Magazines work by using a spring to push a fresh round up in front of a bolt or slide. That cartridge is then pushed into the chamber either manually or by a compressed spring. The magazine under the bolt is exerting varying upward pressure on it and that those varying amounts of pressure change the downrange POI. Magazines have varying pressures, single stack magazines have a straight up, lighter pressure while double stack magazines will have a higher pressure as well as applying pressure from either side depending on round placement. Other factors in the magazine that can influence the bolt carrier group are springs, feed lips, and followers.
There are several ways to try and work with this. When competitive shooting never use you magazine as a rest. This will apply excessive and inconsistent pressure on the bolt. Lots of NRA sponsored events don’t allow this anyway, train as you compete. Use a reliable lead sled or rest. Try to use the same one if possible, if you cannot, sand bags or you range bag will work as long as the magazine is off the ground. Clean and maintain you magazines as shown below.
These instructions are for the military style metal, G.I. issue mags. The principal is the same for all magazines:
1.) Pry the tab at the rear of the magazine down so that the detents can clear the spine.
2.) Grab the tab with your needle nose pliers and pull the tab, sliding the floor plate from the bottom. Be careful the tab is under spring tension.
3.) Remove the spring and follower from the bottom of the magazine body.
4.) With the spring and follower out, wipe down the inside of the magazine by pulling a clean microfiber cloth through the hollow tube of the magazine body a couple of times.
5.) Wipe down the spring and follower to remove any remaining dust and sand. Depending on your environment, apply a light coat of lube if desired.
6.) Ensure that there are no dents and everything is in the shape it is supposed to be.
Save any serviceable parts and reassembly in the opposite order. 5 → 1
Match the magazine to the firearm. This can be accomplished by labeling your magazines. There are all kinds of ways to do this. Simplest is to use a white marker and a method that you can use to match the magazine to the weapon. Some manufactures have “dimples” on the magazine you can color in a pattern to label them
Using the above tips should help you improve your POI.
U.S. Army TM 9-1005-319-10