Seating depth (CBTO), Hornady ELD-M 52gr 223 Rem, Redding Comp Seater with VLD stem

[SGK]

So I've just been loading some 223 Rem to fire-form some new Lapua brass. I was having a frustrating time with bullet seating and trying to get my Redding die right. When I got one round right (i.e. hit my target CBTO) the next one would be incorrect. Measured CBTO was going all over the place.

So I decided to measure a few of the bullets. (I'm using the Forster Datum Dial Kit both for measuring the bullets themselves and CBTO of loaded cartridges.) The actual bullets, in a very small sample, varied from 0.4015" to 0.4090", so 7.5 thou. Seems pretty crap. (There was a 5 thou difference in OAL of these bullets.)

Initially I was thinking this was the cause of the problem. However, if my Forster Dial Kit was seating the bullet it would merely seat the longer BBTO ones deeper in the case. Not great but once seated, the CBTO ought to measure the same (absent operator error). Of course, the Redding VLD stem is doing the seating and the point on the ogive where this touches the bullet is very likely different from where the Dial Kit touches but, again, if this difference remained constant then the longer BBTO bullets would simply be seated deeper. Given measured CBTO was moving around from one round to the next - I was getting differences in excess of 4-5 thou - without the die being adjusted suggests either operator error, an issue with the die, or that the very small length from where the Dial Kit touches the ogive vs where the seating stem touches is varying. If it's the latter, a variance that large over such a small distance seems REALLY crap.

I've put the rounds that measured long back through the die and the measurement doesn't budge.

Perplexed...


These are just fire-forming rounds but they could just as easily not be.

 

[SGK]

Related to this, why don't seating stems meet the ogive at a point much closer to where the bullet will hit the rifling? See pic. The leftmost mark is where the Forster Datum Dial Kit meets the bullet. The holes on the Dial appear to be 1 thou less than nominal bullet diameter. In contrast the so-called VLD stem meets the bullet much lower down the ogive.

 

[Evlshnngns]

I would sort the bullets, then seat a batch by sorted length. ELD mismatch

 

[SGK]

Doesn't fix the problem unless I had a contraption to sort based on the length between the two diameters (aperture of Dial Kit vs aperture of seating stem).


FWIW I was looking at the ELD-M because with a 1:10 twist I can't stabilise the heavier 224 bullets. If the ELD-M are crap then I guess I have to look at the flat base Bergers or the Sierra MatchKing.

 

[ppaul]

SGK, the "contraption" exists it's the Bob Green comparator!

 

[SGK]

Yes. I just read the post by @mikecr here:

The BGC rests on two datums at once.
#1 a bullet inserted to stop at a datum near land contact
#2 an indicator with a seating stem (like Wilson's) rests against the bullet nose forward of #1
The measure here is the distance between the two datums, and is showing ogive radius variance.
The value in this 'comparison' from bullet to bullet is in matching them -so that all other measures off ogives are qualified (to any matched standard).

A tool like the Forster Datum Dial Kit can sort BBTO with the point on the ogive being specific to that tool. But if the Dial Kit aperture contacts a bullet at diameter different from the seating stem you haven't gotten particularly far.

Pity it is so expensive ( and doesn't come in this calibre). I guess I'd first like a view on whether to ditch the Hornady bullets...

 

[Texas10]

Have you pulled the seating stem and checked the fit to the bullet? I have found in situations like you describe that the bullet tip is hitting the top of the cone in the seater, or the taper of the cone is a mis-match to the profile of the bullet. I've drilled them to provide relief for the bullet tip (meplat), or changed seaters to find one that fits better.

 

[SGK]

There appears to be plenty of clearance for the bullet tip

 

[ronemus]

I had much better results using a Forster seating die; the geometry and metallurgy of the stem are much better. The Redding and RCBS stems will bell, and eventually will gall the sliding sleeve - then thing really get wild. I've put tens of thousands through my Forster seaters and they're still going strong. The Forster also contacts the bullet lower on the ogive than you're showing for the Redding.

 

[SGK]

The issue isn't the seating stem. It's in the variance between the two points, i.e. a bullet production issue.

What's typical of good target bullets for BBTO variance and, for those that have the BGC tool, for the variance in length/angle measured along two points such as those in pic in post 2? I'm beginning to think these 224 ELD-M are just crap. I now want to take a closer look at the 30 cal 168 gr ELD-M I have.

 

[SGK]

Hmm... I measured a sample of 15 of the pack of bullets I was having trouble seating consistently earlier today (22 cal 52 gr Hornady ELD Match). First I measured BBTO with my Forster Datum Dial Kit. Then I grabbed my Redding seating stem and measured it and the bullet together, zeroing out the full length of the stem. The results were interesting - the last column surprised me greatly when I calculated it.

52 gr 224 ELD-M

BBTO BBTS OAL OAL less BBTO BBTS less BBTO
1 0.4020 0.5285 0.7930 0.3910 0.1265
2 0.4085 0.5350 0.7980 0.3895 0.1265
3 0.4090 0.5350 0.7965 0.3875 0.1260
4 0.4020 0.5285 0.7930 0.3910 0.1265
5 0.4050 0.5320 0.7950 0.3900 0.1270
6 0.4020 0.5285 0.7940 0.3920 0.1265
7 0.4085 0.5350 0.7980 0.3895 0.1265
8 0.4085 0.5350 0.7980 0.3895 0.1265
9 0.4020 0.5285 0.7930 0.3910 0.1265
10 0.4055 0.5315 0.7950 0.3895 0.1260
11 0.4010 0.5275 0.7915 0.3905 0.1265
12 0.4080 0.5340 0.7960 0.3880 0.1260
13 0.4085 0.5345 0.7970 0.3885 0.1260
14 0.4015 0.5280 0.7920 0.3905 0.1265
15 0.4085 0.5345 0.7955 0.3870 0.1260

Min 0.4010 0.5275 0.7915 0.3870 0.1260
Max 0.4090 0.5350 0.7980 0.3920 0.1270
ES 0.0080 0.0075 0.0065 0.0050 0.0010
Avg 0.4054 0.5317 0.7950 0.3897 0.1264
StD 0.0033 0.0031 0.0022 0.0014 0.0003

So bullet base to o-give (where my Forster Dial Kit touches the o-give) varies a lot as does the length from bullet base to seating stem touch (BBTS). (OAL varies as well.) But the length between the first two of these (BBTS less BBTO) is basically consistent.

This really confused me. With no change in the die, the length from cartridge base to seating stem touch should be constant. That might result in varying COAL if the tips (point from seating stem touch to end of bullet) vary and it might result in more or less of a bullet being inside the case (as BBTS varies). And if the length BBTS less BBTO is constant then I should be seeing constant CBTO when I measure each loaded case with the Forster Datum Dial Kit. But I am not.

(Ugh, sorry, my formatting of the table disappear)