Home | Ezine | Forums | Links | Contact
NitroExpress.com: homemade doubles

View recent messages : 24 hours | 48 hours | 7 days | 14 days | 30 days | 60 days | More Smilies


*** Enjoy NitroExpress.com? Participate and join in. ***

Double Rifles, Single Shots & Combinations >> Double Rifles

Pages: 1 | 2 | 3 | (show all)
mickey
.416 member


Reged: 05/01/03
Posts: 4647
Loc: Pend Oreille Valley, Idaho
Re: homemade doubles [Re: NitroX]
      #33488 - 21/06/05 04:25 AM

Nitro

Size is important if you want a rifle that has some handling characteristics. The distance of the firing pins will determine the size and weight of the barrels.

A friend once had a 600NE with a set of .375 barrels. The .375 weighed more than the 600 because of the amount of extra steel needed for the smaller holes.



--------------------
Lovu Zdar
Mick

A Man of Pleasure, Enterprise, Wit and Spirit Rare Books, Big Game Hunting, English Rifles, Fishing, Explosives, Chauvinism, Insensitivity, Public Drunkenness and Sloth, Champion of Lost and Unpopular Causes.


Post Extras: Print Post   Remind Me!   Notify Moderator  
NitroXAdministrator
.700 member


Reged: 25/12/02
Posts: 39059
Loc: Barossa Valley, South Australi...
Re: homemade doubles [Re: mickey]
      #33499 - 21/06/05 01:02 PM

Yes that is true. I remember reading that to use the Greener Empire action something around a .577 Light NE was suitable. Going much smaller might be an issue.

So that was the question, what sort of shotgun action would be suitable for say a 7mm or a .333 range of barrels? Strength and size considered?

Thanks.


--------------------
John aka NitroX

...
Govt get out of our lives NOW!
"I love the smell of cordite in the morning."
"A Sharp spear needs no polish"


Edited by NitroX (22/06/05 12:24 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
CptCurlAdministrator
.450 member


Reged: 01/05/04
Posts: 5268
Loc: Fincastle, Botetourt County, V...
Re: homemade doubles [Re: NitroX]
      #33504 - 21/06/05 01:34 PM

NitroX,

My small bore DR's are all on frames the size of a 28ga. shotgun. I measured them against a 28ga. pre-war J.P. Sauer I had, and they matched, including firing pin spacing. Of course, they are rifle frames, not shotguns, but that is the correct size for the purpose.

What shotgun action makes a good "donor" and what size, I don't have a clue. It seems that good small bore shotguns come pretty dear these days. Instead of wrecking one for a home-made rifle I think one should just consider buying the rifle.

Interesting concepts, though.

Best,
Curl

--------------------
RoscoeStephenson.com

YOUR DOUBLE RIFLE IS YOUR BEST FRIEND.



Post Extras: Print Post   Remind Me!   Notify Moderator  
balltip
.224 member


Reged: 05/06/05
Posts: 5
Loc: Just north of Gothenburg, Swed...
Re: homemade doubles [Re: NitroX]
      #33567 - 22/06/05 07:27 AM

Oh, this one took off!
Being away from the net for a few days and I see that there has been some discussions going on. Oh well, I believe that some good has come out from all this!

Yes Unspellabe, you got a point. Shear force is what counts when it comes to holding the barrels in a mono block. Let us now (just for the FUN of it - I won't be around til monday to "defend" my opinions cos I am going away for something that we up here in the cold north refer to as "midsommar" - midsummer. Yep, we actually still celebrate the sun up here in the sense that we have kept up the tradition of partying our socks off on the longest day of the year! ) take a look at what kind of forces that affect the barrel-to-mono block-joint.
Assuming we are using a cartridge generating a chamber pressure of 25.000 psi (I am in way ower my head here cos I really should be making these calculations using the metric system. Oh well..)
Then we get a chamber pressure of exactly that - 25.000 psi. Yep, Pounds per Square Inch.
Now, how large an area does this theoretical cartridge have on it's base? Again assuming that it has an diameter of ½", it would be (and now my maths is failing me but isn't circular areas calculated by taking multiplying PI (3.14) with the (radius square 2)
But to make it simpler, let us say that the base area of the case used is 1/4" square.
Now that means that the shearing force the solder joint would need to have not to break under the pressure from the shot fired would be 1/4 of chamber pressure (this not taking into account that the case itself does cling a tiny bit to the walls of the chamber. However, a brass case won't stand to all that much pressure so we will just forget about that to keep things simple).
1/4 of chamber pressure would in this case be (25.000 divided by 4) = 6.250
One square inch of relatively soft solder will hold about 4.000 pounds before it shears - see link;

http://www.efdsolder.com/prod_alloys.htm

Sorry, but melting temps are graded using Centigrade.

If we then assume that the area holding the barrel joint is equal to 6 square inches (see earlier post that I made, I don't wanna take you through that calculation again except for saying that one square inch is equal to 6,45 square centimeters) the joint will hold 4.000 x 6 = 24.000 pounds.
Now that is pretty much to hold down a thrust force of 6.250 pounds, isn't it?

And now - PLEASE correct me if I made any faults in my calculations!

When it comes to choosing the "right" size of shotgun for building a rifle I would say that the smaller you can get your hands on, the better. A 24ga would propably be great! Husqvarna made a series of double rifles in 9,3x74R on their model 310 (anson deeley type) 20ga action. I even aquired one of those rare shotguns (about only 500 20ga model 310 were made) just to build my own set of barrels. But then again I sold that one off in about 2 days time... Easiest sell I will make. Ever! Quite profitable too...

The good part about using a smaller shotgun than 12ga for building a double rifle is that the distance between the center of the bores versus the action itself gets smaller. Hence less torque on the barrel to action joint.
Really neat doubles are built on small actions. So a good start would be 16ga or less. I have heard that at least one of Husqvarnas double rifles were made on the 310 in 12ga - still chambered for the 9,3x74R.
Just remember NOT to use any old shotgun - go for a good solid quality one - and have it proofed!

A relatively cheap action that still is somewhat available is the Merkel model 8 in 20ga. A good starting point! If lucky you can pick one up at about $800 US. At least here in Sweden, that is.

When it comes to barrel diameters necessary I am not the man. All I know is that the outside diameter of the rifle barrel on my Merkel SLII combo gun in 20ga/7x57R is relatively slim. But as I don't want to run off to the gun safe and take an exact measurement right now I'll post the exact O/D of the chamber only if somebody asks. But take a look at any drilling or combination gun, and you will see that the diameter of the rifle barrel thins out rapidly. So there is no need for THAT much material to keep the demons of pressure at bay.

To sum his my post up I would like to add that whatever you do - IF you build yourself a double rifle - make pretty darn sure that you have somebody at hand that can show you hands on how to, and that you get it proofed before you actually fire it from the soulder!

Kind regards

Per


Post Extras: Print Post   Remind Me!   Notify Moderator  
500Nitro
.450 member


Reged: 06/01/03
Posts: 7244
Loc: Victoria, Australia
Re: homemade doubles [Re: NitroX]
      #33569 - 22/06/05 08:10 AM


NitroX,

Don't get caried away - 577 Nitro FOR Black (sometimes referred to as LIGHT Nitro)
NOT a full 577 Nitro.

We don't want people killing themselves !!!
(Well, I suppose it depends who)

A Greener action will handle anything up to 577 Light Nitro, ie 500 Light Nitro


500 Nitro


Post Extras: Print Post   Remind Me!   Notify Moderator  
NitroXAdministrator
.700 member


Reged: 25/12/02
Posts: 39059
Loc: Barossa Valley, South Australi...
Re: homemade doubles [Re: 500Nitro]
      #33573 - 22/06/05 12:33 PM

I have edited my post.

So a Greener will only handle the 2 3/4" case for the .577 NE? Or are you saying it can handle the 3" case but only Nitro for BP loads?



--------------------
John aka NitroX

...
Govt get out of our lives NOW!
"I love the smell of cordite in the morning."
"A Sharp spear needs no polish"


Post Extras: Print Post   Remind Me!   Notify Moderator  
4seventy
Sponsor


Reged: 07/05/03
Posts: 2210
Loc: Queensland Australia
Re: homemade doubles [Re: NitroX]
      #33624 - 22/06/05 07:51 PM

For anyone thinking about building a double on a shotgun action here are a few things to think about.

For a cartridge like the 375 flanged magnum, chamber pressures could be in the region of 50,000 psi or higher.
If a proof load is used at plus 30 percent this will mean that the chamber pressure could be around 70,000 psi for the proving load.
That's seventy thousand pounds per square inch.

I think it unwise and unsafe to calculate any monoblok to barrel join shear rating at 100 percent.
To do so assumes that the solder join is 100 percent perfect and as the join is hidden from view an assumption is all you have, there is no visual proof.

Shear strength should be calculated, but when dealing with a cartridge being fired in a barrel chamber there are other important stresses on the barrel to monoblok join which need to be considered.

Back thrust / axial force is directly related to pressure and is directly proportional to it.

While axial force needs to be factored in to the safety calculations, so does chamber pressure as both can affect the ability of the soldered joint to withstand the loads and stresses it must endure.

Chamber pressure alone (in home built doubles) can in some situations degrade the solder join when a soft solder is used between barrel and monobloc.

The bottom line is that you may never get any warning that the join is weak or has weakened.
IMO this is a risk far to high to accept.

Are there are any manufacturers who build double rifles on the monobloc system using shotgun actions and who rely on nothing more than tin/lead solder to hold the barrels into the monobloc?

More later........


Post Extras: Print Post   Remind Me!   Notify Moderator  
unspellable
.300 member


Reged: 06/03/04
Posts: 187
Loc: Iowa
Re: homemade doubles [Re: 4seventy]
      #33631 - 22/06/05 10:37 PM

Seems to me that a mono-bloc lends itself to X-ray inspection. Since the solder is quite dissimilar to steel, at least the joint coverage or extent of wicking should show up in an X-ray. This would be no substitute for prooving, but I'd do an X-ray inspection before prooving. If the joint looks poor in the X-ray it can be redone before you blow things apart with a proof load.

Post Extras: Print Post   Remind Me!   Notify Moderator  
CptCurlAdministrator
.450 member


Reged: 01/05/04
Posts: 5268
Loc: Fincastle, Botetourt County, V...
Re: homemade doubles [Re: unspellable]
      #33648 - 23/06/05 12:42 AM

Does anybody know what method Beretta uses to assemble their barrels? Beretta has to be the premier maker for the use of true monoblocks.

I say "true monoblocks" to distinguish what is being discussed here. The method here is to take chopper lump, dovetail lump, or shoe lump shotgun barrels, cut them off in front of the chambers, ream them out to accept the shank of a rifle barrel, and attach the rifle barrels by some fashion. While the breach end of the shotgun barrels resembles a monoblock it is no such thing. It is an assembly itself, not an integral piece, as in a Beretta.

The point has been made that the heat required to braze or silver solder the barrel shanks into this assembly has the potential to cause the assembly itself to separate. Were it a true monoblock there would be no such risk. Of course, I am not addressing the issue of whether the heat might affect the strength of the steel.

I have read several books about building double guns (the real way, not "home made"), and in each account it is said that the maker brazes or silver solders the assembly at the breach, and then uses "soft" solder for the other parts (ribs, wedge, forend hook, etc.). The point is stated that the balance of the assembly process can proceed without fear that the joint(s) at the breach might come loose.

Interesting discussion here, although I will never be trying any of these things.

Regards,
Curl

--------------------
RoscoeStephenson.com

YOUR DOUBLE RIFLE IS YOUR BEST FRIEND.



Post Extras: Print Post   Remind Me!   Notify Moderator  
4seventy
Sponsor


Reged: 07/05/03
Posts: 2210
Loc: Queensland Australia
Re: homemade doubles [Re: CptCurl]
      #33707 - 23/06/05 05:12 PM

Curl,
Good point about "true monoblocks".
If I was intending to build a double for serious use as opposed to casual use and build it for a serious cartridge which developed high pressure and intended to use a shotgun action, I would insist on a true monoblock and would not consider using a cut up set of barrels.
I would also want the barrels to be silver soldered to the monoblock.

If on the other hand i had a shotgun action which i wanted to build into a double rifle, and that shottie used dovetail or chopper lumps, i would not want to use a high pressure cartridge.
To avoid any risk of melting the dovetail or chopper lump join i would use high temp solder to join the barrels to the "untrue monoblock".
Force 44 Hi Temp or equivelant would be my choice and then the rest of the barrel assembley could be done in force 44 without risk of melting any of the barrel to u-t mono to lump joins.

I own 3 doubles built on shottie actions and all three use true monoblocks and all three use silver solder at the mono barrel join.

Also a good point about Beretta.
Cheers


Post Extras: Print Post   Remind Me!   Notify Moderator  
4seventy
Sponsor


Reged: 07/05/03
Posts: 2210
Loc: Queensland Australia
Re: homemade doubles [Re: unspellable]
      #33723 - 23/06/05 07:44 PM

X-ray is an interesting idea.
I'm not sure whether it will clearly show flaws in the solder join though.

Also, with the use of tin/lead solder at the mono to barrel join, X rays bring further problems.
If the X ray did show flaws in the join the best time to discover this would be before any more work is done to the barrels like rib laying etc.
Any flaw with the join is not going to be fixed merely by reheating and re soldering.
The barrels will both have to be removed from the monoblock, be cleaned and prepared again and refluxed and retinned and reassembled and resoldered.
It would be far easier to do this before the ribs are laid of course.

So let's assume that you get a good showing of the join in the x ray and all appears well.
This may happen on the first, second, third or tenth time, it really doesn't matter, you now have a good tin/lead join.

Time to go ahead then and finish the barrel set, and lay the ribs along with any other attachments, barrel hook, sling eye, sights etc.

Now for the bad news.
You have a good or perfect join at the barrels to monoblock.
You know this because of the x ray, but that x ray is about to become worthless because when you lay the ribs etc the temp required will remelt the monoblock to barrel tin/lead join.
The perfect x rayed soft solder joint has now been compromised by being remelted after the x ray was done.

Any clearance between the barrels and monoblock will worsen the problem by allowing movement to occurr at the join.

Another x ray will be required and if it were to show that the join is no longer perfect the entire barrel set will have to be stripped and redone with the possability of the same thing happening all over again.

A quality join of barrel to monoblock using a silver or high temp solder can eliminate many of the problems regarding the use of tin/lead solder for this join, IMO.


Post Extras: Print Post   Remind Me!   Notify Moderator  
CptCurlAdministrator
.450 member


Reged: 01/05/04
Posts: 5268
Loc: Fincastle, Botetourt County, V...
Re: homemade doubles [Re: 4seventy]
      #33731 - 23/06/05 10:03 PM

4seventy,

Would you tell us some details about your 3 DR's built on shotty actions? I would be interested to know the calibers, the action sizes, the original makers of the actions, how and when the DR conversion was done, and by whom. Also the end result in terms of shootability and accuracy. How well have they held up, and how much shooting have you done with them? Where did the "true monoblocks" come from. What do they weigh?

Were your conversions proofed? If so, by whom and to what standards?

Can you give a comparison of the economics of your conversions at the times they were done, as compared to sourcing a similiar, original DR from the open market?

Lots of questions, lots of curiosity.

Best regards,
Curl

--------------------
RoscoeStephenson.com

YOUR DOUBLE RIFLE IS YOUR BEST FRIEND.



Post Extras: Print Post   Remind Me!   Notify Moderator  
CptCurlAdministrator
.450 member


Reged: 01/05/04
Posts: 5268
Loc: Fincastle, Botetourt County, V...
Re: homemade doubles [Re: 4seventy]
      #33732 - 23/06/05 10:05 PM

Al,

You might even post some pics if you have them.

Curl

--------------------
RoscoeStephenson.com

YOUR DOUBLE RIFLE IS YOUR BEST FRIEND.



Post Extras: Print Post   Remind Me!   Notify Moderator  
4seventy
Sponsor


Reged: 07/05/03
Posts: 2210
Loc: Queensland Australia
Re: homemade doubles [Re: CptCurl]
      #33864 - 26/06/05 11:26 AM

Curl,
Thanks for the interest in those guns.
I believe the story behind two in particular are rather interesting indeed.
It may take a while but I will do a story on them at some time and include some photos.


Post Extras: Print Post   Remind Me!   Notify Moderator  
4seventy
Sponsor


Reged: 07/05/03
Posts: 2210
Loc: Queensland Australia
Re: homemade doubles [Re: 4seventy]
      #33950 - 27/06/05 04:41 PM

In reply to:

Chamber pressure alone (in home built doubles) can in some situations degrade the solder join when a soft solder is used between barrel and monobloc




I mentioned this in an earlier post and thought I might add a little to it.

When a double rifle is built from scratch it is possible to ensure that the thickness of the barrel chamber wall is adequate to handle the required plus 30% proof load of the cartridge to be used.
This will of course mean that the chamber wall thickness will quite easily handle the normal pressure of that cartridge.
On the other hand, when building a double rifle from a shotgun action where either the barrels will be sleeved into a monoblock or a cut off chamber section of barrels, the chamber wall thickness of the barrels alone may by necessity be quite thin.
Maybe too thin to totally contain the chamber pressure without some expansion taking place.
Sometimes this barrel chamber wall may only be around 1/8" or 125 thou.
This can be compensated or assisted by the fact that the monoblock will be surrounding and supporting the barrel chamber and therefore increasing the overall thickness of the total chamber wall.
Well maybe, maybe not.
If a clearance was used between the barrel and monoblock to assist solder flow,(a common practice) this would mean that a "sandwich" has been created where a thin layer (a few thou) of solder is filling the gap between the barrel steel and the monoblock steel.
If a hard solder is used in this sandwich there is a good chance that the total combined thickness of barrel chamber wall plus monoblock wall will be available to contain the pressure.
If a tin/lead solder is used in the sandwich and the barrel chamber wall alone cannot fully contain the pressure of a possible 70,000 psi proof load, the solder could be subjected to a compression load far beyond what it can safely endure.
If this happens the solder join will/could be severly compromised.

All just opinion of course.......nothing more



Edited by 4seventy (27/06/05 06:10 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1 | 2 | 3 | (show all)



Extra information
0 registered and 68 anonymous users are browsing this forum.

Moderator:  CptCurl 

Print Topic

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled

Rating: **
Topic views: 19172

You rated this topic a 2.
Jump to

Contact Us NitroExpress.com

Powered by UBB.threads™ 6.5.5


Home | Ezine | Forums | Links | Contact


Copyright 2003 to 2011 - all rights reserved