I had the opportunity earlier this year to review a Beeman R11 courtesy of Jim (JBRuss) and found that I really enjoyed the gun. Read review here:
http://www.network54.com/Forum/546945/message/1168829697/Beeman+R11+Review
Immediately upon firing it, I wanted to test out my fledgling tuning skills on it. The gun had a nice cocking and firing behavior, but showed a fair amount of twang. Other than the twang, the gun was the epitome of what a well run in springer should be. Accurate and reliable with a crisp trigger.
I had spoken to Jim about tuning the gun for him and he graciously agreed to let me have a go at it. I got the gun earlier this week and was looking forward to the weekend when I could tear it apart.
Here I should interject that I am a new tuner. I have tuned several of my own guns and enjoy the process, but I am by no standards a ‘pro’. In fact, if any pro’s read this, they may be thinking ‘Why did he do this or that?’ There may be some elements I overlooked, or could have done better. I don’t know. I do know that my prior tunes have been successful in taming firing behavior and I’ve been happy with the results.
With that, on to the tune.
Remove the stock by using a flat head screwdriver on the screws on the side of the gun and by removing the trigger guard. Take care to use the proper size head to not mess up the larger screw at the front of the trigger guard.
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On this gun, the small nut at the rear of the trigger guard was held in place well. On my R7, R9, and B26, this nut was loose and came out. Take care not to lose this nut as this is what the rear trigger guard screw goes in.
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Next, remove the barrel and block from the body of the gun. To do this, lay the gun down with the muzzle pointing to your right. Remove the screw head, taking care not to lose the tiny washer inside. Turn the gun over and remove the screw/pin, again being mindful of the lock washer. It will screw out only so far before you must pull it out.
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The barrel block can then be separated from the body of the gun. There will be a thin shim on either side of the barrel block. Take care with these as they can be brittle. The cocking arm will then slide right out of the cocking shoe. You may then remove the cocking shoe from the piston.
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Then remove the trigger housing. There are two pins that must be removed. They are not load bearing so you can gently tap them out with the appropriate sized punch. Remove the trigger block, watching out for the safety with spring that will fall out on the side.
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You will then notice that there are 4 square pins and a notch in the tube holding the spring in place. Put the gun in a spring compressor and gently apply some pressure. This will make removing the square pins much easier. Use an Allen head to push the square pins out from the side. Once you have one side out, you can go directly through the tube to remove the other side.
You can then decrease the pressure on the spring compressor and move the notch out of place and gently decompress the spring. There is a fair amount of pre load so be mindful of this. After the spring is decompressed fully, remove the gun from the spring compressor and slide out the spring and piston.
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This is as far as you’ll need to disassemble the gun. Here are all the parts disassembled.
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The Macarri spring and guides are a touch bit shorter than the stock spring. This is normal from what I have seen.
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Next, you will want to clean all the grease from the parts. I use various things to clean from rags, to brushes, to toothpicks. Denatured alcohol helps rid grease as well. Here you can see the piston and piston seal was full of grease. You can use a wooden dowel and a cloth to clean out the inside body of the gun. Be careful as the inside of the body of the gun has some sharp edges!
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Since this is a well run in gun, I did not mess with the trigger at all. The trigger felt great from the start and if it's not broke don't fix it... especially with it not being my gun.
After cleaning, apply a thin coat clear tar to the OD of the spring guide (something I did not do right away as I couldn’t get the guide off the spring...explained later), a little heavy tar on the spring, and a touch of moly paste to the back side of the piston seal and to pivot points on the gun such as the barrel block.
Various sites say different things about the actual amount of tar to use on a spring. Most say to use only a small amount to cover the coils and perhaps have a tiny amount of spider webbing between them. I normally use enough to spider web the middle part of the spring and use less toward the ends.
After proper lubrication, put the piston and seal back in the gun, taking care not to nick the seal on the way in. Place the spring in and push it down all the way. Back to the spring compressor to gently compress the spring and maneuver the notch back in the slot from where it came. While still applying light pressure with the spring compressor, replace the square pins. You shouldn’t have to beat them in…if it is aligned properly, they will push all the way in with your finger.
Remove the gun from the compressor and reassemble the trigger block. To do this, engage the sear as if the gun was cocked. Slide the safety button with the spring in the side of the gun (it will only go in one way) and slide the trigger block in. Replace the two pins. The shorter pin will go at the bottom of the tube and the longer on the top. They should go in easily with only a light tap of a wooden dowel. The safety should remain in a fire position. Disengage the sear by pulling the trigger and the safety should pop out to safe position.
Replace the barrel block taking care not to harm the thin shims. You will need to place the cocking shoe back in the piston. I have heard of folks using a small amount of tar on the trigger shoe to smooth out cocking. I used a tiny amount of tar under the trigger shoe and where the cocking arm will attach. Replacing the barrel block can be very tricky as you will find the holes do not line up easily. Take your time here. I will use a small screwdriver to hold the holes in alignment from the bottom as I start the long screw/pin from the top. Once started, it will only screw in so far before you must use a wooden dowel to give a couple of light taps to get it through the block where it will have threads again. After tightening it down, replace the screw head on the other side. Tension can be adjusted later.
Replace the stock and give it a test shot….
I fired off several shots with Beeman Kodiaks to burn off any residual dieseling. After that, I took some shots to notice the cocking and firing cycle. Cocking and firing the gun was a joy. Cocking showed no noise at all and a very smooth cocking motion. Firing the gun proved the twang was eliminated and the gun had a very nice firing cycle, shooting with a ‘thwack’ and a very linear and mild recoil.
Chronying the gun, I found that velocity had dropped by about 45fps. I’m thinking that this could be attributed to one of two things, although I am not certain. We opted not to replace the seal on this gun. I used the original seal. It may just need to run in with the current parts in order to achieve max velocity. The other, more likely reason is that since I couldn’t remove the spring from the guide, I didn’t use any clear tar on the OD of the guide. The guide was very tight on the spring. I disassembled the gun and used a toothpick to apply clear tar in between the coils on the guide and then reassembled. After a few more shots to test out, I chronied the gun again to find I had gained about 15fps. The gun is shooting JSB Exacts at around 820fps for 12.60fpe. I’m quite certain that with more shooting, the gun will run in properly and velocity will increase to at least what it was doing beforehand. Remember that while normally likely, a velocity increase is not the primary goal in a tune. Smoothing out the cocking and firing of the gun should be your primary concern. If you get a velocity increase in the process, that’s icing on the cake.
I will keep the gun a bit longer to do more testing with it and to just shoot it a while before sending it back to her rightful owner, who I hope will be pleased with the results. Thanks again to Jim for the opportunity.