Measuring Ogive to Base
- Thread starter Poconolg
- Start date
Gary Wells
New member
cw3o8:
It would depend entirely upon what type of comparator you are talking about. Although not designed for home use, I have used optical comparators in aerospace facilities that will read in thousands and be just about as accurate as a coordinate measurement machine (CMM) which will read in tenths of a thou.
It would depend entirely upon what type of comparator you are talking about. Although not designed for home use, I have used optical comparators in aerospace facilities that will read in thousands and be just about as accurate as a coordinate measurement machine (CMM) which will read in tenths of a thou.
I had the opportunity to purchases an optical comparator, it came complete with instructions; it did not take me long to make up my mind. I choose a Pratt and Whitney electronic gage. I found it very annoying because it has a small range that started at .00005" and maxed out at 0005. I removed the electronics and then turned the Pratt and Whitney gage into a dial indicator stand; that is what L. Willis calls a digital head space gage and reloaders do not know the difference.
F. Guffey
JeepHammer
Moderator
This might be a difference between military & civilian terminology & common useage,
Or from the older folks to current useage...
We always called 'Bullet Jump'... Free Bore (Freebore) since there wasn't contact between bullet & chamber/barrel/rifling.
The second term that seems muddy is the 'Throat', 'Forcing Cone', etc.
From my very old gunsmith books and chamber drawings, traditionally lead bullet chambers, say 'Forcing Cone', while later jacketed bullet chambers say 'Throat'.
The third issue I see is 'Accuracy' used where it should say 'Consistent'.
Building ammo you are trying for a CONSISTENT product, so when you make changes you have a 'Zero' or starting point to move FROM.
A definitive, provable change from one cartridge build to another.
'Accuracy' is the end result, the 'TERMINAL' results.
'Accuracy' involves EVERYTHING, from the loose nut behind the trigger, to sights & sight lines, to weather conditions, to everything involved with internal & external ballistics.
This is one of my pet peeves, but I confuse the two all the time myself when I'm talking/writing because they are confused in common useage so often.
Someone says 'Accuracy' when they should have said 'Consistent' and I'm right there on the band wagon with them!
I SHOULD know better, but my brain simply complains later instead of correcting me on the spot...
-----
Anyway, more to the point,
Measuring the Ogive to case head IS a much more accurate way to make CONSISTANT rounds for ONE SPECIFIC CHAMBER. No doubt about it! No argument...
The problems start when you don't have an exact, measured & absolute distance from Throat/Lands of the rifling to the case head.
This measurement also changes with wear of the throat, so you have to keep up with your throat erosion/wear of the lands of the rifling.
Freebore/Bullet Jump (whatever) is all over the place, some fast magnums came from the factory with 0.300", while some came with virtually zero, both shot equally well.
I find the intermediate velocity/pressure rifles shoot pretty well with minimal jump.
As for finding the actual (absolute) length of the cartridge, that's sometimes a pain.
The issue I have with most 'Gauges' is rounded, or radius on hole on the gauge.
A radius let's the bullet sink deeper into the gauge, which screwed up the absolute reading, instead giving a 'Relative' measurement.
A square edged hole can be a challenge (like with Datum line gauge adapters), but it's an accurate reading.
Since you are working with a taper in the chamber, matching that taper precisely (which will change with wear) is almost impossible, so generally it's accepted machinist practice to use a square edge on the gauge/stop which produces the best absolute measurement.
The issue I have with the premade 'Nut' gauges is the holes have radius, and the nut sides aren't precision ground, so each set of flats are a different size, you have to measure the 'Nut' (gauge) and subtract the distance between flats.
MUCH easier when all flats are the same distance, like 2", you simply subtract 2" from relative reading g for the absloute reading...
I suggest you hold the gauge 'Nut' in your hand BEFORE you measure, since body heat will expand it and change your initial measurement of the gauge...
When you are working 3 or 4 places behind the decimal point, this matters...
The BIGGEST screw up doing this is getting the CASE Datum line to bolt space correct BEFORE you try and install a bullet!
If the case isn't fitting the chamber LENGTH, distance from Datum line on case shoulder to bolt face, it doesn't matter what the ogive to case head distance is.
The only exception is zero 'Jump', the bullet against the rifling taper.
The case is simply going to slop around in the chamber and screw up you 'Jump' distance anyway...
This takes an ACCURATE measurement of the headspace of your chamber ('Headspace' defined as the CHAMBER, bolt face to Datum line on the chamber shoulder.
You simply beat the brass into a shape that fits the headspace in the chamber.
Datum line gauge adaptors are notoriously inaccurate when you attempt to find the ABSLOUTE headspace length, again because they have a radius at the measuring contact point... And when made of aluminum in particular, they expand with body heat during useage.
From a tool & die maker, I drill/hone the opening (hole) to exactly the Datum line diameter, and I DO NOT radius the opening so the gauge stops the case at exactly flush with the face of the gauge.
I do the same thing with ogive gauge adapters.
With razor sharp, exactly 90* opening faces, it makes getting the measurement a little more difficult since brass/bullet tend to hang up on the edge once in a while, but it gives EXACT readings.
If you don't beat the brass, the brass WILL beat you.
When I'm doing bench rifle rounds, it's all about EXACT PRECISION/CONSISTENCY,
Not 'Within' any +/- range, and since I've invested that much time already, might as well get it dead on to the 4th decimal place...
Or from the older folks to current useage...
We always called 'Bullet Jump'... Free Bore (Freebore) since there wasn't contact between bullet & chamber/barrel/rifling.
The second term that seems muddy is the 'Throat', 'Forcing Cone', etc.
From my very old gunsmith books and chamber drawings, traditionally lead bullet chambers, say 'Forcing Cone', while later jacketed bullet chambers say 'Throat'.
The third issue I see is 'Accuracy' used where it should say 'Consistent'.
Building ammo you are trying for a CONSISTENT product, so when you make changes you have a 'Zero' or starting point to move FROM.
A definitive, provable change from one cartridge build to another.
'Accuracy' is the end result, the 'TERMINAL' results.
'Accuracy' involves EVERYTHING, from the loose nut behind the trigger, to sights & sight lines, to weather conditions, to everything involved with internal & external ballistics.
This is one of my pet peeves, but I confuse the two all the time myself when I'm talking/writing because they are confused in common useage so often.
Someone says 'Accuracy' when they should have said 'Consistent' and I'm right there on the band wagon with them!
I SHOULD know better, but my brain simply complains later instead of correcting me on the spot...-----
Anyway, more to the point,
Measuring the Ogive to case head IS a much more accurate way to make CONSISTANT rounds for ONE SPECIFIC CHAMBER. No doubt about it! No argument...
The problems start when you don't have an exact, measured & absolute distance from Throat/Lands of the rifling to the case head.
This measurement also changes with wear of the throat, so you have to keep up with your throat erosion/wear of the lands of the rifling.
Freebore/Bullet Jump (whatever) is all over the place, some fast magnums came from the factory with 0.300", while some came with virtually zero, both shot equally well.
I find the intermediate velocity/pressure rifles shoot pretty well with minimal jump.
As for finding the actual (absolute) length of the cartridge, that's sometimes a pain.
The issue I have with most 'Gauges' is rounded, or radius on hole on the gauge.
A radius let's the bullet sink deeper into the gauge, which screwed up the absolute reading, instead giving a 'Relative' measurement.
A square edged hole can be a challenge (like with Datum line gauge adapters), but it's an accurate reading.
Since you are working with a taper in the chamber, matching that taper precisely (which will change with wear) is almost impossible, so generally it's accepted machinist practice to use a square edge on the gauge/stop which produces the best absolute measurement.
The issue I have with the premade 'Nut' gauges is the holes have radius, and the nut sides aren't precision ground, so each set of flats are a different size, you have to measure the 'Nut' (gauge) and subtract the distance between flats.
MUCH easier when all flats are the same distance, like 2", you simply subtract 2" from relative reading g for the absloute reading...
I suggest you hold the gauge 'Nut' in your hand BEFORE you measure, since body heat will expand it and change your initial measurement of the gauge...
When you are working 3 or 4 places behind the decimal point, this matters...
The BIGGEST screw up doing this is getting the CASE Datum line to bolt space correct BEFORE you try and install a bullet!
If the case isn't fitting the chamber LENGTH, distance from Datum line on case shoulder to bolt face, it doesn't matter what the ogive to case head distance is.
The only exception is zero 'Jump', the bullet against the rifling taper.
The case is simply going to slop around in the chamber and screw up you 'Jump' distance anyway...
This takes an ACCURATE measurement of the headspace of your chamber ('Headspace' defined as the CHAMBER, bolt face to Datum line on the chamber shoulder.
You simply beat the brass into a shape that fits the headspace in the chamber.
Datum line gauge adaptors are notoriously inaccurate when you attempt to find the ABSLOUTE headspace length, again because they have a radius at the measuring contact point... And when made of aluminum in particular, they expand with body heat during useage.
From a tool & die maker, I drill/hone the opening (hole) to exactly the Datum line diameter, and I DO NOT radius the opening so the gauge stops the case at exactly flush with the face of the gauge.
I do the same thing with ogive gauge adapters.
With razor sharp, exactly 90* opening faces, it makes getting the measurement a little more difficult since brass/bullet tend to hang up on the edge once in a while, but it gives EXACT readings.
If you don't beat the brass, the brass WILL beat you.
When I'm doing bench rifle rounds, it's all about EXACT PRECISION/CONSISTENCY,
Not 'Within' any +/- range, and since I've invested that much time already, might as well get it dead on to the 4th decimal place...
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Again; already covered, problem: The reloader has a problem with deciding what is head space and they get confused with 'what' has head space. My cases do not have head space.
And then? They are real slow about coming around, I am the fan of transfers and standards, I have head space gages, my head space gages are standards. When I want to check a comparator with a case friendly radius I check the comparator with a standard.
If I do not have a standard I make it. Again, I make datums, I collect datums and there are times I have purchased datums. Other reloaders? They seem to be MAD or upset with the day they ever learned to read. Not me, if a reloader can not drill a straight hole and if they do not understand an accurate datum (round hole) to be accurate it must be finished with a reamer.
None of this stuff hangs me up, if I do not have the correct round hole datum I use the tool as a comparator. Without a standard, for most, it is difficult to compare readings with SAAMI specifications. I measure the length of the chamber from the shoulder to the bolt face without a head space gage at least three different ways, I can measure the length of a chamber with a gage that is too short, I can measure the length of the chamber with a gage that is too long. At one time I thought all reloaders could measure the length of the chamber without a head space gage, that was a long time ago.
F. Guffey
Joe-ker,
It was a long held belief by handloaders, including many benchrest shooters, that the primer was this delicate assembly and you wanted to insert it into the primer pocket only far enough to feel the feet of the anvil just kiss the floor of the pocket. The makers of primers, validated by experiments by Naval Ordnance at Indian Head (NOIH), have said you actually need to seat primers to compress the anvil's tip down into the priming mix by a few thousandths. This pre-loads compression of the priming mix between the inside bottom of the primer cup and the tip of the anvil; compression that will become rapidly and dramatically greater when the firing pin strikes. This is variously referred to as "setting the bridge", meaning setting the thickness of priming compound between the anvil and cup, and "reconsolidation", meaning factory assembly consolidates the components and squeezing the primer in re-works that consolidation. Either way, it improves the sensitivity of the primer and makes the ignition more consistent.
The exact specification varies by source. Federal says to reconsolidate small primers by 0.002" and large primers by 0.003". Old military information provided by Olin and Remington to the government for primers, both large and small, used for various purposes recommended 0.002"-0.006" of reconsolidation. Later versions of the same documents have changed them to a recommendation by NOIH to use 0.002"-0.004" regardless of size.
I think, since Federal uses a different form of lead styphnate than the others do, you would ideally follow their recommendation with their primers, but use the NOIH numbers for all other.
The only tool I am aware of that lets you measure reconsolidation directly is the K&M Primer Gauge tool. You can, however, with shims, set up the Sinclair hand priming tool for fixed seating depths by controlling how far its ram protrudes from its base, but you need to measure the depths of the primer pockets first to know where to set it. The Forster Co-ax press priming tool uses a fixed seating depth, too, that has been found best for brass on average. There are now some other primer seating tools on the market with detent adjustable ram protrusion.
Or, you can wing it. Reconsolidating takes some push. So feeling where the anvil kisses the floor of the primer pocket and then adding a pretty good push on the seating lever generally gets you somewhere around where you want to go.
It was a long held belief by handloaders, including many benchrest shooters, that the primer was this delicate assembly and you wanted to insert it into the primer pocket only far enough to feel the feet of the anvil just kiss the floor of the pocket. The makers of primers, validated by experiments by Naval Ordnance at Indian Head (NOIH), have said you actually need to seat primers to compress the anvil's tip down into the priming mix by a few thousandths. This pre-loads compression of the priming mix between the inside bottom of the primer cup and the tip of the anvil; compression that will become rapidly and dramatically greater when the firing pin strikes. This is variously referred to as "setting the bridge", meaning setting the thickness of priming compound between the anvil and cup, and "reconsolidation", meaning factory assembly consolidates the components and squeezing the primer in re-works that consolidation. Either way, it improves the sensitivity of the primer and makes the ignition more consistent.
The exact specification varies by source. Federal says to reconsolidate small primers by 0.002" and large primers by 0.003". Old military information provided by Olin and Remington to the government for primers, both large and small, used for various purposes recommended 0.002"-0.006" of reconsolidation. Later versions of the same documents have changed them to a recommendation by NOIH to use 0.002"-0.004" regardless of size.
I think, since Federal uses a different form of lead styphnate than the others do, you would ideally follow their recommendation with their primers, but use the NOIH numbers for all other.
The only tool I am aware of that lets you measure reconsolidation directly is the K&M Primer Gauge tool. You can, however, with shims, set up the Sinclair hand priming tool for fixed seating depths by controlling how far its ram protrudes from its base, but you need to measure the depths of the primer pockets first to know where to set it. The Forster Co-ax press priming tool uses a fixed seating depth, too, that has been found best for brass on average. There are now some other primer seating tools on the market with detent adjustable ram protrusion.
Or, you can wing it. Reconsolidating takes some push. So feeling where the anvil kisses the floor of the primer pocket and then adding a pretty good push on the seating lever generally gets you somewhere around where you want to go.
"There is some debate about how deeply primers should be seated. I don’t pretend to have all the answers about this, but I have experimented with seating primers to different depths and seeing what happens on the chronograph and target paper, and so far I’ve obtained my best results seating them hard, pushing them in past the point where the anvil can be felt hitting the bottom of the pocket. Doing this, I can almost always get get velocity standard deviations of less than 10 feet per second, even with magnum cartridges and long-bodied standards on the ’06 case, and I haven’t been able to accomplish that seating primers to lesser depths.
Dan Hackett writing in the 1995 Precision Shooting Reloading Guide"
Dan Hackett writing in the 1995 Precision Shooting Reloading Guide"
JeepHammer
Moderator
Guffy, everything has been covered somewhere, nothing new anywhere here...
I don't filter through every word of every post, I have a life.
Just hitting the high points, the stuff that bears repeating if it's important, so it doesn't get lost in the sales propaganda or ramblings of other posters (myself included).
Absloute vs. Relative is a big deal, needs both repeated hits to express importance, and explained to novices in each case when they reach this level.
I don't filter through every word of every post, I have a life.
Just hitting the high points, the stuff that bears repeating if it's important, so it doesn't get lost in the sales propaganda or ramblings of other posters (myself included).
Absloute vs. Relative is a big deal, needs both repeated hits to express importance, and explained to novices in each case when they reach this level.
Don Fischer
New member
How do you adjust a seating die .001"?
I do not know how he adjusts the seating plug .001": it is something like 'on the other hand' because all of my seating dies are adjustable, I measure the height of the stem above the top of the die with a height gage or a depth gage or a dial caliper etc., after zeroing the stem I lower it .001", I understand; seating dies are available with dial indicator mounted on top of the die body, I understand Herter sold tools in the old days; again I am the fan of transfers, I make a transfer and then use it to adjust the seating die.
F. Guffey