Anti-rotation hole in upper receiver

Are these really necessary? I have a Noveske rail and installed it without the pin because my receiver doesn't have the hole, and I'm not sure that its worth the money to have it done professionally, not to mention weakening the upper slightly by drilling another hole above the gas tube hole.

It seems to me that 6 bolts into the barrel nut will do just fine in keeping the rail from rotating. I don't think an aluminum rail is an effective lever to loosen a steel nut anyway, or am I wrong? I'm just curious if these serve any real function beyond just existing to assure the whatifs that their rail wont rotate.

The Hodge rails also use this feature (carry over from the Mega Wedgelock design, it seems) I can see that barrel nut/rail design needing such a feature since the rail is held on by friction and could theoretically rotate on the nut if enough force were applied.

I have a Noveske rail installed without the pin as well. I searched on the Net quite a bit and plenty of people are running them that way without issue. I'm not concerned about the hole weakening the upper, but I don't feel it was worth the hassle and expense of having it done.

I have a Matrix Arms rail on a dedicated .22 LR upper which clamps onto the barrel nut with no anti-rotation element. It surely could spin on the small steel barrel nut with a bit of force but people seem to run them with no problems. I can't turn mine just gripping it, and I'm the official jar opener for the queen.

Andy

"Anti-rotation" is a feature because of some poor designs, especially combined with poor installation. Because of variation in upper forgings all the tab type are only really rotation limiting, making any sights on the rail useless if it becomes loose.

You are correct that the designs that bolt directly to the barrel nut do not need "anti-rotation".

I wrote to SMOS arms about not having an upper without a pre drilled hole for their rail. They said that it is not really needed if the barrel nut is installed correctly with the appropriate amount of torque. Still I prefer rails that don’t need to be timed.


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ADCO will drill such a hole for you for a fee. They also sell uppers.

Thank you for the informative replies. I just wanted to confirm what I suspected, that the pin is more of a redundancy than a necessity. When I installed my rail it torqued about 60ft/lbs to time properly, so I'm sure I have nothing to worry about.