For those that have a DR in 450/400.

1) What length are the barrels?
2) What is the muzzle dia?

Trying to get an idea of what contour to start with for a 450/400 DR build. I know in the past the bolt guns that I've had built have all had muzzle diameters that allowed ~.150" of barrel thickness at the muzzle. That said, all of them have been modern, high pressure cartridges, not the lower pressure NE calibers.

My Krieghoff has 24 inch barrels and are .670 at the muzzle. They certainly don't need to be that thick; make it based on balance, not thickness.

quote:

Originally posted by dpcd:
My Krieghoff has 24 inch barrels and are .670 at the muzzle. They certainly don't need to be that thick; make it based on balance, not thickness.

Understand balance vs weight. Just trying to get a starting point. Plan is to weight the stock and action, and then a pair of barrels that are near that weight, and work from there to get the balance at or very near the hinge point.

Weight aside, what is a 'safe' muzzle dia for the 450/400?

Chrome moly steel is so strong that you could make the muzzle quite thin with no problems; remember, at the muzzle, pressure has dropped off to a few thousand PSI. The muzzles on my Chapuis are .080. You probably won't make your 400 that thin for balance reasons, but you could safely do so. Of course, how you taper the barrels will affect the balance more than just muzzle diameter.

quote:

. . how you taper the barrels will affect the balance more than just muzzle diameter

Agreed.

2Barrels

With any luck ronvella will chime in here. He recently had some barrels ground down for reduced weight and balance on a DR he is building up on a Bruno ZP action in 9.3x74R. You may be able to get him to measure the barrels at 2" intervals to give you an idea of diameter and final taper. There's a build thread on NX.

quote:

Originally posted by dpcd:
Chrome moly steel is so strong that you could make the muzzle quite thin with no problems; remember, at the muzzle, pressure has dropped off to a few thousand PSI. The muzzles on my Chapuis are .080. You probably won't make your 400 that thin for balance reasons, but you could safely do so. Of course, how you taper the barrels will affect the balance more than just muzzle diameter.

I think most doubles will mike under .100. My Verona 30-06 O/U mikes at .066.

quote:

Originally posted by Rhodes:
2Barrels

With any luck ronvella will chime in here. He recently had some barrels ground down for reduced weight and balance on a DR he is building up on a Bruno ZP action in 9.3x74R. You may be able to get him to measure the barrels at 2" intervals to give you an idea of diameter and final taper. There's a build thread on NX.

Found the thread on NX. Looks like Ron used Shilen #2 profile barrels for the 9.3x74.

Based on my experience, unless you are going to contour the barrels yourself, most barrel makers do not make a barrel contour that will be as small as most double rifles (and double rifle makers) want, even on a "custom order". I understand that Montana Riflesmith now has equipment that will allow them to make double rifle tapers and will make them, but I have not personally ordered a set of barrels from them.

I did order a set of double rifle contoured barrels from Lothar Walther. They did make what I wanted (mostly), but it took forever (over a year) and I can't really recommend them, unless you can wait a long time. Those were in .375 (muzzle diam. of .550") and will be for a .375-2.5" NE.

Back to your basic question, I have measured several "original" double rifle barrels. I plan to have a section in the 3rd edition of the book (appendix ??) that will list my research on original double rifle barrel tapers. The muzzle diameter does not tell the whole story. It is important to look at the whole barrel taper as well.

Below is some information from 5 different Rigby double rifle barrel sets that I measured (the table did not import well, but I think you can figure it out - sorry). Note that all dimensions are diameters (in inches), except for the barrel "Length".

Rigby .450 Barrel Tapers
(5 different barrels)

Breech, 3” from Breech, 6” from Breech, Muzzle, Length
1.029, 0.89, 0.787, 0.638, 26.0”
1.029, 0.906, 0.83, 0.638, 26.0”
1.045, 0.913, 0.876, 0.638, 26.0”
1.063, 0.942, 0.878, 0.638, 26.0”
1.038, 0.918, 0.824, 0.618, 26.0”

Really, if you can't contour a barrel, you probably won't be able to build a double rifle. How will you thread, chamber, crown, make firing pins, etc, unless you have a lathe and know how to use it? Again, just my opinion, having built several DRs on shotgun actions. NOT meaning to impune or question anyone's skills at anything. Another note, Douglas will make any contour you want if you send them a sample. It used to be $35.