Recommend bedding compound?

M

michaelcj

New member
Looking for recommendations on what bedding compound to use.

Last one I did was years [decades?] ago and I used accuraglass.

I just started the final inletting on a 1903A3 action that I had barreled in 7x57.

Stock is "classic" style, as is the whole project [Think Sedgley]

Only need enough for this one project so…suggestions on any "newer" compound that can be easily found in small quantities?

Mike
 
Competitive shooters like Devcon plastic steel or MarineTex; both shrink the least when cured and hard. Mix a little cooking flour with it so it's not so runny.

Ace Hardware usually has Devcon in stock.
 
I recommend Acraglas or Acraglas Gel, both for availability and ease of use. They may not be the "best", but they are very, very good.

Acragals was not invented for glass bedding, it is a marine grade epoxy resin used in boat building, private labeled for Brownells' and widely distributed. Heck, you can even find it at WalMart in Sporting Goods!
 
I like Marine-Tex, but I like the way Acraglass gel gets shipped with color/dye included.

A couple of weeks ago, I came across a box of Acraglass that was well past it's shelf life. That stuff acts weird when it's old. I was only going to use it as a stiffener/filler in a 1st generation Savage Axis stock (yes, the one that was about as stiff as a wet noodle). For some reason, the stuff expanded around the edges and bubbled up.

Marine-Tex and Devcon may have a shelf life too. But at least I now know what expired Acraglass will do.
 
I did some tests years ago with a dozen or so bedding epoxies. Two steel flats clamped on 1/4" precision pins with a blob of epoxy between them. Release agent was Simonize car wax rubbed as thin as possible on the flats. After 2 days of curing, Devcon plastic steel and MarineTex tied and had shrunk the least. Bisonite was a close second. Accuraglass shrunk the most.
 
I use Devcon steel putty.
Don't buy a lifetime supply.
Put a date on it when you get it.
Maybe you can use it 5 years old, but not 10 years.
Boeing labels the Devcon and throws it out soon.
Store it in the house. If it is mixed when cold it never gets hard. If it is too old it never gets hard.
I get it from Brownells.
Just about any epoxy is good for 20ksi in compression.
But I pay much more $ to get Devcon steel putty so I will not have to fight time nor gravity.
The epoxy at Home Depot is cheap, but it goes off fast and runs out of the rifle like water.
I have modeling clay to use as a dam, but I like foam rubber better.

Before glass bedding or pillar bedding, practice assembling and disassembly while imagining it is dripping with epoxy that you do not want to get on you.

Before you put epoxy in a $400 stock, practice bedding some old beater guns with $5 stocks from the gun show.

Use masking tape and put release agent on the outside of the masking tape. I used to use die wax, but I now realize I often want to be able easily dissolve the release agent later. So I am now painting on 5W motor oil as a release agent on the masking tape.

There are two schools of thought on glass bedding; 1) touch everywhere, 2) touch only behind the recoil lug and in two little rings around the action screws.

I think Bart is in the first school and I know I am in the second school.
In any case, you have to plan on how the barrelled action and stock are going to separate. The first one I did, the stock was captured.. and I had to break the stock in little pieces to get it off.
 
Actually Devcon shrinks so little that I repaired an axle bearing seat with it. I bought a Bronco that had a 'repaired' rear-end, and what they did was put a bearing race in a wallowed out housing. After it went out, I disassembled it, packed the wallowed seat with Devcon, placed the race in that, re-assembled it, then let it set and cure. It ran for another 50,000 miles, until I sold it.

At our shop, we did similar things on wallowed out holes for bushings, and bearing seats in heavy machinery. Here, we built them up undersize with Devcon, then bored them back out, and placed new races or bushings in them. That stuff works.

Devcon:

Flexural Yield Strength: 5600 psi

Compressive Yield Strength: 8260 psi

It's actually as good as or better than some aluminum.
 
Last edited:
Last one I did was years [decades?] ago and I used accuraglass.
Click to expand...

Accuraglass still works well in applications where you are filling cracks, or need the epoxy to migrate into place.

In my opinion, the best epoxies are the Devcon stainless or aluminum filled.

These cure to an amazing hardness and when mixed, have the consistency of peanut butter.

Used Tex marine, gray for the pillars and white for the bedding, on a Ruger


I have used a lot of Bisonite, still an excellent choice for Garands/M1a’s. Used Bisonite in casting pillars in a M700, then once the wood was routed out, poured Bisonite in the voids.

 
I have tried scorehi and devcon steel putty. Scorehi is good, but devcon is better. I use it a lot other than bedding, including building up front sight post.

One thing to watch out; the mixing ratio is NOT 1:1 as in other epoxies. 4:1 black to white, or it will take much long to cure, and you will run out the white much too soon.

-TL
 
Much of the shrinkage is about the percentage of solid filler.The steel,or glass,or aluminum has zero shrink.A 50% fill will give 1/2 the shrink of straight resin.

If you should trap a stack of filler,it becomes a solid shim.That matters if you are patching a void or working in stages.What you do not want in your final result is the receiver stressed over a high spot.

Likewise,the thickness of the bedding compound dictates the total amount of shrink..A 1/8 in thick layer of compound will pull twice the linear shrink a 1/16 layer of compound will.

My opinion,given it is a vicious kicking,stock breaking 7x57.and our OP is a home hobbyist

I'd suggest Accraglas gel.It does not run.

Its very friendly and forgiving to use.It has a friendly work time,and cleans up with vinegar.

I suggest a two stage process,step one,just clearance a little around the rear tang and guard screw,and then choose a feature in the front to position the front of the receiver.that could be the sides and bottom of the recoil lug,to clearance.

If you bed these two small areas,you have established the height and centering of the receiver in the stock.Now,without changing these surfaces,you can go back and clearance all that you want to bed.I suggest a scribe line all around the outside of the receiver to work to,and .030 might be good.I'd use a Bridgeport if available,but other than that,very sharp carving chisels,scrapers made of feeler gage stock(grind them to shape,leave a burr,drag the burr .The burr is the cutting edge)

Use the same care you would if you were hand inletting a stock to create about .020 to 050 space around the receiver,if you want a full bed job.

With the pads you have created in step one,you can reassemble the rifle as if it were pillar bedded,the receiver suspended in correct position with clearance all around.

That's not a full lesson,but it is one way to start.

IMO,a good option is to do the front receiver ring ,recoil lug,and the flat floor between the mag well and recoil lug.I'd also do the rear tang under the rear ring up to the mag well.After those cure,I'd use Prussian blue high spot and scrapers to make sure nothing else was high,as to stress the receiver.
 
I've used about everything out there for bedding materials over 50+ years. They all work, but some work better, as mentioned. If areas around pillars are kept to a relatively thin, say 1/8" or less, and uniform depth, shrinkage is not as much a factor as if there were deep areas and thin areas.

Some better gunsmiths use several layers of bedding material to avoid shrinkage problems. Most set pillars first, then rout out other areas to uniform depth. I've done it both ways with good results.

I like the thicker ones like Devcon for most bedding work, but for repairing cracked stocks and oil-weakened buttstocks, nothing beats Acraglas, because it runs into thin cracks and comes with dye to match wood colors. Some people even put the dye on the surface to match woodgrains. I also use chopped fiberglass insulation for a filler, to increase Acraglas viscosity. It helps quite a bit to minimize flow and adds compressive strength.
 
Many people also use Acraglas as it was made specifically for bedding:

http://www.brownells.com/gunsmith-to...-prod1054.aspx
Click to expand...

Those one shot kits are a neat idea, but Brownells wants more for one than this kit which will do a dozen guns:

http://www.brownells.com/gunsmith-t...bedding-adhesives/acraglas-gel--prod1038.aspx

Either way Acraglas GEL is an excellent choice for bedding material. It's the perfect consistency (like warm peanut butter) and dries slowly for lots of work time.
 
Thanks HiBC…all good points and I have used Accraglass in the past, if fact I probably have a 15 year old unopened "kit" somewhere [ yup, I'll get fresh stuff].

Your " 2 stage" advice is great and I hadn't thought of that before.

I am a "home hobbyist" but build stringed instruments so well stocked and experienced with chisels and scrapers…. unfortunately no Bridgeport.

And HEY stop dissing my sissy gun! :)

Mike
 
Last edited:
Hi all I'm new to the forum but experienced with bedding for accuracy. I just wanted to add a couple comments for anyone researching the topic. If you are researching bedding alternatives, any well engineered product will have data based on following the mixing instructions.

Volume shrinkage: is the change in volume of a compound after it is cured. The lower this number is, the better the compound acts as a molding material, and that's the point to make a tight molded fit to your rifle.

Compressive strength: most glass bedding is loaded in compression. The higher the compressive strength, the more resistant the material will be to deformation upon torquing or recoil. Fiber fillers and ceramic or glass floc increase this characteristic more than steel because they have strength many times higher than steels (and probably bond better with the epoxy matrix)

Resistance to solvents: most thermoset polymers (epoxies that heat up or cure under heat) cure by cross linking to form stable mollecules. This process promotes better solvent resistance and is why devcon, acraglass,etc are used in this application.

The above characteristics are vitally important to the makeup of a good bedding compound. There are many alternatives available for consumers but you will not find them in the hardware store. Instead do an online search for "mold making" or composite materials suppliers. Add the strongest fibers fibers to the highest strength lowest shrinkage thermoset you can find, and you will have a superb bedding material.

Food for thought: most bedding compounds are very dense and add weight to the rifle system. What if a low density ceramic could be utilized for bedding? Light weight and ultra strong??
 
You must log in or register to reply here.
Back
Top