MS>JS> MS>SG> Yes, I've seen some CB caps, or better yet some
MS>JS> standard-length
MS>JS> MS>SG> Shorts
MS>JS> MS>SG> and LR loaded down to CB levels.
MS>JS>
MS>JS> MS>    Will they function a semiauto pistol action?
MS>JS>
MS>JS> No.  Not without extensive modification that will render the gun
MS>JS> useless
MS>JS> for reguar ammo.
MS>    What about just interchangable springs?
Springs won't do it -- the key to reliable operation of a blow-back
semi-auto is the mass of the breech block or bolt.  You can actually
take the recoil spring OUT, reassemble the gun and fire it with a CB cap
and see that it won't extract and eject.
What you have to do is reduce the mass of the bolt.  You can do that by
skeletonizing -- but then you can't use the same bolt for regular .22 LR
ammo.
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