Why to bed over the tops of the pillars

[Greg Brooks]

Preface. Whatever you think gives you the best chance to win do it. I am no expert. I am not saying one method is superior to another .. but I have a preference based on my own experience over the years.

Tried both. Rimfire Benchrest imo is the most unforgiving discipline for accuracy that I have ever tried (tried almost all of them). The two perfect targets I’ve shot in competition (this past year) were both bedded on top of epoxy instead of pillars.

As an experiment this past winter I rebedded a gun (professionally bedded by one of the top manufacturers in the industry) that shot very well but suffered from vibration problems imo.

After I carved out the existing ProBed2000 and rebedded over the top of the clipped “T” style interface pillars, that gun shot a 2500 indoors within the next month. Took it to the Triple Crown of Rimfire in May, placed 3rd.

Second comp gun experiment. Bedded my back up gun when we put it together (over the pillars to begin with), shot a 2500 first time out - outdoors in Michigan. That was the 4th perfect target over 25 years in the state.

I bed all of the stocks I do over the pillars now, for many of the reasons Al has highlighted. All of the stocks I plan to make here soon on the CNC will be bedded over the top. I have the utmost respect for CigarCop. His rifles are world class excellent. I have no reason to doubt his opinion and experience, much more talent and experience than I’ll ever have .. but for me I have to sandwich epoxy between the action and pillars.


Kind regards,
Greg

 

[Will Henry]

I generally checker the tops of the pillars and bed over them. If I'm honest, I do not totally love aluminum pillars and prefer to cast epoxy/glass pillars, then bed over them. WH

 

[Carl S]

I had a customer come in with a stolle panda,22ppc which he used for fox-varmint shooting.he wanted the crown cleaning up.slight pitting on the crown face.he asked about the bedding as one could see a gap all around the action-stock.significant shrinkage.i said does it shoot well.he said yes.i replied why touch it then.he didn't like the pitts and the gap between action and stock.when the action screws were removed the barreld action fell out of the stock,no resistance. pillars where present with no bedding on the tops.so I recrowned the barrel.removed the old compound leaving the pillars as is and rebeded the action.i use devcon.bedding came out good.rifle returned to customer everyone happy.i had a conversation with him a few months later and I asked how the rifle was.he said as good as it was before.

 

[Aero]

Seems like the metal on metal camp would be all in on v-blocks. I've always thought a metal block that fit the action perfectly would be a good way to go, but would it need to be made out of the same material as the action to work the best? I've bedded quite a few rifles that had various aluminum bedding blocks and I can't remember one that didn't show at least a little bit of accuracy improvement after bedding.

 

[BoydAllen]

Metal to metal anytime. Metal doesn't shrink!!

Years ago, I had a very enlightening phone conversation with George Kelbly about pillar bedding and its history. Keeping this short, he told me that back when they first started using metal pillars they found that they got better accuracy if the pillars were not in direct contact with the action, that even a thin coat was better than metal to metal. I took him at his word, and when I did my first pillar bedding job, I put spacers between the pillars and the action, and used it as a fixture to glue them into the stock as a separate step, then I had about the same amount of bedding compound all around the action when I finished the job, doing what amounted to a thick skim bedding job. Back in the day it was common to cast pillars in the stock using Devcon aluminum putty and then, after it hardended and shrank do a second over bed with the liquid form of the same product. That worked just fine and I believe that it would be competitive today. Doing the pillars and bedding in a single step bedding job is, I think, more of a matter of reducing the time involved in doing a bedding job, and truthfully, most shooters will not shoot the difference.

 

[mikecr]

I thought pillars are there so that you're not torquing action screws against the stock.
I never considered them as bedding, and assumed that 'pillar bedded' as merchandised is a misnomer.
None of my stocks have had pillars contacting the action, but appear like this:

 

[Edd]

I thought pillars are there so that you're not torquing action screws against the stock.
I never considered them as bedding, and assumed that 'pillar bedded' as merchandised is a misnomer.
None of my stocks have had pillars contacting the action, but appear like this:
View attachment 1484236

That looks like a LRI bedding job. If it is, your pillars are contacting the action. According to Chad, Nesika used that style pillars to get the desired epoxy thickness. Then, after the epoxy cured, they would mill the little nubs away. LRI leaves the nubs.

 

[centershot]

Great topic.
As a fun shooter type of guy, I remember years ago that pillars were not mentioned. Everyone used Acreglass to bed the rifle. Sometimes I even used the fiberglass stuff to make it stronger. The only benefit I could see was that the recoil lug was mated with the stock.
The first hunting rifle that I pillar bedded, I used Devcon putty for the pillars and the liquid for the action. Since then I have used expandable pillars, home made pillars, rounded top, flat top and even got a piece of G-10.
I never thought of putting a skim layer of bedding compound over the aluminum pillars. Having a hard time understanding why you would do this. Actually, having an action bedded on the sides looks nice,but what does it accomplish? Yes, bedding the recoil lug is still important.
Not a very scientific posting, but it has worked for me.

 

[gme]

so I've built rifles with the action interfacing on metal V blocks, pillar and skim bedding, each has it's advantages and disadvantages, pillars in contact with the action give the action screws a solid "connection" with the action without any compressible material in between, I go that route with a composite or wood stock. on a metal stock (or v block) I much prefer to lap the action to the chassis, if done correctly it gives all the support without the fragility of the epoxy. I personally believe that the best method is glue in, but has obvious trade offs in conventional stocks, but on the rifles I build on my chassis system it works perfectly

 

[DumpHollow]

so I've built rifles with the action interfacing on metal V blocks, pillar and skim bedding, each has it's advantages and disadvantages, pillars in contact with the action give the action screws a solid "connection" with the action without any compressible material in between, I go that route with a composite or wood stock. on a metal stock (or v block) I much prefer to lap the action to the chassis, if done correctly it gives all the support without the fragility of the epoxy. I personally believe that the best method is glue in, but has obvious trade offs in conventional stocks, but on the rifles I build on my chassis system it works perfectly

I have an R1 F-TR rifle with Borden tube gun action, Borden built. My option was not to glue-in. It has served me well, however I agree that it should have been glued.

 

[TaperPin]

I can sometimes forget to think about the basics - and just to recalibrate my head, took a strip of lightly oiled smooth steel and a 6061 round
about the size of a pillar and a fine thread 1/4” bolt torqued to 60 inch lbs.

It moved so easy I had to double check the torque. Maybe the oil caused it, but real people oil their guns. As low as the coefficient of friction was between the aluminum and steel, there‘s a good chance it’s even less between smooth epoxy and steel.

I‘m a round receiver guy and a curved pillar isn’t going to let the action move side to side, but the heavy hitters must be compressing the bedding behind the recoil lug a tiny amount and rebounding like a miniature rail gun at every shot.

There’s no doubt in my mind that a flat bottom receiver cannot be held in place with pillars alone and depends on bedding on the sides of the action to stay in place.

 

[AlNyhus]

There’s no doubt in my mind that a flat bottom receiver cannot be held in place with pillars alone and depends on bedding on the sides of the action to stay in place.

On flat bottomed actions, I provide for clearance around the entire action. When using a recoil lug, clearance around the periphery of the tang is especially important.

There is actually very little clamping force needed to keep an action in place....whether flat, round, faceted or any combination of shapes.

Good shootin' -Al

 

[Judd]

Great conversation and interesting perspectives shared, thanks…I love these type posts we have here.

I was always told the sole reason for the pillar is to prevent people from crushing and cracking their stocks by over tightening the stock screws. If that’s the case, seems like as long as it’s close it will serve its purpose.

 

[BoydAllen]

Those of you who have been in and around benchrest for several decades may remember a guy who wrote articles that appeared in Precision Shooting Magazine, Merrill Martin. Years back, before the magazine was printed in color, he described an experiment that directly relates to this thread.

Although he was quite well off, at the time he was experimenting with a rifle that had a Savage action, chambered in .308, in which he was shooting heavy bullets. He fitted the stock with aluminum pillars that were contoured to fit the action and fired test groups. After that he took the barreled action out of the stock and saw fret marks on the tops of the pillars, indicating movement.

I should mention that the combination of heavy bullets, and a suitable rifling twist produces more reaction torque that needs to be controlled by the bedding than is the case with lighter calibers and bullets.

In any case, as was his custom, he came up with a solution that was entirely his own. He dusted the tops of the pillars with fine silicon carbide abrasive, to enhance the friction between pillars and action and then shot more test groups, which were better than the previous ones.

Under microscopic examination we see that machined surfaces have considerable texture with the result that two machined surfaces really only make contact between the high spots of their surface finishes. I believe that skim coating pillars creates a layer that interlocks with the details of the textures of both parts, the pillars and the action, greatly increasing the friction between them and creating more stability in the joints than bare metal can. This is particularly important for round actions.

Mr, Martin was the father of moly coating bullets. He came up with the method to do this, originally to improve his results with plain based cast bullets that were required in a type of benchrest shooting that he competed in. Soon after that he used the same method on jacketed bullets, wrote articles that appeared in Precision Shooting, explaining his methods, and was granted a patent on that process. He was the one that originated putting a coating of carnuba wax over moly plating on bullets. He was a true innovator.

 

[TaperPin]

Those of you who have been in and around benchrest for several decades may remember a guy who wrote articles that appeared in Precision Shooting Magazine, Merrill Martin. Years back, before the magazine was printed in color, he described an experiment that directly relates to this thread.

Although he was quite well off, at the time he was experimenting with a rifle that had a Savage action, chambered in .308, in which he was shooting heavy bullets. He fitted the stock with aluminum pillars that were contoured to fit the action and fired test groups. After that he took the barreled action out of the stock and saw fret marks on the tops of the pillars, indicating movement.

I should mention that the combination of heavy bullets, and a suitable rifling twist produces more reaction torque that needs to be controlled by the bedding than is the case with lighter calibers and bullets.

In any case, as was his custom, he came up with a solution that was entirely his own. He dusted the tops of the pillars with fine silicon carbide abrasive, to enhance the friction between pillars and action and then shot more test groups, which were better than the previous ones.

Under microscopic examination we see that machined surfaces have considerable texture with the result that two machined surfaces really only make contact between the high spots of their surface finishes. I believe that skim coating pillars creates a layer that interlocks with the details of the textures of both parts, the pillars and the action, greatly increasing the friction between them and creating more stability in the joints than bare metal can. This is particularly important for round actions.

Mr, Martin was the father of moly coating bullets. He came up with the method to do this, originally to improve his results with plain based cast bullets that were required in a type of benchrest shooting that he competed in. Soon after that he used the same method on jacketed bullets, wrote articles that appeared in Precision Shooting, explaining his methods, and was granted a patent on that process. He was the one that originated putting a coating of carnuba wax over moly plating on bullets. He was a true innovator.

That’s really interesting - makes perfect sense.

I heard of a low tech way to measure small movements by attaching a micrometer head and oscilloscope wire to one side and an electrical contact powered through a test light and small battery on the other - oscilloscope is used because the contact made is very short in duration. The micrometer head allows an easy way to determine zero with no recoil then back way out and sneak back in until contact is made under recoil.

Hopefully there will be some extra time this spring to try it out.

 

[Jonnyofalltrades]

How very unusual. A thread about bedding techniques (a highly personal and subjective matter), and nobody is "screaming" with all caps, or calling everyone that disagrees every name under the sun. Weird.
I get a lot of pleasure from reading old gun literature, and often marvel about how the more things change, the more they stay the same. These things have always been up for discussion.
I wonder if some of the extremes of bedding shrinkage we see could be caused by products not mixed correctly. I know that my results have stepped up several notches since I started warming up products before mixing, and then mixing about double as long as I thought was appropriate.

 

[mikecr]

pillars in contact with the action give the action screws a solid "connection" with the action without any compressible material in between,

I don't want action vibrations extending back & forth through pillars.
I want it isolated to/stopped at bedding.

With pillars not in contact, tightening of actions screws draws the entire action to the entire bedding area.
If the bedding mix is right there should be very little compression, but enough to fit & form.
There is nothing interfering with this.

If your pillars are in solid contact with the action, then you're essentially bypassing bedding.
You're not compressing the entire bedding to fit & form, but reducing much of it to that solid/small pillar contact area, which would not compress like bedding compound.
If continued curing shrinks bedding at all in this situation, you would have gaps/light contact and probably be better off with no bedding from there.

 

[Olde Man]

My prefered method of bedding is a three step process. I attached the pillars to the action and glue them in to get the desired orientation of barreled action to the stock. I then bed the action to the stock. After the bedding has cured I rough up the bedding and skim bed with a 1/16" o ring placed on the action screws. This gives a consistant 1/16" layer of bedding that will shrink evenly over the whole bedding job. It goes without saying that the spacing is less between the sides of the action and the stock. I feel that the difference in shrinkage at that point just makes it fit like a bug in a rug.

 

[Kracken McGraw]

This has been a interesting read on bedding, but doesn’t a good bedding job on the recoil lug take away 99% of this worry?

 

[Cigarcop]

This has been an interesting read on bedding, but doesn’t a good bedding job on the recoil lug take away 99% of this worry?

Well if the bedding is shrinking, wouldn’t that area shrink too?