The Case of the ‘De-Accurized’ Ruger M77-17

I was pleased to see an old friend of mine, Rob, at my door the other day, and hastened to invite him inside. Rob is a friend from my drag boat days, and the builder of winning Top Fuel engines and hydros. Since he was lugging a rifle case, I cleared the pool table for him to set it down on. (I took three tries on the 8-ball, however). The gun he brought to me was a Ruger M77-17, but you must have guessed that from the title.

This particular one was equipped with a black, synthetic stock and was so fresh out of the box that he hadn’t yet had time to install a scope on it. Since the Ruger M77-17 was the first .17 HMR firearm I’d seen when another friend brought one by, I was somewhat familiar with it. One of my gunsmithing students specializes in Ruger 10-22 rifles and other Ruger rimfires, so I was familiar with Ruger’s rimfire designs, having being around so many that Bruce had modified.

Outside of my shop, however, I wasn’t very familiar with these rimfires. Rob’s problem, as he saw it, was that the gun was much more accurate than his ability to shoot; he wanted me to reduce its accuracy so that he could feel superior to it. After checking to see if I had been really listening to him, he told me he was kidding and told me what he really wanted.

The rifle shot cloverleaf-shaped 100yard groups right out of the box, but since I had had such good luck when accurizing some other guns for him, he wanted it bedded and the barrel floated to achieve the same increase in accuracy as his other rifles. With Rob’s background in building 6,000-horsepower engines, and from his renting time on my lathe from time to time, I knew that I could get some straight talk from him when I asked questions.

We discussed what he expected of the gun, whether he would be shooting from a bench or standing and shooting off-hand, so I could determine what would be needed to increase its accuracy and repeatability. We decided to smooth and lighten the trigger, bed the receiver, and float the barrel. I’m a big fan of floated barrels and had never failed to increase the repeatability of a rifle by full-floating the barrel. With this plan decided, I began to assemble the tools I’d need to do the trigger job.

After the trigger was smoothed and down to a 2-pound pull, I taped around the trigger assembly, using clay wherever there was a place for bedding compound to grab. After bedding the action and letting the compound harden overnight, I mounted the stock in the mill’s vise and removed black plastic until I had what I felt was a reasonable clearance around the barrel.

Bedding and barrel floating went well, so I mounted his scope with its 56mm objective, after having to go to Ruger for ultra-high mounts that would fit the scope and rifle combination. Keep in mind here that this is a .17-caliber rimfire rifle with a pretty large scope on it. If it’s not already too late to make along story short, Rob went out to shoot the gun and came back dragging his knuckles on the pavement.

The rifle had progressed from nice halfinch groups to something like 3-inch groups with more frequent fliers than most airlines can boast. I decided that this wasn’t a good time to try to sell Rob some stock in my gun shop. After checking out the gun and all the work that I had done, I could find nothing that was any different from the other bedding/floating jobs that I had done countless times, and always with success. I then called Bruce, my Ruger guru, and learned what I had done wrong.

It went against all that I had believed in and had preached for years. Can you diagnose the problem from the information given above? (answer on the next page.)

Answer to This Month’s Gun Clinic (continued from previous page) I have never been a believer in "pressure points" where the stock is in hard contact with the barrel, so was surprised to hear Bruce tell me that I had to go back and re-establish a pressure point about an inch or less from the end of the forearm. The barrel-wedge-and-screw method that Ruger employs on all of its rimfire rifles just isn’t sufficiently sturdy to maintain one barrel setting.

The loose slip-fit of the chamber end of the barrel to the receiver is necessary for the easy removal that Ruger wanted, but the tolerance necessary for that ease of removal makes a poor barrel-retaining system. On my own 10-22, which has been sleeved for a .17 High Standard cartridge, the barrel stub was knurled until it was a medium press fit so that I could float the barrel. A cure for this would be to mount the scope onto the barrel.

After reestablishing the pressure point against all I previously believed, the rifle now shoots onehole ten-shot groups at 100 yards. Better yet, my customer and friend has a rifle that truly shoots better than it did when he bought it. That was the goal in the first place. ■