Trick question: Diameter of a 50-cal bore?

[Twanger]

So they've been kicking around the subject of "cooling rods" on the Savage forum.

This is a 24-inch long half-inch diameter rod that you keep in ice, and then put in the bore of your gun between shots to cool the barrel down. This keeps the bore cool, and the gun shooting good, even when it's 90-100 degrees out in the summer.

So the big question is: What is the land-to-land diameter of a 50-cal bore? Specifically a 209X50 Encore's bore?

[ncboman]

nobody'll play?

I'll take a guess and say .502.

btw, I'm not sure what an ice cold cooling rod does to a hot barrel but I know heated rocks will fracture in cold water.

ncboman

[Altjaeger]

Simply a wild swag w/ a dash of fallible memory I will call it .480.

[Lumox]

Take a bottle of compressed Co2 and gas the inside of the barrel for a quick cool down. Of course anytime hot steel is cooled too fast it might just warp. Maybe they should try one of those carbon fiber wrapped barrels that are supposed to be less effected by heat??

[Twanger]

I bought some 0.503 aluminum rod last night and it easily fits exactly 1-inch down the bore of my Encore, then the QLA at the muzzle ends and that's where she stops. :mad:
I can tell it's close though. I may put a rod on my wood lathe and see if I can file or sand it down enough to fit.

[Rattus58]

My guess is that Thompson is exactly .500. There is an old habit that old hunters used to do... slug the barrel... take a 54 caliber ball and big rubber hammer... OK.... just a thought.... but slugging the thing would be good thing.

Aloha.... Tom :cool:

[swamp]

.504

[ncboman]

.504

Is that a fact or a guess?

ncboman

[swamp]

Is that a fact or a guess?

ncboman

a guess...

my second guess is .501

[Lumox]

So, what do you suppose is going to happen to the rifling as you go sliding that tight fitting aluminum rod in and out of your barrel?

[Bill Gunn]

So, what do you suppose is going to happen to the rifling as you go sliding that tight fitting aluminum rod in and out of your barrel?

My SWAG would be... If you get it to fit really nice and close, and get it nice and cold... When it warms up and expands, and the barrel cools, and contracts, you may no longer have a 50 cal. muzzle loader barrel, but you will have an expensive piece of steel, with an aluminum rod forever stuck in it..

That process is exactly how you get a tight fitting sleeve or bearing, onto a shaft. And the only way to get it off is to heat the hell out of it, and pound it off. Something you won't be able to do with a rifle barrel...

[ncboman]

that's assuming some things I'm not sure about regarding how the interior of the barrel moves during thermal variances.

ncboman

[Twanger]

BTW - I didn't invent this idea... This is something that people have been talking about doing on the Savage forum. They are keeping the bore cool between shots to keep the groups smaller. I think the temperature differences between the cooling rod and bore are not huge - the rod is 32F and the internal surface of the bore is probably 150F, and these barrels are thick pieces of metal. It's not like dumping a light-weight frying pan at 400 degrees into the kitchen sink.

I believe if the rod fits with them both at 70F then we won't have a problem if the rod is colder (smaller) and the bore is hotter (bigger).

[Bill Gunn]

I believe if the rod fits with them both at 70F then we won't have a problem if the rod is colder (smaller) and the bore is hotter (bigger).

I agree with that too, but how do you figure in the "Dirt" (Burned, and unburned powder) in the barrel that wasn't there when you made it a tight fit so it would cool ?

It may be a great idea... I'm just saying "Something to think about".
I just hold off sighting in my ML's until the weather's cold to kinda match the hunting conditions.
The main reason I do that is that I would think any kind of plastic sabot would act quite differently shooting well below 32*F vs. say 75*F.

[GF.]

Sounds like trouble to me.... What do the serious bench rest shooters do? Or are their barrels pretty much immune to ill effects?

I suppose and old BPCR-style 'blow tube' is pretty much out of the question, eh?

Damn. Stuff like that's enough to drive a guy to using spit patches & ball :D

[GMWW]

Interesting idea. I wonder how much condensation would be drawn into the barrel with the cold rod?

[Lumox]

A blow tube attached to a bottle of compressed Co2 or some other dry cold gas perhaps????

Of course shooting full bore projectiles would solve the problem of the plastic sabot's melting from the heat.

[ncboman]

Interesting idea. I wonder how much condensation would be drawn into the barrel with the cold rod?

Very good point.

The whole idea seems kinda foreign but interesting nontheless.

fwiw, I would do it to my rifles without being sure it does no harm. When flintknapping I run into chert with freeze fractures from time to time. For some reason this topic made me think of that. :o :D