HERESY! Hot-melt bedding HERESY!

So you got your new “shoulder cannonâ€. You had your gunsmith do a really fine bedding job, and he installed an extra cross-bolt. And he even counter-sunk the cross-bolt holes and “let in a Dutchman†(special made wood plugs) on each cross-bolt hole. Are you finished?

Let’s think about that.

Why do you need those cross-bolts? Because those cross-bolts transfer the recoil stress to the wood of the stock. This stress begins in the metal of the receiver. The cross-bolts only “see†any stress because the metal of the receiver MOVES microscopically inside your perfect bedding job. With each shot, the action “works†the cross-bolts. Sometimes you can actually see the wood just behind the cross-bolts compressed after years of shooting.

Now let’s do some simple math. Say your cross-bolts are 3/8 inch diameter by ½ inch long. Say they were installed PERFECTLY, so that the wood all around the cross-bolts is equally compressed, so shares the recoil load equally Now you have four of these cross-bolts, and they have a total surface area of 2.36 square inches. [Chances are, your cross-bolts are not NEARLY this good. Most likely your cross-bolt holes were drilled slightly over sized, and the wood never compressed around the full circumference of the cross-bolts.]

Now, instead, suppose you had taken your new rifle to a Gunsmith who was born closer to this century, and who had heard of DuPont’s hot-melt technology. What exactly did he do differently from his forefathers?

After first doing a top-notch glass bedding job, during which he brought the metal of your receiver and barrel (no, not the “free-floating†forward portion of the barrel) into intimate contact with the wood of the stock, he checked the barreled action for fit within the stock one last time. Then he put the barreled action and stock separately into his large oven, and let it soak at perhaps 350 degrees F for several hours. Then, using light cotton gloves, he removed the stock from the oven, along with a glass jar of now-melted hot-melt compound. Using the obvious imprint of the receiver and barrel in the bedding inside the stock, he carefully painted over this imprint with the hot, melted compound. Then he quickly reassembled the barreled action into the rifle, and tightened all the screws. He noticed a very few drops of still-molten glue form as the action was once again brought into intimate contact with the bedding of the stock, as some of the hot-melt compound squeezed out. These few drops formed in areas which the Gunsmith had previously treated with a light coating of paraffin, for just this purpose.

Then the gun was allowed to cool back to room temperature. The few hardened drops of hot-met were broken off, and the tiny smears of paraffin removed.

So your rifle was NOT hot-melt bedded, right? Well, next time its time to do a Class A cleaning, and you have gotten out your finest wood chisel and removed those beautiful Dutchmen and pulled your barreled action out of your rifle, look at the imprint which the barreled action made in the bedding inside your stock. Add up all the area where the action and barrel made “intimate contact†with the bedding. My guess is that this total area will GREATLY exceed the 2.36 square inches of contact area which your cross-bolts MAY have provided. Then do the math.

If you DID get a hot-melt bedding job, and it is time for that Class A cleaning, either find an oven or wrap your rifle in black cotton cloth and put it in a large, sealed cardboard box with several sunlamps for several hours. It will come apart quite easily.

WTF was that all about. 1/2" long cross bolts? Four of them?

I thought cross bolts were for keeping the stock from splitting.

Beats me, Jim.
But whatever he's smoking I hope he doesn't share.

Not sure if I feel comfortable taking firearm tips from Betty Crocker.

quote:

I thought cross bolts were for keeping the stock from splitting.

Jim, I guess you are pulling my leg...

If a Gunsmith of YOUR reputation on this Forum really BELIEVES that, then we are in more trouble than I thought...

I can tell this is going to be a FUN Thread!

Already, in less than an hour, I’ve been accused of smoking “funny stuffâ€, of perhaps being Betty Crocker, and told that “cross-bolts are for keeping the stock from splittingâ€.

Yeah, this is going to be FUN.

Let’s wait until a few Gunsmiths with some sense about them log in, and see how this goes.

I promised you I would be called a heretic. The only thing I kind of dread is that the big-bore manufacturers might start using hot-melt as an economy measure, like Boeing, NASA and most places already have.

If the point is to try to keep the stock from cracking it makes sense to spread out the load as much as possible, which is claimed for the hot melt. Except for the heating up part to get the gun apart it sounds like a good idea.

There are bedding jobs and then there are bedding jobs. If the barreled action isn't almost impossible to pop loose from the stock it probably isn't bedded as well as it could be.

With a good glass bedded stock over the cross bolts not being to strengthen the stock, then what the hell are cross bolts good for? Looks?

Someone please enlighten me.

quote:

If the barreled action isn't almost impossible to pop loose from the stock it probably isn't bedded as well as it could be.

Thanks, Will. That is where the economy shortcuts might creep in. In a “production†rifle, bedding is an expensive, labor-intensive process. This process could be shortened by sloppy use of hot-melt.

I hope that does not start.

quote:

then what the hell are cross bolts good for? Looks?

Exactly, Jim. In a properly bedded rifle which was subsequently hot-melt bedded, cross-bolts are entirely vestigial. And, like most vestigial features, will continue to be employed long after they are supplanted by the superior bedding using hot-melt. For looks alone, or maybe for those who LIKE to dig out those wooden plugs.

quote:

Originally posted by Henry22LR:

quote:

If the barreled action isn't almost impossible to pop loose from the stock it probably isn't bedded as well as it could be.

Thanks, Will. That is where the economy shortcuts might creep in. In a “production†rifle, bedding is an expensive, labor-intensive process. This process could be shortened by sloppy use of hot-melt.

I hope that does not start.

Doesn't Winchester do that now?

Maybe we are talking symantics here, but I have never seen a crossbolt that did not extend from one side of the stock to the other, maybe 2" or more. If Scrollcutter in involved, they even have some nice engraving, which I would never cover with a plug.

Now I will say I have bedded a rectangular "lug" in the stock behind the normal lug, which is a little wider than the normal lug in order to transfer recoil a little more broadly across the stock, but again, not 1/2", more like 3/4-1".

I will also admit I am not a gunsmith, but have tried a lot of different bedding material, from regular glass to steel bed to even rubber inner tube cut to fit as well as hot glue (got that idea from a Browning A-Bolt I have) and given the right circumstances, they all worked relatively well. Surprisingly enough, the more flexible the stock, the better the flexible bedding worked. The only issue I had with the hot glue, which is really what Henry is basically talking about is that you can not color it to match anything.

Larry, during recoil the back side of your rectangular lug transfers recoil to the wooden stock. So what is the total area, length times width, of one side of your rectangular lug? And did you use two?

Do you think installation of your lug gave your stock a weakness, a potential place for a fracture to happen?

Kobe

Henry
Are you trolling here? Kinda looks like it to me.
FYI, Kobe makes a living working on guns. What do you do?

Ever taken apart a newer Winchester M70? Most I've seen have hot glue. Some CZ's as well.

How did you become an authority on crossbolts?

Pissing in Kobe's direction shows that you don't know what happens to a stock under recoil. Or else, you're just trolling.

Based on your posts above, I'm not sure you have any interest in learning anything.

Your quote:
"Let’s wait until a few Gunsmiths with some sense about them log in, and see how this goes."

Are you saying you're the only one with sense about this subject?

“Based on your posts above, I'm not sure you have any interest in learning anything.â€

Actually, I’m VERY interested in learning. For instance, from you I just learned that you think modern Winchesters and some CZ’s have hot melt in them. Did you have to heat them to disassemble them? If not, was the bedding extremely “tightâ€, as described by Will above?

“How did you become an authority on crossbolts?â€

By firing a LOT of crossbows (JUST KIDDING).

I do know that drilling two fairly large-diameter holes through ANY stock is inviting disaster, and should, if possible, be avoided.

“Are you saying you're the only one with sense about this subject?â€

Nope. Now who is the troll?

Henry, the "lug" as I remember it was about 1"wx.25"x.25". Did the lug weaken the stock, well that one is difficult to answer because in the sense that I did mess with the integrity of the wood by cutting the slot for it, then yes. But since the bedding compound has a greater strength than the wood, no. Since I don't shoot hard kicking rifles, I can't answer whether it really disbursed the recoil properly or not.

Btw, gunmaker said "hot glue", as I did. Not sure if there is a difference between that and hot "melt", but I do know that most anything that sticks can have a "release agent" that will cause it to separate from the host (for lack of a better word) without re-heating. A single wipe of vegetable oil worked quite well for my hot glue project. As a side, the hot glue project did have a significantly positive affect on the accuracy of the rifle it was used on. Remington ADL syn 308 went to less than an inch shooter after as compared to 1.5" before. It probably would have happened with any type bedding.

BTW, you have heard from three of the most knowledgable gun people I know of between Kobe, gunmaker and Westpac. If they can't build it, make it better or fix it right, no one can.

quote:

There are bedding jobs and then there are bedding jobs. If the barreled action isn't almost impossible to pop loose from the stock it probably isn't bedded as well as it could be.

This is true! A lot of people can screw up a good bedding job by trying to get the barreled action out of the stock. Pry this way then pry that way is the perfect way to screw up the bedding. A fixture can be made to pull the action straight up out of the stock to avoid this tipping back and forth to relieve it from the stock. Haydon does this and it works like a charm!

quote:

"Let’s wait until a few Gunsmiths with some sense about them log in, and see how this goes."

I agree with the post that Kobe put above your comment. Must make me a senseless gunsmith.

I'm still curious what you do for a living?

If you changed you tone a little maybe you would get some answers from the more sensible gunsmiths. I was going to post some info for you based on stocking many safari rifles and the remedies that worked. But now that I feel so senseless I just keep walking into the door over and over and don't know why? Maybe I should turn the knob before I try and walk through the door. Do you think that's a good idea?

I've taken apart some Winchesters with the hot melt in the recoil lug area. I suppose this was to help bed the recoil lug against the wood since it wasn't touching anything without the glue. I'm not an expert on hot melts, but like anything else there are different grades of the stuff. Most of what I have used is rather flexible. That's not necessarily bad. There's a company in New Zeland (I think) that puts a couple of strips of flexible urethane into their aluminum bedding blocks for bedding match rifle actions. Now there is some sensitivity to the durometer of the urethane as well as how much the actions are torqued down. As far as how good hot melt will work when just "squirted" into the bedding between the action and stock is a matter of conjecture on my part, but I'd say that if you shoot the rifle very much it would probably beat the hot melt out of the recoil lug area. This area takes a lot of pounding. However the areas around the lug, such as the sides of the action and tang, would probably fare pretty well since you are primarily damping vibration in those areas. In fact the hot melt would probably do that particular job better than the epoxies we currently use. Would it be any better overall than Acraglass or Bisonite or whatever, probably not. I just don't see it having the required longivity for bedding high power rifles. Might work well with a rimfire.

My response to Koby has apparently created quite a stir, and I realize now it was too brief:

A stock that has split has suffered a catastrophic failure. Rest assured that this did NOT happen overnight, but only after numerous rounds were fired. Otherwise it would have been returned to the maker for a stock replacement early on, hopefully accompanied by a very wordy apology.

Stocks split because each recoil is like a hammer-blow to the action. These hammer blows must be absorbed by the stock A split stock is evidence of a long-standing “working†of the action within the bedding. A split stock is but the catastrophic failure which only INDICATES that this rifle had a defect: too loose an action within the stock. The loose action, during recoil, builds up velocity (and thus momentum) relative to the stock. This velocity causes a displacement of the action within the stock, which is perhaps a microscopic displacement, but rest assured: it is THERE. At the end of this perhaps microscopic displacement, the action literally SLAMS into the stock, and the stock eventually splits. So a split stock is the final, ultimate proof of an action which was not properly bedded.

In a properly bedded stock, NO RELATIVE MOTION exists between the stock and the action. In a properly bedded stock the metal surfaces move WITH the wood surfaces, and this motion never exceeds the compressional limit of failure of either the wood or the metal. Both materials are said to be within the “linear†region of their stress/strain curves. So there is no buildup of momentum, and none of the slamming together of wood and metal which eventually splits the stock.

So, Gentlemen, this what I meant, and I apologize for not saying it before. I also apologize for the “senses†statement, but being accused of smoking “funny stuff†and being Betty Crocker weren’t much to my liking, either.

And ONE day, I will have to get one of you Gunsmiths to rebarrel MY rifle, and I don’t want ANY of you TOO pissed-off with me!

Gunmaker, I am a 65 year-old retired Physicist, and I have used most every type of adhesive ever produced during a long, successful career.

Henry
The reasons that I believe big bores split:

Action forced into the stock while inletting causing web of wood between mag and trigger well to split. Rear crossbolt should reinforce this. Too sloppy an inlet with too much wood removed around the trigger and mag box compounds this problem. I make my triggers and mag boxes fit very close to keep as much wood inside as possible.

The sides of the stock around the mag will bow under recoil even with a properly bedded recoil lug and barrel lug and drive the wedge shaped tang of the action splitting the stock just behind the tang. Slimming the sides of a big bore makes this more of a problem.

I don't inlet a block of metal behind the recoil lug. I think this removes too much wood from where it needs to be. The crossbolts I use (10-24 covered in ebony or Talley's spanner bolts) are intended to keep the stock from splitting when the sides bow. I don't use them to take direct recoil.

Don`t bogart that weed Henry!!!!Pass it around.

Before I would try hot melt or anything else synthetic for bedding a rifle, I would want the answers to some fairly basic questions:

1. Does it expand when it sets, or does it shrink? Expoxies commonly used for rifle bedding pretty much ALL shrink slightly. This by its very nature can cause a tiny bit of looseness. If it was to expand when setting, it would per se tighten the bedding.

2. If so, how much shrinkage or expansion?

3. Is it compressibile? Does it return to its original "set" size after being compressed by recoil? If not, how much is it left undersized? (In other words, how much will it loosen by repeated shooting pressures?)

4. How brittle is it when set? (Relevant to how long it will last.)

There are other questions, but those would be my first ones. (One of my last ones would be: "Okay, given hot melt may have desirable characteristics, is there anything easier to use which is available?" I don't much like heating current epoxy bedding materials after they have set.) While I'm asking, how thick does the hot melt layer have to be, to be effective? (Is there really room for it on top of a "glass-bedding" job?)


I've shot rifles in many kinds of competition for many years, bedded in all sorts of ways...some on foam rubber strips, others on jute packing, some in epoxy mixed with glass fibers. Some in plain old wood glue. Others in standard bedding materials such as AcraGlas, Bisonite, Devcon, Marine-Tex, Micro-Bed, etc. All worked. Some lasted longer than others. Some were easy to work with, some were not.

I guess, I am asking, at the end, what started all this? And to what end?

If it is to prove that every day something new comes out which may be useful or handy, I think we all know that.

If it is to prove that some "hot-melt" materials may have superior characteristics to currently popular epoxies...well, I'm not surprised. But how about just listing the advantages and the comparative specs which cause them to be superior? We can all figure out where to go when we have facts in hand rather than aggression in our faces.

So now, are you gonna tell us what makes the stuff superior, which ones you recommend, which to avoid, and why?

This MAY be a useful thread when all is said and done....but I'm not yet willing to bet the title to the home place on it.

quote:

Originally posted by Henry22LR:
Gunmaker, I am a 65 year-old retired Physicist, and I have used most every type of adhesive ever produced during a long, successful career.

Well I'm a 56 year old gunsmith who, until this very minute, was enrolled in a correspondence course in Proctology. But after this brief exposure to a Physicist, have decided that I don't need any schooling to identify rear ends. All I have to do is read their postings.

As an engineer I understand what Henry is saying but he made an ass of himself in the effort.

Westpac,
You are too damn funny!!
Butch

I cant get a stock in my oven Guess I'll take my shingle down and sell my tools. hehehe....

quote:

...and I have used most every type of adhesive ever produced...

I heard sniffing glue wasn't good for you. Makes some folks bake their guns.

Hot-melt is more neutral than epoxies as to expansion/contraction during “cureâ€. This is because there is no reaction that occurs during cure. For instance, contact cement has a volatile liquid mixed into it, to keep the cement itself liquid. But during cure these volatiles evaporate into the air, so a sizeable portion of the contact cement actually goes away, and the layer of contact cement shrinks accordingly. Expoxies cure when short-chain molecules “cross-link†into longer chain molecules. There is an INCREASE in “orderâ€, and a general slight shrinkage. But nothing actually goes away, like in a solvent-based adhesive like contact cement. There is always gas generated during the cross-linking of an epoxy, but this can become encapsulated as tiny microbubbles, and keep them small because they never get a chance to expand.

Hot-melts usually shrink very slightly, but only because they are heated for use, and generally hotter things expand.

Hot-melts are not INTENDED to ever REPLACE a first-class bedding job. For that, I usually use tiny air-filled microspheres in an epoxy matrix. I bought my microspheres years ago from Emerson-Cummings. You can buy blocks of this stuff already mixed and cured these days: it is called “syntactic foamâ€. If you have never messed with any of it, its is a really useful material to be aware of. Looks a lot like ivory.

Once your first-class bedding is done, there should be no more than 0.001-0.002 spacing left between metal and wood or metal and epoxy. And THAT is the “final fill†which the hot-melt fills. Assume, for the moment that “cured†hot-melt expands with temperature at a rate of ten micro-inches per inch of thickness per degree C. If your hot-melt bedding layer is 0.001 inches thick, then over a 100-degree C temperature range it will expand by one micro-inch, or 1/1000 volume expansion. It is so soft that it easily complies, and adds little stress to the interface on which it lives.

The point of bedding is to turn a mixture of metal, wood, and plastic into a “composite†structure, which functions as a whole.

[QUOTE]Originally posted by Henry22LR:
HERESY! Hot-melt bedding HERESY!



Say they were installed PERFECTLY, so that the wood all around the cross-bolts is equally compressed, so shares the recoil load equally Now you have four of these cross-bolts, and they have a total surface area of 2.36 square inches. [Chances are, your cross-bolts are not NEARLY this good. Most likely your cross-bolt holes were drilled slightly over sized, and the wood never compressed around the full circumference of the cross-bolts.]

How about if I just use 4 dual opposing 3/8" X 1/2" Lag Bolts? That ought to compress the wood pretty good.

If I do use your method, are "thin" cotton gloves Ok for 350 F? I always use thick oven mitts when I remove the cookie pan.

How do I keep the wax from running every where? Best I can tell it changes state around 150F.

quote:

Originally posted by GLZ:
[QUOTE]Originally posted by Henry22LR:
HERESY! Hot-melt bedding HERESY!



Say they were installed PERFECTLY, so that the wood all around the cross-bolts is equally compressed, so shares the recoil load equally Now you have four of these cross-bolts, and they have a total surface area of 2.36 square inches. [Chances are, your cross-bolts are not NEARLY this good. Most likely your cross-bolt holes were drilled slightly over sized, and the wood never compressed around the full circumference of the cross-bolts.]

How about if I just use 4 dual opposing 3/8" X 1/2" Lag Bolts? That ought to compress the wood pretty good.

If I do use your method, are "thin" cotton gloves Ok for 350 F? I always use thick oven mitts when I remove the cookie pan.

How do I keep the wax from running every where? Best I can tell it changes state around 150F.

That's where I'm scratching my head as well. If it starts changing state as the temperature rises, I can't see how this would work in a hunting rifle.

The sun shines on Texas. I was reminded of that yesterday when my truck was sitting in the direct sun and the thermometer hit 105. Sitting in the truck with the doors open the interior temp had to be 30 or more degrees hotter. When I stepped outside (where it was 105) it felt like someone turned the AC on. I can only imagine how hot it would have gotten with the truck buttoned up.

Try grabbing the barrel of your firle after a few shots. Try that with a large caliber. I never measured the barrel temperature, but it is too hot to touch.

Or try leaving your rifle in the direct sunlight for a little while and grabbing the barrel.

Point here is why would you consider using a bedding compound on a working rifle that changes state as the temperature rises? I suppose if you hunt in the Arctic, it may not be an issue. But if you use your rifle in the Southwestern US or in Africa, you'll have an issue there.

I am not a gunsmith. I just hunt and shoot, and have been doing so for over 40 years. I have seen more than my fair share of the latest and greatest come and go, particularly when those new innovations are put to use in the real world. If this stuff can be re-melted after it is applied, I wouldn't consider it.

Henry, please address gunmakers last post. Perfect bedding isn't going to do much in preventing the stock from bowing outwards under heavy recoil. Most people aren't shooting single shots here.

I've bedded and crossbolted more than a few stocks over the years, including some heavy kickers. All were done with "conventional" materials, methods, and procedures. Have never had one fail. I have no desire or see any reason to use hot melt for stock work. And BTW, I'm a Rocket Surgeon.

quote:

Originally posted by Henry22LR: Well, next time its time to do a Class A cleaning, and you have gotten out your finest wood chisel and removed those beautiful Dutchmen and pulled your barreled action out of your rifle...

Believe me, I'm no gunsmith. I only own one rifle with crossbolts--a Winchester model 70, 416 Rem mag. Perhaps this style is different than what you described, but I don't need to remove anything other than the stock screws to separate barreled action from walnut. I would just as soon not do a 'class A cleaning' if it involved using a wood chisel, for Christ's sake!

Or perhaps your 'physicist speak' went over my head?

quote:

Originally posted by Henry22LR:

I can tell this is going to be a FUN Thread!

Is it fun enough for you yet?

I haven't had this much fun in a while!!
Butch

My first thought was that this thread was posted on the wrong forum. My second thought hasn't changed. I believe it should have been posted over on the "Retired Physicist looking for a good time" forum.

Althouh, as installed by some factories/gunsmiths, crossbolts may act as a recoil transference device (I like the sound of that!), they are really a means of re-inforcing the stock to prevent splitting. I don't like a crossbolt against which the recoil lug bears. I dont think it will fit as well as Acraglas. So' I like to put my crossbolt behind the recoil lug; roughly midway between the guard screw and the magazine well. The rear 'bolt goes ahead of the trigger group of course. No one can dispute that this 'bolt is solely to prevent stock splitting at this point.
A barreled action which is difficult to remove from the stock may or may not be well bedded. It may be difficult to remove because the wood under the bedding compound swelled. Or becasuse the bedding compond itself swelled.
Back in the day, many BR gunsmiths felt that a properly bedded round receivered rifle would, after the guard screws were removed, fall out into your hand if the rifle was turned over. It would go back in just as easily and there would be no significant movement as the screws were tightened. Later on, some gunsmiths decided it was better to bed the rifle as usual then rough up the bedding and use a "paint coat" during final assembly after which the rifle was not disassembled again. This was felt to be the next best thing to a "glue job" and was popular on hunter class rifles which could not be glued together (rules!).
Ultimately, the purpose of the stock bedding is to:
(a) Locate the barreled action in the stock in a stress free yet secure manner.
(b) strengthen the stock
(c) Seal the stock against moisture.
(d) provide a precise fit for the tranference of recoil to the stock.
One custom gun maker once told me that a well bedded rifle doesn't even need any finish applied to the inletting since the precise fit of the action to the wood would effectively exclude any moisture anyway. His inletting was good enough that one could almost believe it; but I don't.
Now to the "hot melt bedding" as described: I don't actually think it is a bad idea! If one first bedded the stock with a suitable epoxy compound (I like Acraglas Red Box), cleaned it up, and installed the barreled action as described; it should provide an improved micrscopic fit. The epoxy bedding would still have to be properly done and provide a stress free bedd so that the screws could be tightened up with the "hot melt" glop in place. But the idea doesn't seem too far fetched. I may even try it on an "F" class rifle I'm messing with at the moment. I'm pretty progressive for a more mature kind of guy!
An interesting post, Henry.
Lloyd,
You may remember the Forslund brothers (Albert is gone now). They were great experimenters and would have happily embraced any methodology which might have given them an edge. I could see Albert being all over the "hot melt" bedding. If he kept using it, you could rest assured; it worked! Regards, Bill

Gunmaker and Bill Leeper are correct. The cross bolts are to prevent the stock from splitting. During recoil the force rearward from the recoil lug and the resistance to the recoil from the shooter causes the wood in the magazine well area to bend outward creating forces that may/will split the stock from the magazine well forward to the action screw and possibly from the magazine well rearward to the inletting for the trigger. The cross bolt normally do not help with the recoil forces straight back.

Headache