Time to resize some .308, what route to take?
- Thread starter 119er
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Thank you everyone for your detailed responses. Seems like I will just buy a 1.630 gauge and size my brass to that standard! If my chamber is truly 1.632, that should serve me fine. Hopefully that will suppress my demons! I have this habit of going off the deep end when things don't make sense. I must see it through to a solution, or explain it in some way!
Next is determining the ability of the die to size the case. We started with getting everything to agree. SAAMI is nice to know, I can not expect to size a case that agrees with SAAMI for the simple reason it does not fit my chamber. And I can not assume my dies are perfect, there are ways to determine if the die has the ability to size a case to minimum length/full length size, problem, there are times a full length sized case back to minimum length are too small/short for my chamber.
F. Guffey
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I just went to the range this afternoon and fired 10 rounds with the gas off. Average is 1.588" in my gauge. I am going to order a 1.630 go gauge to calibrate.
Assuming that I bumped the shoulder back .005", that would be 1.583" A case that I have sized to 1.580" still fails the case gauge by a long shot. ~.019".
The unfired cases are about 1.563" and are stretching .025"! Is this not excessive?
When I get my gauge in, I guess I can see where I am really falling and hopefully my case gauge is wrong! To size it back to that gauge seems like a crime!
Assuming that I bumped the shoulder back .005", that would be 1.583" A case that I have sized to 1.580" still fails the case gauge by a long shot. ~.019".
The unfired cases are about 1.563" and are stretching .025"! Is this not excessive?
When I get my gauge in, I guess I can see where I am really falling and hopefully my case gauge is wrong! To size it back to that gauge seems like a crime!
Reloadron
Contributing Member
I believe once you have a good known 1.630" headspace gauge all of this will come together. At least the numbers will make sense as you apply a correction factor. With that out of the way you can focus on your dies and see what's going on. There is quite a bit of good material in this thread and some really good posted images.
I can't understand why or how your cases can stretch so much? That is strange. It just isn't typical of any M1A I have seen. Again, once you have a good known gauge hopefully things will come together.
Ron
FLIGHT762
Member
119er, If you set your F/L die up to resize your cases where the case rim is even with the bottom step of your Lyman drop in gauge, you'll be very near 1.630".
One thing I have noticed with my Sinclair bump gauges is they show more stretching on the shoulders than my Hornady .400 bump insert. I've found my Hornady bump inserts to be more repeatable than the Sinclair ones. Sinclair inserts use a tapered shoulder and Hornady uses a round hole.
All of my ammo that gets fired in my M-1A's gets bumped to SAAMI minimum to insure reliability and less chance of a slam fire. You do understand with the M-1A, your brass lasts 4-5 reloadings. Going past that you risk case failures.
The only other suggestion I have is for you to buy a .400 Hornady insert and see what your measurements are with that.
One thing I have noticed with my Sinclair bump gauges is they show more stretching on the shoulders than my Hornady .400 bump insert. I've found my Hornady bump inserts to be more repeatable than the Sinclair ones. Sinclair inserts use a tapered shoulder and Hornady uses a round hole.
All of my ammo that gets fired in my M-1A's gets bumped to SAAMI minimum to insure reliability and less chance of a slam fire. You do understand with the M-1A, your brass lasts 4-5 reloadings. Going past that you risk case failures.
The only other suggestion I have is for you to buy a .400 Hornady insert and see what your measurements are with that.
That is what is causing my dilemma, sort of. A case that is sized .003" under the max that the rifle will chamber is still .019" above the upper step on the Lyman case gauge. To get to that lower step would be around .025" which seems like a lot of slop considering the common convention is that a .005" shoulder set back is sufficient.
I have the Hornady inserts too. Once the actual headspace gauge gets here I will start a log and record my measurements. Currently I believe that the case gauge is buggered up or extremely conservative. I know the cases are only good for 4-5 loads but I'm not convinced they'd make it that long being worked so far back and forth.
FLIGHT762
Member
This^^^^^^^^^^^^^^^^^^^. The last thing I would do is measure your "Gas Off" cases and set your F/L die to -.005" under those measurements with the "D" .400 Hornady gauge.
Reloadron
Contributing Member
What you are doing looks like this:
Just not sure what was meant when you mention the depth end of the caliper.
Ron
Sunray
Member
"...Just trying to be thorough..." You're over thinking the whole thing.
Loading for a semi-auto is no different than loading for any other rifle except you must check the case lengths, trim, chamfer and deburr as required, FL resize only(SB orregular FL sizer. SB's size a few thou smaller and usually aren't necessary. The die must be set up properly too, but that doesn't require gauges or anything else either.) and watch the OAL. You don't need to fuss over the shoulders or worry about headspace at all. Cartridges do not have headspace and the card that came with the rifle means nothing. It's just proof the headspace is good out of the factory. Of course, if your rifle is still under warrantee, SA Inc. will void it if you shoot reloaded ammo. CYA thing for them.
An unfired case is not a gauge of any kind. Nor are they ready to load.
Loading for a semi-auto is no different than loading for any other rifle except you must check the case lengths, trim, chamfer and deburr as required, FL resize only(SB orregular FL sizer. SB's size a few thou smaller and usually aren't necessary. The die must be set up properly too, but that doesn't require gauges or anything else either.) and watch the OAL. You don't need to fuss over the shoulders or worry about headspace at all. Cartridges do not have headspace and the card that came with the rifle means nothing. It's just proof the headspace is good out of the factory. Of course, if your rifle is still under warrantee, SA Inc. will void it if you shoot reloaded ammo. CYA thing for them.
An unfired case is not a gauge of any kind. Nor are they ready to load.
The dial caliper has an inside and outside end, the opposite end can be used to measure depth, something like a three-fer one unless the small end is referred to as being depth and height gage, not sure but I believe it could be called a four-fer one.
F. Guffey
Reloadron
Contributing Member
I understand all of that. The original poster mentioned he is using the Hornady Lock-N-Load Headspace Gage which is what I pictured in post #39, but he is using the Sinclair bushings. What I don't understand is the reference to using the depth end.
Using the Hornady case gauge you wouldn't be using the depth end of the caliper would you? Has me wondering how the gauge is being used. I understand the use of the caliper and what it can be used to measure. I don't understand the original poster's statement.
Thanks
Ron
Okay, here goes.
This is the set-up I am using. It is a Hornady "Headspace comparator" body with Sinclair inserts that are cut with a chamber reamer.
This is the unfired case, 1.563", as it came from Lake City in the Lyman .308 case gauge and it's reading on the comparator. This brass was neck sized to ensure proper tension as it passed the gauge upon receipt.
Next is a case I sized until it freely chambered in the rifle. I then let the action (M1A) slam closed on the case in the chamber several times to see if it reduced the size any further. It did by several thousandths and the result was 1.580". As you can see it stands out of the case gauge by a considerable amount. Also seen is the depth end of the calipers I used to get the .019" above the case gauge upper step or gauge maximum dimension.
This is the dimension of a fired case with the gas system turned off. The ten shot average was 1.588". Then photographed case was a random case from that lot and obviously above the average.
This shows no interference from the case head dimensions.
The average for fired cases with the gas turned on is 1.593" but is not really of concern.
Where my concern lies is with the fact that the unfired Lake City case and the Lyman case gauge seem to be in agreement while the dimensions of what the rifle chambers are much different.
What we have is a rifle that will chamber X, but a gauge that wants X -.019" at least to be within its maximum "spec".
This seems like a large difference to me.
What is the difference, functionally, between out of spec bolt headspace and a case that must be pushed the .019" distance(not including mechanical headspace) into the chamber before the primer is detonated?
If this is within the accepted range of tolerance, then okay. It just seems excessive to me. Especially in terms of case stretch and potential for head separations. I'm not trying to create a miracle for my brass as I know it is abused by the platform. Also, I am not exactly fretting over these issues. I simply want to better understand what is happening and how to limit the stress on the brass if for no other reason than "just because" it is interesting to me.
Hopefully, with the 1.630" headspace gauge coming I can get some sort of calibration from that known dimension. I don't like blindly adjusting a die and squishing brass even though it works fine for many people. I have done it too, but want better.
This is the set-up I am using. It is a Hornady "Headspace comparator" body with Sinclair inserts that are cut with a chamber reamer.
This is the unfired case, 1.563", as it came from Lake City in the Lyman .308 case gauge and it's reading on the comparator. This brass was neck sized to ensure proper tension as it passed the gauge upon receipt.
Next is a case I sized until it freely chambered in the rifle. I then let the action (M1A) slam closed on the case in the chamber several times to see if it reduced the size any further. It did by several thousandths and the result was 1.580". As you can see it stands out of the case gauge by a considerable amount. Also seen is the depth end of the calipers I used to get the .019" above the case gauge upper step or gauge maximum dimension.
This is the dimension of a fired case with the gas system turned off. The ten shot average was 1.588". Then photographed case was a random case from that lot and obviously above the average.
This shows no interference from the case head dimensions.
The average for fired cases with the gas turned on is 1.593" but is not really of concern.
Where my concern lies is with the fact that the unfired Lake City case and the Lyman case gauge seem to be in agreement while the dimensions of what the rifle chambers are much different.
What we have is a rifle that will chamber X, but a gauge that wants X -.019" at least to be within its maximum "spec".
This seems like a large difference to me.
What is the difference, functionally, between out of spec bolt headspace and a case that must be pushed the .019" distance(not including mechanical headspace) into the chamber before the primer is detonated?
If this is within the accepted range of tolerance, then okay. It just seems excessive to me. Especially in terms of case stretch and potential for head separations. I'm not trying to create a miracle for my brass as I know it is abused by the platform. Also, I am not exactly fretting over these issues. I simply want to better understand what is happening and how to limit the stress on the brass if for no other reason than "just because" it is interesting to me.
Hopefully, with the 1.630" headspace gauge coming I can get some sort of calibration from that known dimension. I don't like blindly adjusting a die and squishing brass even though it works fine for many people. I have done it too, but want better.
OK, I see what's happening. The Sinclair insert does not measure at the headspace
datum line (Dia 0.400") at all. It merely replicates the shoulder angle of the chamber
and is therefore referred to as a "bump" gauge.
It consequently produces nothing that can be compared to a SAAMI headspace dimension.
Your strange reading of 1.591" is therefore not strange... because it's not remotely
related to SAAMI.
If a case with that reading (1.591) chambers, then use it as your sizing reference point
(just realize it has nothing to do with the supposedly 1.632" dimension that the rifle
manufacturer claimed as actual chamber headspace at the datum line)
datum line (Dia 0.400") at all. It merely replicates the shoulder angle of the chamber
and is therefore referred to as a "bump" gauge.
It consequently produces nothing that can be compared to a SAAMI headspace dimension.
Your strange reading of 1.591" is therefore not strange... because it's not remotely
related to SAAMI.
If a case with that reading (1.591) chambers, then use it as your sizing reference point
(just realize it has nothing to do with the supposedly 1.632" dimension that the rifle
manufacturer claimed as actual chamber headspace at the datum line)
Reloadron
Contributing Member
The pictures were enlightening. I agree with MEHavey and I also think once you get the ordered headspace gauge most of this will make sense. The original Hornady Lock-N-Load Headspace Gage 5 Bushing Set with Comparator uses a different type bushing as MEHavey points out. I would just wait till the headspace gauge comes in that you ordered. Then you will have a good working reference.
Ron
Ron
Ron
Ron
Thanks to those who stuck it out with me on this, I should have included pictures sooner. I will post my findings when I can compare with the headspace gauge. Early on I learned that it wasn't correct to compare to SAAMI specs, but it was the relative differences I am getting that spurred my initial question. Now to get a conclusive end to this saga.
FLIGHT762
Member
This may be a stupid question, but are you depriming your fired case before doing your bump measurements?
Fired primers will crater and / or back out and give you higher, false readings.
You should be doing your measurements with the fired primer removed from the case being measured.
Fired primers will crater and / or back out and give you higher, false readings.
You should be doing your measurements with the fired primer removed from the case being measured.
FLIGHT762
Member
Cratered, fired primers will cause false readings. I've been using the Hornady bump gauge for a number of years (I bought it when it was made by Stoney Point) and I bought some of the Sinclair bump gauge inserts when they were first introduced.
After posting my last post, I went to my reloading room to take some measurement with the Sinclair insert and the Hornady .400" insert. I used two digital calipers reset to O with the Hornady gauge and the Sinclair gauge. Both of these calipers have been tested and readings between them are accurate.
I previously calibrated the gauges with a SAAMI 1.630" 308 Go Gauge.
The Sinclair gauge read: 1.561" as SAAMI minimum.
The Hornady gauge read: 1.611" as SAAMI minimum.
I took two fired case fired out of a M-1A and a two fired out of a bolt gun.
Two Fired M1-A cases measured 1.574"-1.580" with the Sinclair gauge.
They measured 1.617"-1.621" with the Hornady gauge.
Two Fired bolt rifle cases measured 1.570" 1.570" with the Sinclair gauge.
1.611"-1.612" with the Hornady gauge.
Here's where it got interesting. When I resized the cases and I showed a .001"-.002" bump back with the Hornady gauge in the bolt gun, The the same cases with the Sinclair gauge would show a bump measurement of minus .004"-.006".
The two M1-A cases F/L resized back to 1.613" (-004") & 1.610"(-.011") in the Hornady gauge and 1.566" (-.008") & 1.564" (-.016") in the Sinclair gauge.
I just don't get consistent, repeatable readings with the Sinclair bump gauge as I get with the Hornady insert. All I can think is the Hornady uses a round hole and the Sinclair uses a tapered 20º shoulder and that is what is causing the inconsistencies and larger amount of bump.
This is why I prefer the Hornady bump gauge.
O/P, you said you have a .400" Hornady insert. I would try your measurements with the Hornady insert and see what you get.
After posting my last post, I went to my reloading room to take some measurement with the Sinclair insert and the Hornady .400" insert. I used two digital calipers reset to O with the Hornady gauge and the Sinclair gauge. Both of these calipers have been tested and readings between them are accurate.
I previously calibrated the gauges with a SAAMI 1.630" 308 Go Gauge.
The Sinclair gauge read: 1.561" as SAAMI minimum.
The Hornady gauge read: 1.611" as SAAMI minimum.
I took two fired case fired out of a M-1A and a two fired out of a bolt gun.
Two Fired M1-A cases measured 1.574"-1.580" with the Sinclair gauge.
They measured 1.617"-1.621" with the Hornady gauge.
Two Fired bolt rifle cases measured 1.570" 1.570" with the Sinclair gauge.
1.611"-1.612" with the Hornady gauge.
Here's where it got interesting. When I resized the cases and I showed a .001"-.002" bump back with the Hornady gauge in the bolt gun, The the same cases with the Sinclair gauge would show a bump measurement of minus .004"-.006".
The two M1-A cases F/L resized back to 1.613" (-004") & 1.610"(-.011") in the Hornady gauge and 1.566" (-.008") & 1.564" (-.016") in the Sinclair gauge.
I just don't get consistent, repeatable readings with the Sinclair bump gauge as I get with the Hornady insert. All I can think is the Hornady uses a round hole and the Sinclair uses a tapered 20º shoulder and that is what is causing the inconsistencies and larger amount of bump.
This is why I prefer the Hornady bump gauge.
O/P, you said you have a .400" Hornady insert. I would try your measurements with the Hornady insert and see what you get.
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