Barrel question

B

Boyd Allen

Active member
As I understand it, buttoned barrels' bore dimensions increase when turned down beyond a certain diameter, and cut barrels do not have this characteristic. I thought that I had read somewhere that hammer forged barrels actually choke down when turned down. Does anyone have any experience with this?
 
Logic would conclude that since hammer forging moves material from the outer diameter inward toward a bore shaping mandrel that any residual stress release would be in an outward diameter wise direction during an o.d. barrel turning operation. Just a logical conclusion on my part with no real world experience as to what really happens..............Don
 
On the other hand, wouldn't there be another effect caused by the bore impacting on the mandrel? What stress status would that induce, I wonder?

Nah, I don't want to go there! John
 
John Kielly said:
On the other hand, wouldn't there be another effect caused by the bore impacting on the mandrel? What stress status would that induce, I wonder?

Nah, I don't want to go there! John
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In the 2005 season to allow for the 11 oz Fudd tuners I had to turn several barrels from their original weight to about 3# 8 oz. These were both cut and buttoned barrels, Done properly there is no dimensional change to the bore. I slugged each barrel with lead slugs to verify the bores had not tapered. I have nenver turned the OD of a hammer forged barrel. I simply put a $25 price on then and take them o the next gun show.
 
I have used some Anschutz button rifled 'match' blanks from Numrich. As received these things are a 1.25 straight cylinder. When slugged you can definitely feel the choke at the muzzle end. The rest of the bore feels like it's parallel, no taper. The slug glides along with very little drag until you get to the choked section.

I have turned several of these down to as small as .825". On one I left a definite shoulder for use with a 40x action. The 40x has a very long tenon due to it's originally being a centerfire action. When slugging this bbl you could feel a dramatic constriction in the area of the shoulder. I decided to then turn off the shoulder and use this bbl on a Hall which uses a .750" thread. The constriction disappeared and the bore felt uniform all the way to the choke at the muzzle. I also left the muzzle slightly larger to add some more choke. I do have another of these bbls on my 40x but I use a Pacnor nut on this bbl which negates the need for a shoulder.

I doubt you could measure the change in the bore due to turning the od and I doubt you can feel the 'before and after' difference via the slug if you turn the od to a straight cylinder. But if you turn in a definite pronounced section change I am sure you will be able to feel it with the slug. This tells me that the id of the bore does indeed change when the od is turned.

Learning to slug bbls and using this to locate the chamber and crown really set me on the path to being able to build decently accurate rimfires. Developing a chamber finishing method was the final step to success. You also must have a borescope.
 
Where do you guys get your slugs? This is something I would like to learn to use, more on centerfire barrels, since that is what I mostly deal with. I'm looking for 22 & 6mm slugs. Thanks for your help.
 
Joe Entrekin said:
Where do you guys get your slugs? This is something I would like to learn to use, more on centerfire barrels, since that is what I mostly deal with. I'm looking for 22 & 6mm slugs. Thanks for your help.
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Hey Bemmer Joe, long time no see! I took a 2-cavity 22 cal bullet mold I had extra and reamed it out to where ai could pour 2 6mm slugs at a pour. I have taken pulled 22 RF bullets and put them in a vise where I could mash them out larger. Not a great method but it did work.
 
I 'pinch' the bullets out of the actual 22 rf cartridges that I plan on using in the rifle. Expensive but I feel that using the actual bullet is the best way. You should be able to buy molds for making 224 and 6mm bullets or you may be able to purchase cast bullets. I use a carbon fiber rod to push the slug.

I do have one Lilja bbl that must be his 'tight bore' offering. It is difficult to push a slug down this bore and it makes it hard to feel what going on. Some sort of bullet sizing die would be useful. I also want to try some 22 cal airgun pellets in this bbl. Having the proper amount of drag on the slug is important. I have also found that you can reuse the slug in the same bbl for a few passes.
 
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