Tuesday, December 22, 2015

Zero Like a Hero Pt 3: Troubleshooting

We've looked at the how and why of zeroing a rifle, but what about when it just won't come together? There are a few things that will cause a rifle to be unable to zero. Luckily, most of them are fairly simple and quick fixes, and cost nothing or next to it.

If your gun simply will not put together a fairly tight cluster of holes in 3-5 shots, and you're certain that it's not shooter error, start by looking for something loose that shouldn't be. This is a fix that you'll likely not want to do at the range, and the range will likely appreciate that.
  1. Unload your gun, and keep it pointed in a safe direction. 
  2. Check the screws on your rifle to ensure that the barrel and receiver are mated firmly to the stock and forearm.
  3. Check that the screws holding your scope base are firmly torqued into your rifle's action. Loctite is a good idea on these screws.  I prefer the blue variety for my gun work.
  4. Check that your rings are tight, and solidly attached to the base. Again, blue Loctite will help eliminate future problems.
These steps will cure the vast majority of problems with a rifle that won't group. Checking that all these screws remain tight is an often-overlooked part of rifle maintenance that should be done regularly. The threadlocker helps a great deal, but even that can walk loose after extended firing.

If your rifle still won't group, there are a couple other things that you can check for yourself. First, inspect the muzzle (double check that the weapon is unloaded, please). You're looking for nicks, burrs, or other damage, as these can cause the bullet to leave the muzzle unevenly, devastating accuracy. Unfortunately, this pretty much requires gunsmith attention, but it's usually on the simpler side of smith work.

The other thing is to try different ammunition. Some rifles are quite particular about what bullet weights and velocities that they like, and it will show when they shoot. My .30-06, for example, likes 165gr bullets just fine, but my groups open up to almost double with 180gr rounds. Unfortunately, this can only be found by firing various options, which can be spendy. It is also one of the least common causes of severe inaccuracy.

Grouping problems that aren't fixed by these steps are probably going to need at least a consultation with a gunsmith.

If your rifle will group, but runs out of adjustment before it gets to point of aim, you'll need to adjust your mounting. The more expensive, but faster and easier way, is to buy adjustable rings like these from Burris. This type of ring has eccentric inserts that allow you to adjust the angle of your scope in relation to your barrel, and consequently your point of impact in relation to your point of aim. You'll need to know your tube diameter and mounting height when you order your rings.
The can with ends removed, split and rinsed.

The cheap/free way to do this is with shims. Shimming accomplishes the same thing, trading cost for time and work on your part. Shims can be placed either between the base and the action, or the ring and the bottom of the scope, or both if necessary. If your rifle is hitting low, shim the rear of the scope. If you're hitting high, shim the front of the scope.

The easiest source I've found for shims is the humble soda can.
  1. Using a pair of scissors or shears, cut the ends off the can, then cut down the side so that the metal lies flat. 
  2. Rinse any residue off your material. 
  3. Cut strips roughly 1/2" wide by 1-1.5" long, then fold them in half, ending up with a doubled piece of material 1/2" x 1/2" or 3/4". 
  4. Insert the shim in the appropriate location, and trim as necessary to fit. 
  5. Add additional shims as needed, until you can adjust your rifle to zero properly.
On the right is a strip from the can, and a finished shim on the left.
This should help you get and stay on target. Get set up and practice as much as you can.


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