So I have searched and read thru all the post about comparator guages but I have not found any details on what gauge to use when measuring. The reason I ask is: As i am working up loads for my Dasher I am running them thru a full length sized and using a comparator gauge that just slid over the neck (just picked one as it's only for comparison) and I measure and size and wow I bumped my shoulder .010. Re adjust to .002 and try it in the chamber. Had to lightly force the bolt all the way. Adjusted the die for .004 and same thing and finally at .005 the bolt closed about 3/4 of the way. I was happy but the next case didn't fit the same. Measured and it was longer (why) went back and checked over my process no luck. Watched Alex Wheelers video seen his comparator and decided to look at the gauges I had and picked one labeled 420 and used it. Guess what compared to fired cases I was not bumping the shoulder at this new location. Adjusted the die some more and all the sudden everything started working consistently. Still wondering if I am using the correct gauge. Where is the Datum maybe I can find a gauge that is the same as the datum. Ohh it's a 6mm Dasher by the way.
Comparator gauge
- Thread starter WANTASHOOT
- Start date
I don't see the 6 Dasher on SAAMI.ORG. Looking at other cartridges it looks like the shoulder bump gauge opening is the diameter half way up the shoulder. You don't need a bump gauge. Look up the post and video's using the bolt closing method. Basically you need a bolt with the firing pin and spring removed and you adjust the die so that the bolt just closes with almost no force. I think your familiar with the method.
Yep using the stripped bolt method just wanted to know how to pick the correct gauge the first time. As it would have helped keep me from being confused with inconsistent results.
I use Hornady's setup. It consist of a Comparator Body, a Headspace Gauge, a Bullet Insert, and an Anvil Base. I set my cases up (for a bolt action rifle) .001" shorter than a fired case. You can't always go by your die setting. Some brass is springy when you resize it. Set them by the gauge. I haves tested for which jump gives me the best accuracy, which happens to be .025" for me. Use the body and bullet insert (along with the anvil base) and measure the length of the round (to one I've checked the actual jump with in the chamber). The inside diameter is just slightly smaller then the ogive. I seat my bullets to this length within .001", not from the tip which can vary quite a bit. This should get you real close. You cannot use anyone else's figures even if they have the exact same comparator gauges. Machining differences will make them read different. If you change bullets, you'll have to remeasure everything again.
Unfortunately there is no standard for gages measuring base to shoulder, so any two you buy of the same mfg will likely be slightly different. I learned this first hand recently. Bought a second set of Hornaday Headspace gages for a friend and accidentally traded off the one I was using. Suddenly my 6mmBR brass was chambering tight but measured correctly, and I was gobsmacked. Re measured everything and sure enough, gage was coming up with different dimensions.
Lesson learned.
BTW: be sure to use the exact same cartridge holder with your sizing die. Not just another one of same mfg, but the SAME one. Label it if you have to with an engraving tool.
Lesson learned.
BTW: be sure to use the exact same cartridge holder with your sizing die. Not just another one of same mfg, but the SAME one. Label it if you have to with an engraving tool.
dmoran
Donovan Moran
@WANTASHOOT -
When I have a new barrel chambered, I also run the reamer part way into a barrel stub (attached picture below) to be used for a comparator and/or bump gauge. Perfect shoulder match to the spent brass !.!.!
Donovan
When I have a new barrel chambered, I also run the reamer part way into a barrel stub (attached picture below) to be used for a comparator and/or bump gauge. Perfect shoulder match to the spent brass !.!.!
Donovan
Excellent as always you guys have come up with the answer and then some. Thank you very much.
These things are worth their weight in gold, IMO.
http://www.whiddengunworks.com/product/case-gauge-3/
http://www.whiddengunworks.com/product/case-gauge-3/
If you have a headspace go-gauge you really can use any datum line that hits on the shoulder somewhere as long as the chamber is cut to SAMMI minimum length {same as the go gauge} you can also use the stripped bolt method to find chamber length and carefully use that case to set the comparator, again with whatever datum line hits the shoulder.
With Ackley improved cartridges I always make my own comparator piece by running the same chamber reamer I chambered the barrel with into the tool to size the correct diameter, then I know I am reading on the case exactly the same as where it would touch in relation to the chamber and right dead at the junction of the neck and shoulder.
Edit: I am surprised to see someone on this forum worried about it...most people on here easily, happily accept up to .008" and sometimes more headspace in their rifles and/or sized cases. Boggles my mind why anyone wouldn't want it zero.......
With Ackley improved cartridges I always make my own comparator piece by running the same chamber reamer I chambered the barrel with into the tool to size the correct diameter, then I know I am reading on the case exactly the same as where it would touch in relation to the chamber and right dead at the junction of the neck and shoulder.
Edit: I am surprised to see someone on this forum worried about it...most people on here easily, happily accept up to .008" and sometimes more headspace in their rifles and/or sized cases. Boggles my mind why anyone wouldn't want it zero.......
BEWARE!!!!!! If you guys keep talking DATUMS Mr. Guffey will come here and clean your clock!
dmoran
Donovan Moran
He may be the only one.......
Yeah, darn it...what was I thinking!!!!!
Not trying to hijack this thread, but it occurred to me while reading about all the experiences here, that my Hornaday HS gage is simply a bored hole in a piece of aluminum bar. It has no taper and therefore only contacts the shoulder of the brass along the rim of the hole.
It seems that a similar piece of alum bar bored with the same reamer as the chamber would make a much better gage.
Does anyone make such an animal? Should I just take my Hornaday insert to my GS and have him ream it to match the neck angle?
Inquiring minds would like to know....
It seems that a similar piece of alum bar bored with the same reamer as the chamber would make a much better gage.
Does anyone make such an animal? Should I just take my Hornaday insert to my GS and have him ream it to match the neck angle?
Inquiring minds would like to know....
A sharp edged hole is used to insure contact in the same area every time. This is standard practice for tools and gages.
A functional gage is what you are asking for. I think Whidden manufactures a chamber type functional gage.
The functional gage only tells you if the cartridge fits. It does not measure or give you any dimensional data.
A functional gage is what you are asking for. I think Whidden manufactures a chamber type functional gage.
The functional gage only tells you if the cartridge fits. It does not measure or give you any dimensional data.
No Hi-jack...this is a good question. "Only contacts the shoulder along the rim of the hole"" absolutely correct...that's called the datum, and that is exactly what it is supposed to do. It contacts the shoulder at precisely that "designated" or SAAMI spec-ed point in diameter.
As to your "much better gauge" part....go back and read my post. I have been doing that for a while. It's a great idea for Ackley Improved cartridges because they are measured at the junction of the neck and shoulder, but not really needed otherwise...that is what the datum line concept does for you. It will read and work as you say, with a shoulder in the tool, but there really is no reason to do it...it will read your cases just perfectly based on the designated diameter. With the Ackley cartridges you are headspacing off of a point that the chambering reamer sets this diameter.
Along the lines of what you are asking, Tony Boyer in his book mentions having his gunsmith run the chambering reamer into a piece of cut off barrel stub to use as a gauge.
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As I have said there has be something about the datum reloaders do not understand. When using a comparator the reloader is required to measure before and again after. I know; if that made any sense everyone would be doing it. And then it gets complicated because reloaders believe the case has head space and every tool is a head space gage. My cases do not have head space and when I measure the length of the case from the shoulder/datum to the case head I am not measuring head space.
Before and again after: If a reloader is able to measure the length of the case from the shoulder to the case head after firing sizing with the perfect .002" reduction in case length between the shoulder to the case head should be a matter adjusting the die of and then measuring. It gets difficult when reloaders fail to determine if the press can overcome the ability of the case to resist sizing. What does that mean? The reloader must determine if there is a gap between the top of the shell holder and bottom of the die. If the case does not get stuffed into the die the part of the case that does not get stuffed into the die did not get sized.
Again, it is complicated, a reloaders should form good habits and measure before and again after firing, and before sizing and again after sizing.
The datum is not a line, my datums are round holes, if my datum has a bevel it is case friendly but can only be used as a comparator unless I use a standard to calibrate or adjust to zero. Point; if I am measuring before and again after the diameter of the hole/datum does not matter if it will allow the neck to inter and stop on the shoulder before the case body/shoulder juncture passes through the hole/datum.
F. Guffey
The smith that that used a cut off barrel made Boyer a chamber gage. Smiths and reloaders never caught on to the ideal because all of the chamber gages made today are knock offs of the Wilson case gage. Meaning the case head is lever with the top of the gage, I have always suggested the case should have case head protrusion. I know that makes no sense but with case head protrusion a reloader could use a tool that would fit over the case head and agains the gage.. And I noticed a few months ago Wilson has started making that tool with a dial indicator; after all these years.
F. Guffey
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