Why tune a R7? Most will say it's a waste of time as the gun is smooth out of the box.
While this is true to some degree, the R7 has many areas that
need addressing right out of the box that most novices aren't aware of.
I'll go over a few of them and what I do to correct them to clear the air on "is it worth it?"
#1 The cocking lever on the R7 rides along the bottom of the receiver when you cock the gun. Often the joint where the two pieces join will grind into the front of the receiver and eventually gall. On some guns, heavily. The cocking lever insert I ad will keep this from happening.
These are two brand new guns. Already you can see the receiver beginning to gall.
#2 The piston on the R7 is not hardened like it is on some of the other higher power HW guns. As the factory grease dries out and becomes hard the piston will often start to gall inside the tube. On one gun I tuned, it had worn the top of the piston down so much that the cocking lever could pass under the piston and the gun would no longer cock. Needless to say, the receiver and piston were ruined and no longer usable. This is where buttoning the piston comes into play. It eliminates the metal to metal contact between the top of the piston and the receiver.
This was from the gun mentioned above. The cocking lever would actually pass under the piston and it wouldn't cock.
#3 The R7 has a tendency to have trigger and safety issues. The R7s safety button is the same used on the R9/R10/HW50S. Often the safety has a problem traveling over far enough to allow the gun to fire. You'll be able to "click" the safety off, pull the trigger and it won't fire. Push the safety again and it'll fire. The position of the trigger and oversized safety in the little R7 makes it a very close tolerance "ragged edge" issue. All these tolerances are addressed and rectified when a tune is done on a R7.
#4 HW quit honing the receivers many years ago. Many of the cut outs, pin holes and slots in the receiver have sharp jagged holes that tear piston seals no matter how careful you are putting them in. Ninety percent of the new guns sent in for a tune have cuts along the bottom of the piston seal. Some bad enough that the gun won't stop dieseling even after 1000 rounds have been through the gun. I replace the seal with a lathe turned seal that has better sealing edge and a built in support ring at the base to keep the seal edge always true with the receiver. This also helps if the tube is slightly out of round or tapered. The factory seal is loose fitting on the piston and has the back ground down to keep it from dragging. This can also make grease migrate to the front of the seal. Replacing the seal with a better one, milling, deburring and honing the receiver eliminates these problems and also makes service in the future less likely to "go bad" on installation of a new seal.
This is two years worth of R7 seals on the left, many from new guns. The right picture is two lathe turned ADV seals. Seals are not available without tune.
#5 The factory guns are loaded with way way way too much grease. This is one way to deal with #1 and #2 if you're not wanting to deal with those issues by spending lots of time hand fitting and machining but it's not the best way to deal with it. The best way is to engineer and modify the parts to where it will be a none issue in the future when the grease has hardened or just been displaced from continued use over time. Too much lube is also bad for accuracy and the life of the spring due to heavy continued dieseling. All this is cleaned out with solvent and a rinse bath to remove all the grease and metal fillings that were left from the factory machining the receiver and other parts.
This piston was pulled from a new gun
#6 Often metal shavings can be pushed back through the spring guide into the trigger assembly. Sometimes the piston stem has a sharp edge that actually shaves metal off the ID of the guide and piles the shavings up into the trigger assembly. The trigger is taken apart cleaned, polished and tolerances for item #3 are dealt with when a tune is done. The stem on the piston is also deburred and checked for alignment to the end plug.
Before and after shots of piston after it have been converted to ADV.
#7 The factory spring guide is short and could fit the spring ID better. After about thousand rounds the R7 spring starts to kink from being supported incorrectly and from being made of standard grade wire. This is about the same time that Most people will say, "After about a thousand rounds it really smoothed out." It's because the spring is so contorted it now contacting the sides of the piston in several places. It will also tighten up slightly on the guide. I make a front and rear guide and use a Maccari™ mainspring from Air Rifle Headquarters. It's of much higher quality than the factory spring.
Customer sent this one in and said he had about a thousand rounds on the rifle.
There are other things done as well. Polishing and deburring many parts. Using correct high temp lubes are just some of the "basics" of doing a good tune. Many R7s can be shot right out of the box with a couple of thousand rounds without much or any problems. That said many are sent to me brand new, because the owner didn't want to settle for "OK". They wanted their investment to be all that it could be, and just to be perfectly "right" from the get go. The uninformed will pick a new gun packed with lube and shoot it beside a tuned gun of mine and say, "neither one twangs. Why would you bother with a tune?" Now you can tell them. Chances are though he won't want to hear it. That's fine. Some want things to be their best and some want to get a reasonable amount of quality for as little as possible. The latter aren't my customers and their reasons for being so are mutually beneficial for both of us ;-)
Many Thanks,
SpringGunning