After getting advice from several people here and in person. I am attempting to find the COL for my rifle.

After at least 10 passes using a fired, unsized cartidge and the bullet that I am intending to reload (slight neck tension, hand seating bullet just past boat tail, gently moving cartidge into battery, locking up, removing after bullet is moved up to the lands) from my .270 Win, I have come up with a COL from my rifle of: 3.463 My question is this: in my reloading manual, it lists 3.340 COL as the industry standard.

Is having a difference of 0.123 between my particular rifle readings and the listed industry standards common? I know that most of you guys may be chuckling at the rookie being so careful. But, I'm very cautious about this stuff as I am in real new and unfamiliar territory here.

I plan to back off my reading between .010-.020 for my seating depth, after taking into consideration my magazine length. should I go less or more? Am I even close to heing correct here? A friend of mine uses the method that I described above and claims it works. I've also watched a vid on YouTube from Ammosmith.com describing how to do this step by step.

I'm interested in using this method only because of my budget. If it isn't safe or recommended, I'll wait.

Thanks for listening to the rookie.

The COL listed in the manuals/industry standard are so that ammo will fit all weapons chambered for that caliber. If you exceed that length then you should only fire the cartridge in the rifle you custom measured for the cartridge. You should also take into account your magazine length if it is not a tubular magazine. Exceeding the suggested COL will typically make the ammo too long for the magazine forcing you to load a single round eact shot.

As AT has stated the max OAL in the manuals is only the max lenght that will fit in ALL factory magazines of rifles chabered for that specific cartridge.
When I find the OAL of my cartridge is going to exceed the SAAMI max I check to see if it will still fit my magazine, if not I shorten the cartridge to the max that will and go from there. Often the load will prove to work very well at the lgt given in the book, sometimes they do better close to the lands. There is no cut and dry as to where the bullet is seated that works best everytime.

My advice is unless you have a single shot,load to the SAAMI max of 3.34" and work up to your max load with it at that lgt. Once you have settled on the powder charge then reduce the OAL in 0.005" or so increments until you find your rifles "sweet spot". This could be as much as 0.10"+ deeper. It takes some experimenting but will prove worth it in the end.

I think your technique is correct and have used this method for many years. I do not pay attention to listed col any more. The Nosler Manual even states that the listed col is an "industry standard" and that a longer col may and usually will shoot more accurately. The main limitation on col is usually the mag box. If it will fit and feed from your rifle's mag, then load em and shoot em.