All of the .1 series of guns (T8.1 and T9.1) come completely ready for First Strike rounds already. There is nothing you have to buy extra besides the rounds themselves and more mags (they only come with 1 mag).
The older, pre-.1 guns need to have a specific upgrade kit installed. Generally, unless you find a really good used package deal, it is much cheaper to just go with a .1 series gun.
Jay AKA Rogue...
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