Never heard of this phenomenon before. Never seen it happen.
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Ogive differences
- Thread starter cdoc42
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Wait....
Your saying your comparing the point of impact difference between a Sierra SPBT GameKing to a Hornady FBSP Interlock?
Ummm, yeah.... There is going to be a difference!
Had you compared a Hornady SST to a Nosler Ballistic Tip, it would have been a closer comparison.
Those 2 are at least close in form.
Your ogive comparison has no merit between a Sierra and Hornady. Form, and cup material are different.
Your saying your comparing the point of impact difference between a Sierra SPBT GameKing to a Hornady FBSP Interlock?
Ummm, yeah.... There is going to be a difference!
Had you compared a Hornady SST to a Nosler Ballistic Tip, it would have been a closer comparison.
Those 2 are at least close in form.
Your ogive comparison has no merit between a Sierra and Hornady. Form, and cup material are different.
really , that is surprising. Next time you develop a load for a rifle you should pay attention . I see it every time now that I know what to look for. Slight variances in powder charge can have the same effect. Tony Boyer in his Book of Rifle Accuracy describes it in Chap 22
here is are a couple of examples. You can do the same thing by changing the load .1 grains at a time. Boyer believes it is the barrel harmonics
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One 5-shot group for each cartridge configuration is statistically insignificant.
I'll believe it's possible with five 5-shot groups for each configuration and virtually the same shot hole positions in each. Boyer didn't prove his theory doing this.
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Don Fischer
New member
I don't know this for a fact as I don't give a hoot but, I've read that each bullet by itself may be a different length and that way the ogive might move. The ogive, or what ever you want to call it, should always be the same size. The bullet will be stopped by the ogive every time at the lands. I have taken and figured out my OLL with a cleaning rod and bullet and used it to set OLL. Guess what, sometime's even though the die is never readjusted, the die must be adjusted to keep a round or two off the lands. Tells me the ogive has for some reason moved I think!
whatever Bart, I could post a half dozen or more targets that show the same phenomena but why bother. I hope this doesn't get this doesn't get your undies in a twist but I will take Tony Boyers word over yours every day of the week. Especially since I have seen it in action with my own eyes
@ Don Fischer. Last evening this thread and another over at Accurate Shooter got me interested in my bullet seating depth consistency is I did some measuring.
First I checked 75 .223's loaded with a light charge of Varget in Lapua brass with 77 SMK's. There were 75 of them and I was shocked at the inconsistency. I was plus or minus .005 from the target BTO. These were loaded last Friday using a arbor press and a Wilson die. After reseating all 75 I remeasured and the differences had dropped to plus or minus .001.
Today shooting from a bench with a bipod and rear bag I shot 6 groups at 200 yards and the smallest was .5 MOA and the largest .8 MOA using that ammo.
Next I checked thirty 6.0 Creedmoor rounds that I had left over from a loading session last April. Alpha brass, 107 SMK and medium hot load of H4350. Only 5 out of 40 was more than plus or minus .001 from the intended length and for some reason gave me a fight to get them back into specs. I suspect a doughnut in the neck but they will all get a neck reeaming before next loading. I shot 4 groups of 5 shots at 800 yards and all averaged less than 1 MOA. It was a light wind but 94 F and sunny so the mirage was kicking. For my ability level I will take 1 MOA if I could get them centered over the X, which is my major challenge in this game
@ Don Fischer. Last evening this thread and another over at Accurate Shooter got me interested in my bullet seating depth consistency is I did some measuring.
First I checked 75 .223's loaded with a light charge of Varget in Lapua brass with 77 SMK's. There were 75 of them and I was shocked at the inconsistency. I was plus or minus .005 from the target BTO. These were loaded last Friday using a arbor press and a Wilson die. After reseating all 75 I remeasured and the differences had dropped to plus or minus .001.
Today shooting from a bench with a bipod and rear bag I shot 6 groups at 200 yards and the smallest was .5 MOA and the largest .8 MOA using that ammo.
Next I checked thirty 6.0 Creedmoor rounds that I had left over from a loading session last April. Alpha brass, 107 SMK and medium hot load of H4350. Only 5 out of 40 was more than plus or minus .001 from the intended length and for some reason gave me a fight to get them back into specs. I suspect a doughnut in the neck but they will all get a neck reeaming before next loading. I shot 4 groups of 5 shots at 800 yards and all averaged less than 1 MOA. It was a light wind but 94 F and sunny so the mirage was kicking. For my ability level I will take 1 MOA if I could get them centered over the X, which is my major challenge in this game
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And cartridges lay in the chamber bottom when fired.
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OK, so we have SAAMI, and the bullet makers, and generations of industry use all using the term "ogive" to refer to a portion, or a section of the bullet. It is an area, not a point.
People who are measuring "to the ogive" are measuring to a point, somewhere on the ogive.
I understand the desire for precision, but for that precision you need a precise term, (which "ogive" is not), a term that is not in use for some other definition.
I agree.
Read the last two paragraphs in my post #13.
It's a "ogive datum diameter" thing that is relevant to only the specific barrel and bullet used. May change with throat wear.
It's related to the distance that a bullet travels from its seated position in the cartridge case to its initial engagement of the rifling. SAAMI calls that distance "bullet jump."
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44AMP, I think I understand your position, but, then, what term do you suggest should be used when we all speak about seating the bullet some distance from the lands/leade/rifling? What part of the bullet should be described when a comparator device of the proper caliber diameter, attached to one's caliper, is used in this exercise?
Don Fischer said: " Guess what, sometime's even though the die is never readjusted, the die must be adjusted to keep a round or two off the lands. Tells me the ogive has for some reason moved I think!"
I have had that experience as well and found the problem to be primers that were not adequately seated. If I have a round that doesn't match my OAL-to-the-"ogive" I stand the round on the benchtop and found it rocks. I gently reseat the primer and the repeat measurement is where I expected it to be.
I have had that experience as well and found the problem to be primers that were not adequately seated. If I have a round that doesn't match my OAL-to-the-"ogive" I stand the round on the benchtop and found it rocks. I gently reseat the primer and the repeat measurement is where I expected it to be.
Flip the base upside down then use the seater off center on the base bottom.
I've done that with mine.
I check each primers seating depth while seating with a dial indicator as I return it to the bin. I am suspecting the guy pulling the handle on the press was the culprit and was sloppy applying pressure with the arbor press when loading. I had 75 loads to measure and got in a hurry most likely. Loads were 3 days old and never left a climate controlled room with .003 neck tension. I will probably go back to using my regular press instead of the arbor unless I lose my mind over this stuff and buy a 21st century hydro seater
If I understand you correctly, hounddawg, you have eliminated elevated primers as the cause of variations in seating depth, as measured with a vernier caliper and comparator of proper caliber diameter.
Let's be sure we're talking about bullets of a given weight from the same manufacturer, out of the same lot number box. What might occur that causes a difference in measurement from one seated bullet to the next?
1) A manufacturing change in the position of "the curved portion of a bullet forward of the bearing surface," as measured with a comparator of proper caliber diameter? (or, "ogive" for lack of a better term)
2) Variation in measuring technique by the reloader, i.e., applying more or less pressure on the caliper per cartridge?
3) The die worked loose between measurements?
Any other thoughts?
Let's be sure we're talking about bullets of a given weight from the same manufacturer, out of the same lot number box. What might occur that causes a difference in measurement from one seated bullet to the next?
1) A manufacturing change in the position of "the curved portion of a bullet forward of the bearing surface," as measured with a comparator of proper caliber diameter? (or, "ogive" for lack of a better term)
2) Variation in measuring technique by the reloader, i.e., applying more or less pressure on the caliper per cartridge?
3) The die worked loose between measurements?
Any other thoughts?
I thought a bit, perhaps "engagement point"?? What we're talking about here is the point on the ogive where it touches the rifling (engages the rifling) when it is far enough forward.
The term would be consistent, always referring to the point on the bullet where the diameter of the bullet touches the rifling, but understanding that the location of that point on the bullet will be in a slightly different place with each different bullet style and each different barrel.
I'll be honest and admit I don't use a comparator, nothing I do with my guns and ammo requires that degree of precision. From what I've read on the forum, comparators seem to cause more confusion than precision, though its quite likely that the guys who do get a benefit from using them simply don't write about it...
Here's something else that occurred to me, similar to the "engagement point" of the rifling on the bullet, its the "engagement point" of the bullet seating stem on the bullet.
Same in principle as the bullet touching the rifling but happening on the nose of the bullet, close to the tip. If you are getting variations measuring to the engagement point of the rifling on your loaded ammo, might not the variations be the result of variation of the seating stem "engaging" the bullet during seating??
Using the same seating stem adjustment, one will get different over all lengths with different ogive profile bullets, easily seen if loading something
like .30 cal 150gr spitzer, spire point and round nose bullets.
thoughts?
I'm not aware of any bullet seater stem whose bullet engagement point contact diameter is even close to where the lands in the throat will first touch the bullet. That's usually a few thousandths less than bullet diameter.
Measure a seater stem's bullet "contact datum diameter." If it's smaller than the barrel's bore diameter, that point will never touch the rifling; anywhere.
Measure a seater stem's bullet "contact datum diameter." If it's smaller than the barrel's bore diameter, that point will never touch the rifling; anywhere.
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