While you can set things up nicely so that you've got a good airseal to begin with (perhaps more important with bolt guns than AEGs)...it's not uncommon for AEGs to shoot very much under what they normally do if they're cold.
At a number of late season games we have people rip off a burst of full auto (blanks) before they chrony. The difference on the chrony is enough to go from, "crap my gun is broken" to "that's where it should be".
But if you've driven a couple of shots through your bolt gun and it's still barely kicking the BB's out...then they're likely jammed up at the hopup rubber.
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