Lightweight Kimber Build with Custom Carbon Fiber Stock

[Hunthigh1]

Unbelievably cool rifle!!

 

[BREAKCONTACT]

Absolutely! I’m putting this out there to encourage others to try it too. I’m no composites engineer, just going for it and seeing what happens.

Overall, the whole stock has at least two layers. I’m working from a box of super generously donated scraps, and I didn’t always take the time to look at what weight the fabric was - I just went by feel, thick vs. thin. From the forend back:

- The forend tip has two thinner layers, I think 3k each. This area shouldn’t see a whole of stress/impacts, and the thinner fabric contours over the tight radius better.
- Where the forend cap meets the straight portion of the forend, the layers overlap, giving strength to the front sling lanyard hole.
- The main section of the forend is two layers, one thick and one thin. I want to say one 3k and one 12k? Then the barrel channel is made up of two thick (12k?) layers. I think this is mainly what makes the forend so rigid.
- The action area of the stock has all the inletting structure covered earlier, and the same thick and thin layers as the forend on the outer skin of the stock. I was originally planning to put extra layers here, but didn’t feel it was necessary after the second layup.
- The grip-to-inletting area junction, down through the grip, and back through the wrist all have 3-4 layers of thinner (3k or maybe 6k) fabric. I used thinner carbon to wrap the contours better, and did extra layers at alternating fabric orientations because these areas have the smallest cross-sections, and need to be very stiff.
- The butt section has the same one thin and one thick layer as the forend. Towards the end of the butt there are some extra pieces of thin 3k fabric, but solely for the purpose of building up dimensions to match the recoil pad.

Overall, I’m very happy with the stiffness. Would I put the bare stock spanning between two logs and jump on it in the middle? Probably not. I think it’s more than adequate, but not ridiculously overbuilt, which achieves the strength and weight I was after.

Awesome, thank you for this. How's the shoot ability of that geometry?

As an aside for anyone looking to buy carbon for doing this yourself, the "K" number of fabrics has to do with tow construction and not thickness, that's the oz/GSM number. And for building a stock with lots of compound and complex curves you would want to use an "X harness satin weave" with higher numbers being more formable fabrics with a tradeoff in stability and some other properties. I'm probably going go go with all 5 harness satin weaves for my attemp, and I might use some unidirectional tapes in some of the reinforcement areas.

 

[BREAKCONTACT]

I should also note, 3k, the higher the K numbers are going to be more difficult to conform to the curves

 

[RepeatPete]

Awesome, thank you for this. How's the shoot ability of that geometry?

As an aside for anyone looking to buy carbon for doing this yourself, the "K" number of fabrics has to do with tow construction and not thickness, that's the oz/GSM number. And for building a stock with lots of compound and complex curves you would want to use an "X harness satin weave" with higher numbers being more formable fabrics with a tradeoff in stability and some other properties. I'm probably going go go with all 5 harness satin weaves for my attemp, and I might use some unidirectional tapes in some of the reinforcement areas.

Shootability? I’m all loaded up to go shoot a lot this weekend, so I’ll let you know. However, my previous stock build had a very similar grip, similar recoil pad height, and a negative comb (although with a funky curve) and I thought it was very easy to get behind.

I degreased and loctited the Talleys, mounted up a SWFA ultralight 2.5-10x32, and still have an ounce and a half to spare.

 

[BREAKCONTACT]

Shootability? I’m all loaded up to go shoot a lot this weekend, so I’ll let you know. However, my previous stock build had a very similar grip, similar recoil pad height, and a negative comb (although with a funky curve) and I thought it was very easy to get behind.

I degreased and loctited the Talleys, mounted up a SWFA ultralight 2.5-10x32, and still have an ounce and a half to spare.

View attachment 747164

That's awesome, looking forward to hear how it does.

 

[RepeatPete]

Magazine:
84M hunters come with a removable box magazine, but apparently the earlier ones had some problems. Mainly that it’s extremely hard to fit the third round into the magazine, and then with three rounds the magazine doesn’t latch into the stock when the bolt is closed because everything is too tight. Mine has both of those issues. The blind magazine version, present in Montana and Mountain ascent versions, can hold 4 rounds. So I ordered the blind magazine box, spring, and follower from Kimber.

The factory DBM is 2.6 ounces and the blind setup is 2.4 ounces. However, just the metal magazine box is 1.8 ounces. So, I decided to try and recreate it in carbon fiber.

I poured a mold off the inside of the metal magazine box with mold rubber. Then went on to wrap that mold in carbon, but the mold rubber compressed too much, and the interior dimensions ended up too tight.
Then I poured another interior mold with epoxy resin, wrapped it with CF using my electrical tape method, and the dimensions were much more accurate.

I am also working through some feeding issues, as I knew could be the case with a Kimber. I polished the feed ramp and softened the edges of the feed rails while also opening them up slightly, which seems to have helped a lot. Then I got a milled Remington 700 follower and spring, per some suggestions from 24 hour campfire. Still playing with what combinations work best.

Factory Metal Box Magazine


Carbon Fiber box magazine


Factory polymer follower


Remington 700 milled aluminum follower


Currently I’m at 4 pounds, 14.5 ounces with the carbon box and the polymer follower, which seems to be the best feeding combination, though not perfect. Needs a bit more tinkering.

 

[Schmo]

Very very well done sir! Absolutely amazing!

 

[RepeatPete]

Well, it shoots as good as it looks - a ~ 1.5” 10 shot group.

 

[mthayr]

 

[RepeatPete]

Well, at about round #95, I noticed a crack in the top of the thin section between the grip and the buttstock. The carbon that cracked was about 1/32” thick - I had sanded almost all the way through and there was essentially no material left. No worries, easy fix. Add more carbon, sand smooth making sure not to sand too much, and re-paint. I also added some Lucid skateboard grip to the grip and forend, and spread some E6000 on the inside of my ultralight sling for some traction.

Bare rifle is now 4 lbs, 14.6 oz, and ready to hunt, with a sling and 4 rounds of 143 ELDX: 5 lbs, 2.3 oz.