Bullet Seating Question

03 February 2004, 07:40

300winnie

I have been reloading now for about 10 years. Each year I get a little more knowledgable and gain more experience. Recently I have graduated to the fireformed brass, measuring comparator lengthes etc. My question is this. I have a regular set of Hornady dies for my .300 Win Mag. and I want to seat my bullets to a comparator length of 3.960" I get the seating die adjusted so that it does this on the first one. Might do it to that length give or take .002's for a few cartridges and then I will get one that reads as much as .005 or.006 thousands off. Is this due to the seating die, or is it the difference in the bullets? Second, when seating to a certain depth for accuracy, am I peeing into the wind by worrying about .005 thousands in either direction? For clarification I shoot for hunting purposes, but would like to keep my groups 1 moa or better.

Thanks for your help.

03 February 2004, 08:53

Stonecreek

Your seating depth is controlled by the distance from the base of the cartridge as it is held in the shellholder to the point on the bullet that is the diameter of the corresponding radius of the bullet seating stem. If the distance from the case head to the bullet's full diameter varies using the conventional seating die, it would be because of variations in the ogive of the bullets. Bullet ogives WILL unavoidably vary. Some are worse than others. The proof is in the shooting, and not in theoretical measurements. Of course, the more consistent the bullets, the more likely they will yield good accuracy, but there are numerous other variables at work.

03 February 2004, 09:27

JustC

you have the option of sorting bullets by bearing surface length,....buying custom bullets,..or seating them far enough in the lands that the pressure required to start them moving will be close to the same no matter the bearing surface length. I prefer to seat them either stiffly in the lands,..or away from the lands. Thus,..equalizing the pressure with varying bearing surface lengths. It won't show up at 100yds,..or even 200yds,....but will become evident by vertical shots at longer ranges when one has a longer bearing surface and instead of being just at the lands,..was actually .004" into the lands. That is just my opinion/theory,..and I am continually trying to prove or disprove it.

03 February 2004, 13:54

Hot Core

Quote:

...I want to seat my bullets to a comparator length of 3.960" I get the seating die adjusted so that it does this on the first one. Might do it to that length give or take .002's for a few cartridges and then I will get one that reads as much as .005 or.006 thousands off. Is this due to the seating die, or is it the difference in the bullets?...

Hey 300winnie, I'll be agreeing with Stonecreek on this one. You will "likely" find the variance in Overall Cartridge Length that you noticed due to the difference in the lengths of the Bullets. Or it could be you are "short stroking" the Press(which I doubt), or varying Neck Tension causing the Seating to have different resistances to the seating.

You can check the bullet length by sitting down with a box of the Bullets and a set of 0.001" capable Calipers. Measure them and line them up in front of you with the "shortest bullet" to the left. You will quickly see the variation and if you do enough, you will normally see the "Bell Curve" by standing back from the table.

If you are "short stroking" the press, it is just a matter of refining your technique. Lower the handle very gently< !--color--> until you feel the Bullet make contact with the Seating Stem. Then use a slow and steady push until the handle completely bottoms. If you are "slamming" it down, you will get inconsistent Seating.

And if the "Neck Tension" of the cases is different, this causes the Bullet sliding in the Case-mouth to be gripped with varying amounts of tension. A simple "Annealing" will likely resolve this issue.

No need to go through a HUGE Annealing fiasco either. Just get a bucket of water and hold the Casehead in your fingers. Heat the Casemouth as you rotate it with a Propane Torch until you feel the Casehead getting warm and drop it in the water. Let the cases set in the sun to completely dry, or set them in front of a heater vent. Just that simple.

Quote:

...Second, when seating to a certain depth for accuracy, am I peeing into the wind by worrying about .005 thousands in either direction?...

You should be concerned about both, - peeing in the wind and the variation in the length, but not the variation in the OCL. You need to be concerned about the variation in length from the Data Line on the Ogive as Stonecreek said. You can buy a "Bullet Comparitor" from Sinclair which will allow you to measure from the Ogive. Or, use the largest SAE or Metric "socket" from your wrenches which will not slip past the Ogive. Be sure to write which socket you use on the box of Bullets.

And standing near an electric fence while relieving yourself will give you the correct incentive to totally correct the first issue.