Re: Bedding Action ??
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SmallBoreSniper</div><div class="ubbcode-body">I know the purpose, but I am still a little confused about how this is done. If I bed the action can I still remove my stock?? </div></div>
Short answer: Depends.
Longer answer: Depends on if you intentionally glue it to the stock or not. (a good portion of Bench Rest rifles are done that way)
Yet an even longer answer: Properly performed, a rifle that is bedded with the intent of being taken apart should be able to do so an almost infinite number of times with no detrimental effects on accuracy or durability. It should just go together and work.
I'll talk about some fundementals:
Q: Exactly what is bedding?
A: Bedding (in any capacity) is nothing more than an effort to make a precision casting for a barreled action to register into when a rifle/pistol/musket, whatever is assembled. It can be done by pouring a resin into the stock, machining some sort of register, or by machining a stock made from a laminate wood material with a heavy resin content.
Example of the last one: This is my 22 250. The most accurate rifle I personally own. No bedding what so ever. I did however write the inlet as a 1:1 surface model and then machine it to fit 1:1 with the action. The resin content in the wood is so high I wanted to try building it without making a casting. 5 shot groups have printed as tight as .098" with Black Hills factory ammunition. I've done this in a variety of weather conditions and don't see stuff moving around.
Q: What's it do? (bedding)
A: Organic materials like to swell, shrink, and warp when exposed to environmental changes in temperature and humidity. The vibrations, resonance, amplitude, and all sorts of other fancy engineering terms that are present when a gun goes bang, plays a significant part in how accurate that firearm is. If a non bedded rifle shoots one way on a cool dry day its not at all uncommon for it to behave differently on a hot and muggy afternoon. These changes often result in a change of group center (a wandering zero) and may also cause a change in group size. (shot groups get bigger/smaller)
Bedding a rifle attempts to mitigate the effects of environmental conditions by providing a foundation for the barreled action that is immune to ambient weather changes.
That's about it. What it won't do is make a silk purse from a pigs ear. If your rifle is a minute of mountain range kind of gun, bedding it might make it a minute of single mountain.
If your rifle is very, very accurate, a properly executed bedding job will make it exceptional. It's a viable, yet relatively small part of the larger picture.
Q: What is pillar bedding?
A: Pillar bedding is nothing more than adding a "footer" for the action screw. The intent is to ensure the tension applied to the fastener does not booger up the stock (in this case natural wood being the most affected) by crushing the fibers. This would be detrimental as the tension applied by the screw helps ensure that a deliberate tension is applied to the receiver when the gun is assembled. A tension that varies from shot to shot or over a period of time will likely result in a zero shift or group size change. The pillar is usually machined from a metal of some kind. For its basic function there's no real wrong answer so long as its capable of resisting the compressive/tensile forces that the fastener applies. Some materials do work better than others though when a resin system is used. Aluminum IMHO should be a last resort. Almost as soon as aluminum is machined the freshly exposed material begins to oxidize. This layer of oxidation makes it a challenge for most resin systems to bond with properly. The adhesive/cohesive actions of the epoxy don't work as well. I much prefer stainless steel in the 300 series as it contains so much nickel and chromium that its largely immune to corrosion. (same stuff most kitchen flatware is made out of)
Q: Can I do this at home?
A: Certainly! Bedding a rifle is not rocket science and does not take a degree in chemistry. It does how ever take some forward thought to execute and have a cosmetically appealing end result. If your patient, have attention to detail, and the tenacity to be willing to fail (learn) then its well within your grasp. Not all bedding jobs come out the same. Personally, I think mine look pretty good (tootin the horn a bit) but it didn't come immediately.
Diligent application of fundamentals and a little creative thinking. That's all. No voodoo, no chicken blood, and no consumption of human flesh before an almighty deity required.
Materials:
The resin system:
Just about any modern resin system could (didn't say CAN, I said could) be used to bed a rifle. Some materials do work much better though as they have a long open clamp time, convenient mix ratio, and less sensitivity to temperature, humidity, UV light while curing.
Regardless of what a person chooses, a good bedding material should have the following qualities:
High Shore hardness
Low percentage of shrinkage (below 2%)
High Compression strength
Reasonable shear strength
High resistance to alkalies and acids
Long open clamp time
Long cure time (long cure time resins typically have lower shrinkage percentages)
Resins that use nylon as a binder or filler should be avoided. Nylon is hydroscopic. It attracts and holds onto water. I think further explanation isn't required.
Resins that contain a ferrous metal should also be avoided IMO. If an epoxy contains steel to me it strongly suggests its susceptible to corrosion due to acids/water.
Release agents:
Everything from pam cooking spray, shoe polish, and commercially made release agents have been used with varying degrees of success. The only thing a release agent does is prevent the resin from bonding to the parts you don't want it to. Some do this better than others for a couple reasons.
I avoid things like wax/shoe polish where surface finish is important to me. I'll use the wax trick on the screws/studs as it sticks really well and resists the effects of shear and compression when things are getting screwed together. (pillars being held in place, etc)
For everything else I use a commercial aerosol mold release agent. It has a very thin film which is important to me since I want my casting to be a mirror image representation of the receiver. With a spray can I can apply very evenly vs having a dunk tank of the stuff that'll surely run, sag, and dribble as it flashes off the carrier. (been there, tried it, and hated it)
Tape:
Buy the best automotive masking tape you can afford. I like the green stuff 3M makes. I mask the stock from one end to the other with it. The only place resin is going permanently is where I don't apply tape.
Masking off large features in an action:
For this the Klean Klay product sold by Brownells is hands down the best stuff I have ever used. It's got a good hardness to it while still being formable. I take a block of it and with a leather mallet I literally pound it into the reciever so that it presses into all the little nooks/crannies and gets a good hold of things. From there you shape it with whatever works for you so that its a seamless transition from receiver to clay. Here's an example of an action fully masked and ready for the final process:
For recoil lugs I use a .5mm thick 3m electricians tape sold by MSC and most other major industrial supply catalogs. Reason is because this is typically the only taped surface that comes in permanent contact with the bedding mixture. I don't want the orange peel finish that masking tape leaves. I want it slick and perfect.
TIPS:
Air is enemy #1 to a bedding job. Bedding a stock well depends on its absence during the process. It starts with the mixing of the resin. Stirring it in a cup is a big no no in my shop. You mix it on a flat surface with a broad applicator. This does a couple things. Epoxy cures, it does not dry. Curing depends on the generation of heat. It's a natural by product. You don't want your epoxy to cure in the mixing cup. By keeping it spread thin you deny it the chance to generate a lot of heat. This will increase your work time as you fiddle with things. You also avoid stirring air into the resin this way. Your not "whipping" it if your spreading it over itself in thin sheets. Any air trapped will easily escape.
Mixing: You have to mix the stuff! I tell folks their hands should be very sore and should have a blister or two the first time they do it. (if your not used to this stuff) The esters, gum resins, and polymers have to mix with one another to really cure up properly. A half ass approach will likely result in soft spots that may look fine initially, but long term break down and fail. MIX THE SNOT OUT OF IT! WORK WORK WORK.
Application. This is as important as the mixing step. You shoot yourself in the foot if you spread it all out nice and thin only to glop the stuff in there just to get it done. Be careful and thoughful as you apply it to your stock/action. Take the time to pop anything suspicious looking with a tooth pick, dental pick, whatever.
Distractions: Wives, kids, cell phones, and the history channel need to be avoided during bedding. Epoxy waits for no one. I say again, it waits for no one!
Patience. The real secret is the prep work. proper masking, application of release agents, and everything else is what makes the difference. Take the time to think things through and pay attention to little things because they do matter.
Here are a few examples of what my bedded stocks look like when completed.
BAT Machine MB action.
Nesika Model T action:
Stiller Tactical single shot action:
Stolle Swindelhurst Rimfire Benchrest action:
Last (drum roll please)
This is a photo I pulled off the net. It's what (hopefully) your bedding job doesn't turn out like.
Hope this was helpful to those who took the time to read it. Sorry for being long winded but there's just no quick and dirty way to describe it.
All the best,
C