rechambering question

[frostop]

Lets say you want to re-chamber a .308 to 300 win mag.

My question is in regards to the reamer and pilot, is there available an extended pilot to keep the reamer in line with the bore, or rely on the reamer and the existing chamber to keep things lined up?


Gary

 

[Edd]

I'm not a gunsmith but if I was I would probably bore the 308 chamber larger before I started reaming.

 

[shortgrass]

What's the twist rate in that .308 barrel? 1 in 12, 1 in 11?

 

[frostop]

Actually I was just using that as an example. I am just trying to figure out if the existing chamber acts like the pilot hole or if there are extended pilots for the reamer that get used.

I have a 338 Jamison(338 wsm) barrel that I may want to rechamber to 338 norma and put on a long action. I think that the existing chamber would be removed in this case, but I haven't put all the dimensions next to each other and compared yet! I do not know what the twist is on the barrel off hand, but that may change the hole idea!!??


Gary

 

[IdahoCTD]

What I would do is dial in the barrel and then bore, with a boring bar, the back of the barrel out big enough to get the front of the 338 Norma reamer in the chamber area and the pilot into the bore. Trying to let a reamer cut it's way into the bore is a recipe for a broken reamer and crooked chamber.

 

[sable tireur]

frostop,

My question is in regards to the reamer and pilot, is there available an extended pilot to keep the reamer in line with the bore, or rely on the reamer and the existing chamber to keep things lined up?

In answer to your question, usually, reamers are made to a standard conformation which does not include extended pilots to reach the bore of a chambered barrel. They have been made but for the few times they might be needed, the standard procedure of boring out the chamber is used.

Regards.

 

[frostop]

Thank you for the replies

The boring bar technique makes sense!!


Gary

 

[J E Custom]

Lets say you want to re-chamber a .308 to 300 win mag.

My question is in regards to the reamer and pilot, is there available an extended pilot to keep the reamer in line with the bore, or rely on the reamer and the existing chamber to keep things lined up?


Gary

Reamers have a tendency to self center in an old chamber and with very little cut depth the pilot will pick up the bore long before the chamber is enlarged enough for the much larger chamber dimensions. On like cartridges we normally set the shoulder back enough to pick up the bore with the pilot.

So in some cases it can be done if well thought out.

J E CUSTOM