doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com MACNAUGHTON Double Rifle - Unknown Caliber

Hello Tinker,

Thanks for the reply.

Yes, that's the "groove" dia as measured on the chamber cast. Since its an odd number of grooves, I can't measure the the bottom of the grooves to get the "bore" dia of the casting, and I don't have any way to take a measurement of the barrel.

gauge pins are the best way of measuring a hole or the bore in this case. Several members of the ACGG are not far from you. You might contact one and see if they could measure it for you.

Hello SKB

Thanks for the reply.

Not that important. Its the groove dia that determines what I intend to reload.

How are you getting the measurements on your five features of that casting?

Are you sure of your number?

what 5 features?

buckstix,
A typical set of "small hole gages", together with a Mic or caliper will provide a decent measurement of a bore( not grooves) of up to .500, right from the barrels. You simply insert the appropriate one, expand it until it stops, remove it, and measure with a micrometer or caliper. Your local machinist/hobby machinist/ gunsmith or some handloaders may have a set.
Mike

Hello Der Ami,

Thanks for the reply.

As I said earlier, its not that important. Its the groove dia that determines what I intend to reload.
_________________________

The five high spots that describe your groove diameter

Mike

This method doesn't work out with an odd number of grooves.
As you likely know, the small hole gage takes a dimension across two points at 180 degrees from each other - and with am odd number of grooves that dimension would be land-to-groove, not land-to-land or groove-to-groove.

Taking a measurement of the bore diameter with pin gages (which will get you very close to that number), then measuring with a small hole gage can get you very close to the actual groove diameter but it will take a bit of math to get you there.

Tinker,
No, the small hole gages are either ball end or half ball end and the appropriate size should bridge the groove. They are limited to 1/2" holes. You are thinking about the much larger "T" shaped ones that go to well over 3". Note I said "decent" measurement, I concede it may be a fraction of a thou. off.
Mike