Basics of Bedding, and other stuff...

Discussion in 'Gunsmithing' started by Ian M, Mar 13, 2004.

  1. Ian M

    Ian M Well-Known Member

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    Q: What are the THREE BEES?
    A: Bedding, Barrels and Bullets contribute a bunch to accuracy. Let's look at Bedding this go-around.

    Q: Does bedding a rifle stock in bedding material improve accuracy?
    A: In the several rifles that I am monitoring the answer is yes. How much varies - since each rifle makes its own rules but they all shoot better and keep shooting well for a very long time regardless of handling and moisture.

    Q: Why does bedding go south?
    A: Wood stocks shift from moisture changes (including sucking up solvent that is allowed to get into the action area) and can compress from recoil forces. They also crack and chip, and shrink and swell during their lifetime.
    Composite stocks can compress from recoil, might have problems with solvent soaking also, sometimes crack or chip also. Bedding compound is really, really tough stuff and it takes the abuse from recoil and makes the steel fit perfectly into the stock.

    Q: My rifle stock has an aluminum bedding block, isn't that enough?
    A: Not a chance. The bedding block is CNC'd to a set of specs (CNC is a nifty term for machined). The action is supposed to match those dimensions but it just plain doesn't. Many reasons, trust me, the action does not fit exactly into the bedding block. Put a thin layer of bedding compound between them and they will fit perfectly.

    Q: What bedding material is best?
    A: There is no "one" individual bedding material that is best, this ain't rocket surgery and any material that ensures a perfect fit between barrel/receiver and the stock, plus sets up hard enough to ensure that the fit stays perfect - that is the base requirement. The soft, putty-like gobs found in many factory stocks do not constitute bedding as such! Might as well use Double Bubble bubble-gum.

    Marine Tex, Devcon and Steel Bed are probably the top contenders. If not for the cost, Steel Bed would likely get top grades - some top gunsmith-dudes told me that they like it best.

    Q: Is bedding a stock difficult?
    A: If you can read and follow instructions, have moderate mechanical and technical skills and some common sense - yes, it is still difficult the first time. Having said that, most people who can walk and chew gum should be able to follow the instructions that come with Brownells kits.

    Putting in pillars and full-action bedding is a little more difficult. Unless you are really good with your hands, or really a tightwad - I suggest that you pay 150 bucks and get a pro to do the job for you.

    Q: What do pillars do, are they essential?
    A: Pillars reduce stock material crushing when the stock bolts are tightened. They probably contribute to accuracy but a really good bedding job will usually result in good accuracy.

    Q: How do you know all this stuff?
    A: I look over the shoulder of very talented guys and steel their ideas and knowledge [​IMG]. Plus I have an active imagination and think that the above stuff might pass a bs test with a bit of luck.
     
  2. Brent

    Brent Well-Known Member

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    Great stuff.

    Now, to touch or not to touch -
    Tape the sides and front of the recoil lug or bed it in tight? Reasons why?

    Hmmmm Ian, you make pillars sound difficult. An active imagination it might take, but still easily doable. My smith told me he thinks I'd get away without them in the big heavy barrel blocked 30-338LI when we finish it up, but ahhhhh, it's definitely getting pillars dropped in for extra measure. [​IMG] I think I'll just do Steel Bed pillars in the little compact M70 308.

    Do you guys bed in the bottom metal?
     

  3. chris matthews

    chris matthews Well-Known Member

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    Ian,
    Great topic! Back to the Basics!!
    Mind if I add a little?

    1. Taping the sides and front of a lug gives two benefits.
    A.It allows the action to be removed from the stock a little easier.
    B. When the chamber area heats up from shooting, some of that heat finds it's way into the lug. Metal expands when heated and if the lug was bedded tight it would have no where to expand except up. This would place a little stress on the barrel/ action thread joint and could cause weird things (ie flyers) to happen.
    2. Bedding bottom metal is a cosemetic thing, especially when pillars are used. i almost never bed the bottom in an HS because the stock chips out very easily when pulling the metal out.
     
  4. Brent

    Brent Well-Known Member

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    Appreciate that Chris. Do you all rarely use pillars too?
     
  5. Ian M

    Ian M Well-Known Member

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    Chris,
    You been there. A while back we loosened the stock bolts on a brand new Stealth and the bottom metal was quite tight. When the floor plate lifted out a significant chunk of HS stock came with it.

    Nicer when the bottom metal is bedded, but I have rifles with and without that shoot very well. Agree on the taping, it is the way to ensure the parts fit nice and come out smoothly after the tape is removed.

    Do you heat the action a bit prior to removing it from a fresh bedding job, works slick. A blow-dryer is a good stock bedding accessory.

    Another little point, since 99% of the front swivel studs on HS stocks become loose after a while, a dab of Marine Tex in the recess where they screw-in makes them permanent. Could also use LockTite but whatever, they all seem to want to backoff and get loose.

    As for pillars. They complicate the job a fair bit, have to be correct length, stock bolt holes have to be enlarged, costy little rascals unless you make your own. But they are no doubt essential parts of the accuracy improvement objective. We recently installed a set of the adjustable ones, once they are in the goo they no doubt do the job but they are expensive and probably no better than home-made ones. Believe Chris makes his own out of steel, that would be nice.
     
  6. *WyoWhisper*

    *WyoWhisper* Guest

    This is great...
     
  7. FatBoy...

    FatBoy... Well-Known Member

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    Ian,

    This is pretty timely; I’m picking up a 6BR in about 2 hours that'll need to be bedded. I had Howard (the rifle builder) make a set of stainless pillars and a finish cap for the front action screw.

    Like you said, adds lots more work and I wasn't comfortable learning on a $750 stock that required a two-month wait to get.

    Steel bed is my poison. I'd like to try Marine Tex, as the GA guys used it on one of my 6.5x284's and it's a work of art.

    Maybe some day I'll get to the point were I could bed one like the pro's.....

    You wanna stir the pot some,, let's bring up the barrel pad!! I HAD to use one on my last rifle, but I'm trying without this time to see if I can get away without it. With a 9lbs barrel hanging off a repeating long action, there was just too much flex and it had vertical dispersion. I added what came out to be a 3.75" barrel pad, the rifle then shot consistent HM scores at 1000y off a sling. I'd love to hear what others do and why.

    FatBoy...

    [ 03-14-2004: Message edited by: FatBoy... ]
     
  8. Ian M

    Ian M Well-Known Member

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    My info says that a barrel pad is essential for heavy barrels - period. For those interested a barrel pad is an extension of the bedding into the barrel channel three or four inches ahead of the recoil lug recess. Gives some support so the barrel is not just "hanging".

    Chris,
    Here is another topic - release agent. Brownells sells a good spray release agent but I have seen good old Johnson's Paste Wax on some benches of top rifle builders. Thin coat of paste wax, give it a nice buffing, works like a charm, just make sure it is everywhere. Not sure, maybe heating the action with the blow dryer softens the microscopic layer of wax and makes removal easier the next day??? Or does it simply make the metal shrink or expand or something so release is easier?

    You rifle builder dudes, how is this for a breakdown of "degrees" of bedding.
    .. minimum - involves recoil lug recess and tang area
    .. basic - involves full action reciever/recess area - top only - no pad, no pillars
    .. basic plus - pillars added, sidewalls optional, pad optional
    ..full action top and bottom - bottom metal bedded, pillars, sides, top from tang to just past recoil lug recess, barrel pad if necessary, likely for heavy barrels.
    ..McMillan method - full action top and bottom, pillars plus full length of barrel channel all continuous

    Ian's method - bedding compound in stock bolts, trigger left on action and it becomes one with the receiver (for ever), Marine Tex'd hair on arm, two fingers welded together (makes it awkward giving guys the finger [​IMG] ), action sitting in stock leaning 20 degrees to one side, maybe not level with stock line also, lost a stock bolt under my bench - it is never going to be found in that mess...

    Way smarter to get a pro to do it if you are a clubfoot like me. [​IMG]
     
  9. Brent

    Brent Well-Known Member

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    I never have tried it before, but I think I'll throw these rifles in the freezer tomarrow for a bit. Hit 'em with a heat gun and that should help break the bond a little more easily.

    This synthetic M7 stock sure ate up the epoxy (JB Weld) with all the holes I drilled in it to lock it in. I ended up using Marine-Tex on the M70. The MT wasn't as stiff as I thought it would be, didn't really run though... nice stuff. With JB, you have time to have a cup a coffie and give it several minutes to thicken on up first. [​IMG]

    Do you guys mask your stocks off, or just clean the excess off with Q-Tips and cleaning patches etc?
     
  10. FatBoy...

    FatBoy... Well-Known Member

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    Brent,

    I mask and clean. I'll tape off any visibale surface that I think the epoxy may come into contact with. Then when it squeezes out, I either trim it at that time, or let it set up and contour it with a razor knife.

    I bed the minimum though. First the ring/lug. Then the tang the next day. Taper on the sides and bottom of the receiver so it's just sitting on the pillars, not squeezed into the stock. Not at all good for a hunting rifle, but fine for my match guns.

    I have started sealing the barrel channel and all non bedded in-letting with black Dupont Centuri. Not sure if it's the best choice, as it seems that 99% IPA will rub it off the filler of the stocks. It looks great though. I haven't had any solvent on the paint yet, so I have no info on how it'll hold up.

    FatBoy...
     
  11. Ian M

    Ian M Well-Known Member

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    Brent, Chris,
    Masking is a very good idea, some guys mask the entire outside of the stock if it is a customer's rifle. Also the modeling clay sold by Brownells is essential for filling screw, bolt holes, any recesses that you do not want bedding compound in. Also makes a dam up in front of the lug recess, stops bedding compound from moving forward into barrel channel, makes a nice clean line. Also a clay dam determines how big the barrel pad will be if you include a barrel pad ahead of the lug recess.
    Amazing how easy Marine Tex is to clean up when it is wet, just a bit of spray-oil on a rag or Q-Tip and comes right off any surface. I have a pressurized can of Knight Oil and it is doing a great job.

    Bottom line, for pillars, full action bedding, bottom metal bedding, barrel pad, plus sides of mag well - probably smarter to let a pro do it. Those guys have done so much that they have little tricks and methods that someone who has never done any bedding would not even think of.
    Full action bedding top and bottom, plus pillars is the way to go with any stock, you can even hear the difference when you close the bolt and dry fire. Even pillars have to be individually sized for length, opened up inside, many pros make their own oversized pillars.

    For basic bedding like tang and lug recess, even I can do that one.

    Is it worth doing - big time. Without bedding composite stocks eventually compress from recoil, maybe also form overtightening stock bolts - then things shift, barrels touch channels etc.. Even HS aluminum bedding blocks pound a bit, plus they usually don't mate evenly anyhow. Good bedding job will fix that, makes you rifle better.
     
  12. Brent

    Brent Well-Known Member

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    I never masked these two off, but if a guy was worried about gettin it all over the place, it's the safe way. I don't get in too much of a hurry with it though and find plenty of time to keep things wiped up nice. Masking off any checkering is probably a real wise move in any event, probably get tied up cleaning it out for a while if you got any in it.

    I like to do the whole thing at once, partly because I don't want to screw with it a second time, and partly because I think it makes the best fit behind the recoil lug. Probably fine either way, but doing the tang afterward leaves the possibility of it being higher in the rear than it was when originally bedding in the recoil lug, this could keep it from contacting fully near the top of the lug where it's most critical.

    Nice tip on the oil thing, Ian. I'll have to try that next time.

    Rubbing with "0000" steel wool takes the wax skin back off and cleans the edges nicely after you get it all cleaned up and the epoxy is now semi-solid. Softens the edges and leaves a clean look to it, and won't remove the blueing, just polishes it up nice.
     
  13. Ian M

    Ian M Well-Known Member

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    Brent, here is another tip just for you. Popsicle sticks. By them in the grocery store, they are essential for cleaning up over-runs. Use a razor knife to make various edges on the wooden sticks, maybe a 90 degree with a slight edge like a blade, maybe a really fine sharp V point, whatever shape will scrape nicely.

    Also we find the waxed paper pads from Brownells are perfect for mixing up smaller batches of Marine Tex, just throw the whole thing away when finished, including any leftover Marine Tex.
     
  14. Brent

    Brent Well-Known Member

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    I remember the popsicle stick tip from??, maybe earlier in this thread, good one too.

    I had the little 2oz container of M-T, just poured the catalyst in and mixed it up on this one. Had to do the whole barrel channel and everything and didn't want to stop to mix more if I ended up short, which I did not. I had enough too do two rifles if the barrel channel didn't need to be done. I had a place order me the 12oz deal of Marine-Tex for the future, should last a while. I usually mix epoxies on a little piece of cardboard, easy to hang on to.

    I never had the time or the pillars for the M70, later on I'll put them in if it doesn't get a new stock here shortly.

    Here's my daughter's M7 before bedding.
    *
    [​IMG]
    *

    My buddy Brian just brought over the latest fiberglass stock he popped from the mold last night, weighs in at 11oz! The epoxy resin is suppose to be 7 times stronger than fiberglass resin, lighter too. The one the other day was 15oz. Need a tactical, a thumbhole and a BR version now.

    Here's Brian's latest stock.
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    [​IMG]