is this primer showing excess pressure?
- Thread starter agd1953
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sansone
Member
is the primer flattened, how deep is the primer/firing pin impact crater 
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Spartacus451
Member
Looks good from here. The edges are still round and well defined. Flattening of the primer is probably the first high pressure sign you will see followed by flow around the firing pin and finally ending up in a punctured primer.
Cosmoline
Member
Looks good to me. Are you seeing any case sign such as stretch lines or an incipient tear?
Top surface of the primer is flattened, it does not have any sign of cratering around the pin strike, there is no sign that the primer is close to penetrating the primer surface. The gap between the primer and brass is not filled in but is narrower that when first primed. It is flatter than the factory remanufactured cartridge primer that I have been shooting. There was evidence that I had too much oil on the face of the bolt, ie wet oil on case head after firing. Gun is Bushmaster Varminter. No sign of case seperation or bright spots on case. checked with paper clip on the inside when I got home and felt nothing
fineredmist
Member
Your charge weight/bullet weight is within Hodgdon specs so that is not the problem. The bolt face must be oil free as any oil on the face will setup hydraulic pressure on the cartridge head a compress the primer. Make sure the bolt head and chamber are oil free and enjoy your shooting.
cracked butt
Member
Looks perfectly normal to me.
Ditto. In fact, it looks like a lower pressure than nominal load to me. That doesn't mean you should add more powder, it means you shouldn't worry about that load.
USSR
Member
Nothing wrong with that primer, as the edges are still rounded. Actually, looking at a primer all by itself is probably the least reliable method of judging high pressure.
Don
Don
sansone
Member
case is good, primer good, if your groups are tight stay right there
Don (USSR), what other method would you recommend. I have heard that case head expansion is not as accurate a determination as it was first thought. I don't know of any other method available to the average Joe. I appreciate every bodies help. It is great to have this website to go to with all the knowledgeable people that the novice can ask advice from. Thanks!
GP100man
Member
hi fellers im new here ,but been reloading a long time &ime the primer is the
most unreliable pressure sign,the thickness of the brass cup & brittleness of the cup& finally thickness. sure if you load near max it is going to affect the primmer & how it (LOOKS ) but thats not an indication of how much pressure was present.
havent weall scrounged once fired brass & looked at the primer & find the primer flat as can be ????
GP100man
most unreliable pressure sign,the thickness of the brass cup & brittleness of the cup& finally thickness. sure if you load near max it is going to affect the primmer & how it (LOOKS ) but thats not an indication of how much pressure was present.
havent weall scrounged once fired brass & looked at the primer & find the primer flat as can be ????
GP100man
nitesite
Member
Looks pretty normal for CCI primers if you ask me. The case mouth almost looks like it's not fully sealing against the chamber wall during ignition, but I think you're doing just fine. I think you can feel okay that there are no pressure issues, since you've taken care to examine the outside and inside of your cases for signs.
How accurate is it? Other than your choice of powder your load is quite similar to one I've loaded over a thousand rounds of with good results.
How accurate is it? Other than your choice of powder your load is quite similar to one I've loaded over a thousand rounds of with good results.
nitesight, I'm still in the testing stage. best group so far is four shots in under an inch at 100 yds, with 25.6 gr. I think that my poor shooting is affecting the results. I'm shooting from a bi-pod. I had vertical strings with 25 and 25.2gr, again, it may be a breathing control issue. I intend to go on in .2 gr increments and if I get close to max load I will go in .1 gr increments. I will try 25.5 and 25.7 as well to see if I can fine tune a little. Any other powder suggestions would be appreciated.
lonniemike
Member
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Is this shot in a turn bolt rifle? Hard bolt lift is a common first sign in a bolt action. Excessive velocityand brass flow marks on the case head are bad signs too. best-o-luck
Read Tea leaves, not primers. You will get better results.
Your primers look good, but judging pressures by primer appearance is not a reliable method.
The absolute most reliable signs of excessive pressure are gross phenomena, observed when pressures have exceeded max. That is leaking primers, pierced primers and blown primers. Another positive sign is stiff bolt lift.
Bolt lift cannot be observed in a semi auto, and you did not state what type of action you have. I only have AR15 type actions in .223. When I develop loads I do a couple of things, one of which I have never heard anyone else discuss.
Firstly I use a chronograph and shoot loads from low, working my way to the loads with the most powder. A chronograph is a most useful tool as it tells you when you are exceeding published velocities. It is a very safe bet that when you exceed published safe velocities, regardless of your powder charge, you are exceeding safe pressures. I have a couple of very tight Krieger barrels, these barrels produce velocities at least 200 fps faster than the same charges give in reloading manual barrels. Or in other match barrels. And the pressures are high as I have found by having pierced primers and blown primers. These fast barrels are tricky as slightly hot loads developed in them in cool weather can and do blow primers in hot weather. And what is worst, there is often no indication of a stiff bolt lift when the rifle is blowing primers. Just wham!, and you notice a coating of oil and grease on your shooting glasses. Always wear shooting glasses.
I have vintage military barrels that shoot abnormally slow (like 200 fps or more) compared to published velocities/loads, and I have not tried to increase velocity because I am not really certain what is going on. And I don’t want to pioneer with my head and heads into that unknown frontier. The more guns you blow up, the more cautious you tend to get.
Another factor that makes primer appearance unreliable is the fact that with dry cases the primer backs out to the bolt face before the case expands to the bolt face. Once the case expands to the bolt face the primer is stuffed back into its pocket. I suspect in many instances the primer has expanded to a muffin shape before getting stuffed back into the case. This will give the appearance of high pressure at times with light loads. I stated dry cases as when I am developing loads for my AR’s, I lubricate my test cases (with case lube) so the case will slide back onto the bolt face at approximately the same speed as the primer. I have no way to determine velocities, but I have noticed that with dry cases primers were flat, but with lubricated cases at the same powder charge, the primers were rounded. Obviously the combustion pressure did not change. When I have lubricated cases for load development, I have observed many times as I increased the powder charge, the primer edges went from round to less round, and then to flat. Or simply round to flat. But even with this technique I have had leaking primers when appearance would not indicate a maximum load. Generally the primers flatten out a grain or more before I have any noticeable pressure problems, so it give me an idea that I am starting to get close to a maximum pressure.
To reiterate, primer appearance is an unreliable indication of pressure. I think chronograph velocities are a better gross measurement technique, and the only real positive indication is leaking, pierced, or blown primers, of difficult bolt lift. If you ever reach that point , simply cut the load by ½ grain and try it out in the hottest weather you can shoot in. And if it blows again, cut the load by another half grain. And keep cutting until the primers stay in, and don’t leak. Wish there was a more exact way to do it, but I don’t own any pressure barrels.
Your primers look good, but judging pressures by primer appearance is not a reliable method.
The absolute most reliable signs of excessive pressure are gross phenomena, observed when pressures have exceeded max. That is leaking primers, pierced primers and blown primers. Another positive sign is stiff bolt lift.
Bolt lift cannot be observed in a semi auto, and you did not state what type of action you have. I only have AR15 type actions in .223. When I develop loads I do a couple of things, one of which I have never heard anyone else discuss.
Firstly I use a chronograph and shoot loads from low, working my way to the loads with the most powder. A chronograph is a most useful tool as it tells you when you are exceeding published velocities. It is a very safe bet that when you exceed published safe velocities, regardless of your powder charge, you are exceeding safe pressures. I have a couple of very tight Krieger barrels, these barrels produce velocities at least 200 fps faster than the same charges give in reloading manual barrels. Or in other match barrels. And the pressures are high as I have found by having pierced primers and blown primers. These fast barrels are tricky as slightly hot loads developed in them in cool weather can and do blow primers in hot weather. And what is worst, there is often no indication of a stiff bolt lift when the rifle is blowing primers. Just wham!, and you notice a coating of oil and grease on your shooting glasses. Always wear shooting glasses.
I have vintage military barrels that shoot abnormally slow (like 200 fps or more) compared to published velocities/loads, and I have not tried to increase velocity because I am not really certain what is going on. And I don’t want to pioneer with my head and heads into that unknown frontier. The more guns you blow up, the more cautious you tend to get.
Another factor that makes primer appearance unreliable is the fact that with dry cases the primer backs out to the bolt face before the case expands to the bolt face. Once the case expands to the bolt face the primer is stuffed back into its pocket. I suspect in many instances the primer has expanded to a muffin shape before getting stuffed back into the case. This will give the appearance of high pressure at times with light loads. I stated dry cases as when I am developing loads for my AR’s, I lubricate my test cases (with case lube) so the case will slide back onto the bolt face at approximately the same speed as the primer. I have no way to determine velocities, but I have noticed that with dry cases primers were flat, but with lubricated cases at the same powder charge, the primers were rounded. Obviously the combustion pressure did not change. When I have lubricated cases for load development, I have observed many times as I increased the powder charge, the primer edges went from round to less round, and then to flat. Or simply round to flat. But even with this technique I have had leaking primers when appearance would not indicate a maximum load. Generally the primers flatten out a grain or more before I have any noticeable pressure problems, so it give me an idea that I am starting to get close to a maximum pressure.
To reiterate, primer appearance is an unreliable indication of pressure. I think chronograph velocities are a better gross measurement technique, and the only real positive indication is leaking, pierced, or blown primers, of difficult bolt lift. If you ever reach that point , simply cut the load by ½ grain and try it out in the hottest weather you can shoot in. And if it blows again, cut the load by another half grain. And keep cutting until the primers stay in, and don’t leak. Wish there was a more exact way to do it, but I don’t own any pressure barrels.
USSR
Member
agd1953,
First, you should have an idea as to what velocity is possible at safe pressures from your rifle using your ammo components. The rifle variables that come into play are your action type, barrel quality, barrel length, and chamber dimensions. The load variables are the case capacity, burn rate of powder, charge weight, bullet weight, and cartridge OAL. You will reach high pressure before reaching high velocity with a short-barreled rifle or autoloader, or by using a powder too fast for the weight of the bullet. Everyone should have a chronograph and use it during load development. They are available for well under $100. Once you have looked at reloading manuals and settled on the components to be used, determine what OAL you will loading your ammo to. In many cases (short action or autoloader), you will be restricted by mag length (your mag length is shorter than your chamber length). However, if you have a long action rifle, you can in most cases load your ammo to a longer OAL so that the bullet is nearer to your rifle's throat. This has several advantages. By seating the bullet out further, you allow more room for powder, you lower the pressure, and in many cases you will find increased accuracy. To determine your rifle's chamber length, I recommend using the Stoney Point AOL Guage and a bullet comparator. The measurement you are looking for is from the case base to the bullet ogive. Because of the variance in the location of the ogive of some bullets, I don't recommend setting the bullet any closer than 0.010" to the lands. Start with a powder charge recommended as a starting point, something well below anything listed as a maximum load. Load 3 rounds at that charge weight, then load a series of several 3 round groups, increasing the charge weight by 0.5gr for each additional 3 round group, keeping the loads seperate. Starting with the ammo with the lightest charge weight, run them over your chronograph. Don't be concerned about the accuracy of the load, you are merely trying to reach a viable velocity for your rifle and load. Now, with your first 3 rounds fired, check your brass. The primers should be rounded on the edge, and there should not be any shiny mark on the base of the case. Assuming this is the case, continue with the next heavier charge weight group of 3 cartridges. Here are the signs that will appear (in increasing pressure order) as high pressure appears: first, the primers will flatten out with no rounded edges of the primer visible; second, there will be some cratering around the indent created by the firing pin strike on the primer; third, (this indicates that you are beyond where you want to be) there will be a shiny mark on the case base caused by the flow of the brass into the ejector hole of your bolt; fourth, (and you're WAY beyond where you want to be) hard bolt lift. If you find the velocity you expected to find, or if you see either the third or fourth sign on your brass, don't shoot any of the ammo you have loaded with heavier charge weights. Further load development should consist of 5 round groups for accuracy and SD/ES numbers from your chronograph of ammo varying by 0.3gr near, but not above your previously determined maximum load for your rifle. Hope this is of some help to you and others.
Don
nitesite
Member
You do, of course, realize that cartridge brass fired in YOUR rifle and then collet neck sized can (1) be more accurate plus (2) also experience less brass flow (compared to full-length sized brass) and longer useful reloading life.
The Bushmaster
Member
That primer looks just fine...Flattened primers are NOT a sign of over pressure. In fact flattened primers might even be a sign of under pressure because the fired case was slow to strick the bolt face after the firing pin set it forward and pressure of expanding gases SLAMED it back against the bolt face after the primer had a chance to back out of the pocket a little...
nitesite
Member
I forgot to ask if you are trimming your cases, and to what length? What rifle are you shooting and what type of chamber does it have?
nitesite, I am small base full length resizing as I am shooting a Bushmaster Varminter semi auto. These where unfired cases and I resized and trimmed them to 1.750" for consistency.
In regard to what type of chamber it has I cam only give you this exert from an email I received from bushmaster, I have the non chrome lined 24" fluted barrel:
Our chrome lined barrels and stainless barrels have bores that are 1/2 the Mil-Spec tolerances with 5.56mm NATO Spec chambers and step crowns.
The non chrome lined 24" fluted 1 X 9 Varminter barrels have bores that can be held to 1/2 the tolerances again with a tighter SAAMI Spec headspaced chamber with the longer NATO throat that will accept 5.56mm ammunition and an eleven degree competition crown. They are manufactured to the same specs as our 20" 1 X 8 DCM barrels except for twist rate. The 20" Predator barrel is a fluted DCM barrel. The 20" DCM, 20" Predator and 24" Fluted Varminter barrels are the most accurate barrels that we produce.
In regard to what type of chamber it has I cam only give you this exert from an email I received from bushmaster, I have the non chrome lined 24" fluted barrel:
Our chrome lined barrels and stainless barrels have bores that are 1/2 the Mil-Spec tolerances with 5.56mm NATO Spec chambers and step crowns.
The non chrome lined 24" fluted 1 X 9 Varminter barrels have bores that can be held to 1/2 the tolerances again with a tighter SAAMI Spec headspaced chamber with the longer NATO throat that will accept 5.56mm ammunition and an eleven degree competition crown. They are manufactured to the same specs as our 20" 1 X 8 DCM barrels except for twist rate. The 20" Predator barrel is a fluted DCM barrel. The 20" DCM, 20" Predator and 24" Fluted Varminter barrels are the most accurate barrels that we produce.
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