Sorting Bullets by BTO, what are we really doing?

[jackieschmidt]

I think it is a given that custom short range bullets of the same lot are so close that trying to measure any difference in any of the dimensions is fruitless.
But what about the semi custom bullets such as Berger, Sierra, and Hornady. Are you getting different OAL’s, base to ogive, or weight differences out of the same box? Or is it just when you buy multiple boxes?

 

[Martin52]

But what about the semi custom bullets such as Berger, Sierra, and Hornady. Are you getting different OAL’s, base to ogive, or weight differences out of the same box? Or is it just when you buy multiple boxes?

Just measured a few Berger 155.5 full bores out of a box of 500, the OAL from this small sample (~50) varies by 0.008.

 

[Ccrider]

Following this trying to learn. It if curiosity, I measured and sorted a couple of hundred 103 V Tacs. They varied in OAL by .020. Is this significant?

 

[jackieschmidt]

Following this trying to learn. It if curiosity, I measured and sorted a couple of hundred 103 V Tacs. They varied in OAL by .020. Is this significant?

I would think that is too much.
I have about 12,000 J-4 and around 4500 Sierra 6mm jackets on hand. They are out f the same lot, or run. I can check the lengths of the new jackets, and they are all within .003 inch in length.
So, assuming they are using jackets similar to these, what is causing the bullets to have a different OAL when finished.

 

[BartsBullets]

Following this trying to learn. It if curiosity, I measured and sorted a couple of hundred 103 V Tacs. They varied in OAL by .020. Is this significant?

I would think that is too much.
I have about 12,000 J-4 and around 4500 Sierra 6mm jackets on hand. They are out f the same lot, or run. I can check the lengths of the new jackets, and they are all within .003 inch in length.
So, assuming they are using jackets similar to these, what is causing the bullets to have a different OAL when finished.

You’ll have to see AFTER you point them up.

Edit
There’s a lot of metal competing for a very small spot at the meplat with long range Bullets. The OAL differences are mainly due to small micro folds in the jacket which creates a little a jagged tip or point.

 

[Texas10]

Glad to see some bonafide experts weighing in!

Question for experts:
1) How closely is the weight of the lead core held?
2) What is the measured consistency in thickness of the bottom (heel) of the jacket?
3) And how does variations in that thickness alter the position of the lead core and therefore resulting center of gravity, and perhaps contour of the ogive?

More grist for the mill.

 

[grovey]

The most consistent over the counter bullet I've shot was the 6.5 mm 139gr Lapua. Surely there are guys out there shooting those custom 60 cent bullets still getting beat by those undesirable over the counter bullets. In my tiny bubble, a 0.002 -0.003 difference in seating could wreck a group.

 

[johara1]

You’ll have to see AFTER you point them up.

Edit
There’s a lot of metal competing for a very small spot at the meplat with long range Bullets. The OAL differences are mainly due to small micro folds in the jacket which creates a little a jagged tip or point.

That is some of it but when you see .060+ difference would say there is an other problem. .020 I can fix .... jim

 

[johara1]

The most consistent over the counter bullet I've shot was the 6.5 mm 139gr Lapua. Surely there are guys out there shooting those custom 60 cent bullets still getting beat by those undesirable over the counter bullets. In my tiny bubble, a 0.002 -0.003 difference in seating could wreck a group.

OAL. has nothing to do with seating depth, you have other problems that cause erratic seeing depth.... jim

 

[CaptainMal]

Gave up dealing with OAL and BTO measures. If you jump and the amount of jump is not critical, those measures mean little. If you jam and again, the amount of jam is not critical the same can be said for concern with the bullet measure. Obviously we are talking GOOD bullets.

Now that Roy Hunter cannot make bullets and I am near out of his old 108's that one of my rifles loves, I ordered in 2,000 Berger 108's.

PFFT.

Like their 105 Hybrids, the weight varies rather dramatically. On some hybrids I have seen a full grain of weight difference. Not sure what it is on these 108's but from early checking it is at least 1/2 a grain. To me that is an issue, almost like changing the powder charge that much and expecting to fall into the barrel compensating range.

I sort bullets from Berger by weight and use the "goofy" ones for fouling and sighters. For my Roy Hunters they just come out of the box. Unfortunately, the box is getting empty.

 

[BartsBullets]

Glad to see some bonafide experts weighing in!

Question for experts:
1) How closely is the weight of the lead core held?
2) What is the measured consistency in thickness of the bottom (heel) of the jacket?
3) And how does variations in that thickness alter the position of the lead core and therefore resulting center of gravity, and perhaps contour of the ogive?

More grist for the mill.

There’s no end to the amount of questions when it comes to bullet making. I could write a book on the subject, BUT I’m not going to! Suffice it to say you’re getting way too deep in the weeds my friend.

Jackie and Al nailed this post early on.
Bart

 

[davidjoe]

I guess you guys should stick to Hornaday A tips overall length is +- .001 no custom bullet maker can come close to that...... jim

I will say this about the A-Tips and a magnum case, don’t sort them out. They will sort you out differently when the match is over, provided there’s wind. I saw for myself in a LR multi-day match, switching over to them at the end. In the true absence of wind, which can never be counted on going in to a match, I don’t think any bullet in a box of the current match bullets will actually cost a nine, though. At least we haven’t seen it shooting the extremes versus sorted at 600, locally. I’ve seen $.30 bullets shoot over 20x’s at 600.

Add challenging winds, and the theory is that the same shooter will score higher in correlation to the difference in BC with equally uniform bullets, whether they be the same or different. Clearest example being that a box of identical Berger 200-20X’s would shoot different scores in severe wind between a tuned magnum Open and tuned TR rifle with the same shooter, all other things equal. (.308 trajectory being a magnum’s without the first bit of the curve).

Consensus is that bullet to bullet uniformity has a smaller effect on score at close range than long range. I would wonder if uniformity also has a smaller effect on the score values of faster, versus the slower moving of two identical bullets. Perhaps minute differences in BC would have a smaller lateral effect but a greater vertical effect, the faster a bullet goes, as aerodynamic resistance curves for an object transition from predominantly forward to upward more steeply (nonlinear), as speed increases.

 

[grovey]

OAL. has nothing to do with seating depth, you have other problems that cause erratic seeing depth.... jim

I didn't say I had problems.... Just that 0.002 -0.003 difference in seating depth can wreck a load in MY factory junk.

 

[Bc'z]

I didn't say I

Have you tried the 136L'S yet.
BBTO measurements I've seen .0025 variation in the 2 lots I have. Pretty damn good if you ask me.

 

[johara1]

Have you tried the 136L'S yet.
BBTO measurements I've seen .0025 variation in the 2 lots I have. Pretty damn good if you ask me.

Barts, Hornada A tips and Sierra 107's and 110's are +- .0005..... jim

 

[Bc'z]

Barts, Hornada A tips and Sierra 107's and 110's are +- .0005..... jim

I pull my Bart's from the box and seat them.
Post# 11 should explain it all.

 

[grovey]

No I haven't... sold my Creedmoor last yr. Also, I based my review of the 139's on just one 1,000 ct box. Based on a Sinclair sorting stand the biggest difference was 0.002, and I soon learned if I measured that same bullet again chances are I could find a spot that was within 0.001. I don't see how you could make them more uniform . I sold the sorting stand shortly afterwards as it was collecting dust. I'm only shooting factory rifles, nothing custom. Tough to get a factory sporter to spit .250 everytime, but that's what it takes to win in the game I was playing. It doesn't take much to make it not capable of shooting that well. That's what my comment was based on.... no more.

 

[mikecr]

I don't buy into BTO holding specific meaning, nor to acting on it.
It includes Ogive Radius(affecting datum), plus Bearing, plus Base Length.
Given different meanings to drag, you cannot determine BC differences while the attributes are summed.
You could isolate bearing, only after qualifying measurement datums for this. And I seriously doubt that normal bearing variances make anymore difference than normal weight variances (likely less).
I have never seen a test that shows it.
Comparing OAL means even less.

How many of you qualify ogives and base angle -before BTO measure?

 

[D Coots]

I didn't say I had problems.... Just that 0.002 -0.003 difference in seating depth can wreck a load in MY factory junk.

No problem believing that.

When it comes to short range BR I believe if .002 or .003 doesn't screw up your load, either you have a hell of a barrel or you had the wrong seating depth to start with.

Later
Dave

 

[david kieffer]

There’s no end to the amount of questions when it comes to bullet making. I could write a book on the subject, BUT I’m not going to! Suffice it to say you’re getting way too deep in the weeds my friend.

Jackie and Al nailed this post early on.
Bart

I would like to read the book . come on bart .please