Author Topic: Breaking in an airgun and routine maintenance.  (Read 1769 times)

Offline Novagun

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Breaking in an airgun and routine maintenance.
« on: June 16, 2013, 07:13:04 PM »
If you have bought a new rifle and taken it out of the box the temptation will be to load a pellet and fire it. Maybe you will do just that but before too many pellets it would be a good idea to clean the barrel. Often new rifles are coated in the bore with oil to prevent rusting. That oil needs to cleaned out so that the pellet can travel smoothly. Lead pellets provide their own lubrication. Use a pull through and patches and some solvent such as turpentine or one of the proprietary barrel cleaners to thoroughly clean the barrel. Keep using patches until they come out clean and dry.

Now you can just shoot the rifle. It will take about a thousand pellets fired to let the rifle settle down. This process allows the piston seal to bed in and it allows all the moving parts to wear in or if you like allow all the little irregularities left from manufacturing to wear smooth. During the break in period the articulating parts like the hinge on the break barrel and the joints in the cocking lever can benefit from a drop of oil. A drop it should be; just one drop, not a squirt.
Make very sure that no oil gets into the compression tube.

The reason for this care follows. When you first shoot your rifle there may be a little oil or grease in the compression tube that you can not get at. On firing, that oil will burn out and you will notice a burning smell and see smoke coming out of the muzzle. After firing a few shots, say 10 to 20 that smell and smoke should disappear. Often it does not.

What is happening is that on assembly the manufacturers will have liberally greased the spring. On cheap rifles this is done to excess as a way to deaden the noise of a poorly fitted spring. Without the excess grease the spring can rattle and vibrate. This grease can and does shake off the spring and settle on the wall of the compression tube. As you cock and fire the rifle and the piston and seal travels forward, the seal scrapes a bit of that grease off and pushes it ahead until the spring reaches maximum compression. The high pressure air combined with the high temperature that it generates will cause the hydrocarbon content of the grease to ignite. Some air rifles are designed to do that as a way of increasing power output. In most if not all air rifles it is undesirable. The ignition of hydrocarbon is similar to the process that makes a diesel engine work. Hence in air rifles the term "dieseling" applies.

Dieseling has detrimental effects on air rifle shooting. The amount of grease burnt on each shot varies and consequently the energy from the burning or sometimes detonating grease varies. This combined with the compressed air makes for variable muzzle velocity and variable accuracy.
The extra heat generated by dieseling can burn the edges of the piston seal and reduce its efficiency. The other bad side effect is that detonation when the piston is at its maximum compression puts a sudden and powerful counter thrust on the spring. If left to recur again and again it will break the spring. In extreme cases it can swell the compression tube and render the rifle unserviceable.

What to do? You can either dismantle the rifle and clean the grease out but that might affect warranty. You could take it back to the dealer and hope the dealer knows what you are talking about or you can just shoot until the spring  breaks and make a warranty claim.

This problem does not arise with a PCP rifle or a Carbon dioxide powered rifle but can occur with a gas ram or even a pump gun.   

Once your air rifle has been broken in it will need very little maintenance. The barrel will seldom need cleaning and should be done only when accuracy starts to deteriorate. The barrel of an air rifle is made of soft steel and should never be cleaned with anything as harsh as a bronze or brass brush and extreme care should be taken to not scratch the bore if using a cleaning rod. It is better to use a soft pull through. One can be made up out of monofilament fishing line. Take care not to damage by rubbing the muzzle or the pellet receiver. Apart from that a single drop of oil on the moving parts, but not the trigger, on rare occasions, nothing more is needed. After every time you use it wipe the exterior of the rifle down with an oily cloth to remove finger marks and moisture and to coat the rifle with a thin film of oil to prevent rusting.

Now is a good time to point out that a spring powered air rifle is a machine with parts moving under stress. This causes vibration that can work screws loose. The stock screws and scope mounting screws need checking every now and then. If they are not tight you will notice accuracy deteriorate.

Because the rifle is a mechanical device some parts do need replacing, but infrequently. Springs do fatigue and break and piston and breach seals do wear. They are not difficult to replace and can be done with  few tools.

« Last Edit: March 08, 2015, 09:13:34 AM by Novagun »