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Pillar bedding discussion..

This is a discussion on Pillar bedding discussion.. within the Art Luppino forums, part of the Gun Professionals category; What is the definition of pillar bedding as it relates to the M1A? Is pillar bedding an advantage? These two questions always bring about different ...


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Old December 11th, 2016, 06:49 AM   #1
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Pillar bedding discussion..

What is the definition of pillar bedding as it relates to the M1A?
Is pillar bedding an advantage?

These two questions always bring about different answers and opinions, leaving the subject subjective...

The advantage of pillar bedding and how to best achieve it has been discussed at lenght. My argument, or position, concerns the mateial/materials used to form the pillar.

As an example: Speaking of the receiver heel that has a lug that is drilled and tapped. The bottom surface is the concern in this instance. There seems to be two popular methods of creating a pillar from the lug bottom to surface of the rear bedding pads of the trigger housing.


1. The area between these two surfaces can be bedded solid using an asssortment of products. Done in a manner that produces a solid material mass from top to bottom. A hole is drilled and a screw is used to torque the two surfaces together..

2. The area between the two surfaces is occupied in part by a metal pillar, surrounded on all sides by bedding material in a manner that leaves the top and bottom of the metal pillar in direct contact with the heel and TH bedding pads. There is no bedding material between the pillar and the surfaces of the heel and pads. If there is bedding material between the two surfaces why install a the metal pillar?

Number two is a true pillar bedding method.. This method is an accuracy advantage in my opinion... What is your's?

Art

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Old December 11th, 2016, 07:20 AM   #2
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Interesting timing to the question, as I am sitting here typing up the product description for my pillar bedding system I will have up for sale on my website later today.

I think a pillar does/can provide several benefits. For one, you want something solid. When you clamp the receiver to the trigger group, what is between them should be stout enough that the tension from the trigger hooks, or from your lug bolt, will seat the receiver onto its mating surface with enough force that it will not move under recoil. Achieveing this by clamping onto horizontal surfaces means you have to rely on friction, a rear lug gives you a vertical surface to bear against, and is more robust.

Wood is slightly compressive, so not ideal, epoxy is better, metal is pretty much solid. In this pecking order of solidness, a metal pillar that has a skim coat of bedding material on both faces will be very nearly as solid as a pure metal pillar.

The skim coating of bedding material does two other things:

1. On a microscopic scale, metal is rarely flat. It is a series of peaks and valleys. When you put two metal surfaces together, the percent surface contact is no where near 100%; it is the peaks of each surface that take all the load, and the valleys are relatively load free. So bedding can help fill in the gaps and increase the bearing area.

2. On a slightly larger scale (and this really applies to lugs), the rear face of the legs is a vertical surface that withstands recoil, and the rear face of the lug will withstand recoil. Trouble is: if the distance between the rear of the legs and the rear of the lug does not EXACTLY match the distance between the corresponding surfaces on the stock, it will be one or the other that takes all the load, not both. By adding in the skim coating of bedding, the stock will be closer to an exact match to the receiver dimensions, and the recoil load will be more evenly distributed.

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Old December 11th, 2016, 07:48 AM   #3
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Excellent ...

Hello Art,

Thank for taking the time to share your excellent information, I have learned much from it.. Your new metal bedding system will be a success with that kind of thinking behind it.. Looking forward to having one to mess with..'

The first attempts at pillar bedding were failures, the rifles actualy shot poorer. Don McCoy was the first, to my knoe poor results.. The Idea slipped into the background for a long period.

Several years ago I started trying to work out the issues of the pillars,, all failures. In a conversation with Ted Brown, he suggested that the usual draw pressure of the trigger guard be eliminated if using a screw in the rear lug. He knew what he was talking about, that suggestion produce great results, thank you Ted... Art

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Old December 11th, 2016, 10:26 AM   #4
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Don McCoy used method #2, Roland Beaver currently also uses #2. Mac made his pilar from aluminum in a T shape and glued them in place inverted so the bolt head contacted the wider part of the T, he used a stainless cap screw and instructed me to only tighten it apx. 20 in. lbs..

EDIT: Art, addressing your last post above, Mac built my rear-lugged M1 in 2004, the draw pressure from the trigger group is minimal, just enough to keep it seated.


Last edited by MeatyMac; December 11th, 2016 at 07:31 PM. Reason: Added a note
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Old December 11th, 2016, 01:08 PM   #5
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Shooting Sight's post.

The advantage of having skills and the knowlege to use them allows one to write such an excellent piece, thank you Art N.

Art states that, a thin layer of bedding maerial is Ok because there will only be slight compression. I'm sorry Art, I don't buy into any compression, plus a thin layer of bedding material has a high risk of flaking off.

It is a labor consuming task to do a pillar, front or rear, and avoid no layer of bedding material to get between.. Since the only pillar bedded receivers I have seen, except my own and the ones I have built,, suggests perhaps I'm the only one that knows how.. I fully intent to teach Banbam how to do the bedding if he ever pushes his chair away from the Dinner table.. .Art

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Old December 11th, 2016, 01:18 PM   #6
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Meaty mac

Don Mc Coy never really got into double lug M1's too deeply, or pillar bedding either, he did not have the time, frankly his builds did not need them, plus he was on hand to fix any issues...

A slight amount of draw on the guard is fine, very slight.. When I used the word eliminate it may have been a poor choice.. You do not want the TH to move around...

Find any good M1's ????? Art L...

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Old December 11th, 2016, 02:06 PM   #7
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When Derick Martin double lugged my rifle in its Mac stock, the trigger group had minimal pressure enough too keep it closed. The best I could describe it was when latched it hung underneath not too loose not too snug it was along for the ride more or less.
Attached Images
File Type: jpg rear lug.jpg (28.3 KB, 18 views)
File Type: jpg front lug.jpg (5.1 KB, 99 views)
File Type: jpg side view L.jpg (8.1 KB, 98 views)

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Old December 11th, 2016, 02:36 PM   #8
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Quote:
Originally Posted by MeatyMac View Post
Don McCoy used method #2, Roland Beaver currently also uses #2. Mac made his pilar from aluminum in a T shape and glued them in place inverted so the bolt contacted the wider part of the T, he used a stainless cap screw and instructed me to only tighten it apx. 20 in. lbs..

EDIT: Art, addressing your last post above, Mac built my rear-lugged M1 in 2004, the draw pressure from the trigger group is minimal, just enough to keep it seated.
The torque of the bolt must be specific to the rifle. Mine is set at 40 in/lbs, and inscribed as such on the trigger housing floor.

Not sure this complicates anything, but not all rifles respond the same it would appear.

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Old December 11th, 2016, 03:30 PM   #9
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Quote:
Originally Posted by Phil McGrath View Post
When Derick Martin double lugged my rifle in its Mac stock, the trigger group had minimal pressure enough too keep it closed. The best I could describe it was when latched it hung underneath not too loose not too snug it was along for the ride more or less.
This was what I was hoping for...a picture of a pillar bedded M1A. So, looking at your photos there's only one pillar on a M1A as opposed to a bolt action with two pillars?

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Old December 11th, 2016, 03:46 PM   #10
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Quote:
Originally Posted by Roadkingtrax View Post
The torque of the bolt must be specific to the rifle. Mine is set at 40 in/lbs, and inscribed as such on the trigger housing floor.

Not sure this complicates anything, but not all rifles respond the same it would appear.

I went and dug out the file on my McCoy rifles, he actually built my rear-lugged M1 in July of 2005 and the torque on the rear lug bolt is 35 in. lbs..



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Old December 11th, 2016, 04:37 PM   #11
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Quote:
Originally Posted by art luppino View Post

Art states that, a thin layer of bedding material is Ok because there will only be slight compression. I'm sorry Art, I don't buy into any compression, plus a thin layer of bedding material has a high risk of flaking off.
The slight compression issue is pure engineering, if you have a pillar that is 100% metal, under 100lb of force, it will compress X. If you have 100% epoxy under compression, it will compress Y.

If you have a pillar that is aluminum for 50% of its length and epoxy for 50% of its length, under compression of 100lb it will compress 50% of X plus 50% of Y (ie about half way between what either would have done alone).

So when you get a pillar that is 99% aluminum and only has a 1% thick skim coat of epoxy, you will get compression that is 99%aluminum and 1%epoxy ..... which is almost the same as an aluminum pillar that is 100%.

On the other part of your comment about thin layers flaking off .... you are correct. I have not gotten into when/how this happens. I did research that anodized aluminum LOVES epoxy. The anodized layer is microscopically porous, and evidently the epoxy grabs into these pores like butter into the nooks and crannies of an English Muffin, and hangs on. So I'm hoping the thin layer concern evaporates, but I know what you are saying, and have seen it - thin layers that are not properly adhered will want to flake.

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Old December 11th, 2016, 04:54 PM   #12
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Quote:
Originally Posted by swagbrdr View Post
This was what I was hoping for...a picture of a pillar bedded M1A. So, looking at your photos there's only one pillar on a M1A as opposed to a bolt action with two pillars?
Pic's of my stock didn't survive the computer transfer there is a pillar under each lug bedded inside the stock, one under the rear and one in the mag well for the front. One short bolt for the front and a longer for the rear. Without some type of pillar the bolts would eat into the bedding.

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Old December 11th, 2016, 05:13 PM   #13
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Interestig

Well, my poition sounds a bit like hair splitting after you post..


For your information as a different method of the lug with screw, here is an early method I used and kept secret. Actualy, it may have been better, perhaps you can speak to it..

The early lug and screw method was similar, but the area under the lug bottom surface was covered with a layer of clay, approx .050"' thick, the edges of the clay were carefully trimed even to the lug edges. The receiver was bedded with the clay on. When the rec. is removed there is a void under the lug bottom surface. No contact what so ever on the bottom..

The idea is, which you probably already figured out, was to use the bedded heel horse=shoe surface as the pressure surface, and to some extent both rec. rails.. My early match rifle all use this method, successfully, very successfully.

The other aspec of pillar bedding or non- piller bedding evolves around the shape and size of the escution. The best design was counter sunk for screw head clearance, the contact surface for the bottom of the 1/4 x 28 socket head screw was taper to the same angle as the drill bit angle, 52 degrees ???.. When these screws seated they were more positive than a flat to flat seating.. Extra work , like all shooters Iwas looking for an edge, never shared this information.. Won the 200 sitting stage at Perry, 297 11X, with that rifle that was later stolen that day... Art

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Old December 11th, 2016, 05:50 PM   #14
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Quote:
Originally Posted by art luppino View Post
Well, my poition sounds a bit like hair splitting after you post..

For your information as a different method of the lug with screw, here is an early method I used and kept secret. Actualy, it may have been better, perhaps you can speak to it..

The other aspec of pillar bedding or non- piller bedding evolves around the shape and size of the escution. The best design was counter sunk for screw head clearance, the contact surface for the bottom of the 1/4 x 28 socket head screw was taper to the same angle as the drill bit angle, 52 degrees ???.. When these screws seated they were more positive than a flat to flat seating.. Extra work , like all shooters Iwas looking for an edge, never shared this information.. Won the 200 sitting stage at Perry, 297 11X, with that rifle that was later stolen that day... Art

Me?????? Yes my screws were counter sunk with cap screws beveled too fit the pillars as you described. I think Derick used a shot out barrel section that he lathe turned/squared one end. He then knurled and beveled on the other side too match the cap screws for the actual pillar.

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Old December 11th, 2016, 09:15 PM   #15
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Quote:
Originally Posted by Phil McGrath View Post
Me?????? Yes my screws were counter sunk with cap screws beveled too fit the pillars as you described. I think Derick used a shot out barrel section that he lathe turned/squared one end. He then knurled and beveled on the other side too match the cap screws for the actual pillar.
This Post was suppose to go to Shlooting Sight, please forward to him....Art

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