Measuring my fired brass with the RCBS Precision Mic my brass is .0025 less then zero spec. From expanding, when F/L sizing, using the Redding precision shell holders the brass will stretch.Using different shell holders with the firing pin assembly & ejector removed, l can get the zero amount of space from bolt face to the base of the case. Mine is .0015 less the the standard spec. How do you check yours
How do you check your bolt actions headspace
- Thread starter cw308
- Start date
JeepHammer
Moderator
'Head Space', proper, is measured from the 'Datum' point on the case shoulder to the head stamp surface on the bottom of the case.
Once a proper head space adapter (inexpensive) is used on a caliper, and you have a case that is SAAMI specification,
Then you can determine actual firearm head space very easily by chambering the properly sized/gauged brass,
Use a slick lubricant on the bolt face,
And a filament of gauge material across the brass head stamp.
A product called 'Plasti-Gauge', available at any serious auto parts store for a couple dollars, will flatten out when the bolt is closed & locked,
A printed strip on the package will tell you how much space there is between bolt face and case.
This will get you VERY close without a very expensive micrometer.
Once a proper head space adapter (inexpensive) is used on a caliper, and you have a case that is SAAMI specification,
Then you can determine actual firearm head space very easily by chambering the properly sized/gauged brass,
Use a slick lubricant on the bolt face,
And a filament of gauge material across the brass head stamp.
A product called 'Plasti-Gauge', available at any serious auto parts store for a couple dollars, will flatten out when the bolt is closed & locked,
A printed strip on the package will tell you how much space there is between bolt face and case.
This will get you VERY close without a very expensive micrometer.
FrankenMauser
New member
Remove extractors, ejectors, and any other "feature" that will interfere with headspace measurements.
Us "go and "no-go" gauges to determine your starting point.
Add shims, as necessary, to determine actual headspace.
I have materials on hand ranging from 0.001" to 0.030". (From paper to brass sheet.) So, it doesn't take too long for me. But, I don't expect every gun owner to have the same hobbies and material (and tool) stock on hand.
Us "go and "no-go" gauges to determine your starting point.
Add shims, as necessary, to determine actual headspace.
I have materials on hand ranging from 0.001" to 0.030". (From paper to brass sheet.) So, it doesn't take too long for me. But, I don't expect every gun owner to have the same hobbies and material (and tool) stock on hand.
Thank you guys for getting back. When checking proper headspace it seems to be always checked by using your bolt & by feel when locking the bolt. Not just bumping back a fire formed case 1 or 2 thousands. In my case when my fired case was shorter, just bumping back .001 without checking with, let's call it " bolt feel " l might wind up with to much headspace. Correct?
This reminds me of Elizabeth, "Let me count the ways", I walked into a gun parts store looking for parts when I noticed a customer asking to have the head space checked on his magnificent rifle. The owner informed the proud owner of that magnificent rifle he could not check the head space because he did not have a gage for the exotic chamber; and then the man left.
I then informed the owner I could measure the length of that chamber three different ways without a head space gage and then I waited. He asked; "HOW!". That was almost a friendly alert. He was busy so I went through one method/technique. More times than not he does not charge for checking the chamber with a go-gage, no go-gage but understands he is not measuring the length of the chamber from the shoulder to the bolt face in thousandths.
F. Guffey
I then informed the owner I could measure the length of that chamber three different ways without a head space gage and then I waited. He asked; "HOW!". That was almost a friendly alert. He was busy so I went through one method/technique. More times than not he does not charge for checking the chamber with a go-gage, no go-gage but understands he is not measuring the length of the chamber from the shoulder to the bolt face in thousandths.
F. Guffey
F.Guffey
I was hoping you would chime in. Is the way I'm checking my cases correct, with the tools I have. Never liked the idea of neck sizing only. I'm looking for every case to be as exact as possible with minimum space left between bolt face & case. If the proper meaning is headspace, then I'm looking for minimum amount of headspace.Thanks Chris
I was hoping you would chime in. Is the way I'm checking my cases correct, with the tools I have. Never liked the idea of neck sizing only. I'm looking for every case to be as exact as possible with minimum space left between bolt face & case. If the proper meaning is headspace, then I'm looking for minimum amount of headspace.Thanks Chris
It helps to know the head space of the chamber, that would be determined by a measurement from the datum/shoulder to the bolt face, The difference between the length of the case from the shoulder the case head and head space is clearance.
The case does not have head space and head space does not changer unless things are going seriously wrong, so we are talking about too much clearance.
Again, there is neck sized and there is full length sized back to minimum length. There is a difference in the perfect world if the chamber is a 30/06 of .005" + case body expansion; after that someone should attempt to explain what difference that could make when considering factors.
F. Guffey
JeepHammer
Moderator
Lengthening the cases, then using 'Feel' on the bolt is SUBJECTIVE,
Subject to your impression of 'Feel'.
.
Using a measuring device is OBJECTIVE, gives you an actual, repeatable, verifiable result.
Plasti-Gauge is the cheapest way to get quantifiable results.
Some guys set a primer 'Shallow' and let the bolt press it into the primer pocket.
Not optimum, since you will get a different result each time you do it, and different primers/brass will produce different results.
Subject to your impression of 'Feel'.
.
Using a measuring device is OBJECTIVE, gives you an actual, repeatable, verifiable result.
Plasti-Gauge is the cheapest way to get quantifiable results.
Some guys set a primer 'Shallow' and let the bolt press it into the primer pocket.
Not optimum, since you will get a different result each time you do it, and different primers/brass will produce different results.
JeepHammer
Never heard of seating a primer with the bolt face, don't like that idea. As far as feel, when I size a case to a SAAMI specs, measured with Mic. for example, at zero reading. I would chamber case, feel resistance all the way until completely closed. Resize to .0015 on the Mic., chamber, then only feel resistance at the bottom of the bolt closure. Wouldn't that tell you that case is sized to the minimum. At that point I would record the measurement of the case & size to that reading. I'm reloading only for accuracy. I read an article on galling bolt locking lugs due to tight chambering. I guess I'm looking for a happy medium. Am I right in my method or am I missing something?
Never heard of seating a primer with the bolt face, don't like that idea. As far as feel, when I size a case to a SAAMI specs, measured with Mic. for example, at zero reading. I would chamber case, feel resistance all the way until completely closed. Resize to .0015 on the Mic., chamber, then only feel resistance at the bottom of the bolt closure. Wouldn't that tell you that case is sized to the minimum. At that point I would record the measurement of the case & size to that reading. I'm reloading only for accuracy. I read an article on galling bolt locking lugs due to tight chambering. I guess I'm looking for a happy medium. Am I right in my method or am I missing something?
The RCBS Precision Mic is a good tool but allow me to share an observation I made using it. Over the years I ended up with two of them in Part #88304 the .223 Remington chambering. I also have several actual headspace gauges.
Using the RCBS numbers the .223 Remington precision mic will read Zero when distance from cartridge head face (bolt face) to a datum on the case shoulder is 1.4636". The datum being where the case shoulder diameter is 0.330". Now at this point I would like to clarify what Mr. Guffy points out.
Cases do not have a headspace dimension, only chambers have a headspace dimension. While I do not have a .223 Remington SAAMI drawing I do have a .308 Winchester SAAMI drawing which is marked up and should illustrate Mr. Guffy's point. The below drawing illustrates both the cartridge and chamber specifications, note how the drawing is marked up and how only the chamber drawing calls out "headspace", the cartridge drawing merely calls out measurements.
Yes, I know everyone loves to call it headspace on a cartridge but the dimension is not headspace by SAAMI definition. Maybe that is why RCBS does not call their gauge a headspace gauge? I know a Google of "cartridge headspace gauge" will bring up a dozen case gauges but again, headspace only refers to the chamber. The term has just become sort of accepted be that right or wrong.
Anyway, back to your RCBS Precision Mic. As I mentioned I have a few in .223 Remington and during use I noticed a quirk. They do not read the same. I know because I checked them using actual headspace gauges. Here is an example of what I am getting at. Using a precision 1.464" headspace gauge one precision mic read 0.000 while the other measured -0.002. Here is what actual headspace gauges look like.
The images are .308 Winchester I believe but you get the idea. How do I know my gauges are accurate as in which RCBS Mic is telling the truth? Before I retired I had my guys run all my gauges on a Zeiss CMM (Coordinate Measuring Machine) which will accurately split millionths of an inch. Anyway I had that -0.002" difference telling me all RCBS Precision Mics are not created equally. Take it for what it's worth on that. I haven't a clue what the RCBS allowable tolerance is on their precision mics.
All of that boring stuff said:
How do I check mine? While I have no shortage of case gauges in all sorts of types I use the RCBS Precision Mic. Figure it this way, when a case fires it fills the chamber expanding in all directions. Then the brass contracts just a little. How much varies but most shooters like to say about 0.001". If the brass did not contract slightly it would be a chore getting it out. When resizing brass most people like to say "bump" the shoulder back, a term which I am not real fond of. The brass will expand most at the weakest point which is generally about 0.200" forward of the base of the case head. Here nor there for the most part. Since in most cases my .223 Remington, .308 Winchester and 30-06 Springfield brass may be loaded for any of several rifles in each caliber I just full length resize back to the Zero on my RCBS Precision Mics. If you are going to shoot the brass in the same rifle you can measure it and run your sizing die down with the ram up till they bump. Size the brass and measure. You want to know where the brass started, the brass after firing and each time you run the ram up, slowly running the die down till the fired brass is about 0.002" from where it came out of the rifle at. All of this depending on your chamber. I also try chambering the brass in my tightest chamber before moving along in the reloading process.
Anyway if you really want a headspace dimension I liked post #4 and #5. Using the mentioned shims will get you a good number. If all of this is unimportant to you then try as I mentioned just moving the brass back to zero in small steps trying the brass in your chamber each step. You doo not want to load a hundred cases that won't fit and won't hit. Use your chamber as your gauge.
Ron
Using the RCBS numbers the .223 Remington precision mic will read Zero when distance from cartridge head face (bolt face) to a datum on the case shoulder is 1.4636". The datum being where the case shoulder diameter is 0.330". Now at this point I would like to clarify what Mr. Guffy points out.
Cases do not have a headspace dimension, only chambers have a headspace dimension. While I do not have a .223 Remington SAAMI drawing I do have a .308 Winchester SAAMI drawing which is marked up and should illustrate Mr. Guffy's point. The below drawing illustrates both the cartridge and chamber specifications, note how the drawing is marked up and how only the chamber drawing calls out "headspace", the cartridge drawing merely calls out measurements.
Yes, I know everyone loves to call it headspace on a cartridge but the dimension is not headspace by SAAMI definition. Maybe that is why RCBS does not call their gauge a headspace gauge? I know a Google of "cartridge headspace gauge" will bring up a dozen case gauges but again, headspace only refers to the chamber. The term has just become sort of accepted be that right or wrong.
Anyway, back to your RCBS Precision Mic. As I mentioned I have a few in .223 Remington and during use I noticed a quirk. They do not read the same. I know because I checked them using actual headspace gauges. Here is an example of what I am getting at. Using a precision 1.464" headspace gauge one precision mic read 0.000 while the other measured -0.002. Here is what actual headspace gauges look like.
The images are .308 Winchester I believe but you get the idea. How do I know my gauges are accurate as in which RCBS Mic is telling the truth? Before I retired I had my guys run all my gauges on a Zeiss CMM (Coordinate Measuring Machine) which will accurately split millionths of an inch. Anyway I had that -0.002" difference telling me all RCBS Precision Mics are not created equally. Take it for what it's worth on that. I haven't a clue what the RCBS allowable tolerance is on their precision mics.
All of that boring stuff said:
How do I check mine? While I have no shortage of case gauges in all sorts of types I use the RCBS Precision Mic. Figure it this way, when a case fires it fills the chamber expanding in all directions. Then the brass contracts just a little. How much varies but most shooters like to say about 0.001". If the brass did not contract slightly it would be a chore getting it out. When resizing brass most people like to say "bump" the shoulder back, a term which I am not real fond of. The brass will expand most at the weakest point which is generally about 0.200" forward of the base of the case head. Here nor there for the most part. Since in most cases my .223 Remington, .308 Winchester and 30-06 Springfield brass may be loaded for any of several rifles in each caliber I just full length resize back to the Zero on my RCBS Precision Mics. If you are going to shoot the brass in the same rifle you can measure it and run your sizing die down with the ram up till they bump. Size the brass and measure. You want to know where the brass started, the brass after firing and each time you run the ram up, slowly running the die down till the fired brass is about 0.002" from where it came out of the rifle at. All of this depending on your chamber. I also try chambering the brass in my tightest chamber before moving along in the reloading process.
Anyway if you really want a headspace dimension I liked post #4 and #5. Using the mentioned shims will get you a good number. If all of this is unimportant to you then try as I mentioned just moving the brass back to zero in small steps trying the brass in your chamber each step. You doo not want to load a hundred cases that won't fit and won't hit. Use your chamber as your gauge.
Ron
CW308, it is not quite what it appears to be, when the bolt is closed on a case with a protruding primer the primer is seated but not completely. The difference between flush and protruding is supposed to represent the difference in length between the case and chamber.
It is something like reduced loads, the case head does not get driven back to the bolt face leaving the primer to protrude in the belief the amount of protrusion represents the difference in length between the chamber and case in the usual places.
F. Guffey
"...Measuring my fired brass..." Tells you absolutely nothing about headspace. Only proper headspace gauges do that. And they actually measure nothing. They only tell you if your rifle's headspace is within tolerance.
If the bolt closes, completely, on a Go gauge, but not on a No-Go, you're fine. Nothing else is required.
1335 x 1666 pixels is waaaaaay too big of a picture.
If the bolt closes, completely, on a Go gauge, but not on a No-Go, you're fine. Nothing else is required.
1335 x 1666 pixels is waaaaaay too big of a picture.
Reloadron
Thank you for all the examples. Can you go through your process in sizing.
F.Guffey
I can see how soft seating the primer would give you the measurement from the datum to the bolt face on a undersize case.
T. O'Heir
I only measure the fired case to see how the case is expanding in the chamber also in setting up my die. If you wanted to set your shoulder back .002 you would have to know the measurement of the fired case.
When reloading for accuracy, mid range, say 200 yards. Are you loading hot, full or neck sizing. I would like to know. I'm loading on the low side, that's why my cases aren't expanding I'm sure. Powder IMR 4064 40.5 under a Sierra 168 gr.HPBT bullet. With a .005 jam it is grouping very good. I am now looking for a accurate jump setting. Tomorrow is my range day, starting my jump at .015 & working my way up. 5 shot groups 200 yard zero.
Thanks again guys for all your input
Thank you for all the examples. Can you go through your process in sizing.
F.Guffey
I can see how soft seating the primer would give you the measurement from the datum to the bolt face on a undersize case.
T. O'Heir
I only measure the fired case to see how the case is expanding in the chamber also in setting up my die. If you wanted to set your shoulder back .002 you would have to know the measurement of the fired case.
When reloading for accuracy, mid range, say 200 yards. Are you loading hot, full or neck sizing. I would like to know. I'm loading on the low side, that's why my cases aren't expanding I'm sure. Powder IMR 4064 40.5 under a Sierra 168 gr.HPBT bullet. With a .005 jam it is grouping very good. I am now looking for a accurate jump setting. Tomorrow is my range day, starting my jump at .015 & working my way up. 5 shot groups 200 yard zero.
Thanks again guys for all your input
First I apologize for the large image. On a pretty standard 1920 x 1080 resolution monitor it isn't that large and it was the only one I had marked up where good detail could be seen.
Mr. Guffey:
Shouting is generally the use of all upper case letters. I never heard anything quite like that regarding a large image.
cw308:
Sure, more than happy to. The following applies to my .223 Remington and .308 Winchester loads which might be fired in any of several rifles. I clean my fired brass before sizing. I select a few cases and use my RCBS Precision Mic and see what I have. For example I have some .308 Winchester sitting here this happens to be some Federal Gold Medal Match stuff once fired. I know that new the cases measured 1.630" because I did measure this stuff. Fired once in an older Remington 700 bolt gun the cases now measure 1.632". Not the best example as the rifle has had work done and has a pretty tight chamber as to headspace. Next for this brass I'll do the usual lube and size. Using for example an RCBS FL sizing die (RCBS #15501). I will run the ram all the way up and screw the die down till it hits my shell holder. I like using the same shell holder over and over again rather than different .308 shell holders. When the die hits the shell holder I snug it and size a case. I measure that case. I know RCBS and most others suggest lower the ram and turn the die another 1/8 to 1/4 turn but I don't. I will slowly turn the die down until I get a case reading 1.630" and then lock the die. Following sizing I trim my brass. Something you want to watch when using the RCBS Precision Mic is the case heads. Rifles like my M1A or AR-10 are not quite as kind to the brass as my bolt gun. Both the M1A and AR-10 have pretty violent ejection so I look at where the extractor grabbed the case and make sure there are no burrs and the case head is still flat. All I do is a visual but keep in mind any burrs, even small ones ruin the readings on the Precision Mic. The case heads need to be flat no bent or burrs.
Keep in mind this is how I go about it. If I am loading for a specific rifle I may change the method I posted. What I posted is sort of general. People tend to develop their own methods and procedure. I also toss my brass after about 4 or 5 times of use. Some wait for split necks or incipient case head separation. While I have a pic I seldom use it to feel the inside of cases. I don't worry much about overworking the brass. Again, this applies to my .223 Remington and .308 Winchester loads. I shoot others which have much different procedures and methods I use.
Finally and again to the forum my apologies for the large image.
Ron
Mr. Guffey:
Shouting is generally the use of all upper case letters. I never heard anything quite like that regarding a large image.
cw308:
Sure, more than happy to. The following applies to my .223 Remington and .308 Winchester loads which might be fired in any of several rifles. I clean my fired brass before sizing. I select a few cases and use my RCBS Precision Mic and see what I have. For example I have some .308 Winchester sitting here this happens to be some Federal Gold Medal Match stuff once fired. I know that new the cases measured 1.630" because I did measure this stuff. Fired once in an older Remington 700 bolt gun the cases now measure 1.632". Not the best example as the rifle has had work done and has a pretty tight chamber as to headspace. Next for this brass I'll do the usual lube and size. Using for example an RCBS FL sizing die (RCBS #15501). I will run the ram all the way up and screw the die down till it hits my shell holder. I like using the same shell holder over and over again rather than different .308 shell holders. When the die hits the shell holder I snug it and size a case. I measure that case. I know RCBS and most others suggest lower the ram and turn the die another 1/8 to 1/4 turn but I don't. I will slowly turn the die down until I get a case reading 1.630" and then lock the die. Following sizing I trim my brass. Something you want to watch when using the RCBS Precision Mic is the case heads. Rifles like my M1A or AR-10 are not quite as kind to the brass as my bolt gun. Both the M1A and AR-10 have pretty violent ejection so I look at where the extractor grabbed the case and make sure there are no burrs and the case head is still flat. All I do is a visual but keep in mind any burrs, even small ones ruin the readings on the Precision Mic. The case heads need to be flat no bent or burrs.
Keep in mind this is how I go about it. If I am loading for a specific rifle I may change the method I posted. What I posted is sort of general. People tend to develop their own methods and procedure. I also toss my brass after about 4 or 5 times of use. Some wait for split necks or incipient case head separation. While I have a pic I seldom use it to feel the inside of cases. I don't worry much about overworking the brass. Again, this applies to my .223 Remington and .308 Winchester loads. I shoot others which have much different procedures and methods I use.
Finally and again to the forum my apologies for the large image.
Ron
Reloadron
Thank you . Your process is the same as mine. I changed my cleaning after 25+ years from a dry tumbler with corn & walnut to a wet tumbler with Stainless Steel Pins, will clean the inside & the primer pockets, the cases look like new. I also F/L size leaving .001 of space between bolt face to case. Used only in a Rem.700 308cal.
Thanks again. Chris
Thank you . Your process is the same as mine. I changed my cleaning after 25+ years from a dry tumbler with corn & walnut to a wet tumbler with Stainless Steel Pins, will clean the inside & the primer pockets, the cases look like new. I also F/L size leaving .001 of space between bolt face to case. Used only in a Rem.700 308cal.
Thanks again. Chris
