ditchman Posted June 21, 2017 Report Share Posted June 21, 2017 What weight is needed to start a piston with a new lubed "o"ring..on its travel down the compression part of the bore...before the gun is assembled Airsporter/mercury/mercury "s" cheers Quote Link to comment Share on other sites More sharing options...
figgy Posted June 22, 2017 Report Share Posted June 22, 2017 Never looked at what weight is needed just felt for a nice smooth travel along its length with no tight or slack points. Quote Link to comment Share on other sites More sharing options...
ditchman Posted June 22, 2017 Author Report Share Posted June 22, 2017 (edited) Never looked at what weight is needed just felt for a nice smooth travel along its length with no tight or slack points. thanks for replying...........i have nice smooth travel...but it seems very tight...need about 20lbs in weight to get it moving...the accuaracy at 12m is very good...5mm groups...but the groups blow at 25m...the gunsmith says the pellets are corkscrewing .!...(dont quite understand this) but he goes onto say...when he fits a new piston ring he will rub it down and keep fitting it in the chamber until he has a nice smooth travel...................which is what you were saying.......... but i cant see the relationship between the overtight piston and cork screwing.......but i can alter the "o" ring size but rubbing it down until i get smooth travel.. its just a suck it and see exercise .............the is a lot of thought and maths that goes into tuning ...and i dont understand most of it ...only the principles.. Edited June 22, 2017 by ditchman Quote Link to comment Share on other sites More sharing options...
bruno22rf Posted June 22, 2017 Report Share Posted June 22, 2017 (edited) I seem to recall reading somewhere that the piston/seal should slide slowly down the cylinder under it's own weight? As for corkscrewing - I cannot think of anything that would cause this other than a poorly made/fitting pellet. Edited June 22, 2017 by bruno22rf Quote Link to comment Share on other sites More sharing options...
ditchman Posted June 22, 2017 Author Report Share Posted June 22, 2017 I seem to recall reading somewhere that the piston/seal should slide slowly down the cylinder under it's own weight? if i modify it closer to your and figgy's post i should be on the right path ....as im seriously way out Quote Link to comment Share on other sites More sharing options...
Bazooka Joe Posted June 22, 2017 Report Share Posted June 22, 2017 but i cant see the relationship between the overtight piston and cork screwing. Neither can I..first I'd clean the barrel & look for crown damage, leave the mod off if it has one to test it. If that didn't sort it I would try a different pellet weight, lighter pellets traveling at higher velocities will corkscrew. Quote Link to comment Share on other sites More sharing options...
ditchman Posted June 22, 2017 Author Report Share Posted June 22, 2017 Neither can I..first I'd clean the barrel & look for crown damage, leave the mod off if it has one to test it. If that didn't sort it I would try a different pellet weight, lighter pellets traveling at higher velocities will corkscrew. the barrell and crown are spot on......i now know the piston is too tight...so i will alter that first.............then try and sorce ANOTHER type of pellet...as the ones i have now i believe to be not a tight enough fit........ Quote Link to comment Share on other sites More sharing options...
oldypigeonpopper Posted June 22, 2017 Report Share Posted June 22, 2017 hello ditchman, if i think back to when i had my oldy english air rifles and quite a few the pistons were a bit tight fitting after a new seal even the leather ones, thats what i was told should be ? as for pellets what we had then called slugs ha ha, they should drop in place with just a light thumb touch, now days with a PCP/ and a cheapy springer i use L T 1 pellet lube Quote Link to comment Share on other sites More sharing options...
ditchman Posted June 22, 2017 Author Report Share Posted June 22, 2017 ive had it apart again.........sanded down the o ring........will try it out when the weather lifts... Quote Link to comment Share on other sites More sharing options...
bruno22rf Posted June 22, 2017 Report Share Posted June 22, 2017 The even darker art of O ring fettling is just around the corner . I would try a selection of different rings from various sources as variables in inside dia and the flexibility of the materiel used in manufacture can make a difference i.e. an O ring id should be smaller than the od of the groove into which it locates - the amount of difference will effect the od of the O ring or, put more simply, the tighter the O ring grips the bottom of the groove, the smaller the od will be. Next comes the composition as various mixtures used during manufacture enable the O ring to exhibit different flexibility during use, obviously the more resistant to flexing the O ring is, the more pressure it will exert on it's component part. Just buy a bloomin PCP and be done with it . Quote Link to comment Share on other sites More sharing options...
timmytree Posted June 22, 2017 Report Share Posted June 22, 2017 Spiralling can be caused by crown or barrel issues or wrong choice of pellets. Some break barrels would clip pellets that weren't seated properly. The best way to see spiralling is to shoot at night with a powerful gunlight, if the pellets are clean the inside of the skirt will light up and show you what's happening. Quote Link to comment Share on other sites More sharing options...
ditchman Posted June 22, 2017 Author Report Share Posted June 22, 2017 The even darker art of O ring fettling is just around the corner . I would try a selection of different rings from various sources as variables in inside dia and the flexibility of the materiel used in manufacture can make a difference i.e. an O ring id should be smaller than the od of the groove into which it locates - the amount of difference will effect the od of the O ring or, put more simply, the tighter the O ring grips the bottom of the groove, the smaller the od will be. Next comes the composition as various mixtures used during manufacture enable the O ring to exhibit different flexibility during use, obviously the more resistant to flexing the O ring is, the more pressure it will exert on it's component part. Just buy a bloomin PCP and be done with it . jesus getta outa here....you will do ma ead in .. these "o" rings i am using are from Knibb's/chambers for the model "S".....i have 4 boxes of o rings ...metric imperial...and a sey of cat o rings which i wont use as they are rolled and not mold injected........... really need someone to recommend me a pellet that will fit this barrel .................. Quote Link to comment Share on other sites More sharing options...
bruno22rf Posted June 22, 2017 Report Share Posted June 22, 2017 What have you tried? Mine shot AA Field pretty well, they dropped down the barrel a couple of mm but accuracy was acceptable. Quote Link to comment Share on other sites More sharing options...
clakk Posted June 22, 2017 Report Share Posted June 22, 2017 My Supersport loves H and N field target trophy ,and if i use cheapo spitfires they spin .. I know as the pellet hole is the side view of said pellet where its spun through .If you buy a selection pack some pellets are pushed in as theyre tight = H and N ,R.W.S and Bisley Magnum,but spitfires ,coppapell and Lanes drop in very loose . Trial n error Ditchman ,your piston will bed in over time.Buy 2 or 3 selection packs and enjoy bladdering potatoes ,cardboard boxes ,and paper targets till you find 1,s your rifle likes . The more you trial the easier your piston will be and it beats T.V any day atb Quote Link to comment Share on other sites More sharing options...
ditchman Posted June 23, 2017 Author Report Share Posted June 23, 2017 My Supersport loves H and N field target trophy ,and if i use cheapo spitfires they spin .. I know as the pellet hole is the side view of said pellet where its spun through .If you buy a selection pack some pellets are pushed in as theyre tight = H and N ,R.W.S and Bisley Magnum,but spitfires ,coppapell and Lanes drop in very loose . Trial n error Ditchman ,your piston will bed in over time.Buy 2 or 3 selection packs and enjoy bladdering potatoes ,cardboard boxes ,and paper targets till you find 1,s your rifle likes . The more you trial the easier your piston will be and it beats T.V any day atb looking on various forums......more and more the brand comes up of H&N....so i will have a go at them.... Quote Link to comment Share on other sites More sharing options...
clakk Posted June 23, 2017 Report Share Posted June 23, 2017 Drop me your address by P.M mr Ditchman and il send you a sample of H n N,and some R.W.S and some Interceptors theyre all around 15 to 16 gr weight but your rifle will tell you whats best atb Quote Link to comment Share on other sites More sharing options...
ditchman Posted June 23, 2017 Author Report Share Posted June 23, 2017 Drop me your address by P.M mr Ditchman and il send you a sample of H n N,and some R.W.S and some Interceptors theyre all around 15 to 16 gr weight but your rifle will tell you whats best atb that is a very kind offer...which i would love to take up...as i am rapidly becoming a "lead mountain".. trouble is im shooting a .177cal..... Quote Link to comment Share on other sites More sharing options...
Whitebridges Posted June 23, 2017 Report Share Posted June 23, 2017 Ditchy me ol' partner, i've got a few different .177's including some old and resized wasps made specifically for old British guns. I'll pop a few in the post, no problem if it helps. Quote Link to comment Share on other sites More sharing options...
ditchman Posted June 23, 2017 Author Report Share Posted June 23, 2017 Ditchy me ol' partner, i've got a few different .177's including some old and resized wasps made specifically for old British guns. I'll pop a few in the post, no problem if it helps. ooohhh yes please... Quote Link to comment Share on other sites More sharing options...
figgy Posted June 23, 2017 Report Share Posted June 23, 2017 The piston seal shouldn't be to tight at all. As when it gets rammed down against the air and compresses the chamber the air forces the seal against the chamber creating the seal. Best to buy a good tuning kit with a better seal. Tuning is a bout polishing all the parts and getting them to be as smooth and polished as can be with as little friction as possible. Bit like porting and honing a head. Get the spring on the polishing wheel until it looks like chrome and do the same with the inside of the chamber. Then get some course emery cloth and gently slide inside and turn it a few times in the chamber to cross hatch to leave score marks around the chamber/cylinder to hold grease. Remove any sharp edges and burrs. Your gun should cock very easily and smoothly with a better lock time. I used to do loads around 25 years ago with very good results. Quote Link to comment Share on other sites More sharing options...
Whitebridges Posted June 23, 2017 Report Share Posted June 23, 2017 ooohhh yes please... I'll post 'em Saturday Ditch. Quote Link to comment Share on other sites More sharing options...
clakk Posted June 24, 2017 Report Share Posted June 24, 2017 Ok Ditchy no problem glad your sorted P.W at it,s best again Quote Link to comment Share on other sites More sharing options...
oldypigeonpopper Posted June 24, 2017 Report Share Posted June 24, 2017 (edited) The piston seal shouldn't be to tight at all. As when it gets rammed down against the air and compresses the chamber the air forces the seal against the chamber creating the seal. Best to buy a good tuning kit with a better seal. Tuning is a bout polishing all the parts and getting them to be as smooth and polished as can be with as little friction as possible. Bit like porting and honing a head. Get the spring on the polishing wheel until it looks like chrome and do the same with the inside of the chamber. Then get some course emery cloth and gently slide inside and turn it a few times in the chamber to cross hatch to leave score marks around the chamber/cylinder to hold grease. Remove any sharp edges and burrs. Your gun should cock very easily and smoothly with a better lock time. I used to do loads around 25 years ago with very good results. hello, plus 1 , theres TINBUM kits on ebay but will make to order if an older air rifle Edited June 24, 2017 by oldypigeonpopper Quote Link to comment Share on other sites More sharing options...
ditchman Posted June 24, 2017 Author Report Share Posted June 24, 2017 The piston seal shouldn't be to tight at all. As when it gets rammed down against the air and compresses the chamber the air forces the seal against the chamber creating the seal. Best to buy a good tuning kit with a better seal. Tuning is a bout polishing all the parts and getting them to be as smooth and polished as can be with as little friction as possible. Bit like porting and honing a head. Get the spring on the polishing wheel until it looks like chrome and do the same with the inside of the chamber. Then get some course emery cloth and gently slide inside and turn it a few times in the chamber to cross hatch to leave score marks around the chamber/cylinder to hold grease. Remove any sharp edges and burrs. Your gun should cock very easily and smoothly with a better lock time. I used to do loads around 25 years ago with very good results. more or less that is exactly what i did....what i also did was to countersink the exit port...and smooth out and polish....cause air is like water...dont like sharp corners... Quote Link to comment Share on other sites More sharing options...
figgy Posted June 29, 2017 Report Share Posted June 29, 2017 Yep porting and honing. The gains can be rather large after tuning so best check on a chrony after. Quote Link to comment Share on other sites More sharing options...
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