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So unhelpful....yet gold.
In other words, welcome to NES.
Not to hijack, but looking at post #5, what the hell is a semi-automatic version of an automatic firearm?
The OP has been around long enough to take it.
Sometimes the bullets will seem to fit, but you could damage the threading through regular use.
Be careful buying a used firearm from a plumber - if the barrel has NPT threading, it tapers, and you'll need corresponding NPT rounds. It's expensive, but fun to shoot - worth looking into handloading. You can get supplies from Cabelas or MSC.