Depending on the gun, the .177 "heavies" can be more accurate, however they do reduce spring life considerably. Here are a couple 50 yard groups my brother shot years ago when I sold him my home tuned .177 R9..Originally Posted by RichardinDorset
http://www.snapagogo.com/uploads/sou...enryTarget.jpg
He was shooting the normal 3 shot "powder burner" groups instead of the normal 5 shot pellet gun groups (normal in the US) but I thought two 3 shot groups at one sitting was commensurate to one 5 shot group.
Concerning the "reduced spring life" comment........
Whatever the reason, I do know that the spring of a .177 R9 shooting 10.5 grain pellets has a shorter life than it does shooting 7.9 grain pellets when shot at 14.5ish fpe, however I don't know if the same applies to the "UK legal power limit".
This was proven to me years ago when my brother only shot 10.5 grain CPH from his R9 and I used to replace a good aftermarket spring about every two seasons (about 15,000 shots). At that time both my brother and I living in West Virginia were each shooting a box of CPs per month except for the slower winter months. After a few years he found that the flatter trajectory of the 7.9 grain CPL trumped the greater resistance to cross winds of the "heavies" for squirrel hunting in the woods so he switched to the 7.9 grainers. After the switch to 7.9 grain pellets I only replaced one good aftermarket spring and that spring spent "half of it's life" shooting the 10.5 grainers.
I personally believe that the issue is "piston rebound" from the high pressure air column before the heavier pellet "pops the leade". The piston is rebounding at the same time the rear spring coils are still surging forward and the "clash" between the front coils in the piston surging rearward and the rear coils surging forward creates unusually high stress concentrated on only a couple coils.
I've read that some guns made with large gage wire like the R1 aren't as affected by piston rebound as the smaller gage wire of the R9 and I've also read that the springs of guns with calibers larger than .177 aren't as prone to spring failure. This is only what I've read and have no personal experience with long term .20/.22 pellet shooting.
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