Too fat? Marginally.

Too short? Yes, all HL's have short barrels to fit the packaging or maybe they had a set dimension for the inner metal barrel and then built the plastic "cosmetic" barrel around it.

The Pershing and Tiger I barrels can be lengthened with a section of styrene tubing and keeping the airsoft function intact at the same time. Check the search function using the appropriate wording and you shall find numerous hits on the subject.