Do fiberglass stocks warp?

[sgt_jamez]

I have noticed a recent change in how the barrel sits in the barrel channel, plus when the action screws are torqued I get bolt binding when moving fore/aft.

The details on the stock (not sure if I am supposed to omit the mfg)
F-class stock
Bedded with Marine Tex (barrel centered in the channel with wraps of electrical tape)
Painted with good quality auto paint and clear coat
Action screws torqued to 40 in/lbs as measured with a Borka ATK and Wheeler digital FAT wrench
BVSS action with a 1" straight taper bull barrel

I took the action out yesterday and did a visual inspection on the bedding. I can't see anything that would cause the action to sit skewed in the stock. The bedding is not cracked or visibly malformed, and no foreign objects or materials were found. The barrel was floated enough that a dollar bill would easily pass the entire length of the barrel channel. Now, when torqued to 40 in/lbs, the barrel makes contact with the stock and the bill won't pass.

Additionally, when the rear action screw is torqued to spec the bolt binds in it's fore/aft travel. I tested this with torque values ranging from 15-40 in/lbs in 5 in/lb increments. At 35 in/lbs, the bolt moved freely. At 40 it was bindung up. Even at 38 it would move ok, but by 40 it was sticking. This leads me to believe there is a high point somewhere that when the action screws are torqued causes the action to flex enough to cause the binding. The high point, I'm guessing is the contact point of the barrel and the stock.

This condition is new. I've only had the stock a short time, and it's only been out to the range I think 4 times. I've always torqued to 40 in/lbs and the binding was never an issue.

I put this barreled action into a factory Savage F-class stock and when torqued to 40 in/lbs the barrel sits straight in the barrel channel, and the bolt moves freely. This leads me to think the stock has an issue but I don't know what else I can do to diagnose and resolve the issue.

Any input on this situation would be greatly appreciated. I can post pics if that would help.

[IMG][/IMG]

[Deadshot2]

If it were my stock I would remove the action and either buy some "spotting compound" from Brownells or make my own from oil based paint thinned with 3-in-one oil. Something in a light color.

http://www.brownells.com/gunsmith-to...-prod7599.aspx

Apply a thin layer of the paint/compound to the action, making sure it's both a thin layer and evenly applied. Just the lower half of he action is all that needs to be coated.

Set the action into the stock and squeeze it into it's fully seated position in the stock using your hands.

Remove the action then examine the bedding for marks from the spotting compound. Ideally there will be continuous contact visible as indicated by a uniform transfer of the paint

If there is only contact at front, center, or rear, then the bedding is not uniform when not under stress. When action screws are torqued the action itself is being distorted and/or stock is being "warped".

My guess is that it will need a complete re-bed to correct the issue.

When bedding it's essential to make sure there are no high spots in the stock first. Then, when the action is set in the bedding compound the action screws not be torqued. Action should merely sit in the bedding compound and be held in place with surgical tubing wrapped only tight enough to hold the action in the bedding and down against the reference points (Pillars, action block, etc).

As for fiberglass stocks "warping", any material can warp. Fiberglass is merely a reinforced plastic resin and if subjected to heat and stress, it can definitely behave like it's warped.

[sgt_jamez]

I will definitely try the spotting fluid trick. I'm curious though, if it were a bedding issue wouldn't this problem have existed from Day 1 after bedding? The offset of the barrel in the channel is a recent change. The rifle wasn't like this 2 weeks ago.

[sharpshooter]

Fiberglass will take a "set" when stressed in any particular direction. I found this out several years ago when I left aBR rifle in a hard case over the course of a winter. The compressed foam put more pressure on one side and left it touching the barrel, and over the course of 6 months it took a set.
The only recourse is to re-bed. I wouldn't even bother with checking for high spots, just rough it out and re-bed it.

[sgt_jamez]

Sharpshooter, what I don't understand is the rapid onset of this. One week it was ok. The next week it's not. The rifle was stored in a safe. Your problem took a whole winter. My stock went nutty in just a few days. Maybe it's my inexperience talking, but I feel like there should be something I can point to and say "this happened". The rifle was not subjected to any undue stress or conditions abnormal to any of my other rifles.

[Texas10]

Here is a link for you to read and why a catalyzed material like Marine-Tex isn't always the best for precision work. http://www.6mmbr.com/pillarbedding.html
Skip down the the paragraph about alternative components and methods.

I prefer to bed with epoxy, as I've been working with epoxys for nearly 50 years. Devcon 10110 is a metal filled epoxy and unlike catalyzed polyesters, shrinkage is virtually nil. I proportion my materials with a gram scale, and use heat to accelerate cures and to post cure (temper) the bedding.

I've built aircraft most of my life, so I know it has to be done right the first time. There are no chances for re-do's in the aircraft business. Fortunately for you, a re-bed is a likely prospect and one that is not hard to do.

What you probably experienced was the shrinking bedding finally overcoming the rigidity of the stock, and it "popped" into a new position. Grind it out and bed it again.

Good luck, and let us know how you did.

[sgt_jamez]

Ok, I'll check the contact patch today as advised. As for grinding out the Marine Tex, what's the recommended method? Dremel and diamond bits?

I have read that post on bedding from 6mmbr.com a number of times before taking the dive. I chose Marine Tex specifically because I read many positive comments about its stability and although I can't remember the source it was supposed to have been tested to have less shrinkage than Devcon. Opinions are everywhere so I chose a compound and rolled the dice. Looks like I crapped out.

[Deadshot2]

Ok, I'll check the contact patch today as advised. As for grinding out the Marine Tex, what's the recommended method? Dremel and diamond bits?

I have read that post on bedding from 6mmbr.com a number of times before taking the dive. I chose Marine Tex specifically because I read many positive comments about its stability and although I can't remember the source it was supposed to have been tested to have less shrinkage than Devcon. Opinions are everywhere so I chose a compound and rolled the dice. Looks like I crapped out.

The marine-tex "gray" is almost like Devcon 10110 but I prefer the Devcon.

As for grinding out the old bedding, a dremel tool with a coarse sanding drum is good. For the recoil lug area I just use a wood chisel and carefully "peel" the bedding from the front of the bedding block. Narrow wood carving chisels for the side and bottom.

You don't need to "Hog out" a lot to re-bed, just enough so that you get about 1/8" of new bedding compound over the old. I emphasize "coarse" on the sanding drum as you want some "tooth" for the new bedding to grab hold of the old.

Before going all the way, since you said this problem occurred all at once carefully examine the stock for any visible flaws that might have allowed it to separate from bedding block.