[DonVoigt]

Miles,
remember you are dealing with a piece that was not "designed" for high volume shooting!
It is an alteration that shortens the space available for the mainspring.\

Theoretically the shorter spring should be the same strength as the long one, but there is not room- so the diameter of the wire would have to be increased slightly, again theoretically.

Since many lugers show some contact at the rear, I'd say it is acceptable, if not "normal".

Practical advice, don't shoot it so much that it causes the problem!

PS- Your MCC gage is done and ready!