OAL gauge question

[jtaustin]

Just got my Frankford COAL gage clamps. Tried it on a Tikka 300 WM and was surprised by the results. The Tikka magazine would only allow a COAL of 3.34" but using the clamps to measure the bullet barely touching the lands gives a COAL of 3.57". Did it several times with the same result. What can be wrong?

 

[MagnumManiac]

There's nothing wrong, your chamber throat is longer than your magazine length allows. This is common in production rifles, it may be on the long side, but you can use hotter loads and still be safe.
IMHO, there is too much bandied about on the interweb regarding how far the bullet is from the lands and accuracy, it is a complete fallacy that a bullet has to be close to the lands for exceptional accuracy, throat design plays a bigger part in accuracy than how close or far a bullet is from the rifling.
I suggest you load your cases to just shy (-.010") of mag length and test for groups, then load some at .010" intervals*DEEPER into the case, upto about 3.290", you may go deeper, but keep an eye on how far the shank is below the neck/shoulder junction, you won't want anymore than about a third of the bullet length past it. If you don't find a good group doing this you may have to try different powders until you come up with a good one.
My favourite in the 300 is RE25 with 180gr and 200gr Accubonds, my rifle has a fair jump to the lands too, it still shoots into .5MoA consistently and the less than regular .25MoA when conditions are perfect, including me!

Cheers.
gun)

 

[BrentM]

There's nothing wrong, your chamber throat is longer than your magazine length allows. This is common in production rifles, it may be on the long side, but you can use hotter loads and still be safe.
IMHO, there is too much bandied about on the interweb regarding how far the bullet is from the lands and accuracy, it is a complete fallacy that a bullet has to be close to the lands for exceptional accuracy, throat design plays a bigger part in accuracy than how close or far a bullet is from the rifling.
I suggest you load your cases to just shy (-.010") of mag length and test for groups, then load some at .010" intervals*DEEPER into the case, upto about 3.290", you may go deeper, but keep an eye on how far the shank is below the neck/shoulder junction, you won't want anymore than about a third of the bullet length past it. If you don't find a good group doing this you may have to try different powders until you come up with a good one.
My favourite in the 300 is RE25 with 180gr and 200gr Accubonds, my rifle has a fair jump to the lands too, it still shoots into .5MoA consistently and the less than regular .25MoA when conditions are perfect, including me!

Cheers.
gun)

Yep excellent response. Too much BS regarding seating depth. I have several rifle that really like jump. In fact, I have 4 that settled in at .100 jump with Berger bullets. Berger used to claim that you had to seat to the lands or jammed and smiths reamed chambers with shallow throats to achieve this.

 

[Dosh]

JT, +1 on both previous replies. All my rifles are Weatherby and the bullet will almost fall completely out of the case before touching the lands. Even Berger's website is now suggesting seating farther off the lands for more accuracy. The "jump" to the lands is beneficial in handling pressures, that's why Weatherby has the freebore. Follow MM's seating and see how your 300WM does. Good luck

 

[Blwebster]

JT, +1 on both previous replies. All my rifles are Weatherby and the bullet will almost fall completely out of the case before touching the lands. Even Berger's website is now suggesting seating farther off the lands for more accuracy. The "jump" to the lands is beneficial in handling pressures, that's why Weatherby has the freebore. Follow MM's seating and see how your 300WM does. Good luck

Thanks for the comments in this tread. Helps me.