measureing bore

[jim/wa]

how do you measurethe exact diameterof your borehaving trouble gettingright patch and ball combination

 

I use a micrometer (caliper)scale thingy that my dear wife bought me for my birthday a few years back. Measures down to third decimel place.

 

[AZ-Robert]

I use a micrometer (caliper)scale thingy...

They look like this:
[url] http://www.trackofthewolf.com...subId=87&styleId=1083&partNum=LYMAN-CALIPER-E[/url]

The kind with a dial instead of a digital readout can be found a little cheaper:
[url] http://www.logcabinonline.com/item3290017.html[/url]

As with a lot of things in life, once you have one you'll find lots of uses for it.

 

[Russianblood]

Now if I could figure out how to measure the bore on my MVTC blunderbuss. It came is the wrong box and the Indians mark the bore diameter on the box as each is different.

 

[paulvallandigham]

First take the barrel out of the stock. sometimes, and only because the Indian gun business learned its trade from the British, the gauge or diameter is marked on the bottom of the barrel, British style.

If not, you will have to make your own gauge. Take the thing to a hardward store, where they sell dowel rods in various sizes. These usually run up to one inch. Try the rods out until you find a go, and a no-go rod for the gun. The bore is somehere in between. All you can do then is buy the no-go dowel, and slowly file or trim it down, until it fits the bore, and you can then take a reading with a micrometer, or caliper. You may have to visit a wood working shop to use their lathe to slowly shave down the rod, but I can't think of any readily available gauge you might otherwise use.If the bore is over one inch, you may have to visit a wood shot to find a dowel big enough to use for the gauge, anyway!

That belled barrel muzzle is what creates the problems. And, I am going to assume that taking the breechplug out is not practical, even if it is possible. Some of these guns have the plugs swaged in, or even epoxied, rather than cut threads and screw them in. So, be careful with it. You can always write the company and ask them if they know what the diameter should be, nominally.

 

[CrackStock]

Barrels with even numbered lands and grooves are easy to measure since there is a reference across to give a measure.

However, some are 7 grooves and this is a problem that requires a round taper to fit inside with a mark to measure the diameter from where the lands stop the taper with calipers to give you a reasonably close read.

(I hope that I have not confused anyone with this explanation.)

CS

 

clear to me...and you are right: odd grooves are hard to get right with calipers in the bore...

 

[BS]

clear to me...and you are right: odd grooves are hard to get right with calipers in the bore...

Especially on a seven groover.

 

[BS]

$10 for a set of stainless calipers:
Link to wttool

 

[Russianblood]

I found a 5/8th dowel was close to bore size and then I wrapped the end with blue painters tape until one more wrap wouldn't go down the bore and then I measured it.

What do you know, my brass barrelled blunderbuss is a 16 gauge! (.668)

 

[paulvallandigham]

Glad that worked out for you. The tape idea is a good one. There is some springiness to it, so the measurement will only be close, but the bores of smootbores are only close in most cases, and in blunderbusses, who knows? At least you can now order proper fitting overpowder cards, and cushion wads. i don't know what you are going to shoot, shot or ball, but I would almost have to try shooting shot out of that BB to see what kind of pattern I won't get! Cheers.

 

Historically, bores were measured with a set of gauges, metal cylinders of known diameter, which were slid thru the barrel. In fact, that is where the term guage comes from. They were, in effect go, no go measurements.

You can make your own if you have a lathe and the skills to do it or you can buy steel rod stock which has been ground and hardened, from most machine tool suppliers. I think they are called pin stock, and come in .0001 increments. They usually cost a couple of bucks each.

 

[Capt. Jas.]

most shotgun gunsmiths use these
[url] http://www.brownells.com/aspx...PROFESSIONAL+SHOTGUN+BORE+MICROMETER+SET[/url]

 

[Joe Yanta]

I bought this micrometer and gauges at a pawn shop for about $10. I just compress the gauge that I need and slide it into the bore. I twist the end of the gauge releasing the spring to expand the gauge in the bore and then twist the end of the gauge to lock the expansion of the gauge. Then I pull the gauge out and measure it with the micrometer.

Joe

 

I bought this micrometer and gauges at a pawn shop for about $10. I just compress the gauge that I need and slide it into the bore. I twist the end of the gauge releasing the spring to expand the gauge in the bore and then twist the end of the gauge to lock the expansion of the gauge. Then I pull the gauge out and measure it with the micrometer.

Joe

Could you explain this a little more, Joe? What exactly is it that you are compressing?

 

[Joe Yanta]

The gauges have two tiny "pistons" on the end assembly. You compress these pistons into the assembly and rotate the handle of the gauge to hold them there. You can then insert the gauge into an object and then rotate the handle in the opposite direction releaseing the pistons (under spring pressure) allowing them to expand to the inside surface of what ever you want to measure. Then you twist the handle knob back locing the pistons where they expanded to. The domes of the pistons are convex so you can get very precise fit on curved surfaces. You then remove your gauge and then with a micrometer you accurately measure from top of piston dome to top of piston dome for your bore diameter.

The measurement was taken at bottom of groove to bottom of groove in my 50 caliber Leman trade rifle which mics out at .500

Joe

 

[pathfinderifh]

Buy a couple of size's of ball's around the size of your bore, a couple of different thickness of patches,go to the range and have fun!

 

[Beerd2]

Joe
that's a cool thingamajig (dohicky?).
anyone know what its' REALLY called?
..

 

[WRussell]

Depends on the manufacturer. Starrett calls them telescoping hole gauges, Brown & Sharpe call them bore gauges. Google should turn up some suppliers.

 

[Ohio Rusty]

I just saw an ad for Harbor Freight tools they have advertised a whole set of those piston ended bore gauges half price for $11.99. I have a set that I've been using for a while. I'm looking for someone with a cannon so I can try out the biggest one.
Ohio Rusty