I loaded up some .375 H&H Sierra 200gn. FP's. (38.0gn of SR-4759, Fed 215 primers in Win brass). This is my first experience handloading centerfire rifle (lots of shotshell and handgun reloading experience). One source shows a min overall length 4.54". Max OAL 4.60". How do I know how far to seat my bullet so that it seats properly for my particular rifle while being within the above parameters?
I've read several manuals but am still unclear on this. I know each load could (and probably will be slightly different OAL) for a given rifle. Do any of you have a technique for this, at least for a starting point? Are min and max OAL's written in stone? Thanks in advance.

You're on the right track. The book shows the min safe OAL to prevent excess pressure, and the listed max OAL is generally to prevent you from having an overlong cartridge that won't function in the magazine. The trick is to find what your rifle likes and can function with. The accepted "best" bullet seating depth is so that the ogive is just short of touching the lands where the rifling begins. One way is to get a Stoney Point, RCBS, or similar chamber measuring tool and using it to determine how much "freebore" your rifle has (how far out can the bullet stick out of the case). Another from an old reloading manual is to make a dummy cartridge with your desired bullet (no powder or primer), blacken the bullet with a marker, and test it until you no longer get marks on the bullet from the rifling.
The problem is that sometimes, depending on the rifle, seating that far out makes your rifle a single-shot with that load since it won't function through the magazine. I have found in my experience to start out with the bullet seated just below maximum seating depth, and experiment until I find where it is the most accurate, which is usually the listed max OAL, and I don't bother with tools for chamber measuring (yet). Single-loading for super accuracy is fine for those that want it; I'm guessing that with a .375 you want more than one shot in the rifle.

Just try seating them to the cannalure and see if they will feed. It works with the Hornady 220 FP in my 375 H&H's.

Thanks Gents. Good info. I loaded my first loads to the cannelure and it was less than Min OAL...that was a concern to me for your stated reason.

Discovered a very good bullet seating section in "Metallic Cartridge Reloading" by Mic McPherson, pp60-62. Very clear technique. Wish I'd seen it sooner! Thanks for your help guys!

"Minimum" overall length is a pretty vague concept for most centerfire rifles. Typically, shorter cartridges will still feed just fine (and proper feeding is the primary reason for specifying a M.O.A.L. because many handguns and some tube-fed rifles are very sensitive to OAL when feeding). In a cartridge like the .375 H & H, seating marginally shorter than some arbitrary "minimum" will have no discernable effect on the pressure of your loads.

Maximum OAL is limited by (1) the rifling leade of your chamber, and (2) your magazine length. If the bullet doesn't contact the rifling when chambered and fits in the magazine, then the cartridge is short enough, no matter what some reference says.

Curiously, accuracy CAN be affected by seemingly small changes in bullet seating depth, but this has to do with barrel harmonics and is not always predictable.

Take a fired case and size the neck only about 1/8". Seat a bullet. Now chamber this dummy round. When the bullet contacts the lands it will shove back into the case because of such a light grip on the bullet. Measure the round, seat your bullets to give an OAL of 1/16" less than you dummy. Make up another dummy but this time size size all of the neck and seat to above OAL. Run this through you magazine and if all if well, you are in business. If it is too long to feed through your magazine (which I doubt) then seat the bullet deeper 1/16" at a time until it will. Easy peasy! Oh yes..by dummy round, I mean no powder and no primer.

I USE CHARGERS DUMMY ROUND TECHNEIC WHEN I RELOAD 9 MMS. MY DUMMY IS A 9MM FMJ TIGHT CRIMPED AT THE PROPER OAL AND I USE LEE SPEED DIES. IT'S EASY TO JUST SLIP IN THE DUMMY ROUND AND SET YOUR DIES TO IT.IT'S GOOD ADVICE I'D FOLLOW IT WERE I YOU.

AFTER YOU'VE SEEN ONE WOMAN NAKID YOU PRETTY MUCH WANT TO SEE EM ALL....

THE 2ND AMENDMENT PROTECTS US ALL.....

I think you mean 3.54-3.60