M98 Action Flex

[Papa72]

I wanted to pass along an observation made yesterday while inletting the new stock for my Mark X .416 Ruger action….

Initially this Mark X wore a Boyd’s Classic laminate stock which had been glass and pillar bedded very nicely, but had no checkering and was too slick for my taste. Failing to locate a practical checkering solution for it I ordered a new Boyd’s Platinum laminate stock with ample checking for about $400. The new stock did need some inletting for the heavier barrel, bolt handle, side safety, and extra wood removal in recoil lug area for bedding.

I had installed Leupold 2 pcs QR bases on the receiver while the action was installed in the original stock. The Vari-X 3iii scope and rings were installed and everything torqued to factory specs. The scope mounted/dismounted easily in this stock. So, after spending a couple hours sanding & grinding on the new stock, fitting and removing the action, and measuring critical areas on the old stock I thought we were done…NOPE! When I tried to remount the scope in the bases while the action was tightened in the new stock the scope would not fit. At all. The ring bosses were out of alignment with the QR holes by enough to prevent them even “starting”.

Long story short…the front action screw was tightened to the point the receiver actually flexed due to some undiscovered pressure point inside the stock. I had no idea such a thing was even possible. The screw was tightened with a standard screwdriver & hex bit by hand force alone. It was tight, yes, but I wasn’t making any grunt faces when it was tightened. So, after loosening that front screw the scope mounted & released normally again. I inspected the action’s side rails for a crack that would explain this flexing but everything looked ok. Pretty good case for the benefit of 1 pc bases vs 2 pc bases, at least.

 

[USMA84DAB]

Your surprise is unfounded - you just have done enough work on a rifle to discover this phenomenon - I have also bent a Turk Mauser by over-tightening the rear action screw. It was quite easy to do this. I had no idea I had done it until the trigger would not fire the weapon. Of course, when I had cranked the screw down until it got "tight", then I brought the woodline of the stock down to the metal. When I released the metal from the bending tension, the action stands "proud" over the wood by 1/2"!!!!! What a severe tuition payment on learning to work on rifles!!!!

Congrats on working so hard to make your rifle awesome that you bent the action. Perhaps this is a right of passage for riflesmith?

 

[Papa72]

Well, I have managed to do all the gunsmithing chores my guns required without too much consternation so far but the action flex issue was indeed unexpected. Turns out a few thousandths wood at the fore end tip barrel channel was enough leverage to torque the action. I’ll take this rite of passage!

 

[Ontario Hunter]

Check to see if you have relief between the magazine box and the bottom of the receiver (underneath the feeding rails). If the box is jammed up against the receiver in the new stock and action screws tightened, it can and will bend the action. Usually this results in trigger binding against the bolt or bolt binding in the track = won't cycle. I am surprised this rifle would cycle if the receiver flexed that much. Or maybe OP didn't get that far to check cycling? Anyway, there should be a very slight gap between box and receiver. If pillars are properly installed with a gap above the box, then everything should pull together properly provided the box or receiver is not binding someplace else. You may need to trim a bit of metal from the top of box sides to obtain the relief needed. Don't worry too much about it. The boxes are typically longer than needed. Or you can add enough bedding fore and aft to float the receiver higher and simply avoid fully torquing the action screws while it's curing (essentially extending pillars).

You are correct, one-piece base/rail is pretty much foolproof. Scope should always be completely reset when changing stocks.