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Skim Bedding

 
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  #8  
Old 01-15-2007, 08:14 AM
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Re: Skim Bedding

[ QUOTE ]
Thanks CS, its just different names for the same thing. Now pillar bedding, and glue in refers to a different animal.

AG

[/ QUOTE ]

"Glue in" is when the action is litterly "Glued in" with epoxie to your stock and cannot be removed without a large blow torch and the application of a hellova lotta heat!! (That's why they call it "Glue in" [img]/ubbthreads/images/graemlins/wink.gif[/img] ).

When you glue in an action, you better like that stock a LOT, cuz it ain't comin' out! And make sure that you have the trigger adjusted the way you like it (for the rest of your life) [img]/ubbthreads/images/graemlins/wink.gif[/img]

Pillor bedding is when two steel or aluminum posts/columns are put into the stock screw holes, and the action is then screw together.
I am not a supporter of "pillors", and I think it vaporware service to keep gunsmith's kids in college.

The reasons why are lengthy and technical, but the summery is that it is not physically possible for them to do what they are claimed to do - the "believers" will argue this all night, and I'm too old, and too busy to waste my time on it.

A properly done glass bedding with one of the known bedding compounds will last the life of the rifle, no matter what the stock, and give you rock hard stability. This goes for Micro-Bed, up to the expensive "spreads" like Brownells "Steel bed" and Devcon Steel (and Titanium) bedding compounds.

Stay away from Acraglass. It is a thick-ish liquid, and drips out of the work before it sets up - it is a bitch to work with (I have a drawer full of tee-shirts on that stuff!!:( ).
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  #9  
Old 01-16-2007, 07:19 AM
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Re: Skim Bedding

Catshooter, I would like to her your theory on the piller bedding, I have never been completely sold on it myself. It seams that you are removing a solid material to glue in another solid material. I just would like to hear your theories.

RH
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  #10  
Old 01-16-2007, 10:15 AM
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Re: Skim Bedding

[ QUOTE ]
CatShooter, I would like to hear your theory on the pillar bedding, I have never been completely sold on it myself. It seams that you are removing a solid material to glue in another solid material. I just would like to hear your theories. RH

[/ QUOTE ]

No theories, just mechanics (with a little physics).

The idea behind pillar bedding is that the pillars will keep the tension on the action the same, thereby keeping whatever accuracy you have, by making the "system" stable.

It is one of those things that have come to shooting from that (in)famous group, the Benchrest shooters.

If they do it, "it must be good", right?

Very rarely are true tests run on these ideas. The kind of test where you take a known action and try it in a standard glassed stock, and then and a "pillar bedded" stock, and have a shooter shoot both in a tunnel without knowing which one they are shooting - it's called a "blind test", cuz the shooter is "blind" to which one he is shooting.

What more often happens, is that Frank or Joe tries something out, and happens to win a match, and it immediately becomes "FACT", that you MUST have it to be competitive. No one ever questions the "science" behind it, or does a blind test... it automatically becomes fact.

And all the 'smiths tool up for the latest fad.

The idea behind pillars is that by placing a steel or aluminum pillar in the stock, the tension of the action screws will remain "constant", since they are pulling against the pillars, and not the stock - therefore, the ringing/vibration of the barreled action will remain "constant", so accuracy will remain "constant".

In BR, consistancy is an important goal. If you have a hot shooter today at the range, but go to the match next Sunday and some mysterious thing has changed and your groups look like they came from a full choke, then all is wasted.

So anything that "Looks" like it is "constant" will win instant approval, even if it doesn't work, doesn't make sence, or doesn't fit science.

The problem with pillar bedding is this - you want the barreled action to be stable in the stock. This applies to BR shooters, AND woodchuck shooters, crow shooters and Prairie Dog shooters, and those wackos, the egg shooters.

The problem is this... you screw a barreled action into a stock - lets say a walnut stock, and crank the screws down to 65 in/pounds. With the 28 pitch screw, this translates to a few hundred pounds (on each screw) of force holding the action in place. It is claimed that the expansion/contraction of the stock will change the pressure, and... well, a BR shooter can't accept ANYTHING changing without his permission!!

With the fiberglass stocks from McMillen and H-S Precision... the argument is that the stock expands/contracts at a different rate than the screws, so the pressure changes, and... " a BR shooter can't accept ANYTHING changing without his permission!!"

So the pillar is supposed to solve these problems. A solid steel or aluminum post that the screw goes into the stock, so the stock can expand and contract at will, and the tension on the screw stays the same against the pillar (well, almost;) ).

Here's the fly in the ointment. With regualr glass bedding, when the action is in the stock, the screws really JUST hold the action to the stock and the recoil lug restrains it from sliding back.
The screws NEVER restrain the action, they only hold it down into the stock... with presumably, a constant pressure.

If you use metal pillars, the coefficient of expansion of steel (pillar) is approximately the same as the action screw. In warm weather, the pillar expands, and the screw expands... but NOT at the same rate as the stock. If the expansion is more than the stock, the screws actually hold the action with less force (if the screws contact the stock, so the frequency of vibration changes ... and since the screws are NOT supposed to restrain the action from backwards motion, the pillars are now taking up rearwards thrust - a badd thing (so says Martha Stewart).

So... the screws hold the action to the pillars, the pillars are epoxied into the stock, so the pillars take recoil, along with the recoil lug - now three things are spreading the recoil, plus the abount of force applied to the action by the screws varies with temperature - whoops, too many uncontrolable things in the mix.

The BR game is in a constant flux as each shooter searches for the "Holy Grail" of accuracy to get an edge on the guy at the next bench. An interesting direction now is that the 1000 yd benchrest guys are now going back to solid wood stocks.

Consider this. With a solid wood stock, when you crank down the screws to 65 in/pounds, the pressure of a few hundred pounds per screw compresses the wood a fair amount. The expansion (or contraction) of the screws is only a few thou... not enough to "de-compress the wood, so the action actually stays more stable in a wood stock (or a glass, or Kevlar stock, if it is compressible).

That's the short of it. I wouldn't spend a dime on pillars.

In other than short range BR rifles, the current trend in glassing accurate rifles is to glass the action with thick tape wrapped around the middle of the action so the action will NOT touch the glass between an inch of the rear screw and an inch of the front screw - in reality, this means from the front edge of the mag well, to the rear of the trigger cut out.

And NO glass under the first inches of the barrel - this winds up to be the most stable bedding that is "sane", and not a glue in, or barrel wrap bedding.


.
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  #11  
Old 01-16-2007, 01:43 PM
Chawlston
 
Posts: n/a
Re: Skim Bedding

[ QUOTE ]
[ QUOTE ]
Thanks CS, its just different names for the same thing. Now pillar bedding, and glue in refers to a different animal.

AG

[/ QUOTE ]

"Glue in" is when the action is litterly "Glued in" with epoxie to your stock and cannot be removed without a large blow torch and the application of a hellova lotta heat!! (That's why they call it "Glue in" [img]/ubbthreads/images/graemlins/wink.gif[/img] ).

When you glue in an action, you better like that stock a LOT, cuz it ain't comin' out! And make sure that you have the trigger adjusted the way you like it (for the rest of your life) [img]/ubbthreads/images/graemlins/wink.gif[/img]

Pillor bedding is when two steel or aluminum posts/columns are put into the stock screw holes, and the action is then screw together.
I am not a supporter of "pillors", and I think it vaporware service to keep gunsmith's kids in college.

The reasons why are lengthy and technical, but the summery is that it is not physically possible for them to do what they are claimed to do - the "believers" will argue this all night, and I'm too old, and too busy to waste my time on it.

A properly done glass bedding with one of the known bedding compounds will last the life of the rifle, no matter what the stock, and give you rock hard stability. This goes for Micro-Bed, up to the expensive "spreads" like Brownells "Steel bed" and Devcon Steel (and Titanium) bedding compounds.

Stay away from Acraglass. It is a thick-ish liquid, and drips out of the work before it sets up - it is a bitch to work with (I have a drawer full of tee-shirts on that stuff!!:( ).

[/ QUOTE ]

Torches are not the best thing to use for removing glue-ins. Most gunsmiths get the gun level and just place a hot iron on the scope bases. It transferrs heat quickly and doesn't ruin the stock with the flame of a torch. Heatguns work as well.

James
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  #12  
Old 01-16-2007, 01:48 PM
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Join Date: May 2001
Posts: 920
Re: Skim Bedding

I used an acetylene torch to remove the action of a second hand rifle I bought for cheap... it was a 40XB rimfire target rifle that wouldn't come apart (which is why it was cheap).

I tried a heat gun and it didn't work. I think the heavy barrel drew the heat away faster than the heat gun could supply it.

I masked the stock with aluminum foil.

.
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  #13  
Old 01-16-2007, 01:54 PM
Chawlston
 
Posts: n/a
Re: Skim Bedding

wooden stocks in benchrest are typically used to dampen the harmonic vibration of the barrel from shot to shot. And, we even glue them to the actions.

James
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  #14  
Old 01-16-2007, 10:05 PM
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Join Date: Oct 2006
Location: White Mountains, AZ
Posts: 285
Re: Skim Bedding

What's everyone opinion on bedding material? Also....when I do get my Sendero SFII should it will have the H-S stock on it.....should I bed it?

To resumarize.....skim bedding and regular bedding are the same right? [img]/ubbthreads/images/graemlins/confused.gif[/img]
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