The Auxiliary Spring Rate Kit for the JP Silent Captured Spring allows custom tuning of the device to a given rifle. While the default spring installed in the JPSCS is selected to offer the best performance for the widest range of configurations, a simple disassembly and reassembly of the JPSCS with a slightly different spring rate can yield truly optimized performance, particularly for rifles without an adjustable gas block.
This kit for the JPSCS2 extra short models includes two lighter weight springs in addition to a spare of the standard weight. These lighter springs are useful if your bolt carrier will not lock back reliably on the last round fired, even when completely gassed (in the case of an adjustable gas block).
The included springs from lightest to heaviest are listed below with the color with which they are coded:
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