Well Mike, as usual you've received some excellent AG advice. I can't say much for the B-40 as I don't have a lot of expirience with under levers,....but from what I've been told, the 40 is a faithful copy of the TX. So listen up and follow the others' advice. Perform the tweeking methods mentioned, and soon enough everything will be hunky-dory in no time at all!
Now for the .177 B-28,...I know a thing or two about these canons! For starters, Andy gave you some pearls right off the bat,....use heavy pellets. Any sub 10 grainned pellet ain't gonna cut it! These monsters are just too dang stout and Preds and CroMags are a waste of time for any serious long range shooting. Inside that, you'll obliterate anything in its path!! So the lightest/best general purpose pellet I'd recommend would be the Kodiaks/H&N Baracudas. The Jsb pels might work but they are soft skirted pellets and in my case still didn't offer enough resistance down the barrel,.. SS velocities. Crosman Ultramags and RWS supermags both fit extremely too tight in the breech of my 28, and the accuracy was not all that great. After mine busted a spring, I reworked my 28 with another factory spring, and the OEM piston seal was in pristine shape,... so everything was good to go for re-assembly. Lubed all the right spots, and still, after every 50 or 60 rounds, it will cycle into "hyper-mode" for 5 to 10 rounds and sling the Baracudas super-sonic! And that's with no detonation happenning! And I've put well over 3K rounds through it since I tuned it! The .17 cal 28's are that dang strong. Last chroney check, Baracudas were flying in the 990 to 1020 range one foot from the muzzle. Accuracy wise,...mine is Very Scary. Almost too good to believe. Dime sized groups off hand at 25 if I do my part. Decapitating bottle caps off plastic soda bottles at 20 is a breeze for plinking pleasure. The 28's are Beasts to say the least, but once mastered, they will serve you VERY well. Wanna sweet ride?,... Get the .22 like Andy suggested. Shoots like a hopped up Diana 34!!! HeHeHe .20 cal would be ideal for this platform but neither BAM nor Diana ask for my expert advice! Oh well?!? Have fun with your new shooters!! tjk