filing sights on 3 inch .357 SP101

Bought a used SP101 and after a couple trips to range off sandbag at 12 yds found it consistently shoots 3 inches left. Elevation is dead on with 158 grain 357 and varies with different grain and brand 357's as well as 38 special loads but all are left about 3 inches. Looking at filing front or rear sights a little and was wondering if any math folks out there could give me some advice on approx. how much to take off as a minimum. Don't want to take to a smith without trying to adjust the fixed sights myself first.Thanks for any suggestions

Before I would do any filing on the sights I would have someone else (or several people) shoot it and see what happens. If all are constantly shooting to the left then look at the front sight as compared to the frame and see if it might be canted a bit which would cause the sights to be misaligned. If it is canted, then contact Ruger.

Thanks Ron. I should have mentioned that I did have two others shoot with basically the same results. I just now ran a string from the center of the rear sight down the center of the frame and when it gets to the front sight it lays on the far left edge of the sight. Think Ruger will fix free of charge as I am not original owner? Not familiar with warranty.

Give them a call and explain what is happening and how you checked it (different shooters and the string check). You can also tell them you bought it used but with Ruger that really shouldn't make a difference. Ask what your options are and what the estimated costs will be. Being nice like this may garner you a no cost shipping label so they can check it out.

i'll give them a call and check it out. can't hurt and i have heard they have a very helpful customer service dept. if the cost is too excessive i'll go to file. really like the gun. thanks