Carbon fiber stocks - DIY tinkering

[hpmr]

Well, after using it for a season my mind started to work on how I could improve it further. As described in a post above, I began to research better components - stiffer foam core and carbon fiber sleeve (the latter heavily inspired by a youtube clip from the Sako factory, showcasing how they make their carbon fiber stocks).

I got hold of a better/stiffer foam core called Divinycell. In addition to being stiffer, it was also easier to work on. I started out with the normal procedure laminating foam core and carbon fiber:



Shaping is primarily done with a sharp knife, wood files and sandpaper.



The action is secured with a M6 bolt going thru the grip. I glued in a flush cup as a socket for the bolt head.



The socket was also secured with a couple of layers for carbon fiber cloth. To make sure the carbon fiber wrapped around the grip area while the resin cured, I used peel ply and thumb tacks.



After a couple of layers carbon fiber sleeve and some sanding, the stock looked like this:



Cutting out the barrel channel:



Two layers of the carbon fiber sleeve amounts to an almost 2 mm thick carbon fiber shell:

 

[hpmr]

I added a Spartan bipod flush mount:





I then finished it of with a layer of cerakote matte clear, and the final weight was 20.3 oz.



The cerakote has impressed me. I can be pretty rough on my equipment, but the coating still stays fine (setup here is 280AI and March 2.5-25x52).

 

[hpmr]

The christening of the new stock went very well

 

[Ice-kub]

That's amazing work! I would love to give something like this a try!

 

[BCsteve]

Looks like you got the hang of it pretty quick!

 

[TaperPin]

560 grams (with sling studs), so approx. 19.7 oz.

That’s really good - anything under 20 oz is a home run.

 

[hpmr]

I did get a few questions in the inbox that I might as well share here. I've tried a few different carbon fiber cloths. On my first stock I used a 200g plain weave 3k cloth. It was okay, but somewhat "stiff" when wrapping it around the core. I did 3 layers with this quality.

On the second (and third) stock I used a braided carbon fiber sleeve. To get the necessary diameter needed to pull it over the foam core mold, I used a 125 mm sleeve (diameter with the weave at 45°, but it can contract down to 37mm or expand up to 162mm diamater. The quality was 430g 6k, so it was quite heavy (and super strong). Two layers with this.

On the forth (making stocks kinda get addictive...) I used a "hybrid fabric" - 200g Carbon fiber and Twaron (=kevlar). Its been good, all though I can't really say it has performed any better than the more standard carbon fiber cloths.

Regarding the process, and making the different cf layers bond, I've been carefully degreasing and/or light sanding the surface between the resin applications. From what I've understood, the resin/epoxy produce an oil-like substance when curing (don't ask me about the details here, as this is not something I understand...) If its gonna be a while between the layers I've made sure the stock is properly degreased, so that the new layer bonds well to the previous.

The raw carbon fiber is a cool finish, but it can be somewhat slippery when wet. The matte cerakote has impressed me, but I prefer a bit more texture on my stocks. On the last two stocks I have used epoxy paint as a base (this is super strong), webbing spray paint for texture, and finally a 2 component matte clear spray paint to lock in the finish. I've been pretty happy with this method.

I'll add some pictures of the third stock to show how the finish turned and (and some hunting pictures for good measure). The goal with this stock was to get a bit more of a "classic" character, but still a reasonably vertical-ish grip.

 

[hpmr]

For my forth and last carbon fiber stock (at least for now...) I took a more traditional path, as it's both a bolt rifle and a more "classical" hunting stock. Having hunted with a straight pull (R93 and R8) for more than 10 years I decided it was about time to get a bolt rifle again. As I carry the rifle in my hand alot while stalking, I prefer a flush magazine (meaning really flush, not like Tikka 3rd or the Hawkins precision hunter magazine), I want the magazine to be double stacked with possibility for top feeding and minimum 4 rds capacity.

That didn't leave me with too many options, so the next gun in the cabinet was a Sako 85 chambered in 30-06. Great caliber, but wrong caliber. I really love the 7mm's.



Being extremely satisfied with the 280AI I've used the last years, a new barrel was inbound. And why stop at carbon fiber stocks?



The stock was made in the same fashion as the last with divinycell foam core. The design and ergonomics lends a lot from the original Sako 75 (one of the best hunting rifle stocks imo), but with some minor modifications.



Rivet nuts were epoxied in to the core making threads for the recoil pad and sling studs.



In addition to the epoxy bond with the foam core, the rivet nuts will be wrapped with the carbon fiber, anchoring them to the shell.

 

[hpmr]

On this stock I used a carbon-kevlar cloth. I can't really tell any big difference/advantages from the all-carbon cloth I've used in the previous builds. After the lay up and vacuuming it came out at 516 grams, ~ 18.2 oz.



Another upgrade (which is both insanely good and expensive) I made to the rifle was a Bix'n Andy trigger (adj 200-800 grams).



I also opted for the same finish as I did on my previous build. The base color is an epoxy paint, webbing spray for texture, and then a top coat with matte clear two component car paint.

I've been using this rifle extensively this fall, and it's been pretty good. Carrying it in one hand for long parts of the day has not been to exhausting. It being a light weight gun was really appreciated when packing out a successfull reindeer hunt.








The next on the to-do list is finish a pillar bedding. Probably not needed, but why not.

 

[gpo1956]

I really admire your workmanship and mechanical abilities!

 

[Mtnmilsurp]

(Name your country/continent) pioneer spirit on display. Guess I was showing my bias because I’m an American as are most posters here. Didn’t mean to step on any toes. Impressive regardless of the origin of the craftsperson (may not be male).

"...inside every European is an American trying to get out..."

 

[hpmr]

I really admire your workmanship and mechanical abilities!

Thanks!

 

[hpmr]

"...inside every European is an American trying to get out..."

This is very true! (At least in my case…)

 

[dster3]

Impressive work! Youve got me thinking about a 22lr of mine that needs a new stock...

 

[CapnKM]

Really nice work on all your iterations. It doesn't seem like you're having any strength issues but if they behave funny under stresses in different directions I'd second what @IdahoFF suggested and say to orient your layup to act (near) isotropic: 0/90 | +/-45 | 0/90 | +/-45 | 0/90.

Forgive me if I missed it, are you using an air-cured resin on your stocks? If so that makes it a tempting prospect for the home-gamer (since I don't have an autoclave).

 

[hpmr]

Really nice work on all your iterations. It doesn't seem like you're having any strength issues but if they behave funny under stresses in different directions I'd second what @IdahoFF suggested and say to orient your layup to act (near) isotropic: 0/90 | +/-45 | 0/90 | +/-45 | 0/90.

Forgive me if I missed it, are you using an air-cured resin on your stocks? If so that makes it a tempting prospect for the home-gamer (since I don't have an autoclave).

Thanks! The stocks have taken some abuse, but they have held up pretty good, so I guess they are solid. For the stocks where I used plain weave the second layer have been 45(ish) degree to the first and third layer. The two stocks where I used the sleeve the fibers were more similar oriented, but it doesn’t seen to affect the strength.

I’m using air-cured resin (in a vacuum bag). Wish I had an autoclave so I could use prepregs, but this is a low tech garage project I’ve been looking at vacuum infusion, that might be the next step. Or maybe try making some forged carbon fiber parts.

Its a slow time for projects at the moment. Time is spent digiscoping deer and trapping with the kids.

 

[TaperPin]

I’ve been looking at vacuum infusion, that might be the next step.

There are some great vacuum infusion videos showing an airplane building trying different epoxies and the effect of different infusion enhancing coarse cloths.

I was quite excited to try it, but obtaining thin infusion rated epoxy in small amounts seems quite hit or miss.

 

[Mt Al]

but this is a low tech garage project

Well....your low tech garage is way higher tech than most!

Very impressive work and thanks for taking all the time to share what you've done.

 

[hpmr]

There are some great vacuum infusion videos showing an airplane building trying different epoxies and the effect of different infusion enhancing coarse cloths.

I was quite excited to try it, but obtaining thin infusion rated epoxy in small amounts seems quite hit or miss.

Yeah, there are lots of good videos, instructions and how-to guides. I find Easycomposites yt channel really informative. They also have kits, (infusion) resin in bulk etc. and ships worldwide.

 

[hpmr]

Well....your low tech garage is way higher tech than most!

Very impressive work and thanks for taking all the time to share what you've done.

Thank you! And sorry if I come off as arrogant calling it low tech. The purpose of the thread was to show what can be done with relatively basic equipment, and with no prior skills or experience with resin and carbon fibers - but lots of patience, trying and failing... Especially carbon fiber skinning in a nice entrance into this game. Similar to other threads on this topic, this one hopefully might inspire some of out the starting blocks

I had to do some adjustments to the last stock after this hunting season, meaning I also have to re-do the finish. I'll try to post some pictures of the process as it progress.