the easiest solution...it would be a lot simpler and easier to locate the stub frame hole off center the required amount for rimfire...might have to play with the bottom diameter of the barrel to get it to fit in the frame.

I'm still missing why you don't just use a rimfire frame...nothing wrong with the 20/5mm RF except the price of the ammo...I can load a "20/5mm AH" for the price of the factory 5mm ammo...basically the same reason I converted my 17 HMR to 17 FB, except your are going the opposite way.

I can see a solution in my mind but can't convert it to the real deal for some reason....gigantic brain fart happening I guess, besides trying to get my 12GAFH out of the gate and all the Christmas goings on...can't walk, talk and chew gum without biting my tongue anymore....

I'm definitely looking forward to watching your progress...

Luck on your project.

dk17hmr · « **Reply #17 on:** December 09, 2008, 12:05:40 PM »

Quote from: NFG on December 09, 2008, 07:40:34 AM

I'm still missing why you don't just use a rimfire frame...

I think it is a pressure issue. 5mm has a much higher pressure than the 17hmr.

I am no machinist, but I agree with others with boring the stub off center.

Would you have to make a collet to hold the barrel off centered?

trotterlg · « **Reply #18 on:** December 09, 2008, 02:00:03 PM »

When I stubbed the 14 Cal barrel into the versapack barrel I put a collar on the stub and turned it round so I would have a reference some day to make another one up. I think what I will do is to bore the 12 gauge stub out until I can offset the new barrel inside it the proper distance. Then I will turn two plugs, one for the front and one for the breach, bore offset holes in them for the barrel and build it up like I usually do, only thing I will have to do is to clock then bushings in the proper orientation so the barrel is at the bottom of the bored out stub. That's the plan any way, I can bore a piece of stock offset and then cut it in half to make sure they have the same offset. I'll post pictures when I get going on it. This is the collar I machined when I did the Versapack. Larry

STUMPJMPR · « **Reply #19 on:** December 09, 2008, 02:08:30 PM »

I used to be a machinist... I read the first post and saw your problem and was just about to tell you indicate you barrel in on a 4 jaw chuck off center to match your firing pin... I think you got it though...lol

Guy Pike · « **Reply #20 on:** December 10, 2008, 12:04:25 PM »

Greybeard; I've been aware of the centerfire conversion option for years but had enough original ammo at the time. Results were as hit and miss for accuracy as the new ammo. i may try a heavier bullet when I can figure out how to re-crimp it. There's someting just a little off with the new stuff and maybe I'll figure it out.Meanwhile; build one that shoots Larry and I'll want one!

trotterlg · « **Reply #21 on:** December 10, 2008, 01:11:03 PM »

I just chose the 5mm rf because it is there, it is no different from doing a 22 Short really. I have a Remington 581 converted to 22 Hornet and a really nice stock 582 in Long Rifle. Larry