If you fit this with our kit then you must use a good chronograph to check your gun, to make sure it does not go over the limit. If you are putting your QB/XS on FAC then this body will make your gun more efficient, so you could fit on none FAC and reduce the hammer spring by cutting a couple of coils off to keep the power below the limit especially when it is hot. Do not fit this as well as our kit on the .22.

Special deal for a limited period. If you fit this with our kit then you must chronograph your gun to make sure it does not go over the limit. If you are putting your QB/XS on FAC then this body will make your gun more efficient, so you could fit on none FAC and reduce the hammer spring by cutting a couple of coils off to keep the power below the limit especially when it is hot. Do not fit this as well as our kit on the .22 unless you are going to reduce the hammer spring.
XS/QB 78/79 Modified Brass Exhaust Valve Body with less lost volume transfer port and few thou larger axis flow bore.  Replaces the standard Brass one that has a transfer port that is too large and loses power. We have done the transfer port to the size we have found to be the best for greater efficiency.

Now comes with small retaining Allen Screw with a larger head to keep the location correct. The standard one allows too much movement and the port can be off centre by quite a lot on some guns.You can see that it aligns near the centre compared to some of the standard brass ones that can move out of alignment.

You also get the Piercer Body High Flow for the SMK QB/XS 78/79 models. This does away with the tube, gauze, filter and steel washer. Do not try to fit the Tube, Filter , washer or gauze into our valve piercer body, our piercer body is designed for more efficiency and power. Helps to bring the gun nearer the UK limit of 12 ft. lbs. Standard they are normally between 6 to 8 ft. lbs.
Always check the power to make sure the gun does not exceed your limit, after changing any parts.