Gluing In Tubegun Stocks
by Germán A. Salazar
by Germán A. Salazar
The Tubegun is gaining popularity very quickly in Highpower circles, both in across the course shooting and prone shooting. In my conversations with shooters who are interested in the tubegun, I find that the process of gluing the action to the sleeve is a bit daunting for some, and this article is meant to shed a bit of light on the subject.
There are two commercial makers of tubegun stocks, they are Gary Eliseo's Competition Shooting Stuff and Kevin MacDonald's MAK Enterprises. I have both types and while they differ in some details as well as the various options, the basic premise of gluing the action to the sleeve is the same. The only difference, is that the CSS is not typically glued-in, although it can be and often is, whereas the MAK is designed to be a glue-in only.
The pictures show the glue-in process on a MAK, actually on several of them. The process is the same for the CSS. Jim Cobb, a great Highpower shooter and composite fabrication expert with more than a passing knowledge of adhesives and bonding processes will take us through preparing the surfaces, applying the epoxy, cleaning the residue and a few tips here and there.The first step is to scuff, clean and degrease the action and the inside of the sleeve (tube). Scotchbrite pads work well for the tube; the action should be scuffed with medium grit paper, something like 320 grit.
Below is a CSS RT10 sleeve with a long action Remington. Note that the action was turned on the exterior. This action was particularly "wavy" with high and low spots and the mock-up in the sleeve showed that there were a lot of points at which it rubbed and it would probably not end up well centered. The solution was to take a light cut on the exterior of the action when the truing work was done. Jim recommends that for the epoxy to develop the best possible bond, the action should be 0.005" to 0.012" smaller in diameter than the inside diameter of the sleeve. In most cases this is possible with no turning of the exterior.
The trigger slot, trigger pin holes, action screw holes and any other holes in the action are then filled with modeling clay.
This action is a repeater Remington (the previous ones are single-shot Borden Alpines). If a repeater model is going to be used in a single shot MAK kit, an aluminum single shot follower should be epoxied into the magazine opening before gluing the action into the sleeve. If the repeater is going to be used in any CSS kit, whether repeater or single shot, the magazine opening should be left as is because the CSS sleeve is open at the bottom and the single shot bottom metal has a built-in follower that will slide into the action.
No epoxy yet, but a quick mock up into the sleeve to make sure things are going well. Note that the trigger pin holes in the sleeve have already been filled. The action screw holes as well as the scope base holes in the top of the sleeve will also be filled.
Applying some release agent to the scope base holes in the top of the sleeve before running the screws in is just a bit of extra insurance against getting unremovable epoxy in there.
Time to start masking surfaces. Note the tape on the barrel right in front of the action. The sleeve taping begins too as it is far easier to peel tape off than to remove a lot of oozing epoxy.
Don't skimp on the tape. You'll trim some away, like the bolt handle slot, but basically you need to cover up the exterior of the sleeve and inside the sleeve behind the tang area which will also load up with oozing epoxy.
Jim uses Hysol, an industrial adhesive that he's familiar with from his work in the aerospace industry. MAK instructions say something as easily obtainable as JB Weld will work perfectly. Jim is an overkill guy, I like that. Hysol will hold the wings on a fighter jet or something like that. This epoxy has the consistency of peanut butter which is convenient as you will see.
Apply the epoxy to the inside of the sleeve and to the action. Jim uses a tongue depressor for this, the cotton swab is for getting into the corners. Jim says you have to rub the epoxy into the surface to eliminate miniature air bubbles that will keep the epoxy from achieving its full bonding capacity. That's the same reasons you have to coat both the sleeve and the action, if you only do one then the bubbles will develop on the uncoated surface.
Here's the Remington repeater that's going into the single-shot MAK again. The single shot follower has been epoxied into place and the entire exterior of the action is now covered in epoxy and ready to install in the sleeve.
By contrast, here's a Remington repeater going into a CSS. The magazine area is left open because the bottom metal has a filler piece in the single-shot version. Of course, in a repeater version of either kit you would leave the magazine opening open.
Yes, Virginia, this is the moment of truth - that brand new custom action is all covered in epoxy and is sliding into the sleeve, never to be seen again. Note the clean work surface, Jim doesn't make a mess - ever. The scope base is screwed on, there is release agent in the screw holes. In later installations, Jim filled the scope base holes in the sleeve with wax and left the base off until the job was complete.
Guide the action in carefully, don't rush, the epoxy will start to ooze from anywhere it can.
Watch the front of the sleeve carefully, a lot of epoxy will accumulate there. Note that some tape has been peeled away to watch the alignment of the parts as it goes together.
The recoil lug (recoil washer) is not typically used on glue-in tubegun. However, after doing a few, we came to the conclusion that it would be handy for purposes of locating the action in the sleeve. Below you see the CSS RT10 with a take-off barrel and the recoil washer being guided into place. The barrel is screwed on very lightly and will be removed as soon as the epoxy begins to set up. The recoil washer is also removed at that time. Once the epoxy is cured, the match barrel is installed with the barrel vise and tightened in the usual way.
Cotton swabs dipped in alcohol are the main method of removing excess epoxy and the first place to attack is the front of the sleeve.
Peel the remaining tape from the outside of the sleeve and get to work removing the clay. You can push a swab stick through the trigger pin holes then pull a string back and forth through them to finish cleaning them. Actually, that's easier said than done and the trigger pin holes retain the clay very stubbornly for a while. Don't worry, though, by the time you're done it'll all be out. The front action screw hole is another tough one to clean out and was or clay tends to get into the locking lug recess where it's tough to remove if the barrel is on the action.
Clean out all the epoxy you can quickly. Remove the tape from the inside of the sleeve and clean the tang area also. The epoxy takes a while to really set up but this is a fairly hectic moment in the process. The clock is ticking quite audibly at this point.
We aren't done yet, but once all the excess epoxy has been cleaned off, it's time to let it cure. Here in Arizona, setting it outside will get the surface temperature up to about 150 degrees quickly. A day or so in the sun will set up the epoxy nicely. Note the action screws with a masking tape "bushing" to center them up in the sleeve holes and ensure correct alignment of everything. Pay close attention to the trigger pin holes they are really the key to alignment of the action in the sleeve. Action screws should be inserted lightly at this point. If you tighten them to any degree you risk pulling the action down to the bottom of the sleeve, breaking the incipient bond at the top of the sleeve and squeezing the epoxy out of the bottom; that will require removal of the action and a quick re-glue. Don't do it!
All the epoxy has now been reduced to a thin layer between the action and the sleeve. If you cleaned up quickly and carefully there should be no runoff anywhere.
While not exactly a glue-in tip, you should be aware that Jewell triggers have a screw that will run into the sleeve on a MAK kit. A couple of minutes with a small round Swiss file will create enough clearance for the screw. The CSS kit has a larger trigger opening so this isn't an issue with it.
Adhesives Update from Jim:
Hysol EA9340 is a viable alternative; about 60-70% of the strength at 150F. Still about 2X-3X stronger than JB Weld. Grainger typically carries this stuff as well.
I use 25 grams per "glue in" or bond job. This is slightly thinner or less thixitropic but will still work great. Works good as a bedding compound also. May need to add thickener, users preference The price is right if it is 15.00 a kit. Ellsworth Adhesive wanted 150.00.
R. S. Hughes Company, Inc.
1162 Sonora Court
Sunnyvale, CA 94086.
Phone (408) 739-3211
Aeropoxy ES6228 Metal Bond ing Epoxy Adhesive from PTM&W is my next choice. I haven't used this but it looks good on paper. Price is competitive/ affordable also. ES6228 Metal Bonding Structural Adhesive: Qt. Kit SKU:WAP6228E - Net Wt: 4.5 lb. Net Vol: 1.86 Qt. Price: $56.60 online from PTM&W. Gel time is right to at 90 minutes. 30 min is too fast for a great job.
I have used several PTM&W resin systems and have had good success.
Next is Henkel Loctite Hysol EA9394, The King of 2 part adhesives from KR Anderson @ 78.00 a pint ( which is really a 1-2lb half empty can) ( can you tell we have consolidation in the adhesives industry) or HYSOL EA 9394 50ML SEMPAK Epoxy Paste Adhesive $16.00 . This is a preweighed kit, probably around 25-50 grams (they are showing as 50 ML) and should be enough adhesive if it is at least 25 grams, they can check with the vendor on the weight.