Better than the funny papers. You just can't make this stuff up..........
Comparator gauge
- Thread starter WANTASHOOT
- Start date
Sinclair’s comparator inserts are cut to the various shoulder angles, not near whatever datum diameter. They’ll fit either their own or Hornady’s comparator bodies.
I do the same. I will never buy a barrel again that has been reamed. Buy a blank barrel and a reamer and you will have a "perfect" measuring tool
dmoran
Donovan Moran
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One day when reloaders and smiths catch on they will stop using barrels for tomato stakes, for me it is nothing for me to cut the chamber off a barrel and save the rest of the barrel for gages. Once the reloader gets into measuring case head protrusion they will wonder why they did not discover the method and or technique before.
I have used take off barrels and new barrels, I can only guess when the chamber gets dark the light goes out.
F. Guffey
Ya mean like this?
My 280 Go clearly marked 2.987". I counter bored the anvil exactly .100"deep so the actual length, head to .375" on the shoulder with the caliper zeroed between the insert- anvil is 2.100" ( 2.00 + .100 )
By the same token a stick of 280 brass...
Again, 1.999+.100" = 2.099". Plenty close enough for Govn't work.
Bill
No, I measure chamber lengths for head space, again, my cases do not have head space. There has to be 4 ways to measure the length of the chamber from the shoulder/datum to the bolt face; some of it goes back 65 years+, some of it could have gone back 105+ years ago had someone been able to figure it out.
F. Guffey
I know there's counting and repetitive OCD. Must also be measuring OCD.
I said Hornady uses a case friendly datum, a case friendly datum will be discovered on this forum in a year or so. I have said there is something about datums reloaders do not understand; my datums will imprint on the shoulder of the case. I do not find the sharp edge at the top of the hole beneficial other than that is the only way they can be accurate. Again, a datum with a bevel is used on a comparator.
And for years reloaders have called the Hornady tool a head space gage because they thought the case had head space.
F. Guffey
Ask him if he has a few old worn out barrel, from the beginning smiths and reloaders turned barrels into tomato stakes, I thought that was silly.
Hornady insert. Again, there is something about datuums a reloaders does not understand. L.E. Wilson has made case gages since 1953. I have no ideal how a reloader can be around something that long without knowing something about it; it was not that long ago they referred to the case gage as a 'drop in gage'.
The Wilson case gage is a datum based tool, in the bottom of the Wilson case gage there is a datum. I will have to say 'believe it or not' or take my word for it but the datum in the Wilson case gage has a radius, they use the radius because it is case friendly. Wilson did not cut case gage with a shoulder because they understood datums, they wanted the case to contact the datum for accuracy.
Hornady/Sinclair tired to make a case length gage without a case body, they would have been successful if they figured a way to cut the datum with a sharp edge; problem, they could not close the caliper on the tool to zero, to determine the amount of error it is necessary to use a head space gage. And then there is that part about verifying a head space gage. I do not remember how many years this has been going on; I accept the Hornady tool is a comparator, the digital head space gage (not) is a comparator. The case does not have head space.
F. Guffey
dmoran
Donovan Moran
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Alex Wheeler
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The only way you will be able to get a measurement that will tell you how the case will fit your chamber is to have your gunsmith make your comparator with the reamer he used to cut your chamber. The datum doesnt mean anything. You already know your die does not perfectly match your chamber (normal) and just becuase you moved the datum back doesnt mean you moved all of the shoulder back. But, this doesnt matter really. If it takes .008" with your tool, just bump it .008" Although thats an excessively bad die/chamber fit. Its normal to see where you need to bump a case .002" to get it back to a zero clearance but not .008-.010" What die?
If one uses the Hornady Headspace Comparator tool clamped onto a decent set of calipers in conjunction with the actual rifle chamber and a stripped bolt, accurate measurements for case length can be achieved.
As an example, using the 0.420 size Hornady comparator locked into the tool body and clamped onto the fixed jaw of the caliper, I can determine that any case measuring longer than 1.6250 inches will not allow the bolt to close without resistance in my 7 RSAUM action. How do I know this? Because I’ve pushed a deprimed and cleaned case ready to be sized into the chamber with the stripped bolt (firing pin and ejector) and attempted to close it. If I meet no resistance, it will measure 1.6250 inches or less in the comparator; if I begin to feel slight resistance to bolt closure, the case will measure 1.6255 inches or greater in the comparator. What does this number mean to anyone else? Little to nothing at all. It is derived from my particular comparator set and my particular rifle chamber/bolt combination. With this number in hand, one can then proceed to resize cases and check the results with the comparator.
Trying to duplicate SAAMI dimensions is all well and good if one is reloading for semi or fully automatic rifles or for a friends factory chamber, but these dimensions should be laid aside when endeavoring to construct a precision round for one’s own rifle that is readily available for measurements. To my way of thinking, one cannot do better than using the actual chamber/bolt combination for determining case fitment and the comparator simply allows one to attach a number to the optimum case length dimension for that rifle. The number is not really needed if each sized case is wiped free of sizing lubricant and checked for proper bolt closure in the rifle. At this point, its only value is it will indicate when the case has been sized excessively and the benefit of fire forming the case has been diminished – allowing one to back the die out a tad.
Ken
As an example, using the 0.420 size Hornady comparator locked into the tool body and clamped onto the fixed jaw of the caliper, I can determine that any case measuring longer than 1.6250 inches will not allow the bolt to close without resistance in my 7 RSAUM action. How do I know this? Because I’ve pushed a deprimed and cleaned case ready to be sized into the chamber with the stripped bolt (firing pin and ejector) and attempted to close it. If I meet no resistance, it will measure 1.6250 inches or less in the comparator; if I begin to feel slight resistance to bolt closure, the case will measure 1.6255 inches or greater in the comparator. What does this number mean to anyone else? Little to nothing at all. It is derived from my particular comparator set and my particular rifle chamber/bolt combination. With this number in hand, one can then proceed to resize cases and check the results with the comparator.
Trying to duplicate SAAMI dimensions is all well and good if one is reloading for semi or fully automatic rifles or for a friends factory chamber, but these dimensions should be laid aside when endeavoring to construct a precision round for one’s own rifle that is readily available for measurements. To my way of thinking, one cannot do better than using the actual chamber/bolt combination for determining case fitment and the comparator simply allows one to attach a number to the optimum case length dimension for that rifle. The number is not really needed if each sized case is wiped free of sizing lubricant and checked for proper bolt closure in the rifle. At this point, its only value is it will indicate when the case has been sized excessively and the benefit of fire forming the case has been diminished – allowing one to back the die out a tad.
Ken
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KVD, correct; but if a reloader did not describe the procedure in lofty terms he would start with measuring the case length from the shoulder/datum to the case head before and again after firing. Why before and again after firing? A reloader should be curious about the effect the chamber had on the case when fired.
I know; it has been established a reloader does not know what happens to the case when fired, they do not know what happens to the shoulder of the case when sized, I have decided reloaders are blessed, they do not have to know, they do not want to know. Back to the effect the chamber has on the case when fired: When measuring the case length before and again after firing the reloader should be able to measure the difference in length of the case before firing and after firing. .005" would be perfect for the 30/06 case, .005" is the difference on length between a minimum length case and a go=gage length chamber. (One more time) I have a 30/06 rifle with a chamber that is .016" longer than a minimum length/full length sized case from the shoulder of the chamber to the bolt face than the case from the shoulder of the case to the case head.
I fire that rifle with the magic .002" clearance but even if I choose to fire a minimum length/full length sized case in that long chamber with .016" clearance the shoulder on my case would not move and the case would not stretch. Back to the top; a reloader should know the effect the chamber had on the case when the case is fired. If the case stretched when I fired it in the long chamber I would think that would be a 'bad thing'.
F. Guffey
It seems if a reloader understood the chamber is go-gage length sizing would not be so complicated. A reloader should manage .005" clearance when sizing a 30/06 case if they were able to full length size the case to minimum length. For those that can not determine the length of the chamber from the shoulder of the chamber to the bolt face there is always fire forming.
Fire forming: chamber a round and then pull the trigger. I had rather form first then fire. Before fire forming I recommend measuring the length of the case from the shoulder to the case head before firing. After firing there is always sizing, measure the length of the case from the from the shoulder to the case head after firing and again after sizing. I use the length of the case from the shoulder to the case head to off set the length of the chamber.
F. Guffey
What a coincidence, I have a long chamber too, I figured it must've some how stretch.
I soaked it in water a few days hoping to shrink and after a week of drying out it had shrunk over .020 and now it's too short !
I now put the barrel in a vise with chamber down and 15 lbs of weight hanging off the end, I'm hoping it will stretched back out again... seems to be working.
My question.. After the barrel been worked from stretching and shrinking how long should I anneal it and at what temp?
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