Measuring Finished Chamber Dimensions

[LVLAaron]

confirm you do not have an oversized back end

phrasing

 

[Jud96]

Thank you guys for the information and input.

I do measure my reamers to record their actual dimensions, because I have had reamers I ordered and took for granted they were right but actually were .001-.0015 over.

I think I’m going to get a 3 point bore mic and some pin gauges in .0005 increments to check the base diameter on my finished chambers. I just want to make sure my setup is working, and I like to inspect all of my work for peace of mind.

 

[LVLAaron]

How are we accurately measuring a tapered bore?

 

[Jud96]

How are we accurately measuring a tapered bore?

That’s my main question. I don’t have much experience measuring bores with as much taper as a chamber, so that’s why I was curious what others were doing.

 

[DaveTooley]

This rabbit hole can get deep and expensive. SAAMI tolerance on say the Creedmoor case is +.002" on diameter. The .200" line is .4714". I would get three gage pins. One .4710", one .4725", and one .4735".
Make up stops to go them so you can set the depth. Example; Rem 700 with a counterbore, set the stop at .200"
Then if the .4735" goes in I want to listen to the call to the reamer maker.

You could ask for an inspection report on every reamer you buy. I have one that goes out into the millionths.

 

[Tim Singleton]

In Daves example if you have a a chamber that a .4735 to .474 gauge will go into the 200 line your setup maybe allowing some wobble

 

[DaveTooley]

How are we accurately measuring a tapered bore?

gage balls are the best way.
Or your very own CMM

 

[Alex Wheeler]

Your .2-1.2" inside mic is fine. Eyeball .050" into the chamber and that will give you close to the .2" diameter. If your less then .0005" over spec on the print your fine, as most reamers are at least .0003 fat. If you hold the reamer you know its good when you cant just pull it out without a twist.

 

[tobnpr]

Cast the chamber and measure it at whatever datums float your boat.
It's not complicated.

 

[Alan Warner]

gage balls are the best way.
Or your very own CMM

Dave,
If I was to invest in the styli for my renishaw for our cmm, each inspection would be at least 150.00 for a good while
For a rifle chamber, g age pins at known depth and math is close enough

 

[LVLAaron]

I like the “wiggle the reamer” method. If I’m going to measure I want exact datums and locations… otherwise the number is wrong. I know we can get “close enough” but if close enough is good enough so is wigging the reamer? Assuming the reamer is correct-enough.

 

[FireMedic]

That rigid reamer holder craze has lots of chambers running big!

 

[Sniperhandle]

The pusher is the most accurate way to get a tight chamber, Either use a Bald Eagle or make one like Dave Tooley's.

 

[liljoe]

I was watching a video from a very well known engine builder and he made the statement "If you can't measure it, you can't fix it".
Joe

 

[Tim Singleton]

Dave's method tightened me up!