Looking for a reasonably priced bore gauge covering .700 to .740

[rhodesengr]

I have been doing a lot of searching for a reasonably priced inside-micrometer, or bore gauge. I have found a bunch of them from industry sources and gun-specific companies but most are quite expensive.

I am mostly interested in measuring 12 gauge chokes so I don't need a lot of length but I need something that covers the range of .700 inches to .740 inches.

It's been a frustrating search because for most things like this there are inexpensive versions that have done me just fine. I have a digital caliper that I bought on Amazon for something like $15. It works as well as a more expensive Mitoyo version I have at work. I splurged earlier this year and bought a 0 to 1" Mitoyo outside micrometer. It was in the $100 range.

I thought I could get by with telescoping feeler gauges and then measure those with my micrometer but that method is not very reproducible.

I have looked at many types. I think I like the three-point type the best. I have looked on
Amazon
McMaster
MSC

and I know about Gun-specific source like The Unloader, 100 Straight, and Skeets (on ebay so maybe a copy?)
This is the most reasonable one I found from an industrial source

https://www.mscdirect.com/product/details/00343004

The Unloader has one for about $230 but seems like you also have to order a fancy wood box that doubles the price.

Most other ones are like $500 and pistol grip type is more like $1000 or more. Ugh.

Anyone know of decent 3-point inside micrometer or bore gauge covering my range for a more reasonable price?

I'll buy one of the ones I've found unless someone here knows of a less expensive one.
Thanks

[Dirtlaw]

I've been gone to long in this area. Dealing with life and as Professor Herbert used to say ...

[ar15barrels]

I have been doing a lot of searching for a reasonably priced inside-micrometer, or bore gauge. I have found a bunch of them from industry sources and gun-specific companies but most are quite expensive.

I am mostly interested in measuring 12 gauge chokes so I don't need a lot of length but I need something that covers the range of .700 inches to .740 inches.

It's been a frustrating search because for most things like this there are inexpensive versions that have done me just fine. I have a digital caliper that I bought on Amazon for something like $15. It works as well as a more expensive Mitoyo version I have at work. I splurged earlier this year and bought a 0 to 1" Mitoyo outside micrometer. It was in the $100 range.

I thought I could get by with telescoping feeler gauges and then measure those with my micrometer but that method is not very reproducible.

I have looked at many types. I think I like the three-point type the best. I have looked on
Amazon
McMaster
MSC

and I know about Gun-specific source like The Unloader, 100 Straight, and Skeets (on ebay so maybe a copy?)
This is the most reasonable one I found from an industrial source

https://www.mscdirect.com/product/details/00343004

The Unloader has one for about $230 but seems like you also have to order a fancy wood box that doubles the price.

Most other ones are like $500 and pistol grip type is more like $1000 or more. Ugh.

Anyone know of decent 3-point inside micrometer or bore gauge covering my range for a more reasonable price?

I'll buy one of the ones I've found unless someone here knows of a less expensive one.
Thanks

I have generally paid between $60 and $90 each for legit swiss made 3 point bore microemters on eBay.
There are not any available in that price range at the moment for a 0.700-0.800 though.
Maybe make an offer to the seller of these two for just the smaller one for half his asking price:

https://www.ebay.com/itm/225247320363

Your next option is a bore gauge like this:

https://www.ebay.com/itm/334996308676

Either way, you will need to get a calibration ring as well and calibrate it yourself or send it out for legit calibration if you need absolute measurements but if you are just checking choke, relative measurements will work fine.

[Dirtlaw]

If you want to know the ID of a bore an approach accurate to within a few tenths is something like this

https://www.amazon.com/HFS-Class-Steel-Gage-0-251-0-500/dp/B081TQ91KQ/ref=pd_bxgy_img_sccl_1/139-7788645-0095046?pd_rd_w=RjSj0&content-id=amzn1.sym.26a5c67f-1a30-486b-bb90-b523ad38d5a0&pf_rd_p=26a5c67f-1a30-486b-bb90-b523ad38d5a0&pf_rd_r=0GVTTT9THJDH4MN4HN2N&pd_rd_wg=1sgxU&pd_rd_r=6fb78898-7f99-4ea8-b8c7-b276e02647fb&pd_rd_i=B081TQ91KQ&th=1

[Dirtlaw]

Larger sizes as you require are more expensive, however.

[G-forceJunkie]

What resolution of accuracy do you need? A couple dozen gauge pins would work if you just need to tell the difference between .720 and .722 If you actually honing chokes and need .0001 resolution, spend the money on a 3 point inside mic.

[rhodesengr]

pins are a good idea. I think I am more interested in a gauge though. Probably get that one on MSC. It's long enough to get down to my actual bore (past the choke step) and cover any 12G choke.

[kcstott]

There's no reason to get a bore mic for a Choke tube. there's no reason you need .0001" accuracy for a choke tube.

Go buy a Starrett micrometer and a set of telescopic gauges.






Snap gauges


Or better yet

Bore gage

[kcstott]

What resolution of accuracy do you need? A couple dozen gauge pins would work if you just need to tell the difference between .720 and .722 If you actually honing chokes and need .0001 resolution, spend the money on a 3 point inside mic.

chokes come in .010" steps the special chokes come in .005" steps in reality you could check it with the ID side of your calipers and be close enough. There's nothing that is going to change on a pattern that .002" difference in choke is going to show.

[rhodesengr]

There's no reason to get a bore mic for a Choke tube. there's no reason you need .0001" accuracy for a choke tube.

Go buy a Starrett micrometer and a set of telescopic gauges.

This more a matter of "want" than "need". I have a good Mitoyo micrometer. I have a decent caliper and I have made decent measurements with that. I bought a set of those telescoping gauges. Seems there is just too much "art" involved to get a repeatable measurement. With chokes you (mostly) know what they are supposed to be so if you get that number, you can say "ok, it's what it's supposed to be." But if you get a different number, then you have to try again. If you really have an unknown hole, you have to use the telescoping things multiple times to make sure you have the right number. At least, that is what I am finding.

The purpose of this is I am comparing actual patterns in rather great detail using AC Jones' Shotgun Insight. I got motivated to do this because numerous folks were posting that Browning brand Invector DS chokes (which is what I have) were various negative things like "don't perform" "crap", "good for paper weights", etc. So I wanted to find out for myself with my gun, my chokes and my load. I bought some Briley chokes to compare. I learned pretty quick that "Full" chokes from different companies have different bores. Browning Full is .700 while Briley Full is .705. So comparing those two head to head is not apples to apples. In process of all this, I found I didn't have a great way to accurately measure the bores. I like having good tools so (needed or not) I am getting a decent, direct reading bore gauge. Maybe more than one.

If anyone wants to see the thread where I am posting my results, it's Trapshooter Shooting section. Same Username.

[ar15barrels]

The purpose of this is I am comparing actual patterns in rather great detail using AC Jones' Shotgun Insight. I got motivated to do this because numerous folks were posting that Browning brand Invector DS chokes (which is what I have) were various negative things like "don't perform" "crap", "good for paper weights", etc. So I wanted to find out for myself with my gun, my chokes and my load. I bought some Briley chokes to compare. I learned pretty quick that "Full" chokes from different companies have different bores. Browning Full is .700 while Briley Full is .705. So comparing those two head to head is not apples to apples. In process of all this, I found I didn't have a great way to accurately measure the bores. I like having good tools so (needed or not) I am getting a decent, direct reading bore gauge. Maybe more than one.

If anyone wants to see the thread where I am posting my results, it's Trapshooter Shooting section. Same Username.

The reason the exit hole sizes are different on different choke tubes is because the bore diameters are different on different brand guns.

Put simpler, it's the constriction from BORE to CHOKE EXIT that matters.
The actual exit diameter does not matter until you know what the bore size is too.
Then you can figure out the constriction.

Cylinder		0.000
Skeet 1			0.005
Improved Cylinder	0.010
Skeet 2 (Lt. Mod.)	0.015
Modified		0.020
Improved Modified	0.025
Full			0.030
Extra Full		0.040

[rhodesengr]

The reason the exit hole sizes are different on different choke tubes is because the bore diameters are different on different brand guns.

Not really the topic of this thread but...
I only have one gun that takes Invector DS chokes, my 725 Trap Max. What I am saying is that chokes marked "Full" (or LF, or EF) aren't the same from brand to brand. My Browning brand Full is .700 and my Briley Full is .705 so no matter what my bore is, the Browning has more constriction than the Briley. My pattern data supports this but my statics aren't great because I only have 3 shots with each Full choke. There is a table I put together in my thread on TS with four or five brands. Not all brands list actual ID. Browning and Muller don't but obviously folks have measured them.

As near as I can measure now with the telescope gauge, my bore is .740. Browning doesn't list actual bore as a specification but searching the forums, people are saying they get anywhere from .740 down to maybe .737 but just based on my attempts so far, that could well be within measurement error for .740.

I can say for sure that the Browning and Briley chokes have very different entrance ID. The Briley's are .740 so they match the actual bore. The Browning's are quite a bit bigger at .756. This explains what I see when I look into the chokes after shooting. I can see where the shot has engaged the choke wall. The Briley chokes show engagement right from the entrance. The Browning ones don't show any engagement for the first few centimeters. The shot enters the choke at .740 but the choke starts at .756. So its fair to say that the Browning has a steeper taper than the Briley but according to AC Jones's work, the taper profile doesn't make any significant difference.

[kcstott]

Telescopic gauges take a bit of practice but so does a bore mic. All these tools require some practice to get good measurements.

You might be better off with a simple set of Minus pins.

Minus pin set

One of many tools I use for such application is this guy. But you do need a ring gauge to set it up.

As Randall said it's the amount of constriction that matters.

If you are in doubt have Teague send you a set of chokes and be done.

[rhodesengr]

If you are in doubt have Teague send you a set of chokes and be done.

Well.... Teague has a chart that quotes constriction but doesn't say what bore they base that on. So, based on what Randal said, you can't tell the constriction if you don't know the bore. Maybe they are assuming the bore for a gun that takes an Invector DS choke is .740 but they don't actually say that anywhere.

[kcstott]

Well.... Teague has a chart that quotes constriction but doesn't say what bore they base that on. So, based on what Randal said, you can't tell the constriction if you don't know the bore. Maybe they are assuming the bore for a gun that takes an Invector DS choke is .740 but they don't actually say that anywhere.

Teague lists bore size right on the web page for the choke system. Choke tubes