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  #16  
Old 08-29-2019, 04:29 PM
hara-julu
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Very nice! popping out an action is always rewarding. With a carbon fibre stock, are there other potential applications for the marine-tex? Like the landing point for your offhand grip, or an platform for biped? I'm thinking about the "hard where it needs to be" aspect of a really light stock. HJ
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  #17  
Old 08-30-2019, 06:43 AM
Gobber
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HJ-
You hit the nail on the head about that rewarding feeling of popping out a bedded action. I always sweat the load waiting for the compound to cure worrying about something getting stuck with a mechanical lock. This one came out really well, almost too well in fact as I can actually see the wrinkles of release agent that puddled a bit before drying. Getting nit-picky, but always striving for the best outcome. A little sanding and shaping will square it away.

Your point of ‘hard where it needs to be’ is well taken and one of the advantages of fabricating the stock in sections. Wherever it needs to be reinforced, just add a few more layers of CF fabric or fill with a CF chop & resin mix. That is one that I will be trying soon on a cam locking fitting. It’s something that I’ve been working on, but it’s only in the concept stage right now.

As for a platform for a bipod, I have gone with a biathlon style slot rail before and it works very well for mounting bipod, hand stop or sling stud under the forearm section. Also nice because it is recessed and leaves a smooth surface for the support hand to slide. On this build I want to be able to use quick disconnects to mount a bipod and/or light on the fly. That lends itself to a section of picatinny rail under the hexagonal forearm tube. But either one could be.

I see where you are going with the ‘other applications’ of Marine Tex in fabricating various attachments. It could be used to make items like a forearm hand stop or a magazine well hand grip, but it is a dense material that is good as a compression medium for holding a receiver against the stock body. For making external attachments, it is a bit heavy and a large chunk of it could crack on impact.

Got something that is way better coming up- lost foam carbon fiber forming is what I like to form the grip. It’s a really cool way to make attachments that are form fitted to most any shape, light weight and as rigid as you want depending on how many layers of CF that are added. For the removable grip, there is an even better method for fine tuning the fit that gives a really good finish when the CF layers are applied. Post #12 describes the first half of the process of forming the plug for the grip. The same process can be used to make most any form desired that will have a CF (or fiberglass, Kevlar, etc) shell applied. How’s that for a teaser
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  #18  
Old 09-03-2019, 05:02 PM
Gobber
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After some sanding, the action bedding is shaping up.
Had that problem of the safety being hard to engage when the action was tightened down and it turned out to be the side wall of the bedding area was in contact with the bolt blocking bar.
After relieving that area, it works like a charm.


A bit of flat sanding to even things up.


Prior to mounting the grip, needed to bed the trigger guard and mount the threaded sockets into the stock body.
Here is a shot of the threaded socket made from grinding down a long connector and then cutting vertical grooves to give better mechanical lock.
The little dab of modeling clay helps gauge the depth that the socket is set while creating a void for a screw to poke through.



This is where another ‘two step forward, one step’ back situation popped up.
I placed the threaded sockets too far forward toward where the trigger guard releases from.
This did not leave enough room for the forward screw to fit inside the grip.
Only became evident when figuring out the positioning of the grip.


Oh well, that is why extra parts are purchased.
So I got to do a destructive test of how well the threaded sockets hold up.
Figured I could lock down a 5mm screw and twist the threaded socket out with enough force.
After clamping vice grips onto the threads of the screw and twisting really hard, all it did was grind off the threads on the shaft of the screw.
The socket did not budge at all. In adding more torque, I could tell the shaft of the screw would snap off well before the socket would break loose. Good to know!
In drilling out the socket’s center with increasingly larger drill bits, it generated enough heat to begin smoking.
The combination of friction heat and a drill bit that was the diameter of the threaded socket finally pulled the last fragment of the socket out. Only took a few minutes, but I am very satisfied with the bonding strength of Marine Tex.


After cutting socket holes further back, I ground down another set of threaded sockets and reset them into place with a mixture of Marine Tex and CF chop.
I added the CF to help reinforce the larger voids left by the previous holes.
The mixture looked like a nasty hair clog pulled from the bathroom drain, but it set up really solid.


I also used the same epoxy hair-ball mixture to bed the threaded socket and rear section of the trigger guard.
Bit of pain to jam it down into the cracks, but it will give a solid, yet non-abrasive, finish for the glass filled nylon of the trigger guard.


After cleaning up the excess, might need to ‘skim coat’ a bit over the surface to give it a smooth finish.
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  #19  
Old 09-17-2019, 08:55 PM
Gobber
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Been a while…

Sometimes life gets in the way of the fun stuff…you know the story…

Now back at it.

Finally- it’s on to the grip.

This is one of the coolest parts of the build. Seriously, because this is how you can make all kinds of great parts.

I realize that these posts are getting down into the weeds so-

TLDR - Formed a grip using a foam core with carbon fiber overlay.



For the details - read on...

A while back I made the initial foam block with a rough cutout.

Now it’s time to shape it into the internal core of the grip.

The Smooth On rigid foam is the medium custom designed for making a piece like this.


You have already seen how to make the initial ‘blank’, which is a block set on a section of poly pipe.

Poly pipe is great because the foam will cling to pipe’s surface but it will pull loose when clamped in a vice.

Basically the surface is a built in releasing agent.

To get the base shape started, mark off the lines where the contours of the hand will lay.


All these grip contours can get really technical, but that’s the beauty of a removable grip- I can get as picky as needed later on.

A really good write up on grip design from a guy who knows his stuff - https://www.pyramydair.com/blog/2019...-stock-part-3/

For now, this stock needs a grip!


Also mark off where the grip will mount to the chassis so there is a comfortable reach to the trigger.


Then determine where the internal grip screws will be located. I know- a bit out of sequence, but you get the point.
]

The plan is to sand the plug down to the general shape and then take it down even a bit further to create a skinny core that can be built up.




Next step is to sculpt the final shape of the grip core.
However, trying to get the exact desired shape from sanding down the foam alone is a pretty lengthy process and when (not if) you remove too much material, it is a pain to glue a chunk back on just to sand it back down.
Been there, done that.

The stuff that makes this so-o-o much easier is a very light-weight epoxy dough.

This stuff is the bomb!


It is really easy to work with by kneading together two equal balls of the dough.
This will give about 70-90 min of worktime depending on temperature.


Wear gloves with this stuff as it starts out quite sticky and limp but as it starts to cure, it gets firm like modelling clay.
Sorry- no pics as it is a mess to work with.
With just a bit of practice, it is very easy to shape, trim and smooth with a bit of water.
It is very light weight and once cured, it is rock hard.




After curing overnight, it is easy to shape and sand to precisely what you want afterward.
Trick is to lay it on thick so you can sand it away.


Strap sanding gives nice contours and flat sanding give good planes.








Note that the dimensions of the final mold plug should be a bit smaller in all areas as the CF builds it back out by 1-2mm.
I am realizing that a narrower grip is more comfortable for extended use- just my $0.02 worth, YMMV, etc.

Once the shape is good, a wet layup with 2 layers of 12K CF gives a nice, rigid structure.


Next morning it’s cured solid enough to de-bag and unwrap.
Lesson Learned - to get the CF to better lay down in corners, mold a slug of clay then wrap it in cellophane. This gives pressure where needed and comes out easy.
It still feels a bit like unwrapping a present to see what you have.


This one came out this morning early (couldn’t wait!)


After a bit of trimming with the diamond wheel and belt sander touch up – it's looking like a proper grip.
Since I can only add 21 pics, refer to TLDR

Last edited by Gobber; 09-18-2019 at 04:11 PM.
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  #20  
Old 09-18-2019, 02:23 PM
Gobber
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So here is another Lesson Learned – the first grip turned out to be what I call a ‘single-position’ grip.
It was shaped to allow the right thumb to rest on the right side of the grip in order to work the toggle action much like most all biathlon stock profiles.
After using it for a while, I noticed two things.
First was that it put pressure on my lower thumb joint that eventually got annoying.
Second was that I missed being able to use a standard wrap-around grip when carrying the rifle or shooting prone.


Solution – form a two position grip.
In forming the plug for this grip, I shaped it with the thumb on the right side only, making sure the lower area fit the crease of my lower palm and filled the voids of the shooting hand.
This accommodates a standing position with rapid cycling of the bolt.
Next I cut out the upper rear area to allow the thumb to wrap around.
Pretty simple change that makes a big difference in comfort and usability.
This one is more fitted to my hand with finger grooves and a bit more width.


This third version is a ‘two-position’ grip that has been slimmed down a bit and has a more generic profile without finger grooves. At some point the foam will most likely be removed via acetone.


More later after some fine tuning of the shape and being fit to stock.

Last edited by Gobber; 09-18-2019 at 03:54 PM.
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  #21  
Old 09-18-2019, 03:48 PM
Gobber
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Cheek Rest

TLDR - Skeletonized comb fitting


Here are the details...

Here is where the K.I.S.S. principle really shines. I wanted a cheek rest that was light, strong and simple to fit.
It doesn’t need to be adjustable on the fly, once it is adjusted, it stays put.

Solution – make the mold from a bit of ¼ round floor molding glued to a metal plate. That’s it and the mold survives several layups.
This is actually the first item I made and practiced vacuum bagging with fiberglass just to get the process down.
The part was simple and small so different versions were cheap to make and actually yielded a useful product, eventually.
It also really demonstrated the difference in weight, thickness and rigidity between fiberglass and carbon fiber.

My photographer was walking by during a previous layup.


Some sloppy stuff going onto the mold.


Not very pretty still stuck to the mold.


After prying it loose.


I extend the lower flat area out a bit to get some excess flat stock for other uses.
A set of plastic automotive pry tools are really handy for separating CF from the mold. Harbor Freight is the ticket.


Ended up with a small ridge at the base of the curve.
Just a cosmetic detail, but will put a small radius on the bottom edge of the mold for next time.


Shaping such a thin piece is quick with a diamond wheel and a bit of sand paper.


For adjustments, an oval mounting hole is cut to allow left to right fine adjustment.
Using a wooden block as a mount, the new Proxxon press makes nice symmetric holes.


Here is the edge profile of how thin the piece is but it is quite rigid


For height adjustments up and down a bit of tubing works great at a spacer.


If there is more surface area needed for back and forth on the stock axis, I will just make one longer.
You can really see the difference in surface finish between peel ply (outer left side above) and against the smooth mold surface (inner right side).
Doesn’t really matter for this one as I will do a light sanding on both sides prior to final clear coat.


The color and finish of the paint could be varied to taste or even a decal could be added for a bit of flair (if you’re into that sort of thing - I ain’t).
For now I like a hard surface but may add a neoprene cover later to see how it works.
I will also make up a mold that has more of a square shape to see how it works.

Stay tuned – working on something slick for the shoulder fitting. Well, it will be slick if it works.

Last edited by Gobber; 09-18-2019 at 04:34 PM.
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  #22  
Old 09-24-2019, 09:25 AM
Gobber
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Ok, need some opinions. I am at the point where I need to pick a forearm type.

Choices are –

Thick walled Half hexagonal tube.



Thin walled Full hexagonal tube



Both have advantages and disadvantages.
Half Hex Thick –
Pro – barreled action easily separated from stock
Con – no thumb over grip without touching the barrel
Pro – very robust thickness
Con – snagging – will have to find a shape for the tip that does not catch on things

Full Hex Thin–
Pro – fully encloses barrel for thumb over top grip (which due to the nature of this build, I never use)
Con – for disassembly there is not enough room to tilt the barrel high enough to remove the action without removing the mag well and trigger pack
Pro – a few grams lighter (but not really noticeable)
Con – not as robust as the thick walled hex section, screw mounts need to be reinforced, more susceptible to crack or break if impacted or torqued (hasn’t been an issue with a previous build)

I will be shaping the end of either one with a profile that will be functional and aesthetically pleasing.

Any thoughts or opinions would be appreciated.

Last edited by Gobber; 09-24-2019 at 09:30 AM.
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  #23  
Old 09-24-2019, 10:15 AM
hara-julu
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Question: Are you going to use this rifle prone? I would opt for the rigid half octagon, allowing for a bottom rail or bipod. An idea for the forearm is one fitted to your hand, so the "hand stop" is integral, just dreaming here... I think this is over-looked in custom stocks, and the pressure on the front hand in prone with an arm cuff can be pretty high. A proper radius "hand stop" with some angle down would complete the stock to arm picture and un-rotate the front wrist.
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  #24  
Old 09-26-2019, 05:59 AM
Gobber
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HJ –
Thanks for your comments on the CF stock project. Your points on a hand stop are well taken, but for this build I am going with a conventional picatinny rail because of the QD mounts I already have on my bipod and light.

However, the idea of a forward hand stop and sling cuff shooting style is one that I have not tried as of yet. For competitive biathlon style shooting, it is required. For me taking a prone long shot at crows that are making a huge mess tearing into neighborhood trash bags, I would want all the stabilizing advantage I could get which would mean a bipod. However, your point gets me thinking about how to improve an off hand stance for taking a more stable quick shot.

True story on the crows though. Had a group of them ripping into bags on trash day that looked like someone had blasted each bag with a shotgun out into the street. Why neighbors can’t just put their trash in a can is a whole different rant. Following week, I am working from home and mid-morning I hear five of these winged hooligans cawing up a storm. One of them posts up on the peak of the roof across the street and will not shut up. I crack the exterior door and line up a shot from four feet inside the front hall creating a ‘keyhole’ shot. At 65 yards, the round hits him hard and down he goes- got to love segmented subsonics. With a suppressed .22lr, the only sound is the very satisfying thud of the impact. Figuring the message is sent, I go to get a bag to dispose of the carcass. Interesting thing about crows, when one of their buddies goes down without a visible reason, the others don’t bug out. They fly right back to the same spot and make twice as much noise. See where this is going, right. I line up the same shot on #2 and down he goes. Very satisfying. At this point the other three are scattered about in trees and they are not happy. Sadly, I was now late for an appointment and had to leave, so I stepped out of my front door and they immediately bugged out. Retrieved the carcasses for disposal and was on my way with a satisfied smile.

Last edited by Gobber; 09-26-2019 at 05:04 PM.
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  #25  
Old 10-17-2019, 10:25 AM
Gobber
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Shoulder Attachment - Been contemplating a shoulder piece for a while that is light, but robust enough to set the rifle down on barrel up.

TLDR - Make a buttstock that is tough, light and adjustable on the fly.


And now, the rest of the story...

Background- For an earlier build, picked up a MEC shoulder attachment that is quite good.
PROS- Very robust, adjustable wings, travel and cant.
CONS- Heavy, only adjustable with wrench and made for use with a thick jacket.
The cool looking rubber nubs are not comfortable against light shirt.
Solved this with a neoprene sock.


Next was a 3D printed shoulder from https://briansamson.shop.
PROS- Great price, fits anything, light weight, comfortable, adjustable wings, travel and cant.
CONS- A bit delicate as you cannot really crank down the tension on the screws or it will crush the underlying structure.


What I realized is that my primary requirement is for a shoulder piece that can raise and lower ‘on the fly’ to various shooting positions without the need for a tool. Biathletes solve this with a solid, two position shoulder piece made for the specific standing and prone positions of competition. That is something I may toy with in the future, but it makes for a big hook at the bottom of the butt plate that will want to snag in the woods. What I want something that I can variably adjust for any position in between.

My concept is to use a cam lever to tighten a clamp fitting over a rod to allow rapid adjustment. It does not need the adjustable wings, because the shouldering surface will be fixed to a profile that works well enough for each position.

So here’s my initial concept - Use a 1 ½” segment of oval CF tubing to act as an internal clamping body.
Pack some CF + resin ‘hairball’ mix around the tube to make a tight fitting interior surface.


Once cured, cut out a gap to allow some flex for clamping that can also slide past the mounting spacers.


For the shoulder piece, settled on a 3 part form that would hold the clamp in place to put three layers of 12K CF to form the shoulder section.


Here it is with the CF wetted out and clamped in place to hold the weave in place.
Lesson learned here was to orient the weave at 45 degree to better conform to the arch.


Here is the cured shoulder piece with the CF clamping sections imbedded and the excess trimmed off.


A shot down the middle after trimming to fit the rod mounted to the stock.
For this one, I lined it with brass tube to allow it to slide easier.


Here it is clamped down in the standing position.


Here it is in the higher, prone position.


It’s all pretty rough looking as I want to make sure it functions properly before trimming it down to a thinner size and sanding it all smooth.
So far, it’s not bad. The shoulder piece is tough, light and comfortable against the shoulder.
I have actually bounced the rifle butt section down on the concrete (unloaded of course) and it’s solid.
Current issue is getting the right balance of the clamping surface ‘grippy-ness’ when cranked down and smooth sliding when loosened. Pretty close, but still a work in progress.
After a bit more use, I'll add a cap to the top of the rod section to act as a stop and make one for the bottom that is screwed into place so I can remove the clamping shoulder section.

More to follow soon...

Last edited by Gobber; 10-17-2019 at 10:29 AM.
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  #26  
Old 10-22-2019, 11:32 AM
Gobber
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Forearm

Settled on the half hex section of CF tubing for this build.
Makes removal of the barreled action much easier that the full hex tube section.


The trick was to line it up evenly with the barrel. Solution was pretty easy.
Wind duct tape around the barrel in two places to center the barrel within the hex tube.
Use this to position the forearm section into the main chassis section and trim the slot into the main body for it to fit.
A bit of explanation to this photo – the barrel has 2 winds of duct tape visible inside the half hex section.
The aluminum tube section slides over those tape collars to fill the rest of the interior space between the 2 split sections of hex tube.
This set up was from a previous build with a solid section of hex tube where I needed to be able to pull the aluminum space out the front after it had cured onto the main chassis.
What can I say, I’m cheap with the tape and just re-used the aluminum spacer.


To anchor it in place, used the same mixture of resin thickened with silica micro balloons and a bit of CF chop to give it a some extra reinforcement.


The next trick was truing it up so the bottom flat of the hex was parallel to the top rail.
After a bit of thought, used a section of aluminum flat bar stock centered on the top of the hex tube and lined it up with the picatinny sight rail. Actually worked pretty well.




Came out really solid. Also mounted the picatinny rail segment to the forearm.
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  #27  
Old 10-22-2019, 12:01 PM
Gobber
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Final Layer

After a bit of use and some final shaping, it was ready for the final layer of 12K carbon fiber. Wanted this one to have a little better ergonomics in the grip area.






To better fit the contours of the chassis section, cut the CF panel at 45degree angle.


Filled the voids by first lining the interior sections with gorilla tape and then with modelling clay.


In order to get the CF to better conform to curved areas, I molded sections of cling wrapped clay into the arched contours.




These clay filler sections were applied outside the layup of wetted CF, peel ply and breather cloth prior to placing in the bag.



All bagged up and vacuum pulled down.


Next morning, it came out looking pretty good.
Had to be careful as that flashing is a real knife edge.


Trimmed out the void areas.


Here you can see where the CF was banded around where the forearm section was set into the main body.


After a bit of trimming, sanding and fitting it was time for a bit of testing.
Fun afternoon putting some rounds downrange.
The adjustable shoulder section worked really well.
Very nice to get into a shooting position and be able to move the butt piece to the most comfortable position.


Last step will be to clear coat the surface.
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  #28  
Old 10-22-2019, 12:25 PM
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Turned out pretty good
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  #29  
Old 10-28-2019, 01:07 PM
Gobber
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Love that toggle action

https://www.smugmug.com/gallery/n-LHR2Qc/i-W6HHZzp/A
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  #30  
Old 10-28-2019, 08:53 PM
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Good job, labor of love.
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