Best action shape for pillar bedding?

[SG4247]

Planning to buy another custom action for a new F-Class rifle, and have been looking at three action shape options:

1.55 inch round
1.4” Multiflat (12 sided pgon)
1.4” Octagon

For guys that have inletted stocks for custom actions with metal pillars, is there any physical advantage to one shape over another?

Even if the action just fits better, or it is easier to inlet and bed - is enough justification for me.

I really don't have a preference based on looks. My goal is consistency and functionality.

 

[Dusty Stevens]

Doesnt matter. The pillar shouldnt touch the action anyway

 

[Mark M.]

Doesnt matter. The pillar shouldnt touch the action anyway

Please explain

 

[tomswede]

What type of stock is it?

 

[Dusty Stevens]

Please explain

The pillar shouldnt be visible from the top.

 

[cdngary]

The pillar shouldn't be visible from the top.

Your saying cigarcop's stock work is so good. All his pillars are visible from the top and they look like they contact the action.

 

[Dusty Stevens]

Your saying cigarcop's stock work is so good. All his pillars are visible from the top and they look like they contact the action.

He does a pretty job for sure.
Metal expands at a different rate than bedding epoxy.

 

[Cigarcop]

He does a pretty job for sure.
Metal expands at a different rate than bedding epoxy.

Funny shit right there.....why I won’t disagree that the two might expand differently, when or how have you ever got an action hot enough to change point of impact or anything else your trying to peddle here..... I’d also like to see or read about your specific testing??
I Want metal to metal contact with the recoil lug as tight as possible (close to a glue in as possible) everything else is going for the ride, stress free is what matters.
I’m waiting

 

[Shrek]

Pillars should stop short of the action and when you bed the action bedding fills the gap. I personally don’t use metal pillars anymore. I over drill the action screw holes to 9/16ths and fill them with Marine Tex grey when I bed the action. The pillars are then completely made of bedding. I then come back and slightly oversize drill the action screw holes so the screws don’t touch except in the action and in the bottom metal or metal escutcheon if it doesn’t used bottom metal.

 

[Shrek]

A flat sided action will resist twisting in the bedding better if that’s a reason. I’ve never had and action in Marine Tex grey ever twist and break the bedding yet so I don’t think this is a real issue for most. Maybe if you’re bedding something like a 338 Lapua you could find the difference.

 

[eddief]

Bigger things to worry about in the bedding process than if you want your pillars to touch or not....I have done them both ways and never seen a difference on paper or steel. My dial indicators tell me yes or no when cured.

I do like "pretty" stress free bedding, shows pride in ones work.

 

[SG4247]

So it seems to me that the round actions are harder to locate the stock perfectly to - when assembling. I am referring to a really good bedding job here, not some factory stuff.

Does a flat bottom action just fit better with a flat bottom type register?

I am looking for a stock in laminate, thought I would by a PRT lowboy, but now it looks like those arent offered now without a full build?

 

[Dusty Stevens]

Heres a simple test. This particular one i built had exposed pillars, bedded in 10110 devcon. It set many records over one season. The next year it was sold. When i checked it out the pillars were .002 higher than the bedding- so the action was suspended between the pillars. I did a quick glue in, it went back to shooting like it did. Now 2 years later the pillars are .0016 higher than the glue after i popped it out.


next is my typical bed job with the pillars set about .025 below the bedding. They do the exact same job. Any BR shooter thats ever left his scope uncovered in the sun before going to the line knows where this can go.

 

[carlsbad]

I like flat sides and flat bottom for bedding. I inlet to just let it slide in and hit the bottom. Autoalignment.

 

[hoz53]

Heres a simple test. This particular one i built had exposed pillars, bedded in 10110 devcon. It set many records over one season. The next year it was sold. When i checked it out the pillars were .002 higher than the bedding- so the action was suspended between the pillars. I did a quick glue in, it went back to shooting like it did. Now 2 years later the pillars are .0016 higher than the glue after i popped it out.

View attachment 1174565
next is my typical bed job with the pillars set about .025 below the bedding. They do the exact same job. Any BR shooter thats ever left his scope uncovered in the sun before going to the line knows where this can go.View attachment 1174571

thats interesting -- in the one where pillars are covered by bedding why dont the expanding pillars push the bedding up? Im thinking of going to bedding only but there have been alot of good shooting rifles built with metal pillars.

 

[SG4247]

thats interesting -- in the one where pillars are covered by bedding why dont the expanding pillars push the bedding up? Im thinking of going to bedding only but there have been alot of good shooting rifles built with metal pillars.

The pillars should not move, because in this case, the bedding wont push up or crack since its backed up by the steel action surface. Unless of course...someone WAY over torques the action screws.

 

[hoz53]

The pillars should not move, because in this case, the bedding wont push up or crack since its backed up by the steel action surface. Unless of course...someone WAY over torques the action screws.

ok thanks for that info

 

[Dusty Stevens]

The pillars should not move, because in this case, the bedding wont push up or crack since its backed up by the steel action surface. Unless of course...someone WAY over torques the action screws.

And that cant happen if you turn down a 1” pillar to .750, leave it 1” for a shoulder then sink it in there. Works perfect and looks good on the outside too

 

[SG4247]

So, I ordered an Octagon shape action based on the feedback here.

I was wondering what influence a big long heavy barrel might have on a various shaped 8.5” long action, as if only one rear action screw was installed and the action was supported by only one point on very front, in a cantilever type fashion.

Ran some stress/stiffness calculations on the four different action shapes today with interesting results:

#1 - 1.55” OD round, very stiff and heavy. You could hang a tank barrel on this action. It don't care.

#2 - 1.40” Octagon, pretty darn stiff.

#3 - 1.40” Multiflat 12 sides, not as stiff as the octagon, but lighter.

#4 - 1.36” OD round, worse than the multiflat, and least stiff overall.

This might not be a huge surprise to this audience, but I haven't given it any thought previously.

So, does action shape/size matter in shooting?

Still not sure, so I thought I would ask...

 

[Gappmast]

What do you guys use for pillar material?