Ruger Blackhawk possibly going super sonic with 9.7g pellets

[JamesJL]

  Bought a black around two months ago and have put around 150 assorted rounds through it. I've only used the proper silicone oil in it and absolutely nothing that can combust or detonate. No dieselinv happening since all the factory crud has burned off. I do not have a charming so I cannot do any real testing. But yesterday I was shooting some gamo rockets and the pellets were fed hitting super sonic speeds. I've been shooting an old steel pot that I use as a makeshift pellet trap with paper plates wedged in as targets. The pellet are literally tearing through the back of the pot, which is not something I expected from to see.                                                                                                                                     
 One would think that the nearly ten grain pellets would be in the 800-900 fps range, but after seeing the damage done and hearing the all too familiar mini sonic boom that is very similar in sound to my .22 plinkster, I'm not sure as to why this is happening. Could this rifle be hitting extra hard for some reason?

[Tommy]

I have a blackhawk and the only time it went over mach 1 was when it deiseld I use 7.9 crosmans and they stay around 950 fps
Tommy

[Tommy]

Is yours .22 or .177?
Tommy

[JamesJL]

My gun is is the .177 basic model. The group's range from a dime size hole to a quarter at ten yards on average, with some flyers here and there. Overall the gun shoots great and is fine in function and finish. I ordered it from amazon, and it came with the packaged 4x32 scope. I've shot accurately with both iron sights and two different low-mid range optics.

[Tommy]

Are you sure the pellets are 9.7 and not 7.9?
Tommy

[JamesJL]

Various sources on the internet state they are 9.6 to 9.7 grains.

[condor22]

 My RWS34P in .177 would go supersonic using 'Gamo Raptor PBA .177 Cal, 5.4 Grains' pellets.  These pellets made a mini sonic boom every time, where other pellets only made noise hitting the target. BTW I couldn't hit the broad side of a barn with the raptor's. Raptor pellets contain iron or nickel, I could pick them up with a magnet, so IMHO don't condone using 'em.  Yep, just checked again, my salvaged hard drive magnet picked up 8 Gamo Golden Raptor pellets and absolutely no crosman pellets. 

[LAalex]

My guess is it's fuel induced in some way.  That platform won't do 23-24 FPE under normal conditions.  JMO.

Scotty

[longhunter]

To achieve a sonic crack, those pellets would have to be going 1100 fps, or better. Not gonna happen with that gun. My airhawk will throw 7.9 gr at a consistent 947 fps.
Was me, I'd be looking at replacing the piston seal. I think you may have lube getting around it and into the comp chamber. That, or all that silicone oil got past the seal and thinned out the grease allowing it to get past the seal.
Either way, stop using chamber oil. It's totally unnecessary , and, if it mixes with the grease on the piston, it will thin it out and the grease won't be effective.
 Silicone oil and grease are not for lubing metal to metal surfaces. They cause galling.
Enough grease ( a very thin film ), already lubes the sides of the piston seal by way of migration. You don't need anything else introduced into the comp tube.

[JamesJL]

I was under the impression that you needed a drop or two as the blackhawks are dry from the get go, and that it also helps the seals or o rings. Thanks for the advice.

[JamesJL]

I guess it's possible that the pellets could be out of spec or loose fitting. Could a lot of air escape around the pellet if it's lose and cause a similar sound, something that sounds like a slight sonic boom? Also, I'm not getting any smoke from the barrel after firing it, just a faint smell of burned grease or factory oil of some kind.

[Tommy]

do not use any oil Just moly the piston and chamber after you clean it out. Any petroleum based oil will fire and hurt your piston There is a great article in the library on lubes check it out first
Tommy

[longhunter]

I was under the impression that you needed a drop or two as the blackhawks are dry from the get go, and that it also helps the seals or o rings. Thanks for the advice.

They're not dry, but, whatever lube they use seems to liquefy after the gun warms up. Usually around 20 or30 shots.

James, the smell you're referring to is that silicone oil you put in the chamber.

[JamesJL]

I guess I should've come here first for info. I have a lot to learn about airguns, especially spring piston rifles. On another note I've never used anything other than two drops of silicone oil on this gun. I knew from the earlier years of my life not use anything combustible. I'll continue doing research and learning more about these specific guns so that I may recognize any issues at hand. Thanks for your time everyone.

[Bullit]

With the modern synthetic piston seals, you don't need to add any oil into the chamber.
With the old leather piston seals, you did it to keep them supple.  Not required anymore.

[Paul68]

The breech seal is a common issue on these guns. If yours has developed a bad leak it could create a lot of noise.