projectile seating depth

[E Rock]

I am using a basic Lee single stage press with Lee carbide dies, loading .40 s&w.

No matter how hard i try to make consistent passes i cannot get an exact over all

length. They vary about .005" and it bugs me that i can't get a closer tolerance

then that.

Does anybody else have that problem with similar equipment? What tolerance do

you guys try to stick to for OAL, plus or minus 1, 2, 5, thousandths?

 

[tul9033]

I give at least 5 thousandths either way before I give it a second thought. A human hair is between 2 and 6 thou. I think you will find variance in the tips of most mass produced projectiles. I used to worry about this way too much. I even have a Redding comp seating die and still get decent swings.
I'd like to see exact matches, but it's not realistic in my experience. Just too many variables.

 

[alank2]

Hi,

I agree, while I like to see them more consistent, say +/- 0.002 to 0.003, sometimes it varies. My theory is that the bullet shape leads to it. You can measure the cartridge different ways by rotating it around the caliper and it can read slightly different. I think it depends on where the bullet seated pressed against a certain part of the bullet top... I wouldn't worry about +/- 0.005... Just make sure you are sizing the 40 cases well enough to get good case neck tension for no setback.

Good luck,

Alan

 

[dennishoddy]

Make sure the bullet seading die matches the style of bullet your loading as well as all the above. .005 isn't much to worry about though.

 

[E Rock]

I've only seen setback mentioned a couple times and I'm not quite sure exactly what that is yet. I understand it could be a dangerous situation especially when loading 40. Something about u dies, case bulge, and being "glocked". I don't know if any or all of these terms are related. So far I am sizing with a lee sizing die only.

I guess I should search and read a little more on setback.
Thanks for the heads up

 

[NikatKimber]

case bulge and the "glock effect" are related. Setback is not. Setback occurs if the bullet is not held tight enough by the case mouth, resulting in the bullet being "set back" into the case when feeding from the magazine to the chamber. This IS a serious issue, and it decreases the amount of volume inside the case for the same amount of powder.

Is your maximum length 0.005" longer than your minimum length? If so, your actual tolerance is +/- 0.0025; which is not bad at all. If some of them are 0.005" longer than what you're aiming for, and some are 0.005" shorter (0.010" total variation), then you might start looking to see if you can find the cause.

 

[E Rock]

That makes perfect since. Knowing that small bit of info, now I will immediately be more sensitive to bullet seating pressure felt in the press and maybe I should tweak the crimp die just a bit more for reassurance!

My total variation is .005, plus or minus .0025 of main goal, I guess that's not to bad. I'm still gonna try to lower that but at least I feel good about what I have now.

Thanks for the info fellas

 

[NikatKimber]

You don't want to overcrimp the bullet either. Simple way to test, is to put the bullet on a hard surface, and use your thumb to push in on the bullet. If it moves, you need more crimp; if not, you should be good. Note: if you're putting all your weight into, you're pushing too hard. On the few it's happened to me, I could almost squeeze the bullet into the case between my thumb and forefinger. I had some cheap (quality) .223 bullets once, that are supposed to measure .224 OD, that instead measured .220 consistently. The crimp was so loose I could pull the bullets by hand, or push it all the way into the case. Took me forever to realize it wasn't the crimp, but the bullet!

 

[E Rock]

Oh great, I'm scared to ask where those came from. I know what I'm doing after work.

 

[Shadowrider]

...I think you will find variance in the tips of most mass produced projectiles. I used to worry about this way too much. I even have a Redding comp seating die and still get decent swings.
I'd like to see exact matches, but it's not realistic in my experience. Just too many variables.

This is it exactly. The only way you would get perfect OALs is if your seating punch was totally flat and only had a point of contact at the furthest forward point of the bullet, which would be the same point you are measuring from with your calipers. As it is, the seating punch touches the bullet somewhere on the ogive, or a corner of the hollow point for instance. If your calipers measured from that same point of contact you would see almost no variance, unless it's a compressed load you are loading. There will be variances among the bullets even from the same box.