Hey i recently did a full power nitro piston conversion to my benjamin .22 classic. During the conversion i took the time to hone the tube and sand and polish the internals.( gas spring, and.piston.) as well as the tube and piston seal. During the sanding process i sanded the the breach seal which dramaticaly after reassembling dropped ths veloxity by almost 100fps. I then replaced the piston seal and breach seal which increased the velocity up a bit but was still shooting slow and would drop velocity back even lower adter being maybe 15 minutes outside and putting probably 20 rounds through it. I then replaced the tube to i think a benjamin trail tube ( the one with the picatiny rail built in) doing this brought the velocity back up to the proper fps (730 ish) fps and was shooting great with minimal fps drop after being out in the cold (690-700 fps). Today was alot warmer then the conditions i normaly shoot in and was getting a chronagraphed string of 730,722,590,490,720 and the pattern would follow shoot a few fhsn extream velocity drop off. I did the breach test with the paper towel or kleenex or what ever and it passed. So i really dont get why my airgun is doing this. Does any one know why it could be doing this?
Nitro piston conversion velocity issues help
- Thread starter Ravenairgun123
- Start date
Are your pellets consistent? An under sized pellet will not seal against the sides of the barrel.
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Crossman premier hollow points....never had a problem with them before 99% sure it has nothing to do with the pellet
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you never mention how the piston seal fit in the tube and what type of lube you used
and of course we don't know what's wrong, how could we
I been posting that it is impossible to tell anyone what is wrong in certain cases and this would be one of those
is it too much sanding or polishing ???? but how did the seal fit in the tube
sometimes guns are better just left alone
and of course we don't know what's wrong, how could we
I been posting that it is impossible to tell anyone what is wrong in certain cases and this would be one of those
is it too much sanding or polishing ???? but how did the seal fit in the tube
sometimes guns are better just left alone
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So you asked what lube i used and how the seal fit. The seal fit tight and snug. And i used like a red synthetic tractor grease lube which i never had problems with and i used the recommended breach seal oil by crosman. Can the incorrect grease or lube cause velocity drop by 100 fps or so? If so thats probably what it is. I reassemnled last night and cleaned the internals and didnt have any drop in a 10 shot string all was 710-730ish .just curious how does the wrong lube or oil cause velocity drop doesnt make sense to me you think it would increase velocity?
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I only have a few years shooting airguns but when I replaced the piston seal on My Gamo I used the recommended lube very sparingly. It was some type of moly grease I got from custom air seals and was gray in color. Whenever you use a lubricant for anything there is the possibility of the viscosity causing the lube to thicken and slow things down. This is true with lubing pellets as well. One would think the lube would make the pellets go through the rifling faster but this is not always the case. The container of grease I got from custom air seals would probably be enough to brush your teeth 3 times if it were toothpaste and Custom Air Seals of Au. said that was enough to do 10 air guns. Many of the seals are impregnated with lube now so very little is needed. My Gamo has over 20,000 shots and when I pulled the piston there was only a film on the parts. Sort of like it was lubed then wiped almost clean.
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Ya looks like it was the lube not going to put anyyhing on it again but the recomended one to two drops every 2500 rounds.
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