Machining an aluminum rifle chassis (stock)

[shermama96]

I'd like to start off with a big hello, I am totally new to this forum and this is my first post.


I own a Ruger american in .223 and the stock is pretty lacking. The plastic stock flexes so much while shooting at a bench that stock really is no longer free floating. When I stumbled upon these so called "chassis" system's I kind of fell in love with the idea. They are super ridged, dissipate heat from the action, and in my opinion kind of look cool even though I'm sure most traditional guys clench a fist at the idea of one.




Being a self-supporting college student there was not way I could afford to spend 500 bucks on one. I have a pretty extensive machining background, so I figured I could make one . I have access to several university shops so lack of tooling is no concern. I have a pretty good idea on my different set-ups and operations, my questions lie mostly in the design. I have a lot of machining experience but have never really bridged the gap between machining and gunsmithing, if you could even call this project gunsmithing. Therefor I don't really know the functionality of some of the stock inletting on the molded stock. I plan on using the internals of the original stock as a reference and the exterior will just be machined to my cosmetic liking. I think I'll copy a lot of the exterior of the first image which doesn't look too complicated considering all be doing all the milling manually without the use of a CNC. I will definitely be using a thread on AR style stock as well just out of simplicity. I have the Ruger American Ranch, which only has a 16.2 inch barrel so my overall piece of 6061 will end up being roughy 1.5x3x 12-16" depending on what I can get for cheap on ebay.


The Ruger American uses what Ruger calls, "power-bedding" to bed the action (I HAVE INCLUDED PHOTOS OF THE STOCK IN THE LINKS). Its the two steel v-shapes that the stock is molded around. The action contacts the stock on the flats of those v's and only those 4 points. There is not recoil lug or anything like that , just those v-blocks. I would imagine that any other cutaway in the stock is just clearance for other parts of the action. So one of my main questions is, if I were to mill the pocket for the trigger assembly as a flat bottom pocket roughly matching the shape in the photo, as long there is clearance for everything, it shouldn't really matter right?





My second major question being, "As long as I mill the magazine well to about the right size, and included the notches at the front and back for the magazine to catch on, that should work fine enough to avoid feeding problems. This one might seem to answer itself I just figured as long as I'm writing this memoir of a post I might as well be doubly sure.


Final question, the shops have horizontal mills, but being on spring break I am not sure if they have a 1 3/8 convexed radius cutter that would be needed to do the main inletting of the barrel, if they don't any ideas on cutting that radius cove without either a horizontal milling cutter or a large ball nosed end mill.

Any help would be greatly appreciated, sorry for the super long post.

 

[shermama96]

The forum is telling me that I need at least 3 post to post links, please let me know if any of the 4 photos did not show up, thanks.

 

[Tozguy]

Interesting project. I have never worked on a Ruger American in 223 but it surprises me that there is no 'recoil lug' or abuttment. A recoil feature might be built in to the V blocks. May we see a photo of the underside of the action please?

Re the inletting, why not just copy the OEM trigger well and magazine well inletting from the plastic stock?
Re the barrel channel, if the gap along the top of the barrel channel is not too wide, the channel itself does not show. You might be able to get creative with the cutters that are available to you.

Update:
From the photos I found on the internet it appears that the V blocks fit into grooves in the action so recoil is taken by one (or both ?) v blocks. It will be important to have the two V blocks cut accurately in the new stock. Personally I would make the front v block to take all the recoil and allow the back one some front to back clearance in the action grooves.

 

[shermama96]

you can see the flats on the receiver that interface with the bedding blocks. As for the question on the trigger well, I plan on copying the shape perimeter of the shape of the trigger well, I know realize my initial question was poorly worded. There are sections in the trigger well at difference heights and different angles as you can see in the photo that appear to offer no functionality and would over complicate the machining. Is it really necessary to machine the stock exactly as shown in the photo, or because the action only contacts at the v's, would it be okay to match the shape of the well but have a flat bottom throughout the well and have all the cuts at the same depth just for the trigger assembly to clear.

 

[Tozguy]

Thanks for the pics.
The new stock does not have to match the OEM perfectly. The new stock should only touch the receiver at the two v blocks and not touch any part of the barrel, bolt or trigger.

 

[shermama96]

Thanks for the pics.
The stock does not have to match the OEM perfectly. The new stock should only touch the receiver at the two v blocks and not touch any part of the barrel, bolt or trigger.

Thank you for the quick replies, I do appreciate the help. I figured that, just wanted to get a second opinion from someone more experience.

 

[Tozguy]

Looking forward to seeing how she turns out
Good luck.

 

[Holescreek]

I just finished my 4th aluminum stock this summer. It' snot hard to do but a horizontal mill would not be my first choice. I cut my barrel channels with a ball nosed end mill with multiple XZ moves to cut the radius appropriate for the action. Depending on the type of rifle I'm building I sometimes remove more material to allow for bedding. On this last rifle I didn't use any bedding at all.

I typically make up a CAD drawing and form my cutouts to fit the components I'm using for the build if I'm not using original parts. On modern rifles where original parts are in order I just mimic the OEM inletting.

 

[shermama96]

I just finished my 4th aluminum stock this summer. It' snot hard to do but a horizontal mill would not be my first choice. I cut my barrel channels with a ball nosed end mill with multiple XZ moves to cut the radius appropriate for the action. Depending on the type of rifle I'm building I sometimes remove more material to allow for bedding. On this last rifle I didn't use any bedding at all.

I typically make up a CAD drawing and form my cutouts to fit the components I'm using for the build if I'm not using original parts. On modern rifles where original parts are in order I just mimic the OEM inletting.

Wow that looks freaking awesome, I'm attemping to make a cad model based directly off the original. My biggest problem is I'll be working in a student shop on a college campus three hours from home, where I live in an on campus apartment. Obviously a firearm in any of these places is a big no no, so my CAD model has to be perfect because I really won't be ably to test fit anything.

 

[Holescreek]

Here's a link to two of my early stocks:

http://www.hobby-machinist.com/threads/54r-aluminum-mauser-stock-project.33197/#post-312378

http://www.hobby-machinist.com/threads/mosin-rehab-project-2015.35842/#post-338008

You're going to find that you're going to need access to a rotary table for modern mag wells or going to need some special jigging to get the side tapers. Other than that it's all about basic milling and processing the cuts in the correct order so you don't cut away a surface you're going to need for clamping later on.