I have an S&W SD40 and have been shooting at around 15-20 yards. The problem is I am a decent shot and keep shooting low and left.I have shot other guns and seem to do fine, I know the rear sight is adjustable but I have never tried to zero a handgun. I thought that a handgun was tested before it left the factory and I would assume that would mean buying a weapon that is pretty darn close to zero. Any help or advice would be appreciated.
The people of the various provinces are strictly forbidden to have in their possession any swords, bows, spears, firearms or other types of arms. The possession of these elements makes difficult the collection of taxes and dues, and tends to permit uprising. – Toyotomi Hideyoshi, Japanese Shogun, August 29, 1558
The guns are test fired at the factory to ensure they cycle, but not necessarily for accuracy. Zeroing a handgun is not big deal. For yours, move your rear sight to the right. That will move the muzzle and point of impact to the right.
It could be the sites but low and left in a right handed shooter is almost always anticipating recoil.
Try this, get some snap caps and have a buddy load your mags. Have him randomly insert one or two of the snap caps. (this is referred to as the "Ball and Dummy" drill)
When you shoot the mag, you will pull the trigger and it will just go click. Watch what happens to the muzzle of the gun. If it remains steady, adjust your sight. If it bounces, it's anticipating the recoil. Do this a few times and it should start to go away on its own. If you want to spend a bit more money, put a laser on your gun and have someone watch the light as you shoot, you will see it jump down just before the shot breaks.
The .40 has a bit more recoil than a 9 so you may be an excellent shot with the 9 and struggle with the 40.
I have the sd40. To fix the heavy trigger I bought the Apex trigger spring upgrade for about $20.00. It has improved my accuracy by lowering the trigger spring tension. I was able to do the upgrade by my self by following the YouTube video. Also watch were you place your thumbs, it can unbalance your aim.