Removing the factory designed, mfg'd and factory installed magazine safety and then shooting an NRA pistol match with the gun would most likely void your score in that match.
That of course if someone brought the condition to the attention of a judge in the Match.

In the high stakes matches this would be taken quite seriously as any bending of the rules is seen as an attempt to gain that 'edge' over the next competitor. Conversley, anything you can use to get the other guy's score thrown out of the match can only help you too!. A point either way makes the difference just like any of the top competitor shooting sports.

I would think the factory mfg'd and installed mag safety falls under the 'Operational Safeties' deffinitions in the NRA Pistol Competition Rule Book.
Through out the rules, the pistols and revolvers in competition must always be in a condition of..
'All standard safety features of the gun must operate properly. "

Deffinition of operational safeties from the Rules:
• 3.7 Operational Safeties- These safeties will include:
1. Manual safety operated by the shooter while handling
the firearm
2. Grip safety operated by normal holding of the firearm
3. Drop safeties incorporated to prevent discharge if the
firearm is accidentally dropped
4. Internal safeties such as transfer bars, firing pin blocks,
hammer blocks, and half cock notches, when installed in firearms
as originally manufactured.

I think #4 would cover the magazine safety though it does not specificly mention it. It does use the language of 'such as'.

What does it all mean,,probably not much to average weekend Bullseye Industrial League shooter.
Not much checking of the trigger pulls for NRA minimum or measuring grips to see if they have too much curl at the bottom.
Shoot for score,,have some fun,,maybe win a recycled plastic bowling trophy at the end of the year.
I used to do it,,it's a lot of fun.

The other point of not removing a mag safety from a pure target pistol is also well taken.
It's a little extra safety. When they say 'magazines out,,slides back,,guns unloaded on the bench',,there's that one more safety involved.
Especially when the shooters all leave their guns unattended and walk down to mark targets in an outdoor match.

If you want to over-ride the mag safety and still not have the issue of haveing an opperable magazine in the gun,,as well as having the slide lock back each time you rack the slide to cock it,,,,take the least quality magazine for the pistol you have and remove the mag spring and follower.
In most cases,with most pistols,, it will still actuate the magazine safety, but you won't be able to accidently 'load' it and it won't lock the slide back each time you re-cock the pistol while dryfire practice. The latter can be kind of annoying.

One certified Bullseye nut I knew even had one with a bit of lead in the thing that weighed the same as the 5rds of ammo and the spring and followed he removed(yes he was a perfectionist). Simply weighed the stuff up on a reloading scale.
That gave him the weight of a full mag for dryfire practice but no chance of a loaded pistol.
IIRC he may have even lightly crimped over the feed lips just a bit too, just to satisfy himself a bit more that the mag could not injest a live round and somehow end up in the chamber and then the wall of his gun room during dryfire practice.

http://compete.nra.org/documents/pdf...istol-book.pdf