Well I don't remember who I told I was going to do this for.... but I have some free time tonight, so I am going to do the stock mod.
I am going to take a Bar10 stock and reshape it to look more like an M40 stock. From the bolt handle back. All you need are a heat gun, a vise, some gloves, and some time.
Alright guys..... well I hope that I don't have to say it, but PLEASE BE CAREFUL WITH THE HEAT GUN! I don't want to read on here that one of you guys burnt down your house, or caused your wife or moms to yell at you
The tools needed...
This is what you will start with..
Well a plane stock of course
Now mount your stock into a vise, or something else that will not move or anything like that..
Ok, now get your heat gun, and start SLOWLY warming up the stock.
Make sure that you go slow and as even as you can. Once you start to heat up the stock, you will start to see a pattern start to form. It looks kind of like a finger print. This is the rubbery film on the stock melting and becoming ply able.
Keep the heat on, and keep the heat gun moving. You don't want to keep it in one area and burn the plastic.
The part that we are working on now is the grip of the stock. The area right behind the trigger group. We are going to heat that up and slowly move it down, till the grip is just about vertical. Now while you are heating start making a plan in your head on how you are going to do this.
Think about how the stock is going to move when you start to form it. The top of the grip, where your thumb sits, is going to be stretched. While the under side, behind the trigger, will be compressed. So make sure that the top and the bottom of the stock are nice and soft.
Once the stock starts to become soft you will have to move quick. You don't want the plastic to be so soft where it starts to bubble, but not to hard where it will crack or anything like that. If you have a heat gun that has two settings, now is the time to switch to the lower setting. This is to make sure that you are able to keep the stock at the heat that you need so you can form it.
You are now going to want to grab a wooden spoon, or something like that. Again make sure that it is an old spoon so your wife/mom wont kick your butt for using it.
Use the wooden spoon, or even a gloved hand, to form the area that you are stretching and compressing. When you are compressing the area that the trigger group sits in you will have to watch the spot where the trigger guard sticks into the stock. If you go to much you will close up that area, but this can be fixed with a dremmel at the end of the process.
Here you can see the stock just before I started to pull it down to get the vertical grip that I am wanting...
Here you can see as I am starting to bend as well. This bump can be taken off at the end with a dremmel and a sanding drum.
When you get everything set the way you like it, let it cool down. It should not be even warm to the touch. Just like your mom making cookies, let it cool before you touch it again!
Once cool go back to your vice, or what have you. Now we are going to lift the back of the stock back up. You can see the finished product in the pic above

. Do the same thing that you did before. Keep the heat on the lower part of the stock, as well as the upper most. You are going to want to make sure that the lowest part of the stock is as warm as it can get without burning it. Do to us stretching this part, and not wanting it to tear or anything like that.
So get the heat going and the same as before, go slow and make it as even as you can. Pull up on the back of the stock, lifting it up until it is where you like it.
Now onto the hand hold portion of the stock. This is probably the hardest part of the entire process.
Put your stock upside down in your vise so you can work without trying to push up.
Like the other two times, heat up the area to be molded and start to warm up. Again slow and not to hot to quick. Once you get it to a nice ply able state, I take the end of the wooden spoon and poke it in the center of the area to be molded. What we are trying to do here is fold the top inside the lower parts. You are trying to make a " V " with this part.
Keep the heat on the stock and keep forming as much as you can. When you get the plastic to fold in on itself, form to the shape that you need.
When you get it to the shape that you want, start to heat the inside as much as you can. This the ONLY time you want to melt the plastic! Keep heating the inside of the " V " until you can see it start to bubble. Now quickly shut off the heat gun, put down and start pushing the two sides together with your hands. I really hope you are wearing your gloves at this point as well
Keep your hands moving and you won't burn them. And keep pressure on the sides till it stays together, and keep pushing on it for a while until it starts to feel cool. The more you move your hands and keep it formed, the faster it will cool as your gloves will absorb some of the heat.
When you are done you should have something that looks like this....
Note that I didn't go to far back, and that I can still use the original sling mount point.
A trick that I used to form the hook of the stock, is to use the area between your thumb and fore finger. Wrap it around and slightly squeeze. This will give you a nice rounded shape.
After all the work this is what your final project should look like.....
Now as soon as the stock is nice and cool, I am going to go back with my dremmel and smooth some of the areas. As well as go in with some body filler and smooth out the seam that we made while making the stock hook.
Due to the top of the stock being lower now than it was before we modified it, I am going to make a cheek riser as well. I get some plastic sheet from my local hardware store. Heat it up over a burner on my stove. Then put the soft sheet on the end of the stock. This will give you a nice tight fit for the riser.
Take your dremmel and cut to shape. Get some bolts, with some Florette style nuts. Drill holes through your riser and the stock. Run the bolt through and you are good to go.
If you want the riser to be adjustable cut slots in the riser, and you are good to go.
If anyone has any questions or what not just ask