What I have Recently Learned About Chambering

[INTJ]

1. I finally figured out how to use the Interapid and directly read off the rifling when dialing in. I am still slower at it than I should be, but fussing with dialing in is probably why my barrels have all shot well.

I do now see the attraction of drilling and pre-boring. That way I could just dial in the throat precisely and just leave the breech end close, but still wind up with everything true. It might save time over dialing the breech end on a bendy barrel.

2. I figured out how not to make a mess with the chamber flush system--be warned, there is a learning curve. And don't hook the BTS directly to the pump......

3. Light contour carbon barrels suck even worse in the lathe than they do developing loads for them. These light contour carbon barrels are very bendy and hard to dial in. I am sure my first bad shooting customer barrel will be a Sendero Light contour carbon. The Magnum and Bull contour carbon barrels seem okay.

4. I don't enjoy chambering Rem 700 actions. To be fair, I moved on from Rem 700s many years ago (to CRF M-70 and custom actions), so I already had a bad taste in my mouth. However, there is more to fuss with considering the the bolt protrusion, barrel recess, and spin-on recoil lug.

An important measurement is the receiver face to the bolt lugs, and I can't get my depth mic in there so I am stuck using a caliper. Yes, I am sure someone makes a custom tool for that, but BAT actions with either a cone or a flat face are much simpler.

5. I finally discovered my Machinists Handbook. It has a bunch of useful info.

6. Short barrels are a pain. Given almost all muzzles are threaded for brakes anymore, I made a 10" extension threaded internally for 5/8-24. I also ordered some 2.25" Delrin rod. Thought I ordered two feet but they sent 10 feet. I plan to machine a couple bushings to hold barrel shanks. One for .120 and the other for .125. That way I can hold the shank inside the headstock so I can thread the muzzle. Then I can add my extension and do the chamber.

7. I have had a PM1340 GT at home for four years now. At work I had them get a PM1440 GT. I can't decide which one I like the best. The 1340 sits higher by about 3", which I find MUCH more comfortable. The 1340 has a shorter headstock. The 1440 has a much deeper chip pan--better for a flush system, and has an enclosed gearbox vs the open Norton style gearbox on the 1440. I like the finer leadscrew on the 1340 though there is no issue with the 1440s leadscrew. They both have the same carriage so going back and forth is easy. My 1340 has a Mark Jacobs circuit board and has a variable speed dial and a super slow jog feature. Those are very nice.

I will add a flush system to my 1340 at home, but I won't use a big carbonater motor like we have at the shop. I just like being able to pull the reamer out and having the flush clear all the chips vs doing it manually.

8. Oh yeah. I now have to make everything pretty, something I didn't worry about with my own stuff. I now put tape on the full length of the barrel, except for the metal I am machining. It keeps scratches off. I also use drywall tape where my aluminum spreaders go on my inboard and outboard spiders. The aluminum and drywall tape keep the barrels from getting marked.

 

[akajun]

#4 is solved with a flat blade depth micrometer
Starett makes one I can’t remember the model
Easy to find and useful for other stuff

 

[DaveTooley]

In regards to #4 here are the measurements I record for every Rem action.
HS
tenon length is HS -010"
CB of the bolt nose, not to the lugs as they aren't in play

When I did everything on a manual machine I would put the CB in with a boring bar. With the tenon .010" short all I had to do is touch the boring bar against the tenon, set my travel indicator to zero. Then go the measured CB depth. That automatically gives .010" end play clearance. As I said using these measurements the lugs aren't in play. Also it hurts nothing to make the CB .715"+ in diameter. The last thing you want is the bolt touching the barrel.

A cheap 2" travel indicator on a magnetic base is worth its weight in gold.

 

[Carl S]

I used to go all around my hat doing counter bores on Rem 700s.watched different videos in the past etc.then quite a while ago I read how Dave does his so simple and in my opinion is the best way.i do all my 700s like that now...no problem wotsoever.

 

[dnellans]

In regards to #4 here are the measurements I record for every Rem action.
HS
tenon length is HS -010"
CB of the bolt nose, not to the lugs as they aren't in play

When I did everything on a manual machine I would put the CB in with a boring bar. With the tenon .010" short all I had to do is touch the boring bar against the tenon, set my travel indicator to zero. Then go the measured CB depth. That automatically gives .010" end play clearance. As I said using these measurements the lugs aren't in play. Also it hurts nothing to make the CB .715"+ in diameter. The last thing you want is the bolt touching the barrel.

A cheap 2" travel indicator on a magnetic base is worth its weight in gold.

Dave - it sounds like you shoot for .010 nose clearance in both end play and possibly even more on diam? Any reason for that .010 vs .005 or .015?

I've never blown up an action so I have no experience to even have an educated opinion on what happens. I just measure each action and do .005 over both, just like the guy who taught me told me to =p

 

[DaveTooley]

Dave - it sounds like you shoot for .010 nose clearance in both end play and possibly even more on diam? Any reason for that .010 vs .005 or .015?

I've never blown up an action so I have no experience to even have an educated opinion on what happens. I just measure each action and do .005 over both, just like the guy who taught me told me to =p

I've never blown up an action but I've had some good example pass through the shop. The .010" for endplay allows room for all the accumulated STUFF that finds it way there. In the event of a catastrophic case separation some things don't matter as bad things are going to happen no matter what. Most cases have a solid head for 180"-.200" . I've never gotten hung up on minimizing end play as long as case protrusion was within reason. .160"+ is fine with me. It worked fine for Remington's three rings of steel. In the event of a big Oh Sh_t the head of the case is going to fill up the bolt nose. Very likely to bulge on one side. If it's a Sako or M16 extractor brass will flow into the extractor slot. I have a Vanguard action that the escaping gas cut the bolt body. That's the worst I've seen. Consider all the problems with clickers. Chambers are too tight and/or the sizing die is a mismatch or the case head expands in a location the sizing die doesn't reach. That's where I think minimum case exposure can cause a problem. As far as the ID of the CB I don't want to run the risk of the bolt nose touching anywhere in the CB. I've had a few rifles that were as wild as billy goat. I freed up some tolerances, worked on the ignition system and they settled down. .010"-.020" extra clearance isn't going to change the outcome of an overpressure event. YMMV

 

[spitfire_er]

I have a momentary foot pedal switch from harbor freight that I run my carbonator pump with. Works great. I originally wanted an on/off and had this laying around and I prefer the momentary switch. Just stand on it when you're chambering, then if you want to clear chips you can back the reamer, tap the pedal and it clears chips for the chamber and the reamer.

 

[Alex Wheeler]

#3 is no problem. We'll talk at DC.

 

[Bogusname]

Do you have the pump from Gre-tan rifles?
Three fluted roughing reamers are great also. Dremel some slots in the pilot screw and it flows the oil nicely.

 

[55fairlane]

#5 the machinist handbook or the the machinery hand book.......when I served my apprenticeship my nose was always in a reference book , an older copy may be better , newer copies don't have as much information on tool room work , but more information on CNC ........

 

[LVLAaron]

#4 - It takes a little bit longer but it's easier - I cut it until the bolt barely closes on it. Then cut .010 more.

 

[INTJ]

Do you have the pump from Gre-tan rifles?
Three fluted roughing reamers are great also. Dremel some slots in the pilot screw and it flows the oil nicely.

Yes. Three phase pump. Noisy. I didn't do the install, and I don't think the drawing from Greg shows what he thinks it does--at least for two of us. That said Greg is a great guy, very helpful, and it is a good system.

After making a huge mess the first time, I built a valve body out of three Ts and two shut off valves. When I first turn on the pump, it now just recirculates to the reservoir. Then I open the valve to the BTS. I can close off the recirculation if I want and increase the pressure, but I never need that much.

 

[GenePoole]

I just use a soda bottle cutout as a shield.

 

[INTJ]

#5 the machinist handbook or the the machinery hand book.......when I served my apprenticeship my nose was always in a reference book , an older copy may be better , newer copies don't have as much information on tool room work , but more information on CNC ........

I have on a older one. 2000 pages maybe? I was spending a lot of time on the internet trying to find major and minor diameters for threads. Lo and behold I remembered my Machinists Handbook, found the page, and bookmarked it--the old way we bookmarked pages.....

 

[INTJ]

#4 - It takes a little bit longer but it's easier - I cut it until the bolt barely closes on it. Then cut .010 more.

I have been making the tenon to the measurements and then cutting the recess according to the math. Then I check clearance with Plastigauge.

With the flat breech actions I usually leave the tenon long then screw on the action with the bolt and measure the gap with a feeler gauge. I then add the deeper gauge plus .008 or .008 and face the back of the breech to that measurement.

That said, the more I do this the more I find that matching to the measurements works very well.

 

[55fairlane]

I have on a older one. 2000 pages maybe? I was spending a lot of time on the internet trying to find major and minor diameters for threads. Lo and behold I remembered my Machinists Handbook, found the page, and bookmarked it--the old way we bookmarked pages.....

I believe you buy both a paper copy and a pdf (I'm old enough to remember CD being g the big thing) that way you can have a searchable &printable copy handy...

 

[INTJ]

I just use a soda bottle cutout as a shield.

I may try that when I set up my flush system at home.

 

[55fairlane]

I have on a older one. 2000 pages maybe? I was spending a lot of time on the internet trying to find major and minor diameters for threads. Lo and behold I remembered my Machinists Handbook, found the page, and bookmarked it--the old way we bookmarked pages.....

If you look in that book the formula for finding root-crest-major-minor diameter at what ever percentage of thread deapth.......what class of fit do you do your threading to?

 

[xr650rRider]

Yes. Three phase pump. Noisy. I didn't do the install, and I don't think the drawing from Greg shows what he thinks it does--at least for two of us. That said Greg is a great guy, very helpful, and it is a good system.

After making a huge mess the first time, I built a valve body out of three Ts and two shut off valves. When I first turn on the pump, it now just recirculates to the reservoir. Then I open the valve to the BTS. I can close off the recirculation if I want and increase the pressure, but I never need that much.

Single phase 120 volt carbonator pump off of Ebay works great but you need to change the spring out in the internal by-pass. They'll put out 200 psig without modifying it. I bought a pack of springs at Ace Hardware that are smaller diameter wire and cut down length until it will by-pass at around 60 psig. I have a manifold with air line and check valves on both oil and air. I have a solid state relay in my PM-1340GT VFD panel that powers an outlet that is switched via the coolant switch on lathe. Flip off coolant, turn on air and that slug of coolant and air is very effective in blowing all cuttings off of reamer.

 

[Carl S]

I made my own flushing system.a power steering pump off a car.electric motor to drive it.fabricate a tank and frame to mount everything on.I have a switch mounted on the lathe so I can turn it on and off when required.regulating valve for oil flow.also a bleed off valve so it doesn't over pressure. oil is constantly circulating and filters are present.it works great and wouldn't be without it.