Novice Tune-Up on a B3-1

[davee1]

70GTvert, I always say...if it don't make sense to you, and no one has any experience to say otherwise...then try it yourself(in this particular case, where your life is not threatened). Whats the worst that would happen? The bronzies wouldnt work, shatter, and have pieces all over the place inside of the B3, or the bronzies might wear away slowly putting bronze dust everywhere. Whats the best that would happen? The bronzies would work and turn out to be an excellent choice, and then hopefully that info would be shared with everyone.

When I drill a hole in delrin...it doesn't break. I don't need to put it between two pieces of wood to keep it from shattering, like what Howie mentioned. That signifies brittleness in my humble opinion. I figure that a brittle material like that is not going to stand up against the compressiveforces inside of a springer in general. If a regular old metal washer gets beat up in a springer, how can a brittle bronze washer hold up?

[hyounker]

Here's McMaster Carr's description of the Oilite Bearings, to further fuel this debate! :

SAE 841 Bronze
Also called Oilite. Porous material impregnated with roughly 18% SAE 30 oil, makes a virtually maintenance-free bearing. Oil acts as a cushion between the bearing and shaft, adding resistance to shock loads (suddenly applied loads) and wear. Use in areas that are difficult to access for maintenance.
SAE 863 Bronze
Also called Super Oilite, this oil-impregnated material is maintenance free like SAE 841, but is made primarily of iron (mixed with copper), which makes it even stronger than SAE 841. Perfect for locations where access to bearings is limited.  

After reading this, I would have to say that it is definitely worth a try!!!  The surprising thing is that the Super Oilites are cheaper than any other.

[hyounker]

Started putting things back together this morning, and ran into an area that I need clarification on.  In Bob's Fast Deer tune guide, he says to use silicone grease inside the compression chamber.  But then later, recommends using Charlie's Chamber Oil to occasionally lube the chamber, if you have a leather seal.

Should I use Charlie's Chamber Oil on the inside of the compression chamber when I re-assemble, since I have a leather seal on this B3.  Or use the silicone grease for re-assembly and the Charlie's Chamber Oil for later lubes?

Thanks for any help.

[moon]

I used a broze looking bearing to space the spring forward.  1/2" i.d. fit over the tube I glued over the spring guide.  I had to grind one end down a bit to fit inside the piston.

[hyounker]

I put it back together using Charlie's Chamber Oil on the piston and inside the compression chamber.

Got everything back together, though I had a hard time getting the spring retaining pin back in.  It didn't seem to line up well in all four holes.  I'm guessing this is probably standard Chinese precision!

I reassembled the rifle with all the original parts.  I haven't received my kit from southsummit yet.  The only exception is the breach seal.  I used a length of fuel hose as suggested by davee1.  I may need to cut a slightler shorter length for that later.  Also, the plastic washer that was between the leather seal and the piston was broken, and I did not replace that before reassembly.

The cocking motion is now smooth as silk!  I was very surprised at how quiet and smooth this became.

I shot a few rounds to watch for dieseling or detonation and those rounds seemed very clean.  I shot about 15 rounds into the woods, just to listen and watch.  All seemed very smooth and extremely quiet.  The spring sound was definitely improved.  All I hear now is a gentle thwaaaap.  I assume this is normal, though I have never heard a tuned B3 before.

I shot 5 rounds through the chrony and averaged about 530 fps, which is about 30 fps less than I shot prior to disassembly.

Do you think the loss in velocity is due to the new breach seal leaking a little, and/or the missing washer?  Or is this normal after a tune?  How do I test the breach seal for leaks?

How much improvement can I expect with a new spring from SouthSummit (if they are still in business!!).

Thanks for the help.

[hyounker]

Dave,

Thanks for the tip on the fuel hose.  I had to drive all over town to find some (Ace didn't have it), but finally found it at O'Reilly's Auto Parts, a black hose marked as 5/16" radiator overflow hose.

I cut it to about .350" and put it in the pocket around the exhaust port.  After closing the action, I got that really smooth "seating" feel.  I opened it up and the hose was squished a little and hanging out of the pocket a little.  All this sound right?  I ask because my velocity is slightly down after the tune and I am wondering how to know if the breach seal is leaking.

Thanks,

[davee1]

Yep, that sounds about right Henry. What I did was experiment with different lengths of hose until it closed up with a little resistance, and I used the chrony to see if there was any improvement with the different lengths. For example, you could try .400" and see how that does. Some hose should extend out of the seat/pocket so that the top of it can seal against the top of the cone and surrounding surface. You probably already have it right...but experimentation sometimes gives you a few more FPS. Do you have any silicone grease? I use that to lube up the seat and hose, and then push the hose in, then close her up...seems to make the hose a little squishier too.

Did your piston seal slide right in? There should be some resistance there too. But, it does actually work though...its going in excess of 500fps. How old is this B3?

[davee1]

Henry, did you try spacing up the spring to its max?

[hyounker]

I'll play around with the length.  After all, I have three feet of this hose now!!

I do have some silicone grease and I'll try that as I experiment.

The leather seal seemed to be a great seal.  Some resistance, but not too much.  The seal didn't look the best, but seemed to seal really good.  I put my finger over the exhaust port and couldn't move the piston forward if I held it tight.

This rifle is at least 15 years old.  I bought this thing at a gun show, shot a few times, then wrote it off as a POS.  Been in the closet until about 2 weeks ago!

I have not installed any spacers.  I wanted to see where I was with stock parts first.

[davee1]

The way you tested the piston seal is a good test Henry. If it holds air like that, then we can't do much better than that. Maybe spring spacing, breech seal experimentation, and some more shots may bring the velocity up. I'm only familiar with the B3s from the last few years...mine are in the upper 600~lower 700 fps range. Some of the B3s just dont go too far. I think taking that washer out from between the piston and seal just made more cylinder volume...which is a good thing. Some guys have even shortened their pistons a little too. The possibilities are endless...and we get back to whats the worst that could happen.

I'm going to try to dig up a link where a guy made an adjustable piston seal out of 1/2" and 3/8" flat rubber faucet washers.

The other thing is you must remember, is that you don't have the QF2 spring in there yet, and that will make a difference.

[davee1]

Here ya go...check outthis document in the link below, and see if there's anything that helps or you want to try. Look for the section about "leather seal expansion washer improvement". You can improve the leather seals tightness against the compression cylinder walls. I've read about others trying this and had some good results. I haven't done it yet, but I plan to.

http://webpages.charter.net/guru1/documents/B-3%20guide%202.0.pdf

[hyounker]

I used that document during my tune, along with Bob's Fast Deer Guide.

I decided against the seal mod after my test.  But, thinking this over, when that piston slams, my test may be flawed.

Have you seen this link?:

http://www.gatewaytoairguns.com/library/Making%20Leather%20Seals.htm

Pretty cool.  I may try this even if I don't need a seal!!!  What can I expect from the seal that comes with the kit from southsummit?  Can't wait for that spring!

Thanks again for all your help.

[davee1]

Yep, but so far I haven't had to make a new seal. Henry, the QF2 kit doesn't come with a new leather piston seal. It has a synthetic seal. There's a different better mainspring, two breech seals, a trigger spring, a sear, some oil that you dont wanna use, and some barrel cleaning rods/end fittings. The cleaning rods I don't use for barrel cleaning, but I save em for something someday. One guy uses em to prop up his skyscreens on his chrony.

Now, some have made the conversion to a synthetic piston seal. The results have varied...some see better velocity and others have seen a drop in velocity. The leather seal is much more forgiving about the inconsistencies in the compression chamber, and there's more seal material in general to seal with. Supposedly, the Chinese QC has come a long way in the last few years, and folks say they are putting out better product now. Since yours is like 15 years old, you may have gotten one with a lot of inconsistencies in the chamber...who knows. So if you wanted to convert to a synthetic piston seal, we are back to whats the worst that could happen. An adapter is needed for fitting the synthetic seal to the piston. Its so much easier just to save the synthetic piston seals for some other chinese guns that you may buy in the future that actually use them. My B3AK is such a gun, and I had spare seals on hand because of the QF2 kits that I had bought previously. But hey...thats up to you.

[howie1a]

To test the breach in any air gun what you do is to take a small  piece of tissue paper and  cover the loading port behind the pellet and  shoot the gun if you get one nice round hole everthing is fine if you get a ragged tore type hole you have a leak and the breach seal needs replacement. howie

[hyounker]

Howie,

Great tip.  Thanks.  I'll give it a try!