Bullet Seating Confusion

[Greyghost243]

I'm reloading for my .300 WSM using H380 behind 165 grain noslers.

I originally seated all my loads to the max OAL which is 3.860" and when I went to chamber a round it was contacting the lands so I bought a Hornady OAL gauge to get the proper seating depth.

I did it several times and came to an average of 2.917". I was under the impression that for accuracy you want your bullet to be approx .001" off the lands. Im confused since even if I back off the recommended .001" the round is still over the max OAL.

I also measured several factory rounds and got an average of 2.747" OAL.

Is there something I am doing wrong or not understanding correctly?

 

[rfwobbly]

The max OAL for 300 WSM is 2.860, not 3.860". Obviously a typo, but details are important.

So you have to use something equal to or shorter than 2.860" if you intend to place the rounds in your gun's magazine. If your longer measure was correct, then you can only use that on hand-chambered rounds.

 

[justgoto]

I was under the impression that for accuracy you want your bullet to be approx .001" off the lands.

It is common for reloaders loading "very low drag" [VLD] bullets to load them close to the lands, it isn't mandatory. I know people that load theirs exactly what the book suggests and they get .5MOA groups regularly. I actually seat some of my VLDs a bit deeper than the book suggests.

Many people start load development with the VLD bullet touching or close to the lands since they are so finicky. Then, when they find a powder charge that preforms satisfactory, they'll try different seating depths to see if accuracy improves.

 

[USSR]

I was under the impression that for accuracy you want your bullet to be approx .001" off the lands. Im confused since even if I back off the recommended .001" the round is still over the max OAL.

The max OAL is determined by each particular rifle, and is not etched in stone. Use your Hornady OAL Gage to determine what yours is, then set up your seating die to produce an OAL that is .010" shorter. Why .010" rather than .001"? The reason is, the location of the ogive on even the best of bullets will vary by up to .010", and the point at which your bullet seating stem contacts the bullet ogive is not the same part of the ogive that your bullet comparator contacts it.

Don

 

[JimKirk]

The SAAMI standards(OAL) are for factory ammo, ammo has to fit a standard to work in "most" guns. You can use it for your ammo as a "guide", but there is nothing that says your ammo has to fit anything but the two items below.

There are two things that control your maximum OAL (for a bolt action gun)

1. Your chamber.

2. Your magazine length, unless you use the gun as a single shot.

If "it" (OAL) will fit your chamber and it will fit your magazine then you are fine.

The experimentation to find the happy medium between what will fit your magazine and what will shoot accurately out of your chamber, is the "fun" part that has taunted reloaders for ages.

Jimmy K

 

[steve4102]

It is important to note that the SAAMI “COL” values are for the firearms and ammunition manufacturers industry and must be seen as a guideline only.
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.

 

[918v]

Chasing lands in factory rifles is counterproductive. Just load to magazine length.