Taking barrel measurments

[Char-Gar]

I am several years deep into building a Krag sporter with a new 2 groove 03A3 barrel shortened at the breech and rechambered back to 30-40. About a year ago, I slugged the barrel and measured the land diameter. I came up with .302 X .314. Sick at my stomach due to the obvious grossly oversized barrel that somehow slipped by Remington and the military inspectors, I just sorta lost interest in the project and set it back on the shelf.

Last night, I was having trouble sleeping and my thoughts turned to that cursed 03A3 barrel. I got up and reslugged the barrel and this time it came out .300 X .308, dead nuts on to what it should be. This morning I got up and did it again and once again .300 X .308.

So how could I be so wrong the first time? I suspect I was cross-eyed that day and did not read the instruments correctly, but who know.

I have been doing this stuff for a very long time and should not make those kinds of errors. This just goes to show that this kind of stuff can happen, no matter how long you have been doing this kind of thing. Anyway, I am glad I was wrong, and the project is off the shelf and back on the bench to be completed.

They say that confession is good for the soul, so here it is.

[famdoc2892]

I have the same question, when I retrieve the slug from the barrel, am I looking for the outside diameter (same as the measurement from groove-bottom to groove-bottom inside the barrel)?

[H.Callahan]

I think it is a case of coming back to it later with a fresh mind. I know sometimes I will come up with a condition that doesn't make a lot of sense and then come back to it later and do it again and come up with something entirely different.

So, I generally mentally apply a "reasonablity test". If what I am seeing sounds fairly reasonable, then I worry about it less. If I am getting something in the "snuh?" catagory, going back later and trying it again a lot of times will get me a different answer.

Of course, if it is something critical, "measure twice, cut once" always come into play!

[rintinglen]

I had a little sliver of lead do me wrong once on my micrometer. I was measuring some boolits I'd sized in a .355 sizer and was quite purplexed when they were measuring .360+. Only after several came up large did I notice the speck of lube holding the little bit of lead. Cleaning the faces of my old Starrett promptly shrank those boolits back down.

[Calamity Jake]

I have the same question, when I retrieve the slug from the barrel, am I looking for the outside diameter (same as the measurement from groove-bottom to groove-bottom inside the barrel)?

That's correct

[Char-Gar]

I had a little sliver of lead do me wrong once on my micrometer. I was measuring some boolits I'd sized in a .355 sizer and was quite purplexed when they were measuring .360+. Only after several came up large did I notice the speck of lube holding the little bit of lead. Cleaning the faces of my old Starrett promptly shrank those boolits back down.

That is my best guess also. I always clean the faces of the mic and check for zero. Always may not have included the first measuement.

[MtGun44]

Dang it - still human are you? ;-)
We all make mistakes, good that you checked rather
than tossing that valuable old barrel!

Bill

[Char-Gar]

I had a little sliver of lead do me wrong once on my micrometer. I was measuring some boolits I'd sized in a .355 sizer and was quite purplexed when they were measuring .360+. Only after several came up large did I notice the speck of lube holding the little bit of lead. Cleaning the faces of my old Starrett promptly shrank those boolits back down.

That is my best guess also. I always clean the faces of the mic and check for zero. Always may not have included the first measuement.

[MBTcustom]

It is important that the part being measured is clean as well as the micrometer anvils. Also, I always slug twice before I decide to call it gospel-truth. Irregardless, I'm very glad you have something to work with again.
Just for the sake of being anal, why dont you scrub that barrel with a copper brush and patch, then slug it one more time, just to be on the safe side.
So far, two out of three says you got yourself a barrel.

[geargnasher]

Char-Gar, I've slugged one of my '06 Winchester Model 70s on four separate occasions with two different kinds of "pure" lead, still .301+"x.309+", maybe I need to store it on your magic shelf for a couple of years!

Gear

[rintinglen]

Char-Gar, I've slugged one of my '06 Winchester Model 70s on four separate occasions with two different kinds of "pure" lead, still .301+"x.309+", maybe I need to store it on your magic shelf for a couple of years!

Gear

You don't want to do that, Gear, that hot Texas summer son will shrink your barrel down to 7.35 mm.

[Grandpas50AE]

Char-Gar, glad you discovered the mistake before scrapping the barrel. Often times at the age we're at, we do something when we're tired and the mind just gets it wrong, and we come back later for a fresh look and discover the error. I think this happens to all of us, so don't feel too bad, it's just one of those things where double-checking yourself sometimes pays off.

[Char-Gar]

I really don't feel too bad about it. I make mistakes all the time and have learned not to expect perfection of myself. Callahan's post about such things being reasonable or not and if not reasonable, then time to take a second look has the ring of truth in it.

From time to time we get folks bringing issues to this board, that when viewed in their totality, just don't make sense. There was a basic error made in measurments or somewhere in the first steps. It is helpful to know that anybody, no matter their experience level, can drop the ball (or micrometer) from time to time.

I have also found that "ball dropping" increases with age.

[Mk42gunner]

When I was a kid just learning how to build things, my dad told me, "measure twice, cut once." When I was in high school, working for a contractor/plumber, he told me, "measure twice, cut once."

As I get older, and my eyesight gets worse, I have modified that to: Measure three or four times, then think about it again, before cutting, (or accepting a measurement).

Good that you caught your mistake.

I have never slugged a two groove barrel, is it possible that you were measuring from corner to corner on the grooves, like is sometimes recommended for meauring a five groove slug?

Robert

[Char-Gar]

Measuring a 2 groove is like measuring a 5 groove Smith and Wesson. You gently rotate the slug between the jaws of the micrometer, while opening the jaws, until you find the high spot. That will be the groove diameter.

No matter where you take the dimension of the slug, it should never be larger than the largest part of the barrel. You can't get a .314 measurement from a .308 barrel.

[theperfessor]

Wish I had a nickel for every time I've misread a mike by exactly 0.025"! And when I use depth mikes or caliper-type inside mikes, where the scale is essentially backward, I always have to think carefully and read the mike several times to be sure I'm working in the proper direction when I read the 0.001" scale and total up the measurement. Happens to everybody, even people that should know better.