Author Topic: .308 Texan Exoskeleton Stock  (Read 1482 times)

rcpro88

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.308 Texan Exoskeleton Stock
« on: April 03, 2018, 02:12:38 PM »
Hey Guys,

A month or so ago I made a titanium barrel tensioning system for my .308 Texan. When in my friends benchrest style gun rest, the Texan with the new tensioner shot a 10 shot group at 130 yards with 8 shots grouping 3/4" CTC and 2 fliers (which if included with the 8 shot group, it would have made it a 1.2" group). Then when I went to a range another day shooting off a bipod, I was getting significantly larger groups/grouped like stock. Since I never shot the stock Texan from my friends gun rest I have no data to compare my barrel tensioner too. So for now the results are inconclusive.

Digging around a little more I found that there have been a significant amount of comments/reviews that criticize Airforce guns for having hold sensitivity. This comes from the apparent flex in the aluminum receiver by the spot where the bottle meets the receiver. Then when the air rifle is shouldered, the torque put on the end of the bottle from your shoulder changes the direction the barrel points (slightly) relative to the scope. Originally I didn't really believe it, but combined with reviews made by reputable sources, modifications like wokgaurd and more famously mad dog stocks have actually given proven results. On top of reviews I find it suspicious that my Texan grouped poorly on a bipod but very well in a heavy benchrest gun rest (lined the Texan up, loaded it, pulled the trigger while standing to the side of the Texan) which virtually eliminated shooter error/held the gun the same every time.

So from here I decided to build a stock for my Texan.


  • St. Louis

rcpro88

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Re: .308 Texan Exoskeleton Stock
« Reply #1 on: April 03, 2018, 02:52:28 PM »
The stock is not yet done! I will explain my design.
Once complete, I will test for improvements, then I plan on "jeweling" her up. I will also mill out a lot of aluminum to save weight but maintain rigidity - hence the "exoskeleton" part.
My design is solely for long range shooting. I want a rifle to be as steady as it would be in a benchrest gun rest but be a hell of a lot more portable as well as built into the Texan so I wouldn't have tons of shit to deal with.
The stock in the pictures is 2 pieces. They screw together and clamp against the lower 11mm dovetail that runs the whole length of the receiver. Getting this fit perfect was my first big task as I wanted the two halves to clamp tightly against the dovetail but not leave a gap between the two halves. I'm designing the stock to fit on any Texan without modification required to the Texan - figured it might have a market if it turns out as expected.   

I have a custom bi-pod I am building for it. The front of the stock has this block towards the end. There is a 3/4" hole drilled through it which allows a titanium tube to slide in and out of the stock/rotate. This will allow me to move the bipod past the end of the receiver as well as allows the Texan to "roll" left and right when the tube is unlocked. Moving the bipod past the end of the receiver moves the pivot point out which means more input in the rear of the Texan is required to move the muzzle of the barrel - making a more stable platform for long range shooting. Each feet will both have fine and coarse length adjustments.

I also plan on making a monopod. The monopod will be able to slide on 2 tubes (when unlocked) to move closer/further from the shoulder rest. These are the same titanium tubes that are used to connect the shoulder rest to the Texan receiver. The foot will be fine threaded but will also have a coarse high adjustment as well.

The shoulder rest will be adjustable (in and out relative to the trigger). That is what the titanium tubes are for ( I was holding it in place in the picture). The shoulder rest will be mounted to the end of the tubes and the tubes will slide into their respective holes in the receiver. This will take all torque off the bottle and hopefully fix hold sensitivity issue.

  • St. Louis

adijorio

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Re: .308 Texan Exoskeleton Stock
« Reply #2 on: April 07, 2018, 08:20:34 AM »
I was really hoping someone would attempt creating a stock like this, as the Maddog just don’t do it for me.  Please keep us updated.
Thanks,
Al
  • Norman, OK

rcpro88

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Re: .308 Texan Exoskeleton Stock
« Reply #3 on: April 07, 2018, 04:19:12 PM »
Making this stock is a slow process. I keep changing the design slightly and progress has been slow since I don't want to ruin the work I've already done.
I haven't ever seen a mad dog stock in person. I've heard good things about them but for their price tag I think I'd rather make my own. Honestly, the mad dog stock I've seen for the Texans kinda makes the overall gun look like 2 guns smashed together and doesn't have a natural/fluid connection/transition between the two which would make the Texan appear it came with the stock off the shelf... That's just my personal opinion!

I made these changes:
The bi-pod system I designed will not be part of the stock. I still plan on making the design but making a whole bi-pod system on top of the rest of the new stock components would take up more time than I have right now. Also making the bi-pod system separate from the new stock will remove a significant amount of weight, so when hunting it can be removed etc.

Instead of going from 2 titanium tubes to hold the shoulder rest/mono-pod, I am going with a single titanium rod that will be mounted to the opposite side of the Texan the charging handle is on. This is partially due to simplifying a significantly more difficult to produce design to something easier as well as better ergonomics. Of course if you are a left handed shooter the assembly would be mounted to the side the charging handle is on.

The trigger guard/mount for ar-15 grip will be milled out of a single piece of aluminum and bolted to the bottom of the new stock.
  • St. Louis

rcpro88

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Re: .308 Texan Exoskeleton Stock
« Reply #4 on: May 01, 2018, 11:24:29 PM »
Have been busy with some other stuff, however, I have made a final decision on the design and here is my progress so far.

After test fitting all the possible ways to add a collapsible stock via titanium rod or tubes I found that the design would be useless as I don't plan on taking the tank off the Texan often as I store the Texan in a hard case in one piece, as well it would make the overall width of the Texan wider than the bottle (too wide for my case).

I decided the best way would be to use a single piece of titanium. It would have been much easier to make this out of aluminum but I'm not too confident the aluminium wouldn't flex as it would have to very little aluminum to make the design work.
The new design will lower the AR-15 grip 1.75 mm.
There will be an aluminum block that comprises the adjustable shoulder rest and mono pod.
The AR-15 grip mount/trigger guard will be milled from a piece of aluminum that will be bolted to the titanium part of the stock.
I still plan on cleaning up the stock, removing weight etc.
  • St. Louis

adijorio

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Re: .308 Texan Exoskeleton Stock
« Reply #5 on: May 02, 2018, 07:49:43 AM »
Nice. That's really coming along.
  • Norman, OK

Briar Patch

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Re: .308 Texan Exoskeleton Stock
« Reply #6 on: May 02, 2018, 08:37:15 PM »
Sweet!
  I enjoy seeing you guys coming up with ideas on ways to improve your guns, and then creating components, refiguring them and then refining them. Just a fun process to watch.
  • Payson, UT

yemx

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Re: .308 Texan Exoskeleton Stock
« Reply #7 on: June 21, 2018, 02:55:35 PM »
Very nice!!!
  • SILVER SPRING, MD

Alan

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Re: .308 Texan Exoskeleton Stock
« Reply #8 on: June 21, 2018, 03:02:14 PM »
I'm too old to start, but instead of taking 3 years of woodworking in high school, maybe I should have taken shop! I am jealous!
  • Roswell, New Mexico
Alan

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rcpro88

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Re: .308 Texan Exoskeleton Stock
« Reply #9 on: September 05, 2018, 04:41:51 PM »
I am still working on the Texan. I have made no more progress as I have moved to a new house and not been able to setup my mini machine shop in the garage to extent i'd need.
  • St. Louis