Bighorn SR3 DIY Build


Sep 1, 2018
I have all the parts for my next rifle build and am contemplating trying to "build" it myself. I am mechanically inclined and can purchase what is needed, but is it a good idea? And does anyone have any good source or instructions for engaging in such a task?

What I have is:
Bighorn SR3 LA
Proof Bighorn pre-fit 280 ai Bighorn shouldered carbon fiber barrel
TriggerTech Special
AG composite stock made for the SR3 LA
I still need bottom metal - probably getting Sunny Hill or Hawkins BDL - and the box, spring, and follower

It doesn't seem that complicated (Torque barrel, attach trigger, fit into stock, attach bottom metal...), but am I overly simplifying it? Or is it worth getting a gunsmith involved? The two areas I think I need some advice in are (1) how to properly put a carbon fiber barrel in a vice without harming it? (2) timing of the trigger if it needs adjusted?

I did not find any threads on this, but maybe I missed it. If so, I apologize.

Thank you for any input.
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Apr 28, 2018
Putting it all together is pretty simple. All you need to do it properly
is a barrel vise, rear entry wrench and maybe a set of go/no go gauges if you want to check for proper headspace with your action. Just clamp the barrel at the steel part on chamber end, coat the threads with and thread on the action by hand. Then torque to 30-40lbs or so. Take apart the bolt and double check headspace and your done. Depending on barrel vise you may want to wrap the barrel to protect it from scratches. Timing the trigger is best left for a smith unless you have access to a surface grinder as the cocking piece will need to be ground to fit your specific trigger. Probably not necessary on a hunting rig but if you want the smoothest bolt then by all means have it done. You cold also try a few different brands of triggers and see what works best as each brand is different and one might overcock less than another.
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Major Hide Member
Mar 22, 2018
Grand Junction, Colorado
Check with Bighorn on proper torque range for the tennon thread, I have two Kelbly actions and go to 98-100 ft lbs.
I think Kelbly recommends 100-150 but that may be overkill I just went to the lower end of the range because they know a hell of alot more than I do about their products.
The Viper barrel vise is a very good and affordable options if you don't plan on removing factory barrels and get a good 1/2" torque wrench for installing and a 1/2" breaker bar for removing barrels if you don't allready have them.
I use a light coat of EP-2 grease on the threads and stage up when I torque a new barrel as in 60-70% of target torque value and break loose once then the second time to full value.
Probably not necessary but I have it stuck in my head to do it that way.
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Dec 10, 2017
I just finished doing the same thing with a Tl3. I used a PR CF barrel. I called proof and they recommended 80ftlbs which is less than Bighorn. Checked @80 and the headspace was correct. I was able to shoot it Sunday and it shot .5” groups.

I went with a triggertech and it super easy to install.

As far a a barrel vise I bought a Mechforce and had no problem with it holding the barrel.