Hi John,
I actually do that sometimes although depending on your guns make and model the point may be moot, ie, OAL for ruger 77 rifles is dependent on the length of the magazine box which I believe is around 3.35". Remington is an entirely different story and will allow bullets to be seated much further out than spec.
I also take a cleaning rod, close the bolt, slide it down the barrel and make a pencil mark at the muzzle. I then remove the bolt, insert the desired bullet into the chamber, held tightly against the lands and grooves with another rod (usually an unsharpened pencil) and then insert my cleaning rod into the muzzle and again make a mark. Then measure the distance between the marks and you have your max OAL to play with.
GL!!