Seating depth test question

[Millet]

Hi Guy,
I'm getting ready to reload for a seating depth test I want to do for my .243 win. I tested and found my OCW which is 44.7 gr H414. Should I load on the lower end or is it safe to do my test loading 44.7 gr when 45 gr is max? Any help would b appreciated!

[mikld]

Common reloading safety practices include starting at or near the starting load when reloading for any new firearm, new round, or new/different combination of components. Nope, don't start .3 below max...

[Millet]

Right.......so at .3 grains below max if i go from .015" off lands to touching land will pressure be too high?

[kilotanker22]

if this load at 44.7 gr is a load that was worked up in the rifle you are shooting with the same bullet. then you should be ok to start to play with the depth a little.

i would start about .050 off of the lands and work outward in .005 increments
and stop when best accuracy is found. i have found that in my 243 with 105 grain amax bullets they like to be seated .050 off of the lands.

[Ifishsum]

Touching the lands can raise pressure significantly, I probably wouldn't try that without dropping the charge back and working back up. Other than that, I have tried varying the seating depth with an already confirmed load.

[ColColt]

I always start at .015" off the lands and progressively go as far as .030" in maybe .005" increments till accuracy improves or degrades. I've never "jammed" any bullet into the lands and just don't think that's a good idea unless you're into hard chambering and pressure.

[Millet]

Ok thanks for the reply guys. Yes this is a confirmed load in my rifle. I'll go ahead a run a test and let you know how it turns out....thanks again!

[steve4102]

Right.......so at .3 grains below max if i go from .015" off lands to touching land will pressure be too high?

Increasing OAL will increase Pressures with jammed into the lands being the highest.

If you are going to experiment with OAL, Start with the Longest OAL you plan to use then decrease OAL your desired amounts. By decreasing oAL you will not be in increasing pressures with each reduction in length.

[cdoc42]

Just a thought. As you increase the distance from the lands, you're seating the bullet deeper into the case. Does that reduced internal case volume also increase pressure? Let me assume the answer is yes. Is it possible that the best accuracy is not really related to the seating depth or the distance from the lands, but the actual pressure generated?

For example, a bullet seated 0.01" from the lands might generate 53,000 CUP and be extremely accurate. But if seated 0.05" away, the deeper case seat generates 53,000 CUP and is just as accurate. No?

[AllenJ]

Should I load on the lower end or is it safe to do my test loading 44.7 gr when 45 gr is max?

If you found your rifles node at 44.7 that is where I'd start. Seat bullets in increments of .010 in lots of 3 (5 would be better) both longer and shorter to see if your groups tighten up. Watch for excessive pressure signs the same as if you were increasing the powder charge.

Are you measuring cartridge base to bullet tip or cartridge base to bullet ogive?

[nemesiss45]

Originally Posted by cdoc42

Just a thought. As you increase the distance from the lands, you're seating the bullet deeper into the case. Does that reduced internal case volume also increase pressure? Let me assume the answer is yes. Is it possible that the best accuracy is not really related to the seating depth or the distance from the lands, but the actual pressure generated?

For example, a bullet seated 0.01" from the lands might generate 53,000 CUP and be extremely accurate. But if seated 0.05" away, the deeper case seat generates 53,000 CUP and is just as accurate. No?

As you seat the buller deeper, pressure is decreased. I believe the pressure continues to decrease until you begin compressing the powder.... but I could be wrong about that last bit

[steve4102]

Originally Posted by cdoc42

Just a thought. As you increase the distance from the lands, you're seating the bullet deeper into the case. Does that reduced internal case volume also increase pressure? Let me assume the answer is yes

In a Straight walled pistol round your assumption would be correct.

In a bottle necked rifle round your assumption would be incorrect.

[kilotanker22]

Be sure to let us know how you make out

[4runnerman]

Lots of different answers here. If as you say you did the OCW test. My 2 cents. By seating bullet deeper does not increase pressure and you have more distance between bullet and lands ( pressure change – not much ). As you seat the bullet farther out- more case is left empty for powder to expand when burned- ( pressure change- Not much ). When you follow the test- It does not say back off on powder charge after you find your sweet spot. I do not mean to tell you to disregard what the book tells you, but remember- The books have a safety margin built into them. Watch your brass after each shot looking for pressure signs, I bet you see none.

[Millet]

Wow... that's some interesting info! Today I loaded 6 sets of 4 of each length in .010" increments starting from .010" off lands to .060" off lands. I'll probably fine tune both ways in smaller increments later. So hopefully I can shoot tomorrow and I'll try and keep you updated.