190 Sub-X seating depths

[Roadrunner1969]

I have been loading some Hornady 190 Sub-X bullets and have been getting inconsistent seating depths. I have found that there can be about .010" difference in the thickness of the plastic tips, which makes measuring COAL a pretty useless exercise. So I have been measuring cartridge base to meplat and that is much more consistent, usually only 1 or 2 thousandths variance at most, if any at all. However, occassionally, one is way off...like about .010", both in base to meplat and COAL, and I don't know why.
Is there a special seating stem? I am using the Lee seating die with standard stem.
Anybody got any ideas?

[dellet]

Best to use a comparator of some type, Hornady makes a decent one. It will measure to the 300” portion of the bullet. Where it will hit the lands. The tips of bullets, basically from that point on the ogive forward are notoriously irregular.

All overall length is really good for is making sure it will fit in a magazine. It’s a numbers you can get with limited tools, and share with others.

Cartridge base to ogive, will tell you if it will fit in your chamber, a much more important number.

[Roadrunner1969]

Well. To improve things I found that Lee will make a custom seating stem to fit your bullet for $8 plus shipping. So I sent them a bullet and paid them...now to wait a few weeks.
In other news, apparently, the small variations in seating depth weren't the cause of the SD numbers. I loaded a ladder using Unique and 190 Sub-X bullets, all seated without adjustment at ~2.070" COAL. I shot for groups only without a chrono, and at 50 yards. Starting at 5.6 grains and ending at 7.0 grains. The groups started out at about 1.125" and progressively got smaller until 6.2 grains, when the group measured .156" (.312" outside to outside), then progressively grew larger until they got to 7.0 grains and 1.5" group.
The groups from 5.9 grains to 6.1 were all around 1/2 moa or better, but the 6.2 grain group was basically 3 bullets through 1 hole. So it appears that the powder and charge had a lot more to do with it than variations in the seating depth.
I'm going to wait until I get the new seating stem to load up a batch to run through the chrono. I am really impressed and excited about this load. The only downer is that Unique is almost impossible to find right now, and so is its twin, Hodgdon Universal.

[Roadrunner1969]

Got the custom stem from Lee and it fits real good. In the meantime I have 30 rounds of Hornady factory loaded subx ammo. I checked the COAL of 10 of those and found that they had a spread of .0065", so apparently the Hornady factory loads aren't all that consistent.

[popper]

It depends more on the fill ratio of the case than exact seating depth, for pressure. The other factor is jump to the lands, for jacketed subs, probably not that important. GRT shows 5gr is 70% fill and 6gr is max pressure & 82% fill. Using your OAL. 5 gr is sub (1050 fps). I use seating depth, not OAL, used 0.7 for the sub-x. I did use your OAL, 2". In my semis I seat 0.01 off the lands/bore for jacketed and a bit more for cast to prevent jams due to dimensional tolerance. I seldom crimp at the cannular.
HS-6 should work also.

[dellet]

It’s absolutely pointless to measure a loaded cartridge from the base of the brass to he point of the bullet. All that will tell you is if the cartridge will fit in the magazine.

Measuring the overall bullet length will show why.

What matters the the measurements from cartridge case to bullet ogive, and bullet base to ogive. Ogive being the place on the nose or tip that is bore diameter. 300” in this example.

In a perfect world, the seating stem will push on this point, so that’s where you need to measure and compare lengths. That’s why the tool needed to make this measurement is called a comparator.

I just measured 25 of the Hornady Sub X bullets. They varied from 1.290”-1.310” in length, with the bulk being 1.300” +/- .001. Measuring the same 25 bullets with a comparator, there was only .003” variance in the group.

So with this set of 25 bullets, overall length could vary as much as .020”, But the seating seating depth only vary .003, and jump would vary the same.

If you were spend the time to correct the overall length to a .003” variance, the seating depth and jump would vary .020”.

Vary the seating depth with data in GRT, or Quickload and see what happens to load density, pressure and velocity.

[Roadrunner1969]

I measured a bunch of the sub-x bullets and got basically the same measurements that you did, with 1.301" being the most prevalent.
For now, I am going to set my seating stem using one of the 1.301" bullets and let the COAL fall where it may. I loaded up a batch using the stock sizing die with expander ball and will load up another batch using an expander mandrel and see what effect that has.