Why to bed over the tops of the pillars

[AlNyhus]

This is on the work bench right now for a rehab. It's an example of why bedding over the tops of the pillars is a good way to go. The bedding was done by a good BR 'smith. The stock is a high quality BR stock from a well known mfg.

Over the seasons, the bedding compound shrunk. You can see that the bedding has moved away from the front pillar. The rear pillar shows even more bedding shrinkage around the pillar. With a coat of Dykem on the bottom of the receiver, the only contact points are the witness marks left on the receiver by the tops of the pillars. The depth mic. shows the bedding to be .005-.006 below the tops of the pillars.

Good shootin' -Al

 

[LVLAaron]

Bedding over the top is also a little easier, in my opinion.

 

[Cigarcop]

Did the pillar shrink?….. I think not…. I’d rather have metal to metal contact any day.
Now I think what you’re saying is bedding shrinks….. won’t it still shrink if it’s on top of the pillar? From what you’re saying it certainly shrunk everywhere else so it would shrink there as well.
JMO and that’s worth nothin!

 

[LVLAaron]

Sure... the epoxy shrinks a tiny bit. After a couple years, you've got an action living only on the pillars. What's the point of the bedding? I've seen a handful with the same issue Al shared. I've recently done a couple with the pillars buried... time will tell.

 

[Acyr]

I think what Al is saying is bedding shrinks evenly across the inlet. If the action is sitting on the pillars the bedding will shrink away from the pillars leaving minimal contact for the action. If you apply bedding compound above the pillars the bedding will shrink the same amount across the entire inlet but maintain full contact with the action.

 

[LVLAaron]

I think what Al is saying is bedding shrinks evenly across the inlet. If the action is sitting on the pillars the bedding will shrink away from the pillars leaving minimal contact for the action. If you apply bedding compound above the pillars the bedding will shrink the same amount across the entire inlet but maintain full contact with the action.

bingo

 

[Edd]

I think what Al is saying is bedding shrinks evenly across the inlet. If the action is sitting on the pillars the bedding will shrink away from the pillars leaving minimal contact for the action. If you apply bedding compound above the pillars the bedding will shrink the same amount across the entire inlet but maintain full contact with the action.

But that isn't what will happen on round actions. If the bedding shrinks the channel will become larger than the action and it will contact along a line on the bottom.

 

[Acyr]

But that isn't what will happen on round actions. If the bedding shrinks the channel will become larger than the action and it will contact along a line on the bottom.

Valid point. So, is setting the action on top of the pillars the best way? Honest question.

 

[Edd]

Valid point. So, is setting the action on top of the pillars the best way? Honest question.

I don't think the pillars should contact the action.

 

[hoz53]

I don't think the pillars should contact the action.

Well this is an interesting thread. I hope some more gunsmiths chime in on it. So if the metal pillars arent contacting the action would we get the same result just letting the whole pillar be bedding material??

 

[Acyr]

So, I think we can agree that different brands of bedding materials all shrink but at different rates. And that flat bottom actions may provide better surface area to bedding contact area during shrinkage. (at least the bottom section) Are glue in's immune to shrinkage issues?

 

[Edd]

Well this is an interesting thread. I hope some more gunsmiths chime in on it. So if the metal pillars arent contacting the action would we get the same result just letting the whole pillar be bedding material??

I am not familiar with anything but hunting stocks but I believe the stock construction needs to be considered. On something like a McMillan stock with a fill as dense as their Magnum fill in the action area, I don't think a metal pillar adds any support value.

 

[Rocketvapor]

Following.
I'll be bedding my first action soon.
I think the shrinkage is percentage based. A thick area, maybe 0.5 inches thick might shrink 1 or 2 percent over time. That would be 0.005 to 0.010". Shrinkage would be both in thickness and away from the pillar sides.
Going over the pillars with a thin coating, maybe 0.010" thick over the tops and shrinkage would be less than 0.0001"-0.0002" (again 1 to 2%) in the thin topping. Maybe eventually showing some cracks but maintaining full contact, even with a round receiver.

 

[TaperPin]

Why have a wide flat bottom receiver if it’s ideal to just have contact at the pillars?

As wild as a barrel is before it pukes out the bullet, I have very little faith in a little aluminum cylinder. In fact, I bet you could insert a snug gauge pin into that pilar and with just finger pressure get it to move 5 tenths.

It would be interesting to see that bedding job when it was new.

 

[Cigarcop]

I think what Al is saying is bedding shrinks evenly across the inlet. If the action is sitting on the pillars the bedding will shrink away from the pillars leaving minimal contact for the action. If you apply bedding compound above the pillars the bedding will shrink the same amount across the entire inlet but maintain full contact with the action.

Andy I’m not trying to convince one way or the other but how do we know it shrinks evenly? Why have the back of the recoil lug bedded against if it shrinks? The sides are just going for the ride but I do know it’s not a pleasure to remove a barreled action from one of my bedding jobs and I’ve yet to have a customer tell me it’s got easier over time.

What I & you both know is I have some great shooting rifles out there that I bed with the pillars exposed and it certainly doesn’t seem to be an issue.
Again just my opinion, I’m not saying any other way is worse or better….. but I won’t be changing my bedding ways until I see a need.

 

[boltfluter]

Seems to me, whichever method you prefer, it is going to need to be freshened up every few years or so. Just my personal opinion and worth every penny! Lol!
Paul

 

[DaveTooley]

Sure... the epoxy shrinks a tiny bit. After a couple years, you've got an action living only on the pillars. What's the point of the bedding? I've seen a handful with the same issue Al shared. I've recently done a couple with the pillars buried... time will tell.

"living on the pillars" I don't think that's a bad thing unless you need the contact on the outer edges of a flat bottom action to manage torque. Bedding will shrink varying amounts depending on thickness. Fiberglass stocks will continue to cure and move after they come out of the mold. I'm in the camp of less contact the better. On round actions I use radiused undersize pillars. They act like v blocks. Let the bedding shrink, I don't care.

 

[Acyr]

Andy I’m not trying to convince one way or the other but how do we know it shrinks evenly? Why have the back of the recoil lug bedded against if it shrinks? The sides are just going for the ride but I do know it’s not a pleasure to remove a barreled action from one of my bedding jobs and I’ve yet to have a customer tell me it’s got easier over time.

What I & you both know is I have some great shooting rifles out there that I bed with the pillars exposed and it certainly doesn’t seem to be an issue.
Again just my opinion, I’m not saying any other way is worse or better….. but I won’t be changing my bedding ways until I see a need.

No doubt you have some great shooting rifles on the line. I also am not trying to say which one is better just trying to learn. When guys like Al post actual proof of shrinkage and its effects, it piques my curiosity.

 

[LVLAaron]

"living on the pillars" I don't think that's a bad thing unless you need the contact on the outer edges of a flat bottom action to manage torque. Bedding will shrink varying amounts depending on thickness. Fiberglass stocks will continue to cure and move after they come out of the mold. I'm in the camp of less contact the better. On round actions I use radiused undersize pillars. They act like v blocks. Let the bedding shrink, I don't care.

I've seen rifles with only V blocks (no bedding) kick everyone's ass. Collectively, we overthink a lot and don't test enough.

I dont have the balls to bed everything all at once (pillars attached to action. So I do the pillars first, and leave them the same height as the inlet, so the bedding is even across the whole thing.

In the end, I'm with you... I doubt it makes much difference one way or another.

 

[NorCalMikie]

Did the pillar shrink?….. I think not…. I’d rather have metal to metal contact any day.

Metal to metal anytime. Metal doesn't shrink!!
Same with a V Block. Metal to metal.