BigGameHunt.net Hunting Forums

[rogie]

After trying several methods of determining at what OAL the bullet comes in contact with the lands on my rifle I have established an average across the board of 3.580. Could this be correct? The Nosler manual lists the max overall length at 3.340. This a Dakota Rifle (not Weatherby). 3.580 and longer length cartridges do fit in the magazine. Bullet is a 180 grain Accubond.
Rogie

[bitmasher]

Maybe depending on the bullet shape and your chamber. An OAL that hits the lands vary some between bullet shapes and bullet manufactures. I believe the max OAL is intended as a safe limit that any bullet type/shape should not be on the lands.

If you are just starting reloading, I would only start with the spec max OAL, then slowly work out from there to see if the barrel is even sensitive to seating depth.

[Don Fischer]

What methods have you used to determine OAL?

[rogie]

I used the method from Noslers 6th edition reloading manual (loose bullet in empty case) which consistantly produced a OAL of 3.612. I also tried a method where you put a loose bullet in the chamber hold it in place with a stick or cleaning rod and then insert a cleaning rod from the barrel in... mark the rod then remove the bullet and measure with the same cleaning rod to the bolt face... mark it and calculate the OAL from the two marks with a caliper. I did this several times and this method produced a OAL of 3.580.
So to be safe I called Dakota and checked with a tech and he told me that they cut the chambers on the model 97's to 3.600 and that he seats his 300 win mag (also a model 97) at 3.580.
I decided to back off another .15 to 3.430 and shoot it from the bench. I'll work it up longer from there to the 3.580 OAL. and watch for signs of increased pressure.
Does that sound reasonable?
Rogie

[Don Fischer]

I use your second method. I found that with the first, I'd sometimes pull the bullet back out a bit, case mouth squeezed a bit to much and the bullet just stuck in the lands. I've also tried sooting the bullet and pushing it into an MTY case and didn't have much luck with it either.

Actually I wouldn't worry over OLL to much just yet. I'd simply seat a bullet back just off the lands and work up a load. Then when you find the best load you can tweek it with adjusting the seating depth.

Another thing to bear in mind is to run all your loaded ammo thru thr rifle before going to shoot it. What you will find is if you are very close to the lands, some will need to be seated just a bit deeper. The problem being very small variations in the bullet length's. The proper way to measure OLL, I don't do this, is to measure from the bullets ogive to the bolt face. There is a special tool you can get to measure that that clips onto the caliper. May be a concern for match shooting but not for hunting. Just be sure that the bullets are all seated to a depth that will allow the longest one to cycle thru the action. If you are quite a ways off the lands, it won't concern you.

[bitmasher]

Sounds reasonable and safe. I use the first method and that last 0.01 is sometimes hard for me to tell whether it was or was not on the lands.

Good Luck!

[rogie]

bitmasher wrote: Sounds reasonable and safe. I use the first method and that last 0.01 is sometimes hard for me to tell whether it was or was not on the lands.

Good Luck!
???on the lands??? I was under the impression that I wanted to be just off, like maybe .010 or .015 short.
rogie

[Hammer1]

My bullets seat .012 from landsin my 270, that works best for me.It will and probably should vary from rifle to rifle, bullet to bullet, charge weight to charge weight. There is no given standard to go by that I know of.

[Full Draw]

Some experts say that if the bullet is touching the lands, then excessive pressure can result. I have heard it explained like this: Think of your car tires touching a curb and the see how much gas you have to give it to get the car to go up over the curb. Now back off the curb a half foot or so and try the same experiment. The momentum of the moving car will allow you to go up over the curb with less effort from the engine. It seems to make sense to me, so I usually will back off the lands a little. There is also the issue of temerature. I have heard of hunters ejecting a unfired cartridge that has the bullet against the lands and pulling the bullet. It makes a horrible mess with powder all over the inside of teh action. Some rifles will also allow you to seat with an OAL longer than the magazine. In that case, you will need to limit the OAL based on what will fit into the magazine and cycle correctly.