Inconsistent COL in .223 w/ 69grBTHP

1StvA · Apr 18, 2015

I'm loading Nosler 69gr BTHP and getting COL that vary +/- 0.005" or more. I've tried 3 different seating dies on two presses with the same results.

Did 50 round test with target COL od 2.255 and longest was 2.263 and shortest was 2.249. I wanted to load to 2.26 to get as close to lands as possible without exceeding length to feed from magazine in my AR.

Anyone else have this issue, and/or have any advice?

DrMike · Apr 18, 2015

Welcome aboard, 1StvA. The problem you observe is not uncommon. The problem is likely not your die, but the seating stem. The standard seating stem does not fit bullets with a VLD profile. Consequently, the nose of the bullet is resting on the bottom of the seating stem rather than being gripped at the ogive of the bullet. A stem designed for a VLD bullet will address this particular issue. Most major manufacturers of dies offer a VLD stem as an after-market product. The other problem that can be even more problematic is that the stem rocks on the bullet allowing it to seat at an angle. While the angle may be slight, it is sufficient to degrade accuracy. A new stem should address this particular problem. Ensure that your brass is trimmed to the same length, which plays a role in OAL, though it is less problematic than is the seating stem.

wingnut · Apr 18, 2015

1StvA-

Measure the OAL of 10-20 bullets. You will probably find the differences you are looking for especially if you are loading blems.

1StvA · Apr 18, 2015

DrMike":4b40xzk1 said:
Welcome aboard, 1StvA. The problem you observe is not uncommon. The problem is likely not your die, but the seating stem. The standard seating stem does not fit bullets with a VLD profile. Consequently, the nose of the bullet is resting on the bottom of the seating stem rather than being gripped at the ogive of the bullet. A stem designed for a VLD bullet will address this particular issue. Most major manufacturers of dies offer a VLD stem as an after-market product. The other problem that can be even more problematic is that the stem rocks on the bullet allowing it to seat at an angle. While the angle may be slight, it is sufficient to degrade accuracy. A new stem should address this particular problem. Ensure that your brass is trimmed to the same length, which plays a role in OAL, though it is less problematic than is the seating stem.

1StvA · Apr 18, 2015

wingnut":212hj5af said:
1StvA-

Measure the OAL of 10-20 bullets. You will probably find the differences you are looking for especially if you are loading blems.

I bought 1,000 from Powder Valley. They weren't marketed as 2nds or blems. But I'll measure some and see. Thanks

UPDATE: I did measure 20. Length varied from a low of 0.891" to 0.908", 17 thousandths difference. Median and average were both 0.899" Most were withing 5/1,000 of median.

I am going to use one of the 0.899" projectiles to calibrate my die to seat with a COL of 2.254 and go from there. I'm also going to get a custom stem from Lee based on one of the longer projectiles to make sure the tips are not touching. I'm betting the PMAGS won't notice that around 1 in 20 rounds may be a couple thousandths of an inch over 2.260! :wink:

HeathSexton · Apr 19, 2015

If you aren't measuring from the ogive that should you a more consistent reading. I have some 75gr HPBT match and the vary a lot from the tip, not so much off the ogive.

wingnut · Apr 19, 2015

Here is some comparative data I gathered some time ago:

Bullet length sampling:

6.5 mm Berger 140g Target VLD
sample size: 101
high - 1.4245
low - 1.4070
diff - .0175
Avg - 1.4154
STD - .002531

6.5mm SMK 142g
sample size:100
high - 1.389
low - 1.379
diff - .010
avg - 1.3838
STD - .002158

6mm Nosler CC seconds 107g
sample size: 99
high - 1.275
low - 1.075
diff - .2
avg - 1.227
STD - .020161

Granted, one can apply meplat trimming, tipping and COAL by ogive.