The roll pin that came with my gas block was too large in diameter, .086" in diameter to be exact and would not start in the hole.  Went to the local shop known to be the best AR shop around and picked up two gas tube roll pins, wanting an extra just in case.  I get home and notice that the roll pin looks a lot shorter than my one that was too big in diameter.  Calipers say it's .256" long.  That doesn't leave a lot of meat sticking out of each side of the gas tube, ~.035 of roll pin sticking out each side to grab the gas block.  I went and hammered it home anyways.  Seems to lock the tab tube in place, but I can't say I'm 100% happy knowing my roll pin is too short.  So my options are:

1. Live with it, gas tube is aligned and isn't moving. Stop being a ninny.
2. Drive back to shop, polity explain the situation, see if they have longer gas block roll pins. Burns a gallon of gas.  Take up a half hour of my time.  Carbon emissions from my car cause more global warming. Polar ice caps melt and we all drawn.
3. Kick in door of local shop raising hell and cursing over a $1 gas tub pine.  Challenge shop owner's manhood, kick his dog, drop trow and poop on the hood of his truck.
4. Stick other roll tube pin in the gas block.  Two is better than one right?  Gas block is railed so it's wide enough that the extra length of two 1/4" roll pins won't stick out of the sides.  Saves the environment of an additional gallon of gas that would be burned.  Less greenhouse gasses emitted means more cold weather and snow for you guys up north.
5. Keep it as is for the time being, when I place that next order from PSA throw in a gas tube roll pin with the order.  Save gas and time.  I can't finish the rifle until you place your PSA order anyways.

You guys seem to be the AR15 experts. What would you guys do?

6. PM me your address and I'll toss a couple in an envelope. They're actually a tad longer than spec and stick out of the gas block about 5 thou each side, but it's never been an issue for me. I bought a bag of many a while ago and am highly unlikely to use them all.

1 and/or 5. They tend to be different. Also, are you using a roll pin holder? That can help drive larger diameter pin.

My gas tube roll pins are .081” x .312”.
Personally I would not use the wrong pin even if I were out just on general principal.
However it sounds close enough to work at least temporarily.