I'm leaving tomorrow off to school where I'll be chambering my first barrel next week. I feel very comfortable that doing a rimless cartridge will be fairly easy for me. But, for some reason, I chose a belted cartridge for my first try. Primarily because the bulk of this class centers around the action and I wanted to be sure I came away knowing how to make a Mauser feed Magnums correctly.

Now my question, there has been lots of talk lately about headspace, belted magnums in particular. What is the best way to set the minimum headspace in belted cartridge? I read Johns Ricks post and this will be primarily a hunting rifle. I'll be chambering it in .338 win mag.

thanks for the help.

-Mike

If this is school related and you will be graded on it, set the chamber the way the instructor taught you to. If you wish to wing it, set it so that the bolt will just close on a magnum go gauge.

What school you taking?

Malm

The instructor should show you how to measure the action and calculate the protrusion of the headspace gauge out of the end of the barrel, while the barrel is still in the lathe and you are making the final depth reams with the reamer.

For a hunting rifle, chamber so the bolt just closes on the go gauge when the barrel is properly torqued in the receiver. After a few barrel jobs, you can hit this dead on while machining the barrel in the lathe and will not have to remove the barrel from the action for a "touch deeper" or have to hand ream with an extension after the barrel is torqued. It is all careful measurement with quality measuring tools. "Measure Twice, Cut Once".

Don't forget to allow about 0.002" or so for "draw" when the barrel is torqued in the receiver. Instructor also should show how to calculate this.

Ask the instructor to show you how to use a dial indicator to measure headspace. This greatly simplifies things and makes the job go quicker.

Needless to say the instructor should also show you how to true the front receiver ring, true the lugs, lap the lugs, and if a M700, how to true the bolt nose and how to set up the counterbore in the barrel to fit the bolt nose properly. Since yours is a Mauser, it is quite simple (no bolt counterbore, no coned breech, and no extractor cut to machine). Careful on a case hardened Mauser, can't do any machining on the bolt lugs or the lug seats in the receiver, you will get under the case and ruin the action. I only do a "light" lap on the lugs on the case hardened acions, and then I am very careful not to get under the case. Spot the lugs in first with Prussian Blue and see what is going on before you get carried away with lapping.

If any of the above is left out by the instructor, then you are not receiving proper instruction.

There is a big debate among Mauser 'smiths as to how to fit the Mauser shoulder and the end of the barrel. I fit both tight, and the rifles have excellent accuracy. Many say to just fit the end of the barrel tight to the C-ring and leave a thou or two clear on the shoulder. Having the shoulder clear is the way the original military rifles were set up, but this was a production shortcut instead of an accuracy treatment.

While you have the receiver apart, drill and tap for 8-40 scope base screws and counterbore the bases for the larger screws.

Instructor should show you how to do this:



And this:



[ 10-19-2002, 08:26: Message edited by: John Ricks ]

Thanks gentlemen! Also, thanks for the reminder about the 8x40 screws. I would have forgotten my mounts otherwise.

John,

I spoke with the intructor and all you mentioned is covered. In addition, we'll be making the barrel mandrels and and other assorted fixtures.

I'll be heading up to Lassen College to take this class. Up til now I've had to rely on the local JC for my welding and machining instruction. The rest has been self taught. I found I got more time on the machines if I bought my own. It'll be a real delight to have some proper instruction and supervision.

-Mike

Having taught Gunsmithing, I assume when you take a gunsmithing course, that you will learn all the techniques required to do the job correctly. I assume you will also get the necessary training on the various machines involved in the trade. They certainly are not expecting you to show up knowing how to chamber a weapon before starting the class are they? What are the prerequisites to attend the class you are taking? Is this a full gunsmithing course or just a specialty class?

Malm

The courses are one week long, open enrollment. I spoke with the instructor before registering and explained the level of proficiency or lack thereof depending on how you look at it. He thought I'd be fine in the class. As a bonus he suggested I bring along the barrel. Technically, chambering isn't covered in this class but, given the distance I'm travelling and the interest I've shown, he suggested we try it.

-Mike

I see, good luck.

Malm

The courses are one week long, open enrollment. I spoke with the instructor before registering and explained the level of proficiency or lack thereof depending on how you look at it. He thought I'd be fine in the class. As a bonus he suggested I bring along the barrel. Technically, chambering isn't covered in this class but, given the distance I'm travelling and the interest I've shown, he suggested we try it.

-Mike