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The length after seating also is another data point.
Bullets seated deeper, could develop higher pressure.
In most instances you will not want to exceed the max OAL if it is to be used in 'any' gun in that chambering.
Any time one reloads, there is a near infinite number of data that could be recorded.
If you are developing your own loads for a specific rifle, then you may want to 'play' with the seating depth, which will determine the lead or jump the bullet makes from case to rifling.
You'll want to record this info if you want to duplicate a round after the die has been adjusted for another bullet.
Some rifles such as Weatherby have free bore. This allows a faster drop in pressure. Determining allowable lead in a bore requires knowledge or investigation of you specific barrel and chamber. The idea of free bore or lead dates back over 100 years. The 98 Mausers had free bore of 1 1/2 calibers to allow long spitzer bullets. To the untrained eye these can appear to be worn rifling.
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another thing about working with seating depths is that if you change brand or style of bullets, you have to start all over and do the same with them.
and you also need enough of the bullet inside the neck to have the proper neck tension and bearing surface. so trying to shallow seat a short bullet can be difficult if not enough of it is inside the neck of the case.
Lots of good info posted so far, but all add my .02 as well.
As you have pointed out the SAAMI Max OAL for the 308 Win is 2.810. This SAAMI max has little or nothing to do with the handloader. It is a SAAMI Max for Ammunition Manufactures so that all factory ammo will fit in all factory rifles. The handloader can tailor his/her OAL to fit their specific Rifle/Bullet Combo.
Here is What Accurate and Ramshot say about OAL.
SPECIAL NOTE ON CARTRIDGE OVERALL LENGTH COL It is important to note that the SAAMI COL values are for the firearms and ammunition manufacturers industry and must be seen as a
The individual reloader is free to adjust this dimension to suit their particular firearm-component-weapon combination.
This parameter is determined by various dimensions such as 1) magazine length (space), 2) freebore-lead dimensions of the barrel,
3) ogive or profile of the projectile and 4) position of cannelure or crimp groove.
The OAL listed in the Manuals should also be seen as merely a guide. It is by no means an absolute or a requirement. It is simply there to show the handloader what OAL was used. Some manuals (Nosler #6) don't even list the OAL tested it is that unimportant. Nosler recommends that the handloader find the Max OAL for their particular Rifle/Bullet combo and reduce by .015-.030.
There are several ways to find your max OAL, the technique by Nosler is just one of many. I personally use the Stoney Point Gauge.
It is important to note that once you find your desired OAL changing it can also change pressure.
In a Bottle Necked rifle round like the 308 Win reducing OAL will also Reduce pressure and increasing it will Increase pressure. The longer the bullet has to jump to the lands the less the pressure. seating the bullet longer reduces this jump thus increasing pressure.
This is a quote from John Barsness of Handloader and Rifle Magazines.
It decreases peak pressure, for two reasons. The longer "jump" of the bullet to the rifling results in a lower peak pressure, since the bullet engraves more easily the faster it's going when it hits the rifling.
Also involved is the "progressive" burning of almost all modern rifle powders. This means the pressure increases relatively slowly from the time of ignition. Thus peak pressure occurs when the bullet beyond the barrel throat, with very slow-burning powders as much as 3-4 inches.
Here are a couple of charts and graphs to illustrate.
Note the decrease in pressure until the bullet is seated extremely deep.
Once again I cannot emphasise my appreciation to all that have responded to my post.I thank each and everyone of you kindly and the knowledge that I have received will be past on to future reloaders..... I have spent half the night experimenting with different loads and different bullet weights and today ill be testing my progress according to the knowledge received...I'll post my progress up later tonight......cheers
Today I went to the rifle range to test out my loads....168gr sierra game kings,the first 4 shots outside centre square were to hone in my scope and the rest were pretty much centred ,I'd say i done alright for my first ever reloads,what do you guys think