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Where do YOU draw the line on Pressure Signs?

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punkwood2k

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Full Member
Minuteman
Nov 19, 2013
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Green Valley Ranch, CO
I did some pressure / charge testing today on my .308 with a new load (175gr Nosler Custom Competition over CFE223 (45.0 to 48 gr). Book Max on this load is 47.4gr, and I went two step beyond that at 47.7 and 48.0. What I find odd is that very slight primer cratering (lifted strike rim) starts way back at 46.5, but doesnt get any worse, all the way through 48.0. No other signs of overpressure at all, no extractor marks, no tight bolt lift, no primer blowback, no out of normal flattened primers, ect..

So, I'm going to keep working this load upwards a little bit at a time, until I see some other sign of overpressure..

My question, is where do YOU personally draw the line at pressure signs?
 
Primer cratering is unreliable. Some rifles just do that.

Usually the first thing to surface is the slight flattening of the primers. If you look very closely at the rounded corner of the primer cup after firing, you'll notice it just barely start to sharpen - the radius of the curve gets a little smaller. If you keep pushing it, it gets more pronounced, until it flows to fill even the chamfer on the primer pocket. You normally see other signs by then (ejector marks, prmimer leaks, cratering).

I stop when I see the first signs of flattening, and even then, the manuals are basically right. No pressure sign is infallible. Use common sense.
 
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Primers are what I look at, stiff bolt, etc. I have found that everything lasts a lot longer at low to moderate pressure, brass, barrels etc. That few extra FPS is not worth the wear and tear. Learn your drops and compensate.
 
Flat primers. Now some people say that it's common with a gas gun, but as far as I'm concerned, in a bolt action, I look for cratering and flat primers. I do not ignore this. BB
 
I usually look for ejector marks, but the tell tale is the next loading and the condition of the primer pockets. I have backed away from hot rodding ammo just to extend case life.
 
It's time to back off and leave a safety cushion when you get hard bolt lift. I frequently run 2-3 gr over max; some, I've developed 6gr over max (7mag) but have found the primer pocket loss isn't worth velocity gain. Get a bigger gun and don't push it to the limit if you need velocity IMO..
 
Yeah, I dont load mine to the ragged edge either.. My sweet spot is .3 to .5 gr BELOW max anyways.. I just like to know the actual limits of my equipment.
 
PrimersFallingOut223tiny.jpg
MY limit for 223

AR15BlueDot18Gr33VmaxDSCF0027.jpg

My limit for AR15s

DSCF0032bulletpinch308brass243chambercropped.jpg

My limit for 308s
 
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Some years ago...25+...a noted gun writer and reloader did some work with using case head expansion as the limit. He found that loading in increments up to .001 case head expansion over virgin brass was his limit for case life. Using the same load that gave him .001 expansion would give many, many reloads. If he continued to incrementally increase the charge, when the case next exhibited increased expansion, that and subsequent loads at that level would continue to expand the case head each time until the primers fell out. I stop at the suggested .001 and am content.
 
LOL @ Clark and Waka...now that's some pressure. Clark, I'm curious, what did that do to your bolt face?

My picture isn't as cool or extreme, but after 1x fired, trashed primer pockets and case wall thinning of nearly .009. I cut the following brass with a dremel so you can see what I was feeling with a paper clip.

260 Remington, pushing 139 scenars wayyyy too fast because my damn chrono broke. I was unaware it was 100+ fps off during load development until I saw signs of incipient case head separation. I will also mention this...the primers showed little signs of being over pressure. They were slightly flat, but not truly flowing like in the picture above. I've seen flatter primers in my 308 than I did with this 260, and no ill effects in the 308. However, the primers in the 260 could be seated with my index finger. Lesson learned: buy a nice chrono. I picked up a Magnetospeed, and it has lived up to the hype. Now I won't be throwing away any more 1x fired Lapua brass...



Look closely in the next picture, you can see the bulging ring just above the case head.



1x fired, cleaned, but NOT re-sized. You can feel the bulge at the bottom with your fingernail.

 
Yeah, I cant use primers as an indicator, I think.. I use CCI 200 primers (large rifle - non magnum), and they have a slight flattening even with my start-up loads.. I compare a fired shell that was loaded with my lowest powder, to an unfired case, and it is obviously flattened, but not excessively.. And the primer flattening doesnt get any worse all the way up through my charges to Max Plus..
 
With revolvers that are stronger than the brass, my limit is sticky extraction.
With revolvers that are have thin chamber walls that will split before cases stick, my limit is wimpy published loads.
With semi auto pistols with poor case support, my limit is case bulge.
With semi auto pistols with good case support that the feed ramp intrudes no further than the end of the case web, my limit is recoil or primer piercing.
With weak old 1888 bolt actions, falling block, lever actions, break actions, my limit is the wimpy published loads.
With strong bolt actions and weak case heads like .223 or .308, my limit is the threshold of loose primer pockets.
With strong bolt actions and strong case heads like 6mmBR or 7.62x54R, the limit is stiff bolt lift or pierced primer.
Break actions and falling block actions can typically go higher in pressure than bolt actions as the breech face is not cut for extractor nor ejector.
With strong lever actions that lock up in the rear, the limit may be brass stretch, or primer pierce, or loose primer pockets.
With weak lever actions, my limit is wimpy published loads.
With non adjustable gas semi auto rifles my limit is recoil or case stretch or loose primer pockets or pierced primers.
With adjustable gas semi auto rifles my limit is case stretch or loose primer pockets or pierced primers.
 
When I start load developing for a new cartridge, I like to start by building 2 identical rifles. I do all of the testing on one of them until I reach the load that blows the action to shrapnel. I then drop whatever is left of that rifle into the range dumpster. Next, I back the load that destroyed the first rifle off .1 grain, and that will be my "go-to" load for the 2nd rifle.
 
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I've shot a handful of factory rounds though an old Mauser where the primers flattened like nobody's business- but it was a chamber problem, not a pressure problem. The trouble is that you cannot completely separate the chamber, brass, and pressure from each other. They're all linked. That's one reason that there is no 100% reliable pressure indicator (except instrumentation, and even that's got some black magic involved). Even low pressure rounds can blow a case if the rifle isn't right, and a very well constructed rifle may not show pressure signs as much as a looser rifle.

The smart thing to do is stop if you see any pressure signs, because it means the brass is starting to fail. But, just because you haven't seen pressure signs does not mean that your pressure is not stupidly high. This is why going above max is not the best idea. Yes, it can be done. But the smarter course of action is to use a bigger case.
 
MtnCreek said:
Clark,

When you say 'recoil', are you talking about the effects on the firearm? (like overcoming the power of the recoil spring)?
Thanks.
Click to expand...

There is an optimum load for a semi so that it ejects and the cases land 5 feet away. This is enough energy to cycle the action without jamming but no energy left over for the bolt to hammer the receiver. The more extra energy left over the more wear on the gun and the nerves and joints of the shooter. It gets to the point with a 20 ounce 460 Rowland, that the recoil is just impossible to ignore. Parts fall off the gun. The hand hurts for an hour from shooting one round. So we pick some amount of recoil and hold the line there.
 
Velocity can tell you a lot, even if you don't think you're seeing other obvious overpressure signs. If you're seriously planning on continuing your search for the upper limit, I would strongly suggest getting some MV data at 47.4 gr and see how it compares to what you would expect to be getting for that bullet out of your specific barrel length BEFORE going on up past 47.7/48.0. Better safe than sorry (ie. without an eye, or even worse).
 
gstaylorg said:
Velocity can tell you a lot, even if you don't think you're seeing other obvious overpressure signs. If you're seriously planning on continuing your search for the upper limit, I would strongly suggest getting some MV data at 47.4 gr and see how it compares to what you would expect to be getting for that bullet out of your specific barrel length BEFORE going on up past 47.7/48.0. Better safe than sorry (ie. without an eye, or even worse).
Click to expand...

So, what would I be looking for in MV data? A Spike? Plateau? Drop?
 
In the crudest sense, an MV of 2900 fps for a 175 gr bullet out of a 24" pipe using 47.7 gr of powder would most definitely tell you the load was way too hot, regardless of whether you had observed any obvious pressure signs. In a finer sense, you should generally expect to see incremental increases in MV with this type of testing as the charge weight goes up. These will typically become much smaller or may even flatten out completely in a node, then rise again as the charge weight goes up further and takes you out of the node. At or above max load, MV can spike dramatically, become very [wildly] erratic for multiple shots of the same charge weight, or both. That should be a clear sign to back off on the charge, and most certainly not to go any higher, particularly if you're observing MVs at the very high end of what you'd expect for a specific barrel/bullet combination.
 
gstaylorg said:
you should generally expect to see incremental increases in MV with this type of testing as the charge weight goes up. These will typically become much smaller or may even flatten out completely in a node, then rise again as the charge weight goes up further and takes you out of the node. .
Click to expand...

Actually, I started to see just that as I was working up through the charges. MV climbed in regular intervals as the charge goes up, until it hit a certain point, where 3 of my charges showed very little increase in MV, then the 4th groups MV seemed to vary signifigantly.. Back home with the calculator, My SD was decent right where the MV's leveled off, which not-coincidentally was determined to be my accuracy node.. And the 4th charge had a huge (41 fps) SD over 5. Not a huge sampling of data to draw conclusions off of, but it at least fits your predicted pattern...
 
So what would you make out of this?
100_4916.JPG

The first one is an unfired primer for comparison with nice round edges.. #2 is 46.0gr, which is 1.4gr below Max, and a paltry 2720fps. #3 is 48.0gr, which is 0.6gr OVER max. Both show identical flattening of the primer, and slight cratering, but no other signs of overpressure.. Are CCI #200 primers just weak and easily flattened? For info, the two cases in question are New, 1st time fired was this test, so pockets cant be loose...
 
punkwood2k said:
So what would you make out of this?
View attachment 27019

The first one is an unfired primer for comparison with nice round edges.. #2 is 46.0gr, which is 1.4gr below Max, and a paltry 2720fps. #3 is 48.0gr, which is 0.6gr OVER max. Both show identical flattening of the primer, and slight cratering, but no other signs of overpressure.. Are CCI #200 primers just weak and easily flattened? For info, the two cases in question are New, 1st time fired was this test, so pockets cant be loose...
Click to expand...

Everyone has their own definition of flattened primers and what they consider normal. By my standards, those primers in the pics look like they have room for higher pressures. You still have radiused edges; I don't call them flattened until they are closer to square.
 
punkwood2k said:
So what would you make out of this?
View attachment 27019

The first one is an unfired primer for comparison with nice round edges.. #2 is 46.0gr, which is 1.4gr below Max, and a paltry 2720fps. #3 is 48.0gr, which is 0.6gr OVER max. Both show identical flattening of the primer, and slight cratering, but no other signs of overpressure.. Are CCI #200 primers just weak and easily flattened? For info, the two cases in question are New, 1st time fired was this test, so pockets cant be loose...
Click to expand...

Both the fired cases look to me to be consistent with what I *usually* see when a load is near max or at max. This is where I stop. I would back off the #3 load. When primers start to crater (as opposed to primers that always crater), it means your'e flirting with pierced primers. I wouldn't be surprised to see a slight difference in case body diameter (right ahead of the groove) between the two fired cases, but maybe not.

Also, it looks like the right hand case might have an ejector mark on the "C" on the headstamp. I can't really tell from the picture. You could probably push these loads a good bit higher, but at risk of blowing primers, decreasing brass life, and other bad things. Published max is generally a good guide for safe loads that are easy on brass.
 
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Was it 110 degrees outside when you tested the load?

What will pressures be in the summer?

My simple answer is that I stay within the guidelines of the books.

Call me a chicken but KBing my rifle next to my face scares me.

I also found better accuracy away from the high end of the max loads.
 
I've always used primer flattening as an indicator. I've laso found the most accurate loads are USUALLY NOT at the max end of things.
 
gstaylorg said:
In the crudest sense, an MV of 2900 fps for a 175 gr bullet out of a 24" pipe using 47.7 gr of powder would most definitely tell you the load was way too hot, regardless of whether you had observed any obvious pressure signs. In a finer sense, you should generally expect to see incremental increases in MV with this type of testing as the charge weight goes up. These will typically become much smaller or may even flatten out completely in a node, then rise again as the charge weight goes up further and takes you out of the node. At or above max load, MV can spike dramatically, become very [wildly] erratic for multiple shots of the same charge weight, or both. That should be a clear sign to back off on the charge, and most certainly not to go any higher, particularly if you're observing MVs at the very high end of what you'd expect for a specific barrel/bullet combination.
Click to expand...


Thanks! That's what I was thinking. Fairly new to working up loads. My last ladder test with RL17 and 208 amax's there was a nice platue at 2450 fps 48.2-49.1 grains. 50.2 was big spike in fps. I never got any pressure signs on the brass or primer. The spike in fps made me leary of proceeding with more higher loads. Good to know my line of thinking was correct.
 
hermosabeach said:
Was it 110 degrees outside when you tested the load?

What will pressures be in the summer?

My simple answer is that I stay within the guidelines of the books.

Call me a chicken but KBing my rifle next to my face scares me.

I also found better accuracy away from the high end of the max loads.
Click to expand...

*THIS* is another question I was going to ask.. It was 55 degrees when I tested it.. Summertime temps max out around 100 degrees.. And I have no idea honestly how temperature sensitive CFE 223 is.. But again, "My load" isnt maxed out at all, this is all hypothetical pressure sign questions.
 
punkwood2k said:
So what would you make out of this?
View attachment 27019

The first one is an unfired primer for comparison with nice round edges.. #2 is 46.0gr, which is 1.4gr below Max, and a paltry 2720fps. #3 is 48.0gr, which is 0.6gr OVER max. Both show identical flattening of the primer, and slight cratering, but no other signs of overpressure.. Are CCI #200 primers just weak and easily flattened? For info, the two cases in question are New, 1st time fired was this test, so pockets cant be loose...
Click to expand...

Those both look fine to me. Take one of your max loads and cut the brass in half with a band saw or dremel, then measure wall thickness. Also try re-priming one of the max load cases, see how easy primer goes in.

In between how it feels when shooting, measures with the chrono, looks when it comes out, and resizes/primes afterward ... there are probably 20 checks that can be done. Those primers aren't what I'd call flat, but just right at the point where I'd inspect further. Use one of the other 19 possible checks, and if any others gives you cause for concern, back off. Reloading as much as anything is about simply paying attention and using good judgement. Watching big numbers pop up on the chrono is fun, believe me I know. I used to shoot 223 WSSM just to see 4300fp+ numbers pop up. But after the novelty wears off, you realize it's not worth it. Safety concerns of course, but also because you never get best accuracy with nuclear loads.
 
punkwood2k said:
*THIS* is another question I was going to ask.. It was 55 degrees when I tested it.. Summertime temps max out around 100 degrees.. And I have no idea honestly how temperature sensitive CFE 223 is.. But again, "My load" isnt maxed out at all, this is all hypothetical pressure sign questions.
Click to expand...

I don't know the specs exactly, but with CFE 223 I was told by Hodgdon 3% max variance with something like a 140*F temp swing (don't quote me on that). For a ball powder it's very temp stable. Still I do all load development at a minimum of 60 degrees, knowing that max I'll ever see is 105, min is -10 ... although I'm too much of a puss to shoot when it's anywhere near -10 :)
 
punkwood2k said:
I did some pressure / charge testing today on my .308 with a new load (175gr Nosler Custom Competition over CFE223 (45.0 to 48 gr). Book Max on this load is 47.4gr, and I went two step beyond that at 47.7 and 48.0. What I find odd is that very slight primer cratering (lifted strike rim) starts way back at 46.5, but doesnt get any worse, all the way through 48.0. No other signs of overpressure at all, no extractor marks, no tight bolt lift, no primer blowback, no out of normal flattened primers, ect..

So, I'm going to keep working this load upwards a little bit at a time, until I see some other sign of overpressure..

My question, is where do YOU personally draw the line at pressure signs?
Click to expand...

A sticky bolt.
 
The chronograph always comes out when I'm working up loads.
The few times I'm pushing for max velocities I'll pay close attention to velocity changes vs charge weight and extreme spread.
When velocity starts to plateau or ES gets crazy, I'll back down.
I'm always looking at primer flattening and brass condition too.
I like long brass life so if primers get too easy to seat after a few loadings, I'll back down.
If brass is flowing and getting pushed around at the case head, I'll back down.
Nothing pains me more than scraping cases that haven't had a long, productive life...
 
I can put up with a flat primer, pouched up primer, but marks on the case head need attention. Lapua 6.5x47 brass rarely shows pressure signs of any kind, it straight to pierced primers, you're done there, pierce enough of them, and you're probably gonna need a new firing pin.

Going as far as Gorski says with a stiff bolt is not smart, you hammer the bolt handle off with a spent, stuck round in the chamber, you've got fucking issues.
The guy who said he uses the chrono at all times when developing loads is spot on.
 
Depends on reloading technique used. I do not FL size match ammo each time. I check-chamber 10 or 15 neck sized cases in the clean chamber of the rifle and check chambering force. A tiny bit of resistance I tolerate. It has been my experience that ammo loaded this way might offer a little more resistance opening the bolt after firing. Otherwise, sticky bolt is too hot. I also look for excessive primer flattening based on what I already know about the rifle, powder, etc. I also look for ejector marks on the case head, imo these also mean too hot. Punctured primers mean too hot, or bad firing pin. Finally, for me, primers taking on the detail of the bolt face is a warning sign.

I keep records of brass by lot and know how many times loaded, know what i loaded in them, and how much effort it should take to size them, whether they should rechamber after neck-only sizing. Anything out of the ordinary gets investigated.

I am pushing match loads pretty hard and I look at several fired cases during a string.
 
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I stop when I get a flat primer and a extractor mark showing
 
All,
Thus far the discussion has regarded fairly modest cartridges but how would pressure signs vary when advancing to larger calibers such as the CheyTac or .50 cal? I have extractor marks and cratering on my Jamison .375 CT brass regardless of the load. When rounds purchased from and loaded by CheyTac were fired, I observed cratering and extractor marks. Is this simply due to the fact that even a "light" load in a weapon like this is running a shit-ton of powder, i.e. 130 gr Retumbo? CheyTac runs 136.5 gr of Retumbo in their .375 CT loads and lists 139 gr as the max. I got a heavy bold lift at 137.5 gr (Retumbo) and deep extractor marks running 350 gr SMK's at .015 off the lands.
 
I have never seen a CheyTac, except on TV, but I cannot believe you have a normal situation? As Charlie Chan might say: SUM TING WONG.

And, it's probably your chambering job. I'd send it back for evaluation. BB
 
Yeah, I may send an inquiry to Dave Viers and see what he says. It cost so damn much to ship this thing, though, that even an evaluation would be extremely expensive.
 
Where do I draw the line: When I cannot get 30 reload cycles before the primer pocket no longer holds primers firmly.

Note: I do get 30+ reload cycles with 155 Scenars being pushed by 47.8 gr Varget with Win cases--which is in no ay a light loading.
 
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