Really need to post a sketch of where the numbers come from, I will do this later, as I have a standard data form for each type action. The Remington needs many more numbers that the M70 or M98!! Anyway, below photo is the overall view of the lathe with a barrel mounted through the headstock and dialed in. Barrel has been threaded and chambered, now I have screwed the action on hand tight. Note the Holland's recoil lug is in place (This is a M700). There is a new, resized, empty case in the chamber (this one is a 300 Win Mag) and the bolt has been placed in the action and closed on the empty case.

The data sheet calculations give me the following numbers: Float of bolt, action hand tight, no cased or gauge in chamber: 0.007". This is 0.005" for final clearance between the front of the bolt lugs plus 0.002" for the "crush" or "draw" when the barrel is fully tightened. I use the same dial indicator set up in the below photo to check this 0.007" float. Data sheet calculations also give me 0.005" bolt float on the empty case, this is 0.003" for final clearance plus 0.002" for the draw up. (Note: The numbers will be different for a big bore dangerous game cartridge, as we want just about anything to chamber, even that ammo you buy in J'Berg that may be in PMC, Kynoch, or who knows what cases)



Below photo shows a close up, with the empty case in the chamber, and the bolt pushed forward against the case. Dial indicator is zeroed.



Below photo shows the bolt pulled back against the lug seats, case still in chamber. We have 0.005" float, the same as the data sheet calculations. So, this one was chambered and machined correctly. If things are not correct, can run the reamer in deeper if needed, or machine the barrel shoulder and end of barrel if the chamber is too deep. As this is a M700 action with the bolt nose counterbore, the counterbore will have to be deepened also if the chamber is too deep. Measure twice, cut once, this is especially important with the M700 and also the M70 with the cone breech.

A big caution on M700's: Brass shavings or chips under the extractor can give a false reading, or, in the case of the action in these photos, with a rivitted extractor, the extractor rivett had a burr that was giving a false reading. Gotta check every tiny detail. I like to remove the M700 extractor from the bolt before checking things, but this can be a pain, as you usually break the extractor when removing it and you have to put in a new one. Even a bend in the extractor makes it prone to failure to extract. (A full truing job on the M700 Bolt requires removal of the extractor so the bolt face can be machined, among other areas.) This is one of the reasons I like to work with CRF actions: Extractor is easy to take off and put back on.



Scope base screw holes look big because I drilled and tapped them out to 8-40.

I will make another post showing how to check the headspace with the barrel tightened.

[ 03-07-2003, 07:44: Message edited by: John Ricks ]

John,

If you have taken detailed measurements from the receiver before doing the job, and transfered these measurements to the barrel, adding in the tolerances for the bolt nose clearance, headspace setting and crush, and then machined the barrel to these measurements, why would you need to use a dial indicator as illustrated in your photo's to measure the headspace? Checking headspace is easily done before screwing the pieces together, using a depth mic and gauge without having to go these extra steps...

Malm

Well, to answer your questions, I use a depth mike like everyone else when maching the barrel and chambering. The indicators are a quick and easy method for verifying correctness. Sort of a final QC check before pulling the barrel out of the lathe. Only takes a minute, so why not? The indicators are already set up on the mag bases, on a shelf above the lathe, ready for use.

Remember, it is a lot easier to verify things with the barrel still in the lathe, than to discover a minute error later and having to set the darn thing up again in the lathe. Plus the indicators quickly show things that the eye cannot see.

I have found that a couple of extra measurements help avoid dumb mistakes like a chip under a gauge.

My purpose in posting the photos is to illustrate headspace to those still learning the barrel chambering skills.

After cutting the counterbore in the barrel (700), I like to have the bolt lug to barrel end clearance at about .004-.005. I call that "tick-tock" and you can measure it the same way that you are measuring h'space. If I have more than the "tick-tock" amount of headspace (clearance between bolt face and back of gage) you cannot measure it with an indicator. So I go for less headspace, obviously. I use depth mic's to know where I'm at while chambering. One trick that I've found is when you are getting close, you can assemble the receiver, bolt, gage, etc. and use a feeler gage between receiver and barrel shoulder to see how much you have to go to achieve "go" with the gage.

John,

I see...

Always looking for an easy way of doing things, I run one of my shop vac hoses to the back end of my lathes spindle, and with a little WD40 and an air hose, I blow those little chips clear. It's a quick way to clean the chamber and the shop vac keeps the little pieces of schrapnel from sticking in the wall of the shop...

Malm

Malm,

Neat idea on the vac hose! I hang a hose on the back of the lathe carriage when using the tool post grinder and the tool post slack belt grinder (two different type of grinders)

I use a muzzle flush colant system where I am pumping coolant/lube down the barrel, so the chips are generally no problem, but you still gotta blow & wipe the chamber clean before gauging. If you are not using a flush system, by all means build one, you will be amazed at the ease of use and quickness, plus better chamber finish, and you can run those reamers at the speeds and feeds they are designed for.

I made a system that works well, if you wish I will post photos. Jay uses a flush system also, maybe he will post some photos.

Jay, if you read into my post you will see that I am using the indicator also to measure the bolt clearance off the end of the barrel. Once you are setup for this (meaning a dedicated indicator on the mag base, on the shelf behind the lathe) it is extremely quick to check things.

The feeler gauge trick also is useful on cutting the cone in a M70. Machine the cone short, screw on the receiver with the bolt in place until the bolt contacts the cone, measure the gap between receiver and barrel shoulder with feeler gauges, then you know how much more to go plus 0.007" or so for clearance and draw. With a dial indicator on the lathe bed, stem on the carriage, it is easy to go the correct distance.

Dial indicators really speed things up when machining, most folks are unaware of the many ways to use them. I will post future photos of some of the indicator setups and different types of indicators.

[ 03-07-2003, 19:00: Message edited by: John Ricks ]

I'm not a machinist, so excuse my ignorance, but what exactly is this process telling you? It seems to me that it will tell you if you have insufficient headspace, but not if you have excessive headspace. For instance, on the 700, if your barrel is threaded and dimensioned properly, would you not read the correct float even if the chamber were too deep. In other words, if you are targeting .005 float before the bolt contacts the barrel and the measurement indicates .005 float, why does that insure that the headspacing is correct? It would seem to only indicate that the float is correct. I think 700's are a special case, since it is pretty easy to set the depth correctly at the back of the barrel, but I would think this is a real problem with mausers, for instance. After all, too deep is the bigger problem. It will be obvious if the chamber is too shallow.

Art, think of the draw up also, so you have about 0.007" or more bolt float on a 700 with the action hand tight on the barrel. Once you try indicators, you will be pleased at the "Quality control" step they give you. I check bolt float first, gotta know this anyway before you chamber the barrel.

Keep in mind that I am using a standard depth mike for the measurements, just like anyone else, so I know if the chamber is too deep. The indicator method just gives me another piece of info to verify that things are OK.

Yes, you can completely ignor the use of a indicator, but I find it useful to QC the work as I go along. Once you are used to it and set up properly, it is very fast, only takes a few seconds to check the work.

I am not trying to convince anyone, just to show another method. I do a lot of barrel work, so QC is extremly important.

Using a indictor also lets you know what the extractor front clearance is on a M70 or Mauser, another piece of information that is important.

[ 03-08-2003, 00:49: Message edited by: John Ricks ]

JR, I use the feeler gage trick for cone bolts on BAT, Nesika, AMT, etc. Have only done Rems and customs, no M70s or Mausers. Rifles are my hobby, I'm not a gunsmith. I only play with accurate toys, longrange varmint or BR, not much hunting stuff. And I have way more indicators than one person should have, from buying complete toolboxes and not being able to let indicators go away, just too handy.
BTW, went and looked at your website, real nice shop, makes me wanna build a new shop and go on a buying spree.

Good example of the 'measure twice cut once' principle here to verify everything before taking barrel out of alignment. I really, really, yes really hate to try to get a barrel realigned with bore centered and maybe even having to pick up the thread again. That said, I still just go with the depth gauges myself, but I am a hobbyist.
Cones...I took a pice of round stock about 1-1/4" dia maybe 3" long and turned one end to a 45 degree angle and put a center in the other end. Now turn a step shoulder at the full dia portion at the end of the angle cut. Rough out the cone cut then put the gizmo in the cone with a tailstock center holding the back end of gizmo. Dial calipers measure gap back to the shoulder cut on gizmo. This gives a reference to depth of cut on the cone. Most actions will usually be within a few thou after you get a standard number for the gap. A picture would help but not possible.

John

I looked at your web site and something there made me remember a question that someone maybe can help with. I saw the belt grinder attachment on your lathe. Several years ago, before I had a lathe, I had a guy I know in a pretty large shop turn a couple of shafts for me. He finished up the shafts with a belt grinder he had that is about the size of the one you have, but it was hand held and resembled basically an electric chainsaw with a belt sander. It was the slickest way I have ever seen to polish up a contoured shaft. He isn't there any more, and I haven't been able to find anything like that available anywhere. I've tried every mail order and internet tool source I can find. Does anyone have an idea where a sander like this is available?

Art, haven't seen the unit John uses, but you might want to look at the Dynafile line. I use one to deburr parts off my CNC mill at work. Unit looks like a minuature belt sander, belt is about 1" wide, drived by an air motor, Hope this helps.
www.dynatoolsales.com