[Jaywalker]

What does a gunsmith do to "true an action?"

Does it have something to do with the alignment of the action's male threads for connecting the barrel?

Jaywalker

[BigG]

No idea what they do but the part that the bbl screws into would be female in my dictionary. :o

[mete]

About the only thing you can do to an action is true up the face of the action so that the shoulder of the barrel will fit snug .On a Mauser both inner and outer shoulders should make full contact.

[hillbilly]

Yes, that's what gunsmiths do with "trueing."

They make sure, using different kinds of precision instruments, depending on the gunsmith, that the action and the barrel are completely and perfectly in alignment with each other.

It makes a lot of difference. I have a Remington 700 Varmint Synthetic in .308 that's been trued, and that sucker will shoot one ragged hole at 100 yards with 168 grain Sierra Matchkings, if I do my job.

It's just a regular, off the shelf Varmint Synthetic, and shoots like rifles that cost three times as much.

hillbilly

[4 eyed six shooter]

Trueing an action involves getting everything in line. The threads of the action are trued to the face of the action. The bolt face is trued to the action and the shoulder of the barrel is trued so that the bore is in line with with the action also. This does help get the last bit of accuracy out of your rifle.
Good shooting, John K

[Jaywalker]

mete:About the only thing you can do to an action is true up the face of the action so that the shoulder of the barrel will fit snug .On a Mauser both inner and outer shoulders should make full contact. So, since the FEmale :) threads are already set, then making a barrel fit squarely means either milling a part of a specific barrel of milling the action to fit a specific barrel, right? Which is it?

Jaywalker

[mete]

You start with the action, setting up the lathe so that the threads are centered and parallel the the lathe center. You then cut just enough off the face of the action so that the face is smooth and flat. Then you cut the barrel, first centering the bore to the lathe. Then cut the OD to make the barrel concentric with the bore and do the same with the barrel threads.Make the shoulder square with the barrel. The shoulder of the barrel and the face of the action will mate ( I hope you're over 21!) flush . This is to insure the most rigid barrel/action joint which then gives you better accuracy.

[Jaywalker]

You start with the action, setting up the lathe so that the threads are centered and parallel the the lathe center. You then cut just enough off the face of the action so that the face is smooth and flat. Then you cut the barrel, first centering the bore to the lathe. Okay, I understand that.

Then cut the OD to make the barrel concentric with the bore and do the same with the barrel threads. "OD" is outside diameter? Does that mean the whole barrel, not just the thread end? This is where I get lost. I assumed that a barrel-maker delivered it with the threads already cut, so I presume we're talking about a "blank," which I hadn't understood until now - assuming I understand it now.

Make the shoulder square with the barrel. Is the shoulder the breech face of the barrel?

So, if I've understood it, we started with the action, and took the threads as a guide, and milled the face of the action based on that guide. Then you take the barrel blank and center it to the bore, which should also now be mateable to the action threads and action face. Then you mill away barrel until the outside of the barrel has the bore as its true center. Then you square up the breech face end of the barrel. At that point everything should be circular, centered, or square, whatever we're looking for. Have I understood it?

Jaywalker

[mete]

While you might get a barrel threaded for a particular action ,don't expect too much from it. OD=outside diameter. The breech end of the barrel is not the shoulder . The shoulder is on the other end of the thread and that contacts the face of the action. The Mauser M98 is different in that the breech end of the barrel should contact a shoulder on the inside of the action and the face of the action should contact the shoulder on the barrel. In addition the threads should be cut so they are a snug fit (one reason why prethreaded barrels aren't very good) .Bolt lugs should have uniform contact too. These are all things that you aim for to get best accuracy.

[Big_R]

Mete hit the barrel part on the head, but there are other things done to true an action, mainly fitting the bolt lugs to the recesses in the action to assure 100% contact during lockup. If it's a precision rifle, truing may also require adding material to the action (usually welding) and milling bolt recesses, etc. to keep the bolt in perfect center alignment with the action.

The bottom line with truing is to make an action/barrel combination that is straight, square and strong.

Ryan

[Jaywalker]

Okay, thanks a lot - I appreciate the explanation. Now I understand the effort necessary and why it runs into a few bucks, as well as why it's effective.

Jaywalker

[Jim K]

There is an excellent article in the November Shooting Times (just out) on rifle "blueprinting". Good reading and a lot of info and pictures.

It certainly shows why the job costs so much and (to me) why I will just have to suffer with less than optimum accuracy.

Jim

[Clark]

This is controversial but I:
1) True the face to the bolt bore of the action.
2) True the inner stop ring [barrel face shoulder] to the face.
3) Cut the threads to fit the reciver
4) Cut the chamber and headspace to the bolt face minus a few thou.
5) Cut the distance between shoulders on the barrel to match the reciever ~.625 in Mausers
6) Torque on the barrel.
7) Align the bolt
8) lap bolt lugs
9) Finnish head space with torque on greased threads at 300 foot pounds.

The part that is controversial is that I am ignoring the threads on the reciever. I am assuming that the error in the threads can be nulled out with thread crush. Some people make a fixture and bore out the bolt bore for sleeving [in Rem 700s]. Some people chase the threads to true them. Some people take the threads as the first reference. I take the bolt bore of the reciever as the first reference. Both systems work, but don't expect both types of people to agree.

The last 5 shot group I shot at 100m was .5", and that gives me some salient knowledge that cannot be overcome with cognitive arguements.

[Jaywalker]

Jim,
Thanks, I'll get the current "Shooting Times," a mag I normally don't get.

Clark,
I should have realized there were more ways to approach it than the one I understood. I learned the term "first reference," though. Thanks. Unfortunately, I don't understand some of the terms here: I am assuming that the error in the threads can be nulled out with thread crush. Some people make a fixture and bore out the bolt bore for sleeving [in Rem 700s]. Some people chase the threads to true them. What's "thread crush," "sleeving," and "chase the threads?"

Jaywalker

[Clark]

Thread crush is where the threads of the barrel first touch the threads of the receiver and some bending and compression of the threads that allows the more rotation [tightening up] with additional torque applied.


Sleeving is a technique used to make the Rem 700 bolt bigger in diameter. A metal sleeve is slipped over the bolt. The receiver is then bored out or reamed to a diameter that has a tight fit with the sleeve. This allows a smaller clearance fit between bolt and receiver.

There is no place to put a sleeve on a Mauser bolt as there are too many features [obstacles].


Chasing the threads is when a boring bar with a 60, 55, or 90 degree thread cutting bit is on the compound of a lathe and the receiver is in a fixture in the chuck and maybe steady rest. The boring bar goes up inside the receiver and cuts a little more off the threads to make them more true to the bolt bore of the receiver. The threads cut on the barrel could then be cut slightly larger if needed.

The reason I believe I am getting away without chasing the threads and still getting good results on the Turkish Mausers and VZ24s is that I can see that the trued face of the receiver is mating well with the shoulder I cut on the barrel.

[Jaywalker]

Clark: The boring bar goes up inside the receiver and cuts a little more off the threads to make them more true to the bolt bore of the receiver. I can't visualize this. Is this cutting them deeper, off one side so that one side is thinner than the other, or what?

Jaywalker

[Clark]

I have not trued the threads, but I would assume that they cut until they get the blue marking die cut off in each thread.

I was listening to two old gunsmiths talk about chasing the threads One ususally did it, and the other complained that one might as well make a new reciever.