Gun shops/smiths in Hertfordshire?

[Willenium]

Yes it's advisable to test while doing any work. A small change can make quite a difference to power level. With a springer (and especially a budget/BSA one) you'll probably not want it running too near the limit, as they often feel noticeably less pleasant to shoot.

[MartynB]

Yes it's advisable to test while doing any work. A small change can make quite a difference to power level. With a springer (and especially a budget/BSA one) you'll probably not want it running too near the limit, as they often feel noticeably less pleasant to shoot.

Plus power can go up as they bed in