Enhanced recoil and hammer springs are one of the few items that I would 100% guarantee will not get siezed by customs if you order over-seas. That being said ASC is always is a good resource.
Keep in mind since you're under 18 retailers in Canada will not be willing to sell to you. You'll have to get your parents/guardian to buy the gun for you and let you take it out to games.

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"Two Wongs do not make a Right"
XT Team - Task Force Wong; Tai-i Wong
-TFW Springer Weapon Assault Team (S.W.A.T.)