Chamber reamer types, which to use when?

[Linko]

Finisher, rougher, resizer

The chamber reamers come in these types. I have never had chambers cut for a rifle. So I have zero knowledge of this work. I have two factory rifles.

A 22 Hornet rifle that I would like to cut to K-Hornet.

I also have a 6 BR Norma that I would like to cut with Daves (PT&G) 90 Berger reamer.

Which type reamers do I need, or do I need more than one type?

 

[Mr.Spradlin]

Here goes
A finish reamer is basically the reamer to make the actual chamber
A roughing reamer is to cut the rough chamber them you finish the chamber with the finish reamer
A resize reamer is the reamer you use to make a FL sizing die to match your chamber.

There are many ways to chamber a barrel. It comes down to what the smith likes. As long as the end result is a precise chamber thats what counts.

 

[swd]

For chambering barrels it's simple just buy finish Reamers and your GTG.

 

[Rustystud]

JGS, Manson Precision, Clymer, Thompson Grinders, all make great reamers, and they give superior customer service.
Nat Lambeth

 

[Kurz]

Linko,

Here is an article with good illustration photos about reamers and the process of chambering a barrel. Some may not agree with the details but it is a good generalized article about the tools and the process.

http://rifleshooter.com/2015/04/chamber-reamers/

A 22 Hornet rifle that I would like to cut to K-Hornet.

I also have a 6 BR Norma that I would like to cut with Daves (PT&G) 90 Berger reamer.

The chamber for the K-Hornet will have to be set back at least one thread before the new chamber is cut. This has been a very common conversion for the standard Hornet chamber.

If the 6BR Norma 90 Berger is a straight 6BR Norma chamber but throated for the 90 grain Berger VLD then you might get away with just having your chamber throated. But it will depend upon the assessment of the gunsmith performing the work.

Regards.

 

['Freak]

Linko,

Here is an article with good illustration photos about reamers and the process of chambering a barrel. Some may not agree with the details but it is a good generalized article about the tools and the process.

http://rifleshooter.com/2015/04/chamber-reamers/



The chamber for the K-Hornet will have to be set back at least one thread before the new chamber is cut. This has been a very common conversion for the standard Hornet chamber.

If the 6BR Norma 90 Berger is a straight 6BR Norma chamber but throated for the 90 grain Berger VLD then you might get away with just having your chamber throated. But it will depend upon the assessment of the gunsmith performing the work.

Regards.

I’m no ‘smith, just curious, why would a 22 Hornet barrel have to be setback a thread's worth before reaming to K-Hornet?

 

[carlsbad]

JGS, Manson Precision, Clymer, Thompson Grinders, all make great reamers, and they give superior customer service.
Nat Lambeth

Exactly what he said. --Jerry

 

[Brians356]

You might want to post this over on the Gun Project Questions & Gunsmithing forum.
-

 

[Brians356]

I’m no ‘smith, just curious, why would a 22 Hornet barrel have to be setback a thread's worth before reaming to K-Hornet?

I'm no 'smith, but my guess is so the loaded parent ammo is a slight crush fit at the neck/shoulder junction, as with most "improved" designs (Ackley's, anyway, the K-Hornet may be different.)

PS
Oops, Hornet is rimmed, so setback should not be necessary.

PPS

However, by setting back, the reamer can clean up the lands completely.
-

 

[Kurz]

I'm no 'smith, but my guess is so the loaded parent ammo is a slight crush fit at the neck/shoulder junction, as with most "improved" designs (Ackley's, anyway, the K-Hornet may be different.)
PS
Oops, Hornet is rimmed, so setback should not be necessary.
PPS
However, by setting back, the reamer can clean up the lands completely.
-

To save a long written explanation by me, here is an excerpt from an article on the .22 K-Hornet by ML McPherson:

"The .22 K-Hornet, an old pre-WWII wildcat, is superior to the standard Hornet and I can shoot standard Hornet ammunition in a K-Hornet with no loss of accuracy or velocity—enlargement of the cartridge case as the round fires allows that portion of the charge not ignited by the primer to reorient, and, as that happens, more granules ignite sooner, which offsets the increase in chamber volume. Most importantly, in a gun with appropriate striker energy, when loaded using an appropriate (mild) primer, the case shoulder of the K-Hornet will hold headspace. K-Hornet accuracy is usually better, and—with neck sizing—K-Hornet cases last longer.


Besides the standard handloading issues affecting load pressure, the K-Hornet introduces a unique problem. Unlike other wildcat chamberings, no standard K-Hornet design exists. Kilborne, the inventor, made his reamers. When one wore out, he made a new one. No two were closely similar in any dimension; and, he ran those reamers a different distance into each chamber he converted from standard Hornet to K-Hornet, so no two Kilborne-made K-Hornet chambers are even closely similar. Therefore, it would be a miracle if any K-Hornet chambered with a different reamer than the one used to chamber this rifle had similar usable case capacity. The resulting chamber volume variation can result in significant differences in pressure from one chamber to the next. Use extra caution whenever working with any K-Hornet."

Regards.

 

[hoz53]

Here goes
A finish reamer is basically the reamer to make the actual chamber
A roughing reamer is to cut the rough chamber them you finish the chamber with the finish reamer
A resize reamer is the reamer you use to make a FL sizing die to match your chamber.

There are many ways to chamber a barrel. It comes down to what the smith likes. As long as the end result is a precise chamber thats what counts.

Is that Mr Spradlin or Mrs Pradlin ?

 

[Mr.Spradlin]

Is that Mr Spradlin or Mrs Pradlin ?

Mr Spradlin

 

[hoz53]

Mr Spradlin

Ok thanks Mr Spradlin

 

[Rust]

I'd say work with the reamer maker. He can get prints from the reloading die maker and grind a reamer to work with die dimensions. You'll have a matched set.

If I were going to deal with a Hornet I'd go with the Ackley chamber 40 degree chamber, still going with the above reamer and die matching.

What was written about inconsistencies in older rifles with K chambers is true and in many cases old Ackley chambers followed suite. Not a lot of dimensional uniformity in early wildcatting days.