Proper primer ignition
- Thread starter smoking-brass
- Start date
I’ll tell you guys a true story of adventure as it relates to sodium azide.
Although we think of it as primer chemical, it is also used as a bacteriostatic (which means something that prevents growth of bacteria). Back in the 80s, they put this stuff in some of the high grade water we use in HPLC (high pressure liquid chromatographs), which is a fancy machine to separate and purify molecules. Well, HPLC is usually run with a mixture of water and an organic solution but apparently the organic solution can make the sodium azide come out of solution and gum out the pumps.
One of the techs in our lab had this problem and so he disassembled the pump head and proceeded to scrape the stuff off – Boom! Yip, it went off! No loss of limbs but it was bad enough that he had to go get stitches….
Although we think of it as primer chemical, it is also used as a bacteriostatic (which means something that prevents growth of bacteria). Back in the 80s, they put this stuff in some of the high grade water we use in HPLC (high pressure liquid chromatographs), which is a fancy machine to separate and purify molecules. Well, HPLC is usually run with a mixture of water and an organic solution but apparently the organic solution can make the sodium azide come out of solution and gum out the pumps.
One of the techs in our lab had this problem and so he disassembled the pump head and proceeded to scrape the stuff off – Boom! Yip, it went off! No loss of limbs but it was bad enough that he had to go get stitches….
smoking-brass
shoot straight....shoot often
Thanks for all the info...I believe a field test of my own is in the near future...I have an extremely accurate load in my 6 br savage target rifle...but I hate the bolt lift with the stock firing pin spring...Will reduce spring tension and see if it effects accuracy...Will get back with the info soon!
Thanks,
Vince
Thanks,
Vince
An article on how the DOD determines firing pin strike force. I have seen other articles somewhere on the net.
http://www.gunandgame.com/forums/powder-keg/88634-primer-cup-hardness.html
I think all of the primer manufacturers recommend seating the primer in the pocket until the anvil tips contact the primer pocket. They don't mention an amount of force. I don't see how hard or soft seat enters into it. If you use force beyond the anvil tips touching the primer pocket you are probably pushing the anvil tip farther into the primer cake or bending the anvil. I am sure the rifle manufacturers use a firing pin spring that has been determined proper. Tony Boyer's book goes into tricks to eliminate binding or friction in the firing pin assembly.
http://www.gunandgame.com/forums/powder-keg/88634-primer-cup-hardness.html
I think all of the primer manufacturers recommend seating the primer in the pocket until the anvil tips contact the primer pocket. They don't mention an amount of force. I don't see how hard or soft seat enters into it. If you use force beyond the anvil tips touching the primer pocket you are probably pushing the anvil tip farther into the primer cake or bending the anvil. I am sure the rifle manufacturers use a firing pin spring that has been determined proper. Tony Boyer's book goes into tricks to eliminate binding or friction in the firing pin assembly.
It's easy enough for us to know what fires and what doesn't through trial & error. But this is not the same as proper ignition, per primer type/brand/pocket depth/flash hole/case headspacing/powder.
I'm sure a similar gage and a great deal of testing could lead to advances in this area.
2thou crush means contact +2thou to preload the pill.
Every primer & pocket varies in dimension & hardness, so crush cannot be determined by feel nor measure soley from casehead.
Only an indicating K&M gets you this.
I'm sure a similar gage and a great deal of testing could lead to advances in this area.
2thou crush means contact +2thou to preload the pill.
Every primer & pocket varies in dimension & hardness, so crush cannot be determined by feel nor measure soley from casehead.
Only an indicating K&M gets you this.
smoking-brass said:
I believe there are too many variables to determine much by just reducing spring tension and looking at the target results. For example: By reducing spring tension you will most probably increase lock time. How do you plan to
physically decrease tension? Changing the spring will change the pin acceleration profile. Clipping the original may
decrease drag caused by binding or not etc.. Even though you always get ignition you are still back to a lot of trial
and error.
I don't think ignite is the proper term for a primer going off even though it is commonly used. If it is set off properly it detonates. It is an explosive material not a propellant. When lead stephanate detonates it produces a shock wave that travels at 5200 meters per second. I don't shoot competitively but it would seem reasonable that anything that makes a 5% improvement could not be detected and assigned to a cause. When a rifle is fired the results are the sum of more than ten combined variables (rifle, fouling, temperature, wind, load, shooter ect.). I think this will continue to be a pissing match because none of us are explosive engineers. Everything is someones opinion. I would like to hear an explanation of what occurs in a hang fire. Only an explosive engineers could properly explain it.
There is an assumption that all primers in a lot behave the same way. As shooters we cannot test individual primers by them selves without external influences. The DOD report I attached to a previous post shows lot variation among primers in pressure generated when a primer goes off. It give the standard deviation in pressure generated when different types of primers are set off.
corrected path.
http://arxiv.org/ftp/arxiv/papers/1203/1203.2701.pdf
Good article on primer contribution to accuracy by German Salazar and others. Long distance shooting. They contend a small primer crush is needed. Plus other info. Considerable work was done on this research project. Lots of money. Looks like I might have to eat a little crow. References given to other primer articles which should be archived. Recommends a Sinclare or K&M primer seater.
http://riflemansjournal.blogspot.com/2009/06/primers-large-rifle-primer-study.html
Another primer seating article by Salazar
http://riflemansjournal.blogspot.com/2009/11/primers-seating-pressure-and-pre.html
There is an assumption that all primers in a lot behave the same way. As shooters we cannot test individual primers by them selves without external influences. The DOD report I attached to a previous post shows lot variation among primers in pressure generated when a primer goes off. It give the standard deviation in pressure generated when different types of primers are set off.
corrected path.
http://arxiv.org/ftp/arxiv/papers/1203/1203.2701.pdf
Good article on primer contribution to accuracy by German Salazar and others. Long distance shooting. They contend a small primer crush is needed. Plus other info. Considerable work was done on this research project. Lots of money. Looks like I might have to eat a little crow. References given to other primer articles which should be archived. Recommends a Sinclare or K&M primer seater.
http://riflemansjournal.blogspot.com/2009/06/primers-large-rifle-primer-study.html
Another primer seating article by Salazar
http://riflemansjournal.blogspot.com/2009/11/primers-seating-pressure-and-pre.html
There surely can be large disparity in primer sensitivity - or at least enough to make one go off - while another brand may not fire under the same conditions in the same gun and same load, etc. Most notable are the Russian primers. It was earlier noted the Russian SRM's can be a bit "harder" to ignite. I have had the same experience with the Tula Large Rifle primers - yet what led to the difficulty in ignition was partly my fault - and is something I had not given any prior thought to. The recent episode involved the firing of some Wolf brass-cased 6.5 Grendel factory ammo that was given to me as part of a trade for a used 6.5 Grendel A/R-15 upper I purchased. The cases used by Wolf were PPU cases. I shot the factory ammo (which shot very poorly). I disected a few factory rounds to weigh the powder, examine the inside of the unfired primer after extraction and check variations on the brass, etc. I had never used this brass and wanted to check it out first hand for myself.
Anyway, I did the "routine" brass prep which included turning the necks for 80% or so clean-up, prepped the primer pockets with a Sinclair primer pocket uniformer and uniformed the flash holes (they used large primers whereas Lapua and Hornady use the small flash holes). In the back of my mind while uniforming the primer pockets, I was thinking to myself that "these sure needed a lot of clean-up - based upon how every single case took a bit more clean-up than most cases I have prepped, all taking just about the same amount of metal removal from the bottom of the pockets.
I figured these cases would be a good candidate for the Tula KVB-7 Large Rifle primers, having used them in bolt guns with fair success. Upon firing when doing load development with these now-reloaded cases, about 30% failed to fire the first time. All fired by the 2nd or 3rd attempt. I knew it was not excessive headspace alone - as I left only .002" for this semi-auto. I had used this same rifle to fire these same caases before this reloading and had used the primer pocket uniformer on thousands of cases before - and had used this same batch of primers many times before - and NEVER had a misfire.
Then the lightbulb came on (however late in retrospect). Wolf apparently had this brass spec'ed for the Russian primers. When I took the primer pockets down a few thousandths when uniforming - they no longer ignited properly. I then measured the height of the unfired Tula primer and compared with the height of CCI-BR2 and Winchester WLR primers I had on hand - and had no issues with. Here are the differences: TULA KVB-7 .126" high
CCI BR-2 .128"
Win WLR .125"
Because the cases were then reloaded with the CCI primers and the Winchester primers (all of which fired the first time) and were seated with the same pressure with a Sinclair hand seater, the lower sensitivity of the Wolf primers really stood out - and noting the Winchester primer was actually taller.
The next question to my mind was "do the other ammo manufacturers using these Russian primers have the primers seated just flush as the Wolf ammo appears as compared to after it is seated in a "non-European" made case?"
I am now tending to believe there may be merit in thinking there is not anything "wrong" with the Russian primers when they don't go "bang" - it is just that we put them into an unsuitable case that was not designed to be compatible with Russian primers. In this case, I modified mine to no longer work with the Russian primers. Because the American primers still worked, folks often think of what does not work the same as inferior.
Anyway, I did the "routine" brass prep which included turning the necks for 80% or so clean-up, prepped the primer pockets with a Sinclair primer pocket uniformer and uniformed the flash holes (they used large primers whereas Lapua and Hornady use the small flash holes). In the back of my mind while uniforming the primer pockets, I was thinking to myself that "these sure needed a lot of clean-up - based upon how every single case took a bit more clean-up than most cases I have prepped, all taking just about the same amount of metal removal from the bottom of the pockets.
I figured these cases would be a good candidate for the Tula KVB-7 Large Rifle primers, having used them in bolt guns with fair success. Upon firing when doing load development with these now-reloaded cases, about 30% failed to fire the first time. All fired by the 2nd or 3rd attempt. I knew it was not excessive headspace alone - as I left only .002" for this semi-auto. I had used this same rifle to fire these same caases before this reloading and had used the primer pocket uniformer on thousands of cases before - and had used this same batch of primers many times before - and NEVER had a misfire.
Then the lightbulb came on (however late in retrospect). Wolf apparently had this brass spec'ed for the Russian primers. When I took the primer pockets down a few thousandths when uniforming - they no longer ignited properly. I then measured the height of the unfired Tula primer and compared with the height of CCI-BR2 and Winchester WLR primers I had on hand - and had no issues with. Here are the differences: TULA KVB-7 .126" high
CCI BR-2 .128"
Win WLR .125"
Because the cases were then reloaded with the CCI primers and the Winchester primers (all of which fired the first time) and were seated with the same pressure with a Sinclair hand seater, the lower sensitivity of the Wolf primers really stood out - and noting the Winchester primer was actually taller.
The next question to my mind was "do the other ammo manufacturers using these Russian primers have the primers seated just flush as the Wolf ammo appears as compared to after it is seated in a "non-European" made case?"
I am now tending to believe there may be merit in thinking there is not anything "wrong" with the Russian primers when they don't go "bang" - it is just that we put them into an unsuitable case that was not designed to be compatible with Russian primers. In this case, I modified mine to no longer work with the Russian primers. Because the American primers still worked, folks often think of what does not work the same as inferior.
AR Shooter
Silver $$ Contributor
This is definitely not my experience in either high power or BPCR shooting. And, a couple of the folks who have written some well respected books (Nancy Tompkins, etc.) will also disagree with your statement. While the primer may ignite and burn completely, inconsistent firing pin strikes will definitely show on the target.CatShooter said:
What you're missing is understanding of the indicated K&M.Webster said:
The K&M accounts for both pocket depth of actual case, and primer height of actual primer simultaneously as a pre-seating operation. You zero the gage to this condition, and then you move the primer to the head and seat the primer to zero +crush. Repeat with the next primer/case.
It's not record setting speed, but you get good at it pretty quick(Like measuring powder instead of throwing charges).
It's in no way a fancy set of pliers, but IMO a product of genius. If you did side-by side testing between the indicated K&M and any other primer seater, regardless of cost, you would see the K&M as equal in function, and superior in results.
Quoting Fred Moreo
"Short action firing pin spring specs per Savage:
Wire dia. - .055"
outside dia.- .390+-.015"
free length- 3.270"
number of coils- 20.75
length after set- 3.120"
to support 30lbs +- 5% @compressed ht of 1.312"
to support 23.5 lbs +- 5% @compressed ht of 1.687"
solid ht 1.200 max.
I have checked hundreds of them on a certified spring scale, and they have all exceeded the max tolerance by at least a pound, some more.
There is a science to this, and reasons why you should never cut coils from a firing pin spring.
For consistent ignition, it takes impact energy of somewhere around 4 in/oz., and this is what this spring was designed to provide with the combination of the other components. Anything less than the optimum will result in cold fires, misfires and such. Too much past optimum results in shock and disruption and usually poor accuracy.
The spring not only has to have enough energy to detonate a primer, but it has to have enough compressed energy after it is fired to support the primer. With out the support, the primer will blank and vent hot gases into the bolt and usually into the shooters face.
Contrary to common belief, the firing pin will not pierce a primer because of excessive protrusion. The firing pin tip will only indent the primer around .025", no matter if it is set longer. The primer cup is backed up by the anvil,
that's all further it can go, unless of course for some stupid reason the tip is pointed.
When the primer is detonated, the cup will stretch around where the tip impacted, making a weak spot. When the cartridge ignites, it produces around 60,000 psi pushing back on that dimple. If there is not enough support, the dimple simply goes back to where it came from, shearing itself on the firing pin hole.The gas pushes on into the bolt, essentially pushing the firing pin back, looking for an escape route. Usually in the process, the spring is compressed past solid height, resulting in a broken cocking piece lock washer, not to mention a face full of something you don't want any part of."
I think he mis stroked on the primer sensitivity.....
"I believe a small correction is in order. According to Otteson, the current US military requirement for primer sensitivity is 48 in-oz. for small rifle primers and 64 in.-oz. for large rifle primers. In other words, all primers should fire when hit with those levels of energy. This takes into account manufacturing tolerances for both primers, cartridges and firearms. At least one large company has established that the average production firearm should produce 75 in.-oz.( large rifle primer) to account for production tolerances, extreme temperatures, firing pin eccentricity, and excessive headspace."
"Short action firing pin spring specs per Savage:
Wire dia. - .055"
outside dia.- .390+-.015"
free length- 3.270"
number of coils- 20.75
length after set- 3.120"
to support 30lbs +- 5% @compressed ht of 1.312"
to support 23.5 lbs +- 5% @compressed ht of 1.687"
solid ht 1.200 max.
I have checked hundreds of them on a certified spring scale, and they have all exceeded the max tolerance by at least a pound, some more.
There is a science to this, and reasons why you should never cut coils from a firing pin spring.
For consistent ignition, it takes impact energy of somewhere around 4 in/oz., and this is what this spring was designed to provide with the combination of the other components. Anything less than the optimum will result in cold fires, misfires and such. Too much past optimum results in shock and disruption and usually poor accuracy.
The spring not only has to have enough energy to detonate a primer, but it has to have enough compressed energy after it is fired to support the primer. With out the support, the primer will blank and vent hot gases into the bolt and usually into the shooters face.
Contrary to common belief, the firing pin will not pierce a primer because of excessive protrusion. The firing pin tip will only indent the primer around .025", no matter if it is set longer. The primer cup is backed up by the anvil,
that's all further it can go, unless of course for some stupid reason the tip is pointed.
When the primer is detonated, the cup will stretch around where the tip impacted, making a weak spot. When the cartridge ignites, it produces around 60,000 psi pushing back on that dimple. If there is not enough support, the dimple simply goes back to where it came from, shearing itself on the firing pin hole.The gas pushes on into the bolt, essentially pushing the firing pin back, looking for an escape route. Usually in the process, the spring is compressed past solid height, resulting in a broken cocking piece lock washer, not to mention a face full of something you don't want any part of."
I think he mis stroked on the primer sensitivity.....
"I believe a small correction is in order. According to Otteson, the current US military requirement for primer sensitivity is 48 in-oz. for small rifle primers and 64 in.-oz. for large rifle primers. In other words, all primers should fire when hit with those levels of energy. This takes into account manufacturing tolerances for both primers, cartridges and firearms. At least one large company has established that the average production firearm should produce 75 in.-oz.( large rifle primer) to account for production tolerances, extreme temperatures, firing pin eccentricity, and excessive headspace."
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Then there is this article by James Boatright:
https://www.davidtubb.com/index.php?route=account/download/free&download_id=28
https://www.davidtubb.com/index.php?route=account/download/free&download_id=28
Quoted from D Tubb.
(Minimizing momentum transfer from the moving striker to the cartridge assembly.)
Minimizing vibrations. This is what I consider consistent ignition. There have never
been any confirmed studies conducted to prove other wise. The primers either go
or they don't 99.9 % of misfires are user error. To my knowledge hang fires
are always powder failure to burn. Most think its the primer because
its indented. Breaking down the case will show the powder has been yellowed
and the primer is spent.
(Minimizing momentum transfer from the moving striker to the cartridge assembly.)
Minimizing vibrations. This is what I consider consistent ignition. There have never
been any confirmed studies conducted to prove other wise. The primers either go
or they don't 99.9 % of misfires are user error. To my knowledge hang fires
are always powder failure to burn. Most think its the primer because
its indented. Breaking down the case will show the powder has been yellowed
and the primer is spent.
Shynloco
You can lead a horse to water, but ........
Interesting thought. But given that the powder was most likely from the same batch, why then would the rest of the casings fire/ignite and the one doesn't? Doesn't seem like a plausible answer that the powder is at fault. Just sayin. My experiences tells me that certain Primers are simply inferior and not worth buying unless its a "sweet deal" type of purchase and the cartridges will be used for plinkin.
Alex
I never said that some powders dont do better with certain primers.
Long slow burning (more flame retardant) extruded granules might
benefit from a hotter primer. But when the Primer goes off and
doesn't ignite the powder column or there is a delay (hang fire)
It is not a striker issue. My personal experience was years ago with Fed 205m
small primer in a Remington UBR 308 case necked down to 7mm 08
I was running 42.0 grs of 4064 powder. Hang fires and misfires were quiet common.
When I went to rem 7 1/2 primer the problem was solved This had absolutely
nothing to do with the striker. Regards Lloyd
Long slow burning (more flame retardant) extruded granules might
benefit from a hotter primer. But when the Primer goes off and
doesn't ignite the powder column or there is a delay (hang fire)
It is not a striker issue. My personal experience was years ago with Fed 205m
small primer in a Remington UBR 308 case necked down to 7mm 08
I was running 42.0 grs of 4064 powder. Hang fires and misfires were quiet common.
When I went to rem 7 1/2 primer the problem was solved This had absolutely
nothing to do with the striker. Regards Lloyd
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