Measuring bore diameter

[fayettefatts]

Is there a way to measure bore diameter without buying a bore gauge?

[TurnipEaterDown]

Even number of grooves: pound a lead slug (slightly oversize ball works) through a lightly lubed bore.
Odd number of grooves: more difficult.

[CastingFool]

Lube your bore and slug before driving the slug into the bore

[wmitty]

It appears you are describing land diameter ( bore diameter) as opposed to groove diameter. The correct way is with pin gages. It is possible to use a bore rider boolit if the land markings are visible on the bore riding surface. The very beginning of the land engraving should be very close to land diameter. The boolit can be inserted in the muzzle and either twisted lightly to mark the tapered bore riding portion or tapped into the muzzle enough to lightly engrave the boolit.

[Castaway]

http://www.texas-mac.com/Measuring_G...ove_Bores.html

[fayettefatts]

Thanks everyone. Yes, I am trying to determine land diameter. Never used pin gauges before and would rather not spend the $ for something that will see such little use. I will try to find some bore riders or some kind of tapered lead and see if I can get an impression that I can measure. Also found some small diameter bore gauges on Amazon that may work and they are reasonable.

[TomAM]

Your local machine shop has sets of gauges, and for a small fee fight be willing to get you a measurement.

[steveu]

Get some cerrosafe and make a cast.

[Good Cheer]

Thanks everyone. Yes, I am trying to determine land diameter. Never used pin gauges before and would rather not spend the $ for something that will see such little use. I will try to find some bore riders or some kind of tapered lead and see if I can get an impression that I can measure. Also found some small diameter bore gauges on Amazon that may work and they are reasonable.

With the twist test (using the lands to machine down a bullet) do a few of them until you get the feel for what you're doing and make a few to check. Don't just do one and run with it.

[Digital Dan]

If you’re paper patching for smokeless you need groove diameter not bore.

[25ring]

If you’re paper patching for smokeless you need groove diameter not bore.

I've been shooting patched to bore paper patched bullets for quite a few years using WC872 & 867 also IMR 3031. Patched bullet is .100 into the case and lightly taper crimped. Accuracy is just as good as my BP loads.

[Nobade]

I'm surprised that works. What cartridge? I've been able to bump bullets with Blackhorn 209 but not with any other smokeless powder.

In my experience I don't really care what the groove diameter is, I want to know what the throat diameter is. I size the bullets so they fill the throat, trying for no more than .001" under the throat size. I want that thing to plug the hole as fast as possible before the gas has a chance to blow past it and ruin everything.

[25ring]

I'm surprised that works. What cartridge? I've been able to bump bullets with Blackhorn 209 but not with any other smokeless powder.

In my experience I don't really care what the groove diameter is, I want to know what the throat diameter is. I size the bullets so they fill the throat, trying for no more than .001" under the throat size. I want that thing to plug the hole as fast as possible before the gas has a chance to blow past it and ruin everything.

I've been using this for 45-90,45-70 38-70,38-55. I run a .443 slick patched to .450-.451 in the 70 and 90.My Sharps has a tighter bore than my HighWall and uses a thinner paper for a slight interference fit.I'm also using wheelweights for all my bullets and size the dry patched bullets in an NOE push thru sizer using my own custom size bushings. FWIW.Mike

[Nobade]

I gotta try that again in my Ruger #1 with the dedicated paper patch chamber.

[25ring]

I used to use a 3 wad stack in the 90 to take up excess space in the case,now I use a combo of floral foam and a .060 LPDE wad compressed .10. That's how much bullet is in the case. Primers seem to make the biggest impact on SD's and ES's. Aprimer change can make a 100fps difference.FWIW. Mike.

[Nobade]

Are you duplex loading those slow powders or using them straight? Sounds like otherwise you're loading them just like you would with black powder?

[25ring]

Are you duplex loading those slow powders or using them straight? Sounds like otherwise you're loading them just like you would with black powder?

I started out duplexing with RL-7 when I was using greasers now with paper patching I load them without since there's a lot more case capacity especially with the 90.Other than that you pretty much load just like BP,powder,wad,compression die,seat,and slight taper crimp.FWIW Mike.

[Nobade]

Thanks, I'll let you know what happens.

[GONRA]

Back in the 1950's, GONRA didit for my 6.5x50.5mm Japanese rifle
by macihning a slip-fit bore plug ,
then crossdrilling 1/16 for "groove rider pin" that
(once fitted) determined groove diameter.

[Bigslug]

Amazon has a 250-piece, .251" to 0.500, 0.001" increment pin gauge set for $136 that will handle anything gun-barrel-related except the very large and the very small.

If you're into this casting thing to any real degree, ESPECIALLY with revolvers, consider it a cheap answer to a real need.