300 Win Mag bullet seating depth determination

[frharris]

I have an X-Bolt Medallion in 300 Win Mag. Great gun. Have enjoyed shooting with factory ammo so far. About 1.5 MOA consistently.

I am preparing to reload for the rifle and was prepping some cases today. I decided to determine the distance to the lands for bullet seating and used a tried and true method. Took an empty case and put in a Barnes TTSX 180 grain bullet covered with Sharpie ink, seated far out and put it in the rifle and closed the bolt. Minor resistance since the case was neck sized and not crimped at all.

I was blown away that the overall length of the extracted case was 3.565 inch OAL. SAAMI spec is 3.340 and a factory Barnes load of the same bullet is 3.304 inch OAL.

That tells me that a factory Barnes bullet is jumping .260 inch to the lands, and a cartridge loaded to SAAMI length is jumping .225.

Is this typical for 300 Win Mag barrels or am I missing something??

I previously reloaded .30-06 some years ago, but cannot recall how far out the bullets were seated. Had a friend tutoring me. Poor student, I guess since my records are long gone.

Thanks for the help in advance.

Ron Harris

[highpower790]

Oal is going to be determined by the ogive of the bullet,and or the magazine the cartridge is feeding from.

[frharris]

I understand the ogive geometry, thats why I was comparing the same bullet: factory Barnes ammo in with 180 gr TTSX and the test cartridge with the same bullet. Ogive should be identical. .260 inch difference in OAL.

Fits magazine but without much clearance.

FRH

[highpower790]

Anything a factory does is going to be done to try and satisfy a wide range of firearms,while you can taylor a specific bullet to "your" rifle.

[J-cat]

Factory magnum chambers are like that.

Don't try to load a solid copper bullet into the lands. You will KB your rifle.

Solid copper bullets need a good amount of jump and tend to shoot best way far off the lands, hence the short OAL of your factory load.

[frharris]

Thanks J-cat. I understand the jump. Barnes recommends .050 inch to lands, which is what I was intending. Even so, that translates to an OAL of 3.515 (3.565 - .050) which seems long compared to factory OAL for the same bullet of 3.304. I'm even using a once fired Barnes case for the test cartridge.

I believe I am doing correctly based upon long-past experience and recent research.

Just looking for a sanity check before I blow up a nice rifle..

FRH

[Spyder]

I was doing the same thing yesterday. I kept trying longer and longer and nothing touched the lands. I settled on (I think, without looking) 3.45 OAL with 180 Partitions, to work up my load. We'll see how it works.

[RandyD]

The OAL will vary even when using the same lot of bullets. Bullets tend to vary in their length, even good quality bullets. The measurement you need to determine is the distance from the face of the bolt to the lands. Using the method of seating a bullet into a sized case until the bullet's ogive touches the lands, is a good method, but you need repeat this procedure, using various lengths and a sharpy to insure you have the precise measured distance, because when the bullet touches the lands, the bullet could be seated into the lands a few thousands of an inch.

[J-cat]

Thanks J-cat. I understand the jump. Barnes recommends .050 inch to lands, which is what I was intending. Even so, that translates to an OAL of 3.515 (3.565 - .050) which seems long compared to factory OAL for the same bullet of 3.304. I'm even using a once fired Barnes case for the test cartridge.

I believe I am doing correctly based upon long-past experience and recent research.

Just looking for a sanity check before I blow up a nice rifle..

FRH

The .050" figure is a minimum. Feel free to load shorter. I would try a bunch of different OAL's short of mag length.

[mjmagee67]

I would load to the book OAL. I don't know what you use your 300 Win Mag for but if it is for hunting then you will get all the accuracy you need with book OAL's. My 1954 Win Mod 70 in 30-06 went from 1.5"ish groups down to .75"ish groups when I went from factory to home rolled. This won't win any competitions but it has put quite a few deer and elk on the table.

[frharris]

Thanks to all for the responses.

I've been shooting various factory loads and the Barnes 180 has been the best. I shot the Fed Fusion I several weights but the Barnes 180 was tops. I intend to use that for my elk hunt this Oct.

In that process, I have collected 200 really nice cases and would like to reload them. I've been loading 357 and 5.56 recently, but the 300 is another step in complexity. Always good to get some solid feedback from the forum.

After elk hunt, I plan to start the 300 WM project in earnest.

Thanks again. Further advise solicited and welcome.

FRH