On measuring inner bore.

[Smokestack]

Hey there.

Been struggling with getting some pin gauges for my rifle and haven't' had any luck with local shops/machinists to help me out on this. Kinda went the simple route and used a digital caliper to try and determine the inner bore of my Pedersoli P53. Not really interested in buying a huge set for $300 in which I only use once and maybe 3 gauges out of.

Average reading gives me anywhere from .576 to .577 which makes sense, but im probably missing the exact diameter with my rather rough approach to this.

Should I just be satisfied with the reading I got from the caliper, or are there any other methods I should give a try in terms of getting my inner bore diameter? Still pretty new to all of this, so any help would be much appreciated.

Thanks a ton.

 

[rkrcpa]

When I wanted to measure cylinder throats on my revolvers, rather than ordering a whole set I ordered the individual pins in the calibers I was interested in. Usually three pins per caliber is sufficient if you have a good idea of your starting point.

 

[Pete G]

Should I just be satisfied with the reading I got from the caliper

Yes. It's not really that important anyway.

 

[mooman76]

You could slug your bore. Use a Fairly heavy brass or even steel rod wrapped in tape. Put it in your well lubed bore. Drive a slightly larger lead slug into the bore and use the weight of the rod to drive it back out. Then measure of coarse.

 

[Erwan]

Should I just be satisfied with the reading I got from the caliper, or are there any other methods I should give a try in terms of getting my inner bore diameter? Still pretty new to all of this, so any help would be much appreciated.
You can use an oversized slug in pure lead and putted this in the barrel with a mallet and after the slug is out make the mesurement with a micrometer...
Other way with molten sulfur and micrometer (that stinkt).
For the last and simplest one with a low fusion metal like Cerrosafe...

Example : Klick...

 

[Erwan]

Hey there.
Should I just be satisfied with the reading I got from the caliper, or are there any other methods I should give a try in terms of getting my inner bore diameter? Still pretty new to all of this, so any help would be much appreciated.

Thanks a ton.

You can use an oversized slug in pure lead and putted this in the barrel with a mallet and after the slug is out make the mesurement with a micrometer...

Other way with molten sulfur and micrometer (that stinkt).

For the last and simplest one with a low fusion metal like Cerrosafe by Brownells or other like Midway...

 

[bang]

It really depends. If you can measure 180 straight across it should be ok. If you have odd like 3 groove it can be awkward to get good measurement.

 

[dave951]

Amazon is your friend. Use a caliper to get in the ballpark. If it reads 579, order single pin gauges off Amazon for about $5 each in 581, 579, and 577, you don't have to get a full set. Put a subcaliber bullet into the bore, use plug gauge to get the actual reading. If 577 is too small but 579 too large, you're 578. If 579 fits, you're on the money, you see the pattern. If a pin gets stuck, turn rifle pointing down to allow the subcaliber bullet in the bore to slide down and "clunk" the pin gauge out.

Slugging these bores is problematic at best. You'll only know the measurement at the muzzle. Best practice is still a pin gauge.