Besbro Spring Retainer

For Besbro A901 blaster!

12/24/21 UPDATE: ADDED Spacer/Insert for plunger side of spring. Should prevent open-ended springs (K27 etc.) from squeezing past the stock resting spot and gumming up the blaster. Experimental.

Modified retainer to allow for a wider variety of springs when upgrading. Max spring OD ~18mm compared to stock ~16mm