How to hone the compression tube?

[Uslanja]

Good day All! I guess when this airgun bug bites you, it bites hard! I picked up an old Chinese break barrel called a Pioneer in .177. Should have taken photos but didn't think about it at the time. Lesson learned, sorry! It has a wood stock, sling mounts and a 25 mm leather seal. No other identifying features that I can see.

Decided to chrony this old girl and see what she can do:
QYS Domed pellet @ 8.48 grain. An unbelievable blistering velocity of 249.01272 FPS producing a very impressive 1.17 FPE.

Must hang on to this canon very tightly

So this is a no brainer.......take it a part and see what can be done with it.........if it becomes junk the only loss is 40$, but I get a metal rear iron sight out of the deal. A mish-mash of different screws everywhere. Trigger group came out real easy with only a single loose fitting pin. Spring followed quite easily with a bottom spring guide but no top hat. The spring is not broken and finished flat on both ends so guessing it is still good to use. The piston was a bit more difficult and resorted to bit of hammering using the slot to get it down the tube far enough to snap vice grips on and hammer it out the rest of the way. But all is not lost....... remember........there is still a perfectly good metal rear sight

The leather piston seal was crumbling and had 3 BBs stuck in it along the edge of the seal but did not mark the inside of the compression tube. There are so many very good videos instructing how to make a new leather seal but the decision was made to install a Diana 25 mm synthetic seal and adapter. Thank you D&L Airgun for that.

Was the inside of this thing ever dirty. Wiping, brushing and picking out gobs of crusty black stuff to no end. Finally had enough of that nonsense.........out to the shop and the always trusty high power spray can of Brake Cleaner was brought to bare. Ahh......looks cleaner now! Should create some mighty fine dieseling........ maybe we can get it close to 500 after all!

But, here is my serious question: wanting to smooth out the inside of the compression tube where all the cutouts are so that the piston seal does not get cut......how is that done? And, how critical is achieving or maintaining round? (Guessing the piston seal will offer some forgiveness?) Is there some way to chamfer the cutouts or is the honing sufficient? Is there a down and dirty solution or should I pick up a brake wheel cylinder hone?

After this Chinese break barrel there is also a Chinese side lever and underlever to fix up. Understanding that the first step to recovery is admitting it.........but I'm not ready yet Is that bad?

Thanks in advance for any advice or suggestions!

Dave

[Rob27]

There are a number of videos around. I have a document and a bunch of pictures that I will try to email to you if I can make them fit. They were created by a former member of this forum.

[Uslanja]

Thank you Rob! Received the attachments and they certainly show me what to do. Especially the deburring of the slots with that stone. One of my wife's hobbies is wood carving and she has just the tools I need. Looks like dinner out again I've been wanting her to carve up one of my rifle stocks with a technique called relief carving. But then I'm a fanatic for keeping things pristine original, so that is creating such turmoil for me. I could buy another stock and let her have at it, but then I will be a fanatic about keeping that pristine original. Oh my..........So much turmoil

I was thinking of going at the slots with a chain saw file to create an inside chamfer but power will make it so much quicker.

Thanks Rob!

Dave

[Normk]

A handy, home made tool for many tasks is to bend some heavy wire, back onto itself, to trap a strip of sand paper in the wire or rod.

One has to be careful not to spin too fast while the hone is not inside a hole. This is just a round one with sandpaper, but one can use fine paper, and especially wet paper to give some good results.

per.

[Uslanja]

Hi Norm! That looks easy to make. Do you think an old coat hanger will work or is it too soft? So just centrifugal force will keep the paper against the metal? How fine of a paper and how polished would be appropriate for the final stage? Should it be mirror shiny? Did not see any gouges, scoring or galling inside the tube so I do not believe there is much to address other than ensuring that the cutouts don't cut the piston seal. Not sure how close the round of the tube is. It looks OK but I have no way to measure it. I'm guessing the flexibility of the piston seal and the air pressure as it moves forward will force it against the tube and follow any irregularities? When I see how crudely this air rifle is made I'm I impressed that it works.

[lauchlin]

I use a 1/2 inch wood dowel cut a slot in the top slid the sand cloth in the wood will not scratch the tube but what ever works for you

[Normk]

Hi Norm! That looks easy to make. Do you think an old coat hanger will work or is it too soft? So just centrifugal force will keep the paper against the metal? How fine of a paper and how polished would be appropriate for the final stage? Should it be mirror shiny? Did not see any gouges, scoring or galling inside the tube so I do not believe there is much to address other than ensuring that the cutouts don't cut the piston seal. Not sure how close the round of the tube is. It looks OK but I have no way to measure it. I'm guessing the flexibility of the piston seal and the air pressure as it moves forward will force it against the tube and follow any irregularities? When I see how crudely this air rifle is made I'm I impressed that it works.

I usually use a section of straight coat hanger wire. Harder, more brittle wire is actually more of a problem, as it using much longer wire than necessary. I've used paper into 1,000 grit and finer.


Lauchlin's dowel works well for larger holes and has less tendency to wobble in larger holes. Thanks for catching that omission.

Centrifugal force throws the paper against the wall of the hole, quite effectively, allowing one to hone an irregular hole, although one needs to try to keep the hone centered somewhat in the hole so as to avoid honing eccentrically.

The cylinder finish would ideally be in the 0.2 - 0.4 micon range, like the finish of a CD, aluminum foil, or eyeglass lenses.

I understand that, like other devices, too smooth a finish may not provide sufficient friction to effectively flare the sealing cup lips, if the gun uses the typical old leather or other cup seal. I admit that I have trouble understanding why compressing air pressure would not serve, but this seems to be a popular recommendation.

[Rob27]

I have a plastic rod that I think was once a support for a potted plant. I wrapped it with tape and scrap paper, then a few more layers of tape to get it close to the ID of what I wanted (different guns have different sized tubes). I used to have different pieces of sandpaper that I would tape on to it and wrap around plus adding in a few layers of paper if I wanted a tighter fit. This got annoying when switching grits so I bought a couple 3/8" dowels and chopped them into 2 foot lengths and now I have a permanent sanding stick with 320 and 600 grit ready to go.
I have thought about using metal, but since I am risk averse I am concerned that I might accidentally scratch the tube that I was trying to make smooth. Also, the folded over front end means that the rod extends in front of the sandpaper so it would be easy to have the rod hit the end of the tube when trying to get the whole tube done. With mine I always have the paper and backing material extend a bit beyond the stick.

[Uslanja]

Hi All! Thanks for showing and telling what you guys do. I wound up using a 1/4 inch steel rod, duct taped a rubber strip on to it and then duct taped the paper to the rubber and all in a direction so that it wouldn't unwind. Surprised how soft that Chinese steel is. Filed an inside chamfer along the cutouts with a small 1/8" file and then honed the inside of the tube. That didn't take very long at all.

Then when the piston was going in to the tube it started to bind at the lower skirt. Quick look and sure enough the skirt was out of round. No wonder I had to drive it out when taking it apart. Without a way to round the skirt a file was used to just take down a bit of the lower edge of the skirt and in it went. The upper portion of the piston where the seal is looks just fine. A piston sleeve was made out of my favourite canned drink (Club Soda, neat) and two flat washers were ground down a bit to slide into the piston. There was no tophat when it was taken apart and not having any idea about how to make one: the thought was the first flatwasher will hold the sleeve in place and the second washer will slide on the first washer and hopefully eliminate any torsion recoil. A wee bit of moly grease on the flatwashers, piston skirt and spring and put it together. There is about 1.5" inch of preload on the spring. A couple drips of pelgun oil down the transfer port. A plumbing flat washer was drilled out a bit and pushed into where a breach seal should have been and a drop of pelgun oil on it.

Now here's the best part..........this is the moment of climatic excitement The Chrony!!

Before this old girl was torn down she was launching projectiles at a blistering speed of 249.01272 FPS. And now: Elon Musk and his Space X Rockets are going to have a hard time catching up with these pellets..........this B1 is now launching lead at a stagering speed of 335.29776 FPS!! There won't be a tin can safe in this yard!

Oh well first pellet gun I have taken apart so I guess I learned something . If was fun!

Does anyone have any idea what the velocity of this B1 should be? Not sure what more could be done to speed it up a bit more unless the spring is tired? The stock has been waxed up along with all the metal and she sure does look and feel like a mighty fine specimen. Even ordered a Chinese Military surplus sling for the old girl.......just to complete her ensemble! I think the House Manager was mumbling something about: why would you spend any more money on that! You're nuts! Or something to that effect Now for another project!

Thanks for all the help!
Dave

[lauchlin]

Great post LOL i think you are going to need another spring ............