Pressure signs - pictures


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taliv
April 24, 2007, 10:46 PM
i don't often push the limits of pressure when reloading, so i figured people might be interested in seeing a pretty good example of some common pressure signs: "flattened primers" and "primers backing out"

the fourth case is exactly how i picked it up off the ground after it ejected from an AR15.

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Shoney
April 24, 2007, 10:51 PM
Pressure sign for rifle brass are good guide posts. But you must remember, there are no reliable pressure signs for most straight wall pistol cartridges.

mrkubota
April 24, 2007, 11:52 PM
Looks more like a headspacing issue to me....or maybe short stoking if this is a short barreled AR. you can see the black soot that leaked out around the protruding primer. Probably the reason it didn't reset back into the pocket like the others.

With a high pressue load you'll usually see the primer flow out flatter into the primer pocket mouth chamfer too.

taliv
April 25, 2007, 12:04 AM
the others are not loose, and i guarantee there are no head-space issues with that chamber/bolt. the bolt and barrel were purchased together from white oak as a headspaced pair, and i checked it myself with the gages. it is a 16" barrel.

steve4102
April 25, 2007, 12:16 AM
What's the load? A backed out primer is usually a sign of Low pressure and not high pressure.

Jim Watson
April 25, 2007, 12:22 AM
They don't look flattened to me. The edges are still fully radiused. The indents look strange, though. How old is the brass? Maybe the one with the backed out primer is just worn out and loose.

scrat
April 25, 2007, 02:26 AM
i agree its more of a bad batch of brass. the one with the loose primer probably has a worn out primer pocket.

snuffy
April 25, 2007, 03:44 AM
What's the load? A backed out primer is usually a sign of Low pressure and not high pressure.

Bingo! Classic sign of LOW pressure and a case that's had the shoulder set back too far. That creates an excessive headspace, regardless if the headspace checks out okay.

The firing pin shoves the shell forward up against the chambers shoulder. It fires the primer. Then the pressure inside the case causes the case to grip the chamber walls, but the pressure does not get high enough to stretch the brass back against the boltface. The primer can still move, it's unsuported, so it backs out of the case. If the pressure was higher, it would stretch the case, at the web area, then the primer would be reseated.

jr81452
April 25, 2007, 03:48 AM
i'd say high pressure was a factor. look at the second in from the right, the pin strike mark is poped out. and the one on the right the pin strike looks like it started to pop out, but the primer backed out before it got out to far.

mc223
April 25, 2007, 05:51 AM
Other than the case at third from left, they look like low pressure to me also. The primer of that other one looks as though the primer was beginning to flow. Or another thing I noticed is that the firing pin dents seem deep as illustrated by the straight area above the radius. This could account for the third from left as the primer material is being streched too far and thinned, then flowing back towards the bolt. If suffeciently thinned this could lead to pierced primers and firing pin damage.
There was no mention of what primer or loading was being used. I would suspect WSR or CCI primers and 748 or 4895.

DaveInFloweryBranchGA
April 25, 2007, 06:18 AM
No flow of the primers causing squared primer corners. No cratering of the primers, though the pic is making the firing pin punch holes look odd. They are certainly deep with a definate thread of pierced primers. A backed out primer. I'll side with the guys that think the cartridge shoulder is bumped back too far and isn't coming forward fast enough in time to prevent the primers backing out. I'll also vote low pressure. Need a little bit more "bang" and less "whoosh" for that short barrel and quick cycle time. Wouldn't hurt to investigate the buffer and buffer spring timing over at AR15.com or another of those AR forums.

Regards,

Dave

USSR
April 25, 2007, 07:27 AM
They don't look flattened to me. The edges are still fully radiused. The indents look strange, though. How old is the brass? Maybe the one with the backed out primer is just worn out and loose.


+1. No signs of high pressure with those cases.

Don

Picknlittle
April 25, 2007, 08:16 AM
Okay,..now I'm puzzled. These pics show exactly what I found when building loads for my 35 Whelen. As loads approached max, some primers were backing out but were not flattened. As I understand flattened primers, I should be able to feel somewhat of a knife edge around the primer base with my fingernail. Mine were all still rounded. The load I finally selected of 63gr BL-C(2) with 200 gr hornady sp did not show signs of backing out during testing, but a few did back out at the range a few days ago.
Same rounded primer edges.

BTW, this is all new remington brass.

taliv
April 25, 2007, 08:38 AM
i'm very intrigued by some of the responses and theories. thanks for the feedback. i'll provide you some more information here, and more of my own opinion.

the load is the same bullet as mentioned here, at a similar velocity. http://btammolabs.com/tests/4.htm and there is no published load data, so I won't discuss the details, but when i spoke to the mfg, they were surprised and indicated it was very, very hot. Based on the chrony results, and the amount/type of powder, I'm fairly certain these are at the upper end of the normal range and not the lower end.

the brass was 2x fired RP (now 3x fired) from a lot of 10,000 pieces, of which i have fired a couple thousand a 3rd time with no issues. I'll post pictures later today of other spent brass from the same group (i.e. fired same number of times) so you can see how much deeper the normal primer indents from this rifle are, and how much more rounded the other primers are.

it's not the pic that's making the indents look that way. they look odd in person and not very deep, but much shallower than normal.

also, it's not a quick cycle time. it's a mid-length gas system with 16" barrel.

my personal theory is that the the pressure made the primer very loose in the pocket (it takes almost no force to move in and out, like, you can blow on it to move it) and when it was ejected, the centrifugal force of spinning or when it struck the ground caused it to slide halfway out.

snuffy's low-pressure theory is interesting, but i've also put probably 300-400 subsonic and nearly subsonic rounds using the same lot of brass through this same gun, and that hasn't caused any primers to back out.

but to your point about the shoulder being set back too far, i DID run these cases through my sizer die twice during this load process. once to size them so they would fit in my case trimmer and again after they were trimmed just because i'm loading on a progressive and it's easier to let them feed through the case feeder than to stick them in station 3 by hand. however, between and after the sizings i verified it was set correctly using a case guage.

Doug b
April 25, 2007, 08:41 AM
Any high pressure loads I've experianced look the opposite of this.

taliv
April 25, 2007, 09:34 AM
kind of a crappy picture cause i had to take it indoors using my surefire as a light source :) i'll try to get a lower angle view later today

case on the left is a normal firing pin strike (55g fmj over 24g 2230c). case on the right is one of the previous 4 above. see how the normal indent from the firing pin is twice as deep and round. indent on the right is flat with a small raised portion in the center.

http://thehighroad.org/attachment.php?attachmentid=57140&stc=1&d=1177508016

Walkalong
April 25, 2007, 09:36 AM
Gotta be a bad piece of brass. If there was enough pressure to expand the primer pocket enough that the primer was loose it would have showed on the primers, trust me on this one. Anyone who has blown a primer can tell you that. :)

Mal H
April 25, 2007, 09:46 AM
I've never seen a firing pin indentation like that without the primer also loosing all or most of its radius and flowing to the edge of the pocket. I wonder if it can be caused by loose pockets (as surmised by several) with the firing pin pushing the primer back into the pocket with just enough power to still fire the primer. That would allow for a lighter than normal indentation.

If you haven't yet measured the case diameter at the web, please do so with a good micrometer and see if there is any appreciable difference from a "normal" case of the same manufacture and fired from the same rifle.

taliv
April 25, 2007, 10:10 AM
0.3291" for the one with the backed out primer
0.3289" for the "normal" one in the last picture
0.3290" for another one of the 4 in the first post

The Bushmaster
April 25, 2007, 10:23 AM
taliv...Your photos do not indicate over pressure. They indicate a head space problem or you have set the shoulder back too far. FLATTENED primers do not indicate over pressure...Besides I didn't see any flattened primers in your photos...

Check your head space and insure you didn't set the case shoulder back too far when you resized them...

The one with the backed out primer indicates that the round fired and did not slam against the bolt face allowing the primer to back out. Most flattened primers start out like that then are slamed against the bolt face thus reseating the primer and causing it to flatten. The less head space the less flattened the primers will be...In most cases...

Mal H
April 25, 2007, 10:47 AM
0.32xxAre you sure? The nominal diameter at the web is 0.3773. Yours shouldn't be smaller by as much as 5/100ths.

I measured several R-P .223 Rem cases I have (fired approx. 2X). They were all 0.3733.

Ignoring the second significant digit (mic problem?), it does look like there is some minimal expansion at the web, but only about .0001" to .0002". That could be attributed to differences in cases and not necessarily pressure. I don't get concerned until there is a .0005" increase or more.

USSR
April 25, 2007, 10:55 AM
I've never seen a firing pin indentation like that without the primer also loosing all or most of its radius and flowing to the edge of the pocket. I wonder if it can be caused by loose pockets (as surmised by several) with the firing pin pushing the primer back into the pocket with just enough power to still fire the primer. That would allow for a lighter than normal indentation.


+1. There are several possibilities here, but high pressure is not one of them.

Don

taliv
April 25, 2007, 11:02 AM
oh, sorry, Mal. i thought you wanted me to measure the diameter over the primer in extractor groove.

over the web
0.3755" (backed out primer) (edit... i copied it wrong first time, and these are max diameters as cases are slightly out of round)
0.3750" (normal)
0.3755" (3rd case in the group of four in first pic)

Mal H
April 25, 2007, 11:10 AM
Ok, that is a sign of excessive pressure. The primers honestly don't look like that is the cause, but the web expansion is a much better indicator.

As Steve asked above, what's the load? You gave the load for the normal rounds, but left it out for the questionable ones.

taliv
April 25, 2007, 11:18 AM
bushamster, as i mentioned previously, i have a couple thousand rounds of normal loads that have all been prepped and processed the same way and I checked the cartridges to make sure they were sized properly with a case gauge. also, the barrel/bolt combo was headspaced by whiteoak. these rounds were numbers 1953-1957. (there were 5 but i lost one, as they were getting flung quite a ways).

the point is that if there were a headspace problem or if the cases were sized incorrectly, it would show up on all of them, because all these cases were run through the same press at the same time and dumped in a big bucket that i grabbed 5 cases from.


edit: mal, that's a good idea. i never thought to measure the case diameter. i assumed they would all be the same (the ID of the chamber) and not vary by pressure.

also, i mentioned the load in 2nd paragraph of post 14.

Mal H
April 25, 2007, 11:30 AM
Ah! Thanks, I missed that.

100 grain bullets! Now it's all becoming clearer. I'm beginning to wonder if the action on the primers is a result of a very short-lived pressure spike and not a prolonged pressure condition. (I'm thinking in terms of microseconds and not milliseconds.)

snuffy
April 25, 2007, 01:40 PM
Dadgum good mystery! A shooting buddy showed me some .223 empties that ALL looke like #4 in the above pics. Now, he's assembled dozens of ar-15's so I knew his headspace was good. After some discussion, I learned he'd done some die adjustments, turning the sizer die down tighter. I asked if he has a case guage. Nope! During the day of shooting he and another buddy had FOUR case head seperations, tieng up the rifles for further shooting. A broken case extractor is on order.

I supplied my cartridge guage,(no longer made by frankford arsenal:fire: :mad: :cuss: ). All the remaining loaded shells were well below the low datum line on the guage. We now have sinclair case guages on-the-way from midway.

I also have the same problem with a savage .308. Low pressure loads,(at the recommended starting level in several loads), the primers all backed out. As the load progressed towards max, the primer apperance was more normal. But the rifle seemed to not like ANY max loads. Heavier than normal bolt lift, and primer flatening. Most disturbing was the apperance of a bright ring on the outside of the case about half way between the extractor groove and the base of the shoulder. NOT where the case head seperation normally occurs, just in front of the web. And yes there IS a "ring" on the inside of the brass!:mad: A case guage is also on the way for the .308.

I had the same thing happen 30 years ago with a .243, you'd think I'd learn what NOT to do!

The Bushmaster
April 25, 2007, 03:57 PM
Snuffy...Shoulder set too far back???

Walkalong
April 25, 2007, 04:22 PM
Snuffy...Shoulder set too far back???

If your sizer die is adjusted for older ( work hardened ) brass, it will be adjusted too far down for softer new or once fired brass which will not "spring back" much if at all. The soft brass will stay where the shoulder was pushed to by the die where the harder brass will spring back out.

If you are using a mixture of brass and just happened to adjust it for the softer brass you could run into problems with the harder brass not chambering due to springing back. If you happened to adjust it for the harder brass the soft brass could get set back to far.

Just a couple of thoughts. :)


100 grain bullets! Now it's all becoming clearer. I'm beginning to wonder if the action on the primers is a result of a very short-lived pressure spike and not a prolonged pressure condition. (I'm thinking in terms of microseconds and not milliseconds.)

An excellent point as well.

steve4102
April 25, 2007, 06:21 PM
If your sizer die is adjusted for older ( work hardened ) brass, it will be adjusted too far down for softer new or once fired brass which will not "spring back" much if at all

Sounds good. I was sizing some 300WSM brass that was fired several times. I check the head to shoulder measurements and they were way to long. I adjusted my sizing die down to bring them back into specs. I left the die set as is and sized some once fired brass, way to short. Could be your problem.

R.W.Dale
April 25, 2007, 07:17 PM
Using the pimer appearance to guesstimate pressure is an exercise in futility. What your primers look like has almost as much to do with the individual rifle than the load.

http://i3.photobucket.com/albums/y96/krochus/FIRE/Casehead-2.jpg

snuffy
April 26, 2007, 01:51 AM
Well the case guage arrived from midway. I checked a couple of shells that were sized ready to be loaded, they were all BELOW the low datum line on the wilson headspace/case guage. Looks like I'll have to back the sizer die out some to get it back where it belongs.

Walkalong, I see what you're saying. I'd say that now that I have the case guage, I WILL be checking cases EVERY time I load for that Savage. I'm also going to have the headspace checked for the bolt/chamber. The cases that were giving me trouble were once fired cases that were picked up at a DU outdoor festival here in Oshkosh. They were fired in every kind of chamber imaginable. So I screwed the die down tight against the shell holder to make sure they'd chamber.

I'm going to get a couple hundred new cases to start off from a known condition.

Snuffy...Shoulder set too far back???

Yup! That's what the case guage tells me!:what:

Bullet
April 26, 2007, 04:00 AM
I use this to check headspace -

http://www.midwayusa.com/eproductpage.exe/showproduct?saleitemid=477756

taliv
April 26, 2007, 09:32 AM
snuffy, you buy reloading components at democratic underground events?!? you're my new hero

snuffy
April 26, 2007, 12:06 PM
snuffy, you buy reloading components at democratic underground events?!? you're my new hero
Today 03:00 AM
:confused: :eek: :what: Oh! I get it, damn, the coffee hadn't hit home yet! LOL. Nope DU, stands for Ducks Unlimited, but you knew that!? Each August they come here to show everybody all the new equipment, including letting anybody shoot a lot of different guns. There's everything from BB guns to .50 BMG.

Taliv, sorry for highjacking your thread. We kinda got off track here. Any new ideas on what might have caused your primer to back out? You are using a case guage, you're sure the chamber/bolt headspace is correct, so that leaves your observation that the case in question simply had a very loose primer that was dislodged either by centrifugal force, or by hitting the ground on the edge of the head. I hate mysteries with no conclusion, we need answers!:D

taliv
April 26, 2007, 02:04 PM
ducks unlimited, eh? i guess i've been reading the politics forum too much. i tell you though, the mental picture of a couple of guys tailgating at a democrat rally, buying and selling bulk bullets and brass out of their trunks, has had me chuckling all day.

sadly, work is intruding on my thinking/posting time. so no progress. I'm trying to figure out how to get my pressure trace strain gauge system hooked up to an AR15. It would be incredibly useful at the moment, but I can't seem to figure out how to mount it since my barrel nut completely obscures access to the surface of the barrel over the chamber.

so my plan at the moment is to back off by 1.3 grains and try again. i'll probably have an update over the weekend.

RecoilRob
April 26, 2007, 07:43 PM
I have been lurking on this one and believed that the primers didn't look all that bad from the pics...but then I got the point of the 100grn bullets.

Wow! That is a big, long and heavy projo for the .223 and I am wondering if this is the reason we don't routinely use them in the .223?

Needs a REALLY slow powder, comparatively, to normal bullet weights but the overlength projo intrudes into the case so much it takes up a lot of powder space. To get any useful ballistics the powder must be a bit quick for the bullet weight.....which could be causing a pressure spike that stretches the brass but doesn't last long enough to classically deform the primers.

Is there really anything to be gained with the ultra-heavy bullets in this caliber? I will stay tuned for the outcome!

Clark
April 26, 2007, 07:56 PM
http://www.thehighroad.org/attachment.php?attachmentid=39071&d=1146189997

You can see the extractor mark and you can see the ejector mark.
This load was fired in my Bushmaster AR15
http://www.thehighroad.org/showthread.php?t=196305&page=2&highlight=.223

Walkalong
April 26, 2007, 09:09 PM
You can see the extractor mark and you can see the ejector mark.
This load was fired in my Bushmaster AR15

Now that... is high pressure. :)

RecoilRob
April 26, 2007, 10:00 PM
That pic from Mr. Clark IS high pressure, but these cases from his link are INSANELY HIGH PRESSURE!!

SSN Vet
April 26, 2007, 10:16 PM
Following along threads like this while I scratch my head and mutter "think, think, think" is exactly why I love this forum. :rolleyes:

Clark
May 1, 2007, 10:42 PM
That is not insane.
I have never been hurt doing that.
I have overloaded .223, .243, 25acp, 257 Roberts AI, 270, 32acp, 32sw,32S&WLong, 32-20, 7.62x25mm, 7.62x39mm 7.62x54R, 8x57mm, .380, 9x19mm,9x23mm,357 Sig, 38 sp, 357 mag, 38sw, 40sw, 10mm, 10.4mm, 45acp, 45Colt, 452/70, .410, and 45/70.
I have been emergency room time from pole vaulting, at football, baseball, mountain climbing, tree topping, roofing, motor cycle racing, bartending, clearing land, kissing some other guy's girl friend, and this week end.....running a grinder.

The mountain climbing IS insane.

http://www.thehighroad.org/attachment.php?attachmentid=57419&d=1178074252

taliv
May 2, 2007, 12:19 AM
hey clark, were those backed out primers in that pic of yours from over or under pressured rounds?

i'm curious because there were a lot of people on the first page of this thread claiming that backed out primers were a sign of under pressure.

i'm personally not an expert on overpressure, since i almost never feel the need to go past published max, but I do load a ton of subsonic ammo, which is obviously low pressure and i've never backed out a primer until i started working with this 100g load.

Clark
May 2, 2007, 02:27 AM
Low pressure can cause primers to back out and not get shoved back in.

I don't remember it now, but the notes on THAT pic say 10% overload:
http://www.thehighroad.org/showthread.php?t=17737&highlight=223

Oohrah
May 3, 2007, 05:06 PM
Have seen the same on blank cases fired in our Ceremonial M-1
Garands. Indeed, low pressure, as one short cycled and a failure
to extract went with it. The new blanks have the neck mouths
crimped in the fashion of the old grenade (rifle) cartridges. The
neck folds were not opened and thhe CRIMPED primer was backed
out about 1/3.
Another sign of extreme pressure or multiple times used, is enlarged
primer pockets that will be felt when repriming if gages are not available
Experienced high pressure with minimum chambers, would not allow
bullets to release correctly when thicker brass in the neck area vs
thinner commercial brass was used.
Don't know why, but feel perhaps a low pressure problem. Burn rate
of the powder vs heavier than normal bullets?:confused:

Clark
June 13, 2007, 06:20 AM
CAUTION: The following post includes loading data beyond currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The High Road, nor the staff of THR assume any liability for any damage or injury resulting from use of this information.
This is a 25acp, 3.2 gr Bullseye, 50 gr, .875", WSP primer
This is ~ 240% charge, as much as will fit in a case, and then compress to half that volume with the seated bullet.
This is 200,000 psi per Quickload, but that means nothing with a straight wall case.
Fired in a Berretta 950
Notice how the primer flows back into the firing pin hole?
The firing pin hole seems to be the pressure limit on the three 25acp pistols I tested.
The same load fired in a Colt 1908 looks the same.


http://www.berettaweb.com/950/Beretta-mod.-950-b-barrel-o.gif

http://www.alliantpowder.com/reloaders/RecipeDetail.aspx?title=Pistols%20and%20Revolvers&gtypeid=1&weight=50&shellid=1010&bulletid=10


http://www7a.biglobe.ne.jp/~yon-yon/history/big/colt_pocket_2.gif
http://www.thehighroad.org/attachment.php?attachmentid=59289&d=1181729279

taliv
June 16, 2007, 05:54 PM
so... a brief bit of context here: i almost always load my ammo slightly to moderately under-pressure. i very rarely load anything near max, or over. i remain confident the loads in the previous posts of this thread are a little hot. however, i've solved the mystery of the primer indentions.

when i shot those loads, i had roughly 1900 rnds through my upper and BCG.

after shooting those loads, i decided to get rid of some old stocks of ammo, which were my usual light 55g win FMJ target load (my aforementioned 24g of 2230c). i shot through them with no problems. mean velocity was a hair over 3000 fps.

now that those were out of the way, i started trying to mimic the M193 round, using M193 pulldowns and 26g of A2230-C. (by way of comparison, M193 is around 3150 fps)

with 10 rounds, I got a mean velocity of 3095 fps with SD of 37 and this:
http://thehighroad.org/attachment.php?attachmentid=59499&stc=1&d=1182028862
(the other 5 looked the same, and the middle ones are also pierced, but rotated slightly around so that the opening is to the right and rear)

light bulbs started going off, and I started investigating my firing pin, which, by the way, is one of those fancy TiN plated jobs. sure, enough, it looked a lot different than it did when I bought it. so I swap it out with a regular aluminum one, and get this:
http://thehighroad.org/attachment.php?attachmentid=59500&stc=1&d=1182029149

for those ten rounds, the chrony showed a mean of 3081 fps with an SD of 24. then I chrono'd another ten with the suppressor on and got a mean of 3097 fps with an SD of 25. all those primers looked perfectly normal.

here are some pics of the culprit. sorry i couldn't get my camera to focus any better on the tip.

and I'm pretty firmly in the "don't coat your firing pins with any crap" camp now. actually, i have been for some time, but it came with the BCG so i figured i'd use it. :)

as you can see, the end is very flat, with sharp corners (soup-can shaped), compared to a normal firing pin, which is rounded in the middle. this pretty well explains the shape of the primer indentions i was seeing. another interesting observation is that at 3000 fps, the pin was happily just making funny dents in the primers, but at 3095, it was consistently piercing them.

on the positive side, I finished the day by shooting another 250 rounds chasing cans around a berm and just generally amusing myself. in a couple weeks, I'll go back to working on those 100 grainers and see if i can't get the primers to stay in the pockets.

another interesting observation is that the plating seems to be coming off the pin further back, at the 2nd place the diameter increases. i've inspected the rest of the BCG and can't find any flaking anywhere else. of course, the rest of it is steel, not aluminum underneath the coating.

and yet another interesting observation is that the SD was much higher when i was piercing primers. and the max and min were higher and lower, respectively, than all the normal rounds.

MAX MIN
3137 3015 when piercing primers
3105 3029 normal, unsuppressed
3124 3053 normal, suppressed

dcloco
June 16, 2007, 11:24 PM
That rifle has a firing pin and or head space problem...get it to the doctor.

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