I was out this morning trying some new loads in my 6MM Creedmoor build and at the range the primers looked flattened. So I stopped came home. Now that I look at them here I believe I can see rounded edges to the primer which would indicate things were OK. Loads where well below max data from the Sierra manua. What is your thoughts?
Over pressure??
- Thread starter 22vartarg
- Start date
MikeMcCasland
Team Texas F-T/R
When you actually get up in the pressures, there won't be any question as to if it's flat or not.
Edit: Agree, no pressure signs via the primers. What'd the chronograph say?
Edit: Agree, no pressure signs via the primers. What'd the chronograph say?
Primers don't always tell the whole story. Some primer cups
can be softer then others. I've had heavy bolt lift on some
where the primer looked like it was just installed. I just fire
formed some brass with old give away Remingtons. The
primers were flattened and shown some cratering, but real
easy extraction. By looking at your pics, your load seems
normal. Any chance to run them on a chrono ??
can be softer then others. I've had heavy bolt lift on some
where the primer looked like it was just installed. I just fire
formed some brass with old give away Remingtons. The
primers were flattened and shown some cratering, but real
easy extraction. By looking at your pics, your load seems
normal. Any chance to run them on a chrono ??
Gets your eyes checked. I'm just kidding. Years back Gmac gave me a 20x Lupe. I've looked at many a primer with it for just one of its uses. I usually let the cycling of the rifle tell me, that and other signs on the brass.
Primer cups lie.
In my opinion there are only 1 thing regarding the primers and pressure that need consideration. If the primers are cratering excessively or look like they may start extruding out the edges of the primer pocket so that it looks like the primer may be pierced or blow out a side then that is too much pressure for that primer and to handle.
A little cratering is fine. But when it starts climbing up your firing pin a little too much you can get a pierced primer. In my opinion that excessive climbing of cratering is the only indication of high pressure on the primer. The brass is the best indication of high pressure.
A little cratering is fine. But when it starts climbing up your firing pin a little too much you can get a pierced primer. In my opinion that excessive climbing of cratering is the only indication of high pressure on the primer. The brass is the best indication of high pressure.
RegionRat
Gold $$ Contributor
I'm with the others, these are not what we call warning signs of high pressure.
If you read up on the concept of judging signs of pressure warnings, you will find that you never ignore any one indictor, but you generally find more than one when you are exceeding the standards.
Good that you stopped when you thought you had an issue, that is better than playing Russian Roulette with your face and hands at risk, not to mention the rig.
If anything is to be learned from the outing... it is to be better prepared when running tests that might mean safety margin calls will be made.
Why not take magnifiers and have good lighting ready if you need to see primer radius changes?
Have micrometers ready and know what your limit would be for case dimensions.
Have the chronograph running to compare your observations to the estimates in your load manuals and know what to expect.
Consider what your path would be if you see abnormal values ahead of time and don't put pressure on yourself to hit speeds you hear about on the internet.
If you like load development and think you will be doing more of it in the future, then practice makes perfect but have your tools with you to avoid false positives or false negatives while at the bench. Play it safe or it won't end up being fun.
If you read up on the concept of judging signs of pressure warnings, you will find that you never ignore any one indictor, but you generally find more than one when you are exceeding the standards.
Good that you stopped when you thought you had an issue, that is better than playing Russian Roulette with your face and hands at risk, not to mention the rig.
If anything is to be learned from the outing... it is to be better prepared when running tests that might mean safety margin calls will be made.
Why not take magnifiers and have good lighting ready if you need to see primer radius changes?
Have micrometers ready and know what your limit would be for case dimensions.
Have the chronograph running to compare your observations to the estimates in your load manuals and know what to expect.
Consider what your path would be if you see abnormal values ahead of time and don't put pressure on yourself to hit speeds you hear about on the internet.
If you like load development and think you will be doing more of it in the future, then practice makes perfect but have your tools with you to avoid false positives or false negatives while at the bench. Play it safe or it won't end up being fun.
They look like they need more power! Seriously. I dont see any pressure indicators. Btw; I take my 2x reader cheaters to the range for case exam.
DirtySteve
Gold $$ Contributor
The only rifle I disregard primer cratering in, is my Savages.. They crater way before I hit a max load..
You primers look fine no visible signs of pressure apparent to me..
You primers look fine no visible signs of pressure apparent to me..
With a few exceptions, primer appearance is a terrible way to judge pressures. Speer has included the photo below in their manuals for years. The link is to a detailed discussion of the topic by a well-respected writer.
RegionRat
Gold $$ Contributor
If folks knew the uncertainty in the so called laboratory methods for measuring chamber pressure, they might call those "terrible" too.
I would disagree with the implication of "with few exceptions" when in reality it is the other way around.
With a few exceptions you will see primers flattening when the majority of cartridge designs are approaching the design pressure limits. Even the 44 mag will show flat primers with high pressure the majority of the time. That said, false positives and false negatives happen often enough to say that judging pressure with primers isn't safe enough to bet your eyes and fingers on them.
The example in the photo is an exception, not a rule. A whole club full of 44 mag revolver silhouette users and not a single instance of primers that didn't show signs tells us that would not be statistically possible if things were like that article describes with respect to the likelihood of no signs. The 357 shooters trying to tip plates over often pushed against or over the pressure limits, and the number who showed no flattened primers was.... zero.
No one person can speak to the wide possibilities of all cartridges, recipes, and chambers, but beginners need to know why we are telling them not to use primers alone while also not turning the math upside down.
At risk of sounding like a hypocrite, I am now going to say that it (false negatives where primers look good under high pressure) can and does happen often enough to strongly discourage loading near limits without a complete education and substantial background and experience. If and when you see primer flattening, do not ignore it. Investigate the reason before you go up in charge. Do not assume that if you don't see flattening, that you are safe. YMMV
I would disagree with the implication of "with few exceptions" when in reality it is the other way around.
With a few exceptions you will see primers flattening when the majority of cartridge designs are approaching the design pressure limits. Even the 44 mag will show flat primers with high pressure the majority of the time. That said, false positives and false negatives happen often enough to say that judging pressure with primers isn't safe enough to bet your eyes and fingers on them.
The example in the photo is an exception, not a rule. A whole club full of 44 mag revolver silhouette users and not a single instance of primers that didn't show signs tells us that would not be statistically possible if things were like that article describes with respect to the likelihood of no signs. The 357 shooters trying to tip plates over often pushed against or over the pressure limits, and the number who showed no flattened primers was.... zero.
No one person can speak to the wide possibilities of all cartridges, recipes, and chambers, but beginners need to know why we are telling them not to use primers alone while also not turning the math upside down.
At risk of sounding like a hypocrite, I am now going to say that it (false negatives where primers look good under high pressure) can and does happen often enough to strongly discourage loading near limits without a complete education and substantial background and experience. If and when you see primer flattening, do not ignore it. Investigate the reason before you go up in charge. Do not assume that if you don't see flattening, that you are safe. YMMV
Jager
Gold $$ Contributor
"Flattened primers" are the most accessible over-pressure sign we have as shooters. A quick glance down at the fired cartridge and we know whether we're still good, right?
Or not. Notwithstanding that everybody does it - glances down at that dimpled, just-fired primer - I also think that "flattened primers" are probably the least reliable indicator of over pressure we're likely to see.
That said, pretty much all the classic "pressure signs" we've been taught to look for - all of which amount to observing excessive metal deformity - are pretty archaic. Kinda like falling over the cliff to find out where the trail ends.
Or not. Notwithstanding that everybody does it - glances down at that dimpled, just-fired primer - I also think that "flattened primers" are probably the least reliable indicator of over pressure we're likely to see.
That said, pretty much all the classic "pressure signs" we've been taught to look for - all of which amount to observing excessive metal deformity - are pretty archaic. Kinda like falling over the cliff to find out where the trail ends.
Absolutely! Load half a dozen cartridges identically but with different makes / models of primer and you'll get a wide variety of post-firing appearances. Although primer choice does affect peak pressures, not by enough to make significant differences to any load that's not right on the limit. Here are two sets of shots from different angles of five makes/models of primer (in rows of three) fired in the same session in 308 Win Lapua small primer brass with a full-pressure but by no means 'hot' load. The third pic with two out of six primers 'blanked' is of some ancient (1970s, early 80s ?) Vihtavuori brand small primers with the same load. After the second blanked, they were put on one side and subsequently demilled.
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