Oh Boy!

I have a new rifle--okay, it will be a new rifle when I get this finish on the stock--and a new Thingy.

When my rifle was barreled, the 'smith took a short--2"--stub of the barrel and reamed a partial chamber in it with the same reamer used for the rifle.

Some of the possibilities are immediate: I'll measure the OA length with a case inserted, and then measure the OA length with a bullet seated in the case. If the second measurement is longer, I'll know the bullet is touching the lands, and use that, along with my micrometer seating die, to seat bullets with exact knowledge of their distance from the lands.

Once I've fired a few cases, I'll be able to use the Thingy--using FL sizing die--to exactly bump the shoulder, say, a thousandth. Or whatever appeals to me.

By, once again, comparing the OA length of a sized cases sitting in the Thingy.

Many of our contributors have more analytic minds than mine, so I'm wondering if there are any uses I'm not thinking of?

flaco

Hey flaco

A "thingy" convert? Excellent. You are coming out of the dark side into the light!!!

Throw away all your duct tape and baling wire and join the enlightened progressive crowd and leave the H C (Hopelessly Conventional) stuff behind!!



That does sound like an interesting concept. I assume that the "partial chamber" is an exact reproduction of the shoulder area, neck, leade and distance to lands as the chamber in your rifle. Sorta like a female chamber cast.

Question. How do you know if you will have the same measurement in your chamber since there may be some headspace on your loaded cases? If the case in your rifle has headspace then the case would not be pushed all the way forward as it is in your thingy. The bullet will then be drawn back from touching the lands the exact same amount as the distance between the case shoulder and chamber shoulder in your rifle.

I suppose you could take a case that has a crush fit in your rifle and that would mitigate the difference.

Question. What barrel length is your rifle? Most custom barrels come in 27" from the barrel manufacturer don't they? I suppose you could request a longer barrel from the barrel manufacturer.

One use I can think of is it would allow you to actually see how much the case body is sized in your dies. Kinda move it around and see if it would be possible to cant the case in the chamber which would cant the neck even if you have shoulder contact.

Let's see what the Hopelessly Conventional side come up with.



Take some pics.

You make some good points, woods.

Since it's only a partial chamber, it tells me nothing about headspace. There's no bolt face to establish the boltface-datum line relationship.

Which means a couple of my assumptions may be off.

What I do know is that the 'smith--okay, it's the target rifle shop I work for, LOL--fired a test round, and the case measured .001" longer than our go
gauge.

Allowing for spring back, this may mean the chamber on the rifle is .002" over the length of the go gauge.

So. If I use the Thingy to measure an unfired case, and try and determine if the bullet is seated far enough out to hit the lands, my bullet may actually be as much as .002 short of the lands.

Still, with the benefit of my micrometer seating die, I believe this puts me ahead of the game in an otherwise largely trial and error game.

I can use the Thingy to establish a bullet seating length very close, if a little over, and then chamber test rounds to create an accurate bullet seating length in relationship to the lands.

To answer your question, barrels come in pretty much whichever length the 'smith orders them.

Our shop, which specializes in long range rifles, prefers long barrels. We received four barrels today, for instance, that are 34" long. They'll finish a little shorter.

My rifle currently has a 28" barrel. We cut it down from 30", because I wanted to use a Boyt case, and the longest I could find is 50".

LOL.

flaco

quote:

Originally posted by flaco:
Oh Boy!

I have ...a new Thingy.

...I'm wondering if there are any uses I'm not thinking of?

Should make an excellent "weight" for catfishing.

quote:

Originally posted by flaco:
Since it's only a partial chamber, it tells me nothing about headspace. There's no bolt face to establish the boltface-datum line relationship.

Which means a couple of my assumptions may be off.

The "barrel stub" ("chamber gauge" or "thingie", if you like) *is* a useful tool to measure the correct amount of sizing to apply to your cases. No, it will not tell you whether the headspace on your rifle is correct, but it will allow you a good, relative measurement of the head-shoulder dimension of your cases (fired vs. sized).

Woods and I (among others) use a Stoney Point Headspace Gauge for this measurement. Assuming it is well made, the barrel stub chambered with the same reamer as your chamber is preferable, as it ensures your gauge has exactly the same shoulder configuration as your chamber does. The Stoney Point gauge attempts to match as many chambers and calibers as possible in this respect - but whether the datum line on your chamber (and fired cases) exactly matches the Stoney Point gauge is another matter. So one can argue an advantage in this respect.

The barrel stub may quite commonly be made by BR smiths. Mike Bryant delivered one with each of the rifles he made for me.

- mike

UH OH !
I think I have thingy envy !
...tj3006

Yep, they're commonly made by target rifle 'smiths, using the same reamer.

And, as I mentioned in my first post, it gives you a good idea of the original leade in the chamber. Of course, as you work through the life of the barrel the free bore will lengthen, so you'll have to "chase" the lands.

flaco

quote:

Originally posted by flaco:
When my rifle was barreled, the 'smith took a short--2"--stub of the barrel and reamed a partial chamber in it with the same reamer used for the rifle.

I'm curious what caliber your rifle is chambered in that has an OA length of 2 inches or less?

quote:

Originally posted by onefunzr2:

quote:

Originally posted by flaco:
When my rifle was barreled, the 'smith took a short--2"--stub of the barrel and reamed a partial chamber in it with the same reamer used for the rifle.

I'm curious what caliber your rifle is chambered in that has an OA length of 2 inches or less?

The word "partial" is the key here. The chamber gauge "thingie" only mirrors part of the chamber. The case needs to be longer than the gauge - i.e. towards the case head end, the case sticks out of the gauge.

- mike