Hummer70
Member
Case uniformity is important but there are several areas not yet covered. The BR boys and very good highpower shooters all seem to converge on the idea of uniform velocity being the ultimate aim especially for long range shooters.
I had lots of conversations with my good friend L.F. (Larry) Moore on this subject and he did more testing on rifle accuracy/endurance/reliability and maintainability than every one on this forum all put together as he had the funding to do it and the ranges and instrumention to do it. Larry was a Small Arms and Ammunition Test Director Aberdeen Proving Ground from 48 till some time in 70s and those of us that had the fortune to have known him will attest to. His best friend was W.C. "Bill Davis" and they did research that will never see the light of day as they are both gone and their test reports are buried deep in the archives at APG.
When I got to Aberdeen there were still half a dozen guys there that worked with and for Larry when he was Section Chief and they told me basically that anyone that challenged Larry's data was a fool. For instance when he measured dispersion on targets three people had to measure and concur with each other as group sizes were measured in millimeters with gage lab certified steel tapes.
Larry's main requirement for those that worked for him was they hold a NRA Master Class Card in Smallbore Prone or Highpower and he wrote the Test Operation Procedure and this was a requirement for those that conducted that testing.
I asked him once why he put that requirement in and he said it was very simple, if he hired a guy with either or both cards (preferred) they would love what they were doing and could not wait to get to work and experienced very few "sick days". I talked to guys in the government that hated him but no one could challenge him.
I would guess of those of us that knew him well I guess I am the last one still alive and I can tell all I wish I had asked him about another hundred thousand questions.
A few things stuck out about his work that has always stayed with me. First off he preferred military cases and his favorite caliber was 30.06. I am only aware of his shooting one other caliber in competition when he showed up at Perry with a 300 Win Mag and took third in the Wimbledon with it. He never shot it again at Perry and the rifle was not in his collection when he passed. He had previously won the Wimbledon with a 30.06 and in his final ten years or so of shooting he had a stable of three left hand Mauser 3000s (all three 30.06) he brought to Perry and to my surprise he had one in 308 I got. I was even more surprised when I borescoped it and it showed evidence of lots of testing. He may have shot 308 in local matches but when it was race day the 30.06 was IT.
Larry also liked the 6.5 caliber but he told me that back in the 50s, 60s, 70s when he was at the top of the game there were just not any outstanding 6.5 bullets. Larry stated to me that if good bullets ever surfaced that the 6.5 would break out of the pack and as we know has done so.
I watched Larry on numerous occasions and as he shot long range when he shot a 9 he would scope the shot and if the conditions did not confirm the results that case was placed back in his ammo box upside down and I assume discarded.
This correlates with what I have observed in my testing and what I have corroborated with others.
When I retired and came home to South Carolina I was extremely fortunate to get property where I have a 600 yard range behind the house and 900 yard capability from another position and the testing began from concrete bench and a loading room three feet behind the bench.
To save lots and lots of writing the achievement of exceptional accuracy is to answer the question of what does one do to achieve it but in answering one question you will most likely find the testing beggs even more questions.
Larry told me the secret was to buy everything in bulk, propellant, primers, bullets and find the best combo because when one of the components is changed all your work up to that point has to start over.
Larry was unique in that he would not tell you directly what you wanted to know but would instead prime you with the pearls as I can only assume he wanted me to do my own research but had primed me with the answer in such a way that I if I did the work I could confirm what he had spent years learning.
For instance I ran a test series where I used the same cases with the same load and the same box of bullets to test primers which were all done the same day at the same temperature/humidity /elevation/rifle and the variation of velocities and the SD just by changing primers was staggering.
To make matters even worse they were not repeatable in other scenarios like changes found when variations were introduced.
I have tried to explain to guys for years when you buy propellant get enough of the same lot number to last you for ten years of shooting. Lets say you shoot 30.06 and are using 4831 and you shoot 4000 rounds a year in competition comes out to 314 pounds of propellant if you don't spill any and 40,000 primers and 40,000 bullets.
Now generally guys seem to get one and maybe two 8 pound jugs. You have just opened yourself up to testing expenses for the rest of your life you really did not need to expend. Or as the saying goes if you do the same thing over and over expecting different results............................ however in the case of loading you will get different answers probably 98% of the time.
News flash, when you change rifles/barrels chances are you will have to start from Ground Zero yet again. Gov't ammo is tested from three different barrels at the same session and the ammo must meet acceptance from all three barrels.
Thusly I was able to develop an appreciation of why the dispersion testing requirements were so large as the spec writers knew how much variation of components could change results.
For instance I tested Winchester, Federal, CCI and Remington Primers for lowest standard deviation. In one test for instance I might have Federal Primers was No 1, Winchester was No 2, Remington was No 3 and CCI was No 4 with 4895.
Reloading the same cases with same bullets and same primers using 4350, the results would totally change and No 1 would now be No 3, and No 4 is likely to be No 1 and so on.
The bottom line is I could find no uniformly outstanding primers across the board because every time I changed propellant it was a whole new ballgame.
To make matters even worse changing calibers put me right back at ground zero and the testing had to start all over again.
Then another buddy on the Brit 300 Meter Team would come to visit me prior to going on to Camp Perry and we shot together for ten to 14 days and he introduced me to Vihta Vuori propellant and he loaded his ammo on my equipment and shot on my range and he was getting SDs of 2 and 3 and groups under a inch at 300 yards. He did not weigh bullets or cases ! ! ! ! !
What he did do was measure case volume using water and alcohol and he spent the winter months at the University Lab where he was a professor and filled his cases with a alcohol/water combo and segregated the cases by VOLUME.
Larry Moore also used the same custom dimension chamber reamer to chamber all his rifles. Ray Steele was another top long range and smallbore shooter and also close friend of ours and they worked together at Frankford Arsenal (FA).
Ray barreled all the ammunition accuracy test rifles at FA and he was a wealth of information as well as he passed to me what he and Larry had learned from their testing at FA. The most important of which was to utilize tight chambers and the benefits they produced. Thusly my threads on long barrel life and long case life were the result of what was passed to me that I have passed to you guys.
OK we will now assume you just unloaded 350 pounds of propellant (same lot number) and 40,000 primers (same lot number) and 40,000 bullets (same lot number) and you have 500 30.06 cases all segregated by volume is there anything else to put a big one in the punch bowl? Yep
Your barrel is going South about 5000 rounds if you are the average high power shooter shooting 30 cal so that gives you variables. The first thought is laying in at least 8 barrels all from the same manufacturer. Well guys that is gonna be iffy as the variation between bore dimensions is gonna be awesome. For instance I bought two barrels from the same vendor at the same time with the same dimensions with HOPES of getting uniform barrels.
I chambered both barrels with same reamer in two Mod 70 Winchester actions headspaced to snug on a GO GAGE. I checked throat erosion on both barrels and the gage showed there was .150" difference where the gage located between the two barrels. Obviously the internal bore dimensions were different between barrels.
Another pearl Larry cast was the repeatability of the FIRE CONTROL which is the gov't term for a sight system. Larry tested sights/scopes as follows:
Shoot three shot group and then crank sights up 20 clicks, right 20 clicks, down 20 clicks and left 20 clicks and shoot another shot at same aiming point. If the adjustments are good the fourth shot will go in the first three.
Now crank sights down 20, left 20, up 20 and right 20 and shoot the fifth shot.
Continue this for all four quadrants and if your sights are good all your shots will be in the same group.
Warning: Don't place big bets with your shooting buddies that the sights you just purchased will pass this test because you paid 900.00. In Rifle Magazine back in the 80s I think it was Larry did a big sight evaluation test a number of sights and found only two variations were "ACCEPTABLE" which was the highest rating Larry gave anything.
OK since we are now in the tall grass so to speak what else are you likely to step on that can ruin your day?
Ignition reliability is another key to success. Uniformity in ignition of the primer is greatly influenced by the velocity and speed of the striker. The deterioration of one of these and all your work just went in the trash. Unless something novel has surfaced since I retired the only way to determine striker energy is by the use of coppers and copper holders and a bench inspection gage. I have holders for 5.56, 7.62 and 30.06.
As indicated in past at the Proving Ground, I witnessed many very interesting things, and while I cannot speak for what is done now but when I was there, misfires were given special examination in an effort to determine the causes. I see no reason why it would have changed. I conducted one test on the M16A1E1 and had five misfires in 244,000 rounds and that created quite a stir. It was found some of the submitted rifles exhibited striker energy below the specification requirements for the M16 rifle.
Most everyone has experienced a misfire and a small percentage have experienced a hang fire. (That is when you hear the click, followed by the bang.) Basically to give the reader some idea of exactly what is expected of US ammunition, the government, Winchester, Remington and I assume Federal and CCI all have an allowable misfire rate of one in a million assuming the primers were properly loaded, stored (not exposed to heat, cold, moisture, oil etc) In reality the ignition rate is much better than this but I guess one in a million was a good round number to start at. One manufacturer told me ten years ago in the previous year of in-house QA testing they had experienced five misfires in 15, 500, 000 rounds that was not attributable to the ignition mechanics or one in three million plus rounds.
Primers need two things for reliable ignition. They need to be hit hard and they need to be hit at very high speed. Primers are tested in a drop fixture. They are placed in a primer holding fixture and a steel ball is released to have a unretarded free fall before striking the fixture. If memory serves me correctly the testing on these is done with a 2 ounce steel ball dropped from a height of 20 inches which will give 40 inch ounces of energy when it arrives at the fixture.
As well a 20 ounce steel ball dropped from a height of 2 inches will give the same amount of energy upon arriving at the fixture. So what is the difference? After all forty inch ounces is forty inch ounces, well not exactly. Only problem is you will not obtain ignition on the second scenario as the 20 ounce ball has not gained enough velocity prior to striking the mechanism and did not obtain enough velocity to initiate ignition. Thus the statement is they have to be hit fast and hard. One without the other is useless.
In the industry they endeavor to establish the All Fire Drop Height. That is the lowest height the ball can be dropped and obtain 100% ignition reliability. In testing primers they will reduce the height the ball is released an inch at a time until they achieve what is termed the All No Fire Drop Height. Then they will replace the primer receptacle with a “copper” receptacle. Most shooters have read a reference to “CUP” or Copper Units of Pressure. It is a copper cylinder made to very exacting standards.
In this instance they are also used in what is referred to as Copper Holders. You have the one used in the fixture and then there are those that are made for each specific caliber. I am blessed with owning a holder for 5.56, 308 and 30.06. Last one I had made cost over $150.00. You may have seen one at a gun show or something and did not know what you were looking at and the guy in all probability did not know what he had either. You are looking for a item that looks exactly like a headspace gage but has a flat bottomed hole in the bottom (where you would look for a primer in a loaded round) about 3/8” deep.
Generally there will be a smaller hole, say .075” drilled all the way through. This is to push the copper back out (from the front) for bench inspection gage testing. There may be writing on it saying what it is and there may not be. You kind of just have to know from experience or in other words there is no writing on a hammer but you know it is by the looks.
The copper is placed so as to receive the energy departed by the striker nose and the ball is dropped at the same height they experienced the all no fire condition. They may take 3 to ten samples. After removing the coppers they are placed on the anvil of a bench inspection gage rigged with a sharp pointed contact (that will find the bottom of the indent without touching the sides.) They record the indents in thousandths of a inch and average the indents. My notes made during that time indicate the All No Fire Indent (ON COPPER) is .007” Where the All Fire Drop Height will exhibit .012” indent (ON COPPER).
The government requirement for the l903, M1, M14 rifle is .020” indent on a copper. A quick comparison shows a substantial difference between the .012” All Fire Indent and the .020” requirement on a weapon system. Or think of it this way. There is nothing but air resistance to retard the 2 ounce steel ball falling however when you wrap a striker with a spring or attempt to drive a striker down a tunnel (inside of a bolt) all kinds of undesirable things can happen to retard the speed at which the striker is delivered to the primer.
There is fairly common knowledge that grit build up in the striker channel of a bolt rifle may retard striker velocity/energy. Friction of the spring rubbing along the striker can cause problems as well. A close examination of the inside of a striker spring may reveal flat spots where the striker rubs against the spring as it is seared up followed by sear disengagement. The travel distance is quite small but still
the wear is apparent.
As well if you or a previous owner has ever experienced a blanked primer (this is where the primer appears natural except the area where you would expect an indent is now gone leaving a clean cut hole there) and the blanked out material is nowhere to be found could be a sign to check everything out. There is good likelihood it has traveled up inside the striker opening and will in all probability wind up embedded (so to speak) on the rough inner surface of the striker channel where it is pounded into the body of the bolt. The inside of a bolt is rough (generally) as it is a drilled cavity. Once it is attached to the striker channel it acts in the same manner as a disc brake and may instigate all kinds of problems, i.e. hangfires, misfires, vertical dispersions etc. It pays to keep the striker channel clean and closely examined to eliminate build up of foreign materials/conditions that will retard striker velocity.
As well in military weapon systems are subjected for conditions the average hunting rifle will never see such as complete submersion in mud, water, dust environments where the dust is the same consistency as baking flour. Something that hunting rifles are subjected to is extreme cold and or lubrication problems relating to striker energy. Obviously this material will work its way into the striker channel and serve the same function – retard striker energy/velocity.
In a cold weather hunting situation springs tend to lose some energy. This coupled with the wrong lubricant being in place on the striker/spring assembly the speed will be severely retarded. Many a rifle has been sold because a guy took it hunting on a cold morning, got a shot at a prize buck and CLICK, nothing happens. I remember I had a friend at Picatinny Arsenal who worked in the machineshop area. He came to me one day and said he had a Browning Lever Action rifle he had purchased from his brother in law for a hundred bucks because it would not fire when he was out hunting. I told him to bring it in for a looksee and he did. He brought in what appeared to be a brand new rifle. In the warmth of the building it sounded like there was sufficient striker action for reliable ignition.
We simply tore it down and took it down to the plating shop and put the action assembly down in the vapor degreaser and took the factory grease out of the striker and action in general and from that day on it shot fine in cold weather. I don’t think the new owner ever told his brother in law why it It Did Not Go Bang.
One thing that needs to be remembered here is the factory folks that make the guns we buy are not necessarily the sharpest folks on the planet. Just because “the factory did it” doesn’t necessarily make it right. As of late I would tend to think if “the factory did it” it is suspect for having a problem or three. And for sure the employees are by and large folks that just need a job and by no reason should they be considered descendents of John M. Browning, Sam Colt, John Garand, Peter and Paul Mauser, or graduates of a certified gunsmithing school or even graduates of high school.
Moreover most don’t even know what they are making and or what it does in the final scheme of things.
So the weapon engineers in the government came up with the minimum requirement of having our rifle small arms deliver .020” copper energy to overcome the elements and conditions the weapon will see in the field. A safety margin to insure reliability in other words. This is basically true except the M16 family of weapons wherein the requirement is .022” copper indent. There is only one harder small arms primer to ignite than the 5.56MM round, that is the Cal. 50 BMG primer.
Obviously there is much more that will have a negative effect on all your efforts but above are a few to ponder in the interim.
I had lots of conversations with my good friend L.F. (Larry) Moore on this subject and he did more testing on rifle accuracy/endurance/reliability and maintainability than every one on this forum all put together as he had the funding to do it and the ranges and instrumention to do it. Larry was a Small Arms and Ammunition Test Director Aberdeen Proving Ground from 48 till some time in 70s and those of us that had the fortune to have known him will attest to. His best friend was W.C. "Bill Davis" and they did research that will never see the light of day as they are both gone and their test reports are buried deep in the archives at APG.
When I got to Aberdeen there were still half a dozen guys there that worked with and for Larry when he was Section Chief and they told me basically that anyone that challenged Larry's data was a fool. For instance when he measured dispersion on targets three people had to measure and concur with each other as group sizes were measured in millimeters with gage lab certified steel tapes.
Larry's main requirement for those that worked for him was they hold a NRA Master Class Card in Smallbore Prone or Highpower and he wrote the Test Operation Procedure and this was a requirement for those that conducted that testing.
I asked him once why he put that requirement in and he said it was very simple, if he hired a guy with either or both cards (preferred) they would love what they were doing and could not wait to get to work and experienced very few "sick days". I talked to guys in the government that hated him but no one could challenge him.
I would guess of those of us that knew him well I guess I am the last one still alive and I can tell all I wish I had asked him about another hundred thousand questions.
A few things stuck out about his work that has always stayed with me. First off he preferred military cases and his favorite caliber was 30.06. I am only aware of his shooting one other caliber in competition when he showed up at Perry with a 300 Win Mag and took third in the Wimbledon with it. He never shot it again at Perry and the rifle was not in his collection when he passed. He had previously won the Wimbledon with a 30.06 and in his final ten years or so of shooting he had a stable of three left hand Mauser 3000s (all three 30.06) he brought to Perry and to my surprise he had one in 308 I got. I was even more surprised when I borescoped it and it showed evidence of lots of testing. He may have shot 308 in local matches but when it was race day the 30.06 was IT.
Larry also liked the 6.5 caliber but he told me that back in the 50s, 60s, 70s when he was at the top of the game there were just not any outstanding 6.5 bullets. Larry stated to me that if good bullets ever surfaced that the 6.5 would break out of the pack and as we know has done so.
I watched Larry on numerous occasions and as he shot long range when he shot a 9 he would scope the shot and if the conditions did not confirm the results that case was placed back in his ammo box upside down and I assume discarded.
This correlates with what I have observed in my testing and what I have corroborated with others.
When I retired and came home to South Carolina I was extremely fortunate to get property where I have a 600 yard range behind the house and 900 yard capability from another position and the testing began from concrete bench and a loading room three feet behind the bench.
To save lots and lots of writing the achievement of exceptional accuracy is to answer the question of what does one do to achieve it but in answering one question you will most likely find the testing beggs even more questions.
Larry told me the secret was to buy everything in bulk, propellant, primers, bullets and find the best combo because when one of the components is changed all your work up to that point has to start over.
Larry was unique in that he would not tell you directly what you wanted to know but would instead prime you with the pearls as I can only assume he wanted me to do my own research but had primed me with the answer in such a way that I if I did the work I could confirm what he had spent years learning.
For instance I ran a test series where I used the same cases with the same load and the same box of bullets to test primers which were all done the same day at the same temperature/humidity /elevation/rifle and the variation of velocities and the SD just by changing primers was staggering.
To make matters even worse they were not repeatable in other scenarios like changes found when variations were introduced.
I have tried to explain to guys for years when you buy propellant get enough of the same lot number to last you for ten years of shooting. Lets say you shoot 30.06 and are using 4831 and you shoot 4000 rounds a year in competition comes out to 314 pounds of propellant if you don't spill any and 40,000 primers and 40,000 bullets.
Now generally guys seem to get one and maybe two 8 pound jugs. You have just opened yourself up to testing expenses for the rest of your life you really did not need to expend. Or as the saying goes if you do the same thing over and over expecting different results............................ however in the case of loading you will get different answers probably 98% of the time.
News flash, when you change rifles/barrels chances are you will have to start from Ground Zero yet again. Gov't ammo is tested from three different barrels at the same session and the ammo must meet acceptance from all three barrels.
Thusly I was able to develop an appreciation of why the dispersion testing requirements were so large as the spec writers knew how much variation of components could change results.
For instance I tested Winchester, Federal, CCI and Remington Primers for lowest standard deviation. In one test for instance I might have Federal Primers was No 1, Winchester was No 2, Remington was No 3 and CCI was No 4 with 4895.
Reloading the same cases with same bullets and same primers using 4350, the results would totally change and No 1 would now be No 3, and No 4 is likely to be No 1 and so on.
The bottom line is I could find no uniformly outstanding primers across the board because every time I changed propellant it was a whole new ballgame.
To make matters even worse changing calibers put me right back at ground zero and the testing had to start all over again.
Then another buddy on the Brit 300 Meter Team would come to visit me prior to going on to Camp Perry and we shot together for ten to 14 days and he introduced me to Vihta Vuori propellant and he loaded his ammo on my equipment and shot on my range and he was getting SDs of 2 and 3 and groups under a inch at 300 yards. He did not weigh bullets or cases ! ! ! ! !
What he did do was measure case volume using water and alcohol and he spent the winter months at the University Lab where he was a professor and filled his cases with a alcohol/water combo and segregated the cases by VOLUME.
Larry Moore also used the same custom dimension chamber reamer to chamber all his rifles. Ray Steele was another top long range and smallbore shooter and also close friend of ours and they worked together at Frankford Arsenal (FA).
Ray barreled all the ammunition accuracy test rifles at FA and he was a wealth of information as well as he passed to me what he and Larry had learned from their testing at FA. The most important of which was to utilize tight chambers and the benefits they produced. Thusly my threads on long barrel life and long case life were the result of what was passed to me that I have passed to you guys.
OK we will now assume you just unloaded 350 pounds of propellant (same lot number) and 40,000 primers (same lot number) and 40,000 bullets (same lot number) and you have 500 30.06 cases all segregated by volume is there anything else to put a big one in the punch bowl? Yep
Your barrel is going South about 5000 rounds if you are the average high power shooter shooting 30 cal so that gives you variables. The first thought is laying in at least 8 barrels all from the same manufacturer. Well guys that is gonna be iffy as the variation between bore dimensions is gonna be awesome. For instance I bought two barrels from the same vendor at the same time with the same dimensions with HOPES of getting uniform barrels.
I chambered both barrels with same reamer in two Mod 70 Winchester actions headspaced to snug on a GO GAGE. I checked throat erosion on both barrels and the gage showed there was .150" difference where the gage located between the two barrels. Obviously the internal bore dimensions were different between barrels.
Another pearl Larry cast was the repeatability of the FIRE CONTROL which is the gov't term for a sight system. Larry tested sights/scopes as follows:
Shoot three shot group and then crank sights up 20 clicks, right 20 clicks, down 20 clicks and left 20 clicks and shoot another shot at same aiming point. If the adjustments are good the fourth shot will go in the first three.
Now crank sights down 20, left 20, up 20 and right 20 and shoot the fifth shot.
Continue this for all four quadrants and if your sights are good all your shots will be in the same group.
Warning: Don't place big bets with your shooting buddies that the sights you just purchased will pass this test because you paid 900.00. In Rifle Magazine back in the 80s I think it was Larry did a big sight evaluation test a number of sights and found only two variations were "ACCEPTABLE" which was the highest rating Larry gave anything.
OK since we are now in the tall grass so to speak what else are you likely to step on that can ruin your day?
Ignition reliability is another key to success. Uniformity in ignition of the primer is greatly influenced by the velocity and speed of the striker. The deterioration of one of these and all your work just went in the trash. Unless something novel has surfaced since I retired the only way to determine striker energy is by the use of coppers and copper holders and a bench inspection gage. I have holders for 5.56, 7.62 and 30.06.
As indicated in past at the Proving Ground, I witnessed many very interesting things, and while I cannot speak for what is done now but when I was there, misfires were given special examination in an effort to determine the causes. I see no reason why it would have changed. I conducted one test on the M16A1E1 and had five misfires in 244,000 rounds and that created quite a stir. It was found some of the submitted rifles exhibited striker energy below the specification requirements for the M16 rifle.
Most everyone has experienced a misfire and a small percentage have experienced a hang fire. (That is when you hear the click, followed by the bang.) Basically to give the reader some idea of exactly what is expected of US ammunition, the government, Winchester, Remington and I assume Federal and CCI all have an allowable misfire rate of one in a million assuming the primers were properly loaded, stored (not exposed to heat, cold, moisture, oil etc) In reality the ignition rate is much better than this but I guess one in a million was a good round number to start at. One manufacturer told me ten years ago in the previous year of in-house QA testing they had experienced five misfires in 15, 500, 000 rounds that was not attributable to the ignition mechanics or one in three million plus rounds.
Primers need two things for reliable ignition. They need to be hit hard and they need to be hit at very high speed. Primers are tested in a drop fixture. They are placed in a primer holding fixture and a steel ball is released to have a unretarded free fall before striking the fixture. If memory serves me correctly the testing on these is done with a 2 ounce steel ball dropped from a height of 20 inches which will give 40 inch ounces of energy when it arrives at the fixture.
As well a 20 ounce steel ball dropped from a height of 2 inches will give the same amount of energy upon arriving at the fixture. So what is the difference? After all forty inch ounces is forty inch ounces, well not exactly. Only problem is you will not obtain ignition on the second scenario as the 20 ounce ball has not gained enough velocity prior to striking the mechanism and did not obtain enough velocity to initiate ignition. Thus the statement is they have to be hit fast and hard. One without the other is useless.
In the industry they endeavor to establish the All Fire Drop Height. That is the lowest height the ball can be dropped and obtain 100% ignition reliability. In testing primers they will reduce the height the ball is released an inch at a time until they achieve what is termed the All No Fire Drop Height. Then they will replace the primer receptacle with a “copper” receptacle. Most shooters have read a reference to “CUP” or Copper Units of Pressure. It is a copper cylinder made to very exacting standards.
In this instance they are also used in what is referred to as Copper Holders. You have the one used in the fixture and then there are those that are made for each specific caliber. I am blessed with owning a holder for 5.56, 308 and 30.06. Last one I had made cost over $150.00. You may have seen one at a gun show or something and did not know what you were looking at and the guy in all probability did not know what he had either. You are looking for a item that looks exactly like a headspace gage but has a flat bottomed hole in the bottom (where you would look for a primer in a loaded round) about 3/8” deep.
Generally there will be a smaller hole, say .075” drilled all the way through. This is to push the copper back out (from the front) for bench inspection gage testing. There may be writing on it saying what it is and there may not be. You kind of just have to know from experience or in other words there is no writing on a hammer but you know it is by the looks.
The copper is placed so as to receive the energy departed by the striker nose and the ball is dropped at the same height they experienced the all no fire condition. They may take 3 to ten samples. After removing the coppers they are placed on the anvil of a bench inspection gage rigged with a sharp pointed contact (that will find the bottom of the indent without touching the sides.) They record the indents in thousandths of a inch and average the indents. My notes made during that time indicate the All No Fire Indent (ON COPPER) is .007” Where the All Fire Drop Height will exhibit .012” indent (ON COPPER).
The government requirement for the l903, M1, M14 rifle is .020” indent on a copper. A quick comparison shows a substantial difference between the .012” All Fire Indent and the .020” requirement on a weapon system. Or think of it this way. There is nothing but air resistance to retard the 2 ounce steel ball falling however when you wrap a striker with a spring or attempt to drive a striker down a tunnel (inside of a bolt) all kinds of undesirable things can happen to retard the speed at which the striker is delivered to the primer.
There is fairly common knowledge that grit build up in the striker channel of a bolt rifle may retard striker velocity/energy. Friction of the spring rubbing along the striker can cause problems as well. A close examination of the inside of a striker spring may reveal flat spots where the striker rubs against the spring as it is seared up followed by sear disengagement. The travel distance is quite small but still
the wear is apparent.
As well if you or a previous owner has ever experienced a blanked primer (this is where the primer appears natural except the area where you would expect an indent is now gone leaving a clean cut hole there) and the blanked out material is nowhere to be found could be a sign to check everything out. There is good likelihood it has traveled up inside the striker opening and will in all probability wind up embedded (so to speak) on the rough inner surface of the striker channel where it is pounded into the body of the bolt. The inside of a bolt is rough (generally) as it is a drilled cavity. Once it is attached to the striker channel it acts in the same manner as a disc brake and may instigate all kinds of problems, i.e. hangfires, misfires, vertical dispersions etc. It pays to keep the striker channel clean and closely examined to eliminate build up of foreign materials/conditions that will retard striker velocity.
As well in military weapon systems are subjected for conditions the average hunting rifle will never see such as complete submersion in mud, water, dust environments where the dust is the same consistency as baking flour. Something that hunting rifles are subjected to is extreme cold and or lubrication problems relating to striker energy. Obviously this material will work its way into the striker channel and serve the same function – retard striker energy/velocity.
In a cold weather hunting situation springs tend to lose some energy. This coupled with the wrong lubricant being in place on the striker/spring assembly the speed will be severely retarded. Many a rifle has been sold because a guy took it hunting on a cold morning, got a shot at a prize buck and CLICK, nothing happens. I remember I had a friend at Picatinny Arsenal who worked in the machineshop area. He came to me one day and said he had a Browning Lever Action rifle he had purchased from his brother in law for a hundred bucks because it would not fire when he was out hunting. I told him to bring it in for a looksee and he did. He brought in what appeared to be a brand new rifle. In the warmth of the building it sounded like there was sufficient striker action for reliable ignition.
We simply tore it down and took it down to the plating shop and put the action assembly down in the vapor degreaser and took the factory grease out of the striker and action in general and from that day on it shot fine in cold weather. I don’t think the new owner ever told his brother in law why it It Did Not Go Bang.
One thing that needs to be remembered here is the factory folks that make the guns we buy are not necessarily the sharpest folks on the planet. Just because “the factory did it” doesn’t necessarily make it right. As of late I would tend to think if “the factory did it” it is suspect for having a problem or three. And for sure the employees are by and large folks that just need a job and by no reason should they be considered descendents of John M. Browning, Sam Colt, John Garand, Peter and Paul Mauser, or graduates of a certified gunsmithing school or even graduates of high school.
Moreover most don’t even know what they are making and or what it does in the final scheme of things.
So the weapon engineers in the government came up with the minimum requirement of having our rifle small arms deliver .020” copper energy to overcome the elements and conditions the weapon will see in the field. A safety margin to insure reliability in other words. This is basically true except the M16 family of weapons wherein the requirement is .022” copper indent. There is only one harder small arms primer to ignite than the 5.56MM round, that is the Cal. 50 BMG primer.
Obviously there is much more that will have a negative effect on all your efforts but above are a few to ponder in the interim.
to make claims that mil spec primers are a marketing gimmick, and these guys advocate the use of the most sensitive primers on the market in weapons such as M1 Garands, M1a’s, and M1 carbines! All of of these weapons have known out of battery slamfires with commercial and military primers. Slamfire incidents are less with the less sensitive military spec primers but to a denier, the only causes of slamfires are “high primers” and your “worn out receiver bridge”. For them, there is no such thing as a sensitive primer or an insensitive primer. 
