GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: Rapid12 on May 10, 2019, 03:34:06 AM
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Are there any gains to lap/polish a barrel higher than 800/1200 grit (25/15microns)?
While polishing sizing dies I have experienced slugs getting sticky and harder to push through when grits go above 800?
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I’m definitely not the expert on this subject . I would think the less microscopic scratched in the finish would make it more slippery . I always lube , wether I’m sizing or shooting .
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I read somewhere that JB bore paste followed with mothers mag/aluminum polish works great.
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What you are experiencing is the smaller surface area. wit very fine scratch pattern, the slug is only touching the high points, therefore less resistance.
However, the high points do cause a rougher finish. If proper lube is used, a well polished bore or die will have much less friction.
I fully mirror polish my dies, and bores as well. the sides of the bullets as they drop form the dies looks like they are fully polished as well. ;)
Knife
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I final lapp at @ 600 , solvent clean and then wax the bore. Works fantastic !
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I don't know if I have done this right or wrong, nor do I even know what JB Bore Bright is in regards to grit. I melt down what ever shot pellets I recovered from my target, heavy on the Crosman HP 14.3 followed up JSb. Melt that down, remove the dross and pour that into the barrel. Push the slug out as far as I can and then cut groves into the lead. I then smothered everything in Bore Bright and begin adding the elbow grease and more Bore Bright until the bore feels uniformed through out.
I have done this to mostly Crosman .22 barrels and I must say the ones from 5 years ago seem softer than the newer ones. Or it could be the bore is tighter and it takes more to get them uniform, whatever the reason, it takes more work. Maybe I'm just getting old :o.
I'm thinking it would be easier if I were to actually use a real grit instead of relying on the hard Crosman pellets for the abrasive aspect. It normally takes a couple hundred strokes before I'm feeling good about the barrel. The bore appears to be very shiny afterward.
I learn so much from the forum members, as an example, up to this point I have never heard about using wax in the barrel.
Scott, what wax brand or type do you use?
Dave
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Knife: True. Higher the surface finish of the sizing die shinier the cast slugs drop out.
Scott: Agree with you fully.
Lapped barrel in steps- 500, 600, 1200, 3000, 8000 grits which resulted in erratic pellet speed variation of 20 fps with concomitant vertical stringing.
Backed down to 1200 grit and pellet speed increased by 15 fps with +/- 2 fps variation.
Pellets were lubed in both cases.
Will back down to 600 grit soon.
Thank you for the replies.
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from my experience too shiny is detrimental as you observed,
I experimented down to submicron diamond paste
I got leading up badly which when checked by pushing a pellet through with a carbon rod
I could feel stickiness.
On a boolit forum guys also spoke about it
and the analogy they gave is that a crayon slides easily on paper
yet sticks on glass
Knife: True. Higher the surface finish of the sizing die shinier the cast slugs drop out.
Scott: Agree with you fully.
Lapped barrel in steps- 500, 600, 1200, 3000, 8000 grits which resulted in erratic pellet speed variation of 20 fps with concomitant vertical stringing.
Backed down to 1200 grit and pellet speed increased by 15 fps with +/- 2 fps variation.
Pellets were lubed in both cases.
Will back down to 600 grit soon.
Thank you for the replies.
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+++ on all three points Lenny!
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On a boolit forum guys also spoke about it
and the analogy they gave is that a crayon slides easily on paper
yet sticks on glass
It makes since but hard to reason.
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I final lapp at @ 600 , solvent clean and then wax the bore. Works fantastic !
??? wax on wax off, what type of wax do you prefer? Bees?
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Me I think every Barrel is different...I think L.W. barrel are made of a free machining steal which will make fore a smoother bore... but hey for some reason say one may have a rough spot that leads up... so maybe you need to clean that up... there are many things that can happen during the manufacture of a barrel... so there is no one answer...can be to smooth.. ::) sorry but I am not convinced... not necessary beyond a certain point just more like it...
Lead will get shaved by micro- burrs,,, and lead sticks to lead...
I like fire lapping my Crosman barrels with some auto rubbing compound or toothpastes that has hydrated silica or Diatomaceous earth... have Jb compound which is basically DE...
DE is very friable and if I remember right particle size is usually 10 um to 200 um (.00039-.0078)... There is a plant about 30 miles from my house, had an employer that worked there... I think they at the time they milled and sorted to three grits 8 micron, 20 micron and 40 micron...
So any ways the point is is that what it(lapping/fire lapping) does... is get all the micro scratches/burrs aligned with the direction of travel of the round.. ;)
ok so now ya got the Wheeler fire lapping kit.... 220 ,320 and 600 grit and it is silicon carbide... pretty sure is what Cedric used for his TJ liner... (Hammer forged moly) barrel... and yes you can ruin a powder burner barrel with it...
here is a grit conversion chart... https://www.washingtonmills.com/resources/guides/ansi-particle-size-conversion-chart (https://www.washingtonmills.com/resources/guides/ansi-particle-size-conversion-chart)
So how hard is your barrel and just what are you tryin' to accomplish..?
This is what some of our ancestors did in fixing worn out pitted bores...
http://www.flintriflesmith.com/ToolsandTechniques/freshening.htm (http://www.flintriflesmith.com/ToolsandTechniques/freshening.htm)
here is food for thought also... https://www.shootingtimes.com/editorial/does-a-rough-bore-mean-poor-accuracy/99084 (https://www.shootingtimes.com/editorial/does-a-rough-bore-mean-poor-accuracy/99084)
then we have to think about what causes issues for a 7.9g .177 @ 10-15 fpe pellet or maybe a 30g BBT .22 @ 20-60 fpe or a 200g Whiteout .308 BBT... etc. etc. etc.
so yeah a lot depends on the individual barrel to me...