with a typical synth stock, when you load it up, if it is tube fed, the first shot or maybe even two, will "settle' in the action/receiver into the stock. then it shoots fantastic. Then you go to reload and start the process all over.
Like sleeping in the perfect position, then suddenly you wake up, you get up, get some water, go pee, etc., then you go back to bed, and it takes a while to get in that perfect sleep position. Same idea, unless you bed/shim slightly , on that action. you can really see this in Savage 22 stocks.