Do these primers look flatten?

[fella5]

I just started to load .223 REM using Lapua Brass, Sierra 80gr MK, Varget and CCI BR4. The COAL is around 2.570 and my base to ogive is 1.052... 0.020 off the lands. Do these primers look flatten to you? I keep on second guessing myself. My best group was using 22.7 (0.801 MOA) and 22.8 (0.872 MOA). Using OnTarget. My groups at 23.9 and 24.0 where starting to group closer after opening back up after my starting load. 24.0 (1.137 MOA) and 23.9 (1.033 MOA). So I wanted to go higher to see if I can get a tighter group. Here are some images, the two on the left are unfired. It was too windy for my chrono to stay put so no velocity reading

[ScottRiqui]

I don't use that powder/bullet combination, but those primers certainly look flattened and spread compared to mine (CCI #41 primers, 62 gr bullets and a mid-range load of H335.)

You've posted some really good pictures, though, so I'm sure lots more people will chime in.

[snuffy]

Do you mean flattenD? So what, they're SUPPOSED to be flattened.

If you mean you're trying to read pressure from how much the primer is flattened, forget it. They LIE!

What firearm were these fired in? Rifle, handgun, machine gun? AR? Bolt rifle?

Without velocity readings, you're groping around in the dark.

[Nnobby45]

Under a lot of pressure, oh let's say 50,000 lb., the case has to stretch rearward until the case head and primer slam into the bolt face. That, of course it what keeps the primer in the case, since it's trying to launch itself in the opposite direction as the bullet. However, there shouldn't be too much flattening.


Flattened and cratered primers, and primers that are loose in the pocket would be indications. Especially loose primer pockets. If you had a sample of a flattened and or cratered primer caused by high pressure, you could see the difference. I think a good manual would provide that info.


Most of them look alright, but when you get to 23.9 and 24 you can see they've flattened out a little more, reducing that dark circular ring area next to the primer pocket rim--but only slightly. Can't say their pressure is too high.


For bolt action rifle shooters, BEWARE if the bolt is difficult to open, or even sticks a little. Then you've really exceeded pressure standards.

[fella5]

I'm shooting an AR-15 with a 16" barrel. I always read and was told to look at pressure signs... Especially the primer.

[Jim243]

No, those look fine, you are using BR4 primers and I would expect to see them a little flatter than a standard primer. No flow to full primer pocket and no distortion of the firing pin dent. Looks like the 22.7 grain would be the best for your rifle. For your AR I would move the OAL to 0.050 off the lands instead of the 0.020 that you are using. Works better in my AR seems that they need a slightly longer jump.

Jim

[Ifishsum]

By all means I look at the primers for danger signs, but you can't read too much into that factor alone really - for example an oversize firing pin channel can cause cratering at starting loads, but it doesn't mean you're over pressure. Yours look okay to me but I don't think I'd go further, personally I wouldn't try to push an AR15 (all semi-autos really) with really hot loads anyway because you won't get much feedback before you're over pressure and blowing primers. With my 20" A2 I tend to get my best groups at 1 to 2 grains under max anyway.

I'm much more comfortable working up to max loads in a bolt rifle, because I'll get other warning signs such as sticky bolt lift. Sometimes I'll get that even when the primers still look fine. What other pressure signs are you looking at? I think the point Snuffy was trying to make is that you can't make a pressure estimation by reading primers alone.

[fella5]

Thanks for all the feedback. The other signs I look at is the base of the case and also the rim of the case to see if I see any ejectors marks. I don't see any of these on my once fired case. I'm thinking maybe I should seat the primers deeper. Currently I have them seated at 0.002.

I will try to seat the bullet futher out from the lands too.

[demigod]

Those primers in the top pic are flat as hell! But if there's no primer flow, you may be OK.

[Loader9]

Hodgdon says that 25.0 grs is max with that bullet. Looks like you're pretty close to max.

[snuffy]

OK, we're getting closer to knowing a few facts. Need more. Like, what twist rate is your AR? A 80 grain match bullet is very heavy-for-caliber, and very long. Both combine to say you need a 1-7 twist barrel to completely stabilize that bullet. Then you probably won't get complete stabilization with starting loads. Then, you're using a "short barrel" for match bullets. The short bbl. won't provide max velocity, again they probably aren't completely stabilized.

Then comes a real question, why were you doing accuracy shooting on a day where the wind wouldn't allow a chronograph to stand? And another ?, at what distance were the targets? 100yds?

My comments that primers lie DID mean you can't judge pressure just from primer appearance. ESPECIALLY in an AR or other semi-auto platform. Case head appearance is another non-factor. Extractor marks have little to nothing to do with pressure.

If you want to get real techie, get a 0-1.00 micrometer that reads to .0001 IF you know how to use it AND read it. Then measure the pressure ring about ¼ to ½ inch ahead of the extractor groove. That's called PRE or Pressure Ring Expansion.

Another tool is required to measure the case head expansion, a knife edged micrometer also capable of one ten thousandths accuracy. It measures expansion at the bottom of the extractor groove, or CHE, Case Head Expansion. Brass flows under pressure and will get bigger at these two locations on a brass case. Accurate measurements will tell you when to stop adding powder.

[Clark]

I don't care about primer flattening.
I do care about case life, from loose primer pockets.

[Gunplummer]

I don't know, some of the firing pin indents look pretty ugly to me. May be a little hot.

[fella5]

Well my AR has a 1-7 twist and the reason I went shooting was because I didn't want to drive to the range and not shoot anything. So I went ahead and shot of my reloads. I looked at some factory Federal brass and the firing pin indent Looks the same as my reload. Oh... Target was 100 yards.

[farmerboy]

they look fine. I dont blame you for driving to the range and not being able to shoot anything, even if most of ammo could have been pretty much wasted as far as patterning goes. There's still cycling, trigger control and just having fun burning some gun powder and getting more use to your firearm, I do that quite a bit as well. Anyways, youre on the right track, keep reloading, keep shooting and keep having fun in the process. Read alot and ask alot and then make your own choices on what you need to do or not do.

[Nnobby45]

I don't care about primer flattening.
I do care about case life, from loose primer pockets.

Ah, Jeez, Clark. Pressure high enough to cause loose primer pockets will likely flatten primers. How do you separate the two if you're concerned with the primer pockets?

[Loader9]

If you want to get real techie, get a 0-1.00 micrometer that reads to .0001 IF you know how to use it AND read it. Then measure the pressure ring about ¼ to ½ inch ahead of the extractor groove. That's called PRE or Pressure Ring Expansion.

Another tool is required to measure the case head expansion, a knife edged micrometer also capable of one ten thousandths accuracy. It measures expansion at the bottom of the extractor groove, or CHE, Case Head Expansion. Brass flows under pressure and will get bigger at these two locations on a brass case. Accurate measurements will tell you when to stop adding powder.

Snuffy is obviously older than dirt and been reloading just about as long. This is the way we gauged pressure 40 years ago. It worked then and is still the best way to determine what max pressure is for a certain load in a particular gun.

[wncchester]

" I always read and was told to look at pressure signs...

That's certainly true.


"Especially the primer. "

That can be true. But it's the poorest high pressure "sign" we can look for, other much more common things such as setting your case shoulders back too far will produce flat primers. Perhaps you should compare your primers to factory loads, at least that will give you something to gage against.

So, why are flat primers so commonly mentioned? Well, it's an easy way to sound knowledgeable, isn't it? But much more relivant signs are:

1. Createred primers (also can be caused by an oversized firing pin hole or a weak pin spring)
2. Sticky bolt lift or extraction.
3. Impressions in the head showing where the ejector port is.
4. Bright brass showing where the head was shaved by the ejection port.
5. Smoky leak circles showing around the primer pocket
6. Primer pockets that get loose after two or three or four firings are less dramatic but are certain signs of excessive pressure.

[GP100man]

I`m comfortable with the 23.4 gr loadin !

Just too many variables to judge pressure with primers , soft cups headspace .

Each rifle is an entity to itself !!

Measure the head of the case near the web of the cases , ya need a new unfired case to compare the ones ya got .

I have blown primers before reachin max velocitys published & the cases extracted fine , so I feel primers are the limiting factor most of the time instead of case integrity.

[fella5]

Well thanks eveyone for your input. I will go out this Sunday with some more ammo and a chronograph. Going to see if the 22.7gr is going to be the one for me. Going to shoot the 100 yard, 200 yard and 600 yard range. I also reloaded some that sit 0.030 and 0.050 off the lands.

[snuffy]

Snuffy is obviously older than dirt and been reloading just about as long. This is the way we gauged pressure 40 years ago. It worked then and is still the best way to determine what max pressure is for a certain load in a particular gun.

Yup, knew him as a baby and know him by his first name! Dirt, that is.

[Unclenick]

I've had a list of pressure signs up on another forum for awhile. It is here. I included alternate causes of the same symptom where I could. As of today, the list is up to 32 pressure signs, though not all are applicable in all guns.

None of the pressure signs tells you pressure in psi. Even PRE and CHE only tell you that the particular piece of brass you just fired has expanded more than you like. It can take firing a number of them to determine whether you have a real pressure sign or a fluke. Denton Bramwell measured one lot of 7×57 with the same load history and pretty much showed a nearly 2:1 pressure range getting the same amounts of expansion from one case to the next. This is against a strain gauge pressure reading that has it's own resolution limits, but at least is very consistent. Reading an actual PSI into case head expansion is akin to running a copper crusher, an already a not-too-precise system, but substituting a completely uncalibrated slug, which the case heads and pressure rings are.

That said, if you watch for all pressure signs, you can get a heads-up that you are approaching a limit for your gun or brass. Any given pressure sign may fail to appear in time, but usually at least one of them warns you to check what you are doing. If you get a sign and you are also exceeding manual recommended load limits, then the chances are greater that the pressure sign is a legitimate warning than if you get it with a starting load. Unfortunately, that's about as precise as you can be. A chronograph is useful as another indicator. Velocity significantly higher than that obtained for the same barrel length with the same powder charge and bullet weight in a manual is pretty solid evidence your pressure is higher than the manual authors had, for whatever reason. The manual authors run their chrongraphs at 15 feet, and you should, too. False high and low readings at closer distances are common, due to muzzle blast.

Regarding primers, Federal recommends that small primers be seated 0.002" beyond the point where the primer anvil touches down on the bottom of the primer pocket. In .223 that will often be around 0.004" or .005" below flush with the case head, though it depends on the brass. There are problems with primers not fully seated as to ignition reliability and pressure irregularity, but I am unaware of any serious penalty for seating them a bit too hard. Indeed, one of the authors of the Precision Shooting Reloading Guide says seating hard is essential to getting velocity extreme spread down to the 10 fps range. You would think it would over crush the pellet and make it less reliable or consistent, but this fellow swears otherwise and I've not seen it, either. In any event, in something like an AR that is not a benchrest gun but that does have a floating firing pin, erring on the side of pushing primer in too hard makes more sense than the opposite.

I recommend a particular technique for measuring primer depth. Assuming you don't have a depth micrometer, setting a caliper on top of a case and pushing the depth stem at the back of the beam down against the primer easily produces false readings. Instead, zero the caliper, set the stem out a quarter inch or so, bring the center of the seated primer squarely up against the stem, then slowly push the stem up with the primed case until it stops against the end of the beam. You are more likely to end up with the case head square and the reading accurate.

[Clark]

Nnobby45
Senior Member

Join Date: November 20, 2004
Posts: 2,009

Quote:
I don't care about primer flattening.
I do care about case life, from loose primer pockets.
Ah, Jeez, Clark. Pressure high enough to cause loose primer pockets will likely flatten primers. How do you separate the two if you're concerned with the primer pockets?

I find that measuring any changes around the extractor groove is a better pressure indicator and precursor for loose primer pocket than either waiting for the primer to fall out or measuring the primer pocket with pin gauges.
That is because the spent primers can stay in there like hanging chads, and the expansion is often not symmetrical. The non symmetrical expansion can be found by turning the calipers relative to the outside diameter of the extractor groove, but round pin gauges are blocked if any part of the primer pocket maintains the original diameter. When I developed this system, ~ 5 years ago, it was suggested that I find "D" shaped pin gauges, but I have not done that.

The best measurement I have found [for detecting primer pocket changes] is dial calipers on the extractor groove before and after firing.
The extractor bevel is aligned with the jaw bevel. That means the dial is pointed toward the case mouth.
The force of the jaws on the extractor groove is kept constant, and the case is rotated.
A min and a max are noted.
The cartridge is fired and the measurement is repeated.
If any change in the brass is detected, that is the end of the work up and the powder charge is reduced from there by a safety margin for useful loads.

I don't have any other followers of my technique yet, but I think I know what I am doing.

[snuffy]

I don't have any other followers of my technique yet, but I think I know what I am doing.

Well ya do now, or will as soon as I go to the range next time! Clark, thanks for thinking outside the box for us! I can occasionally do that, but I never thought of that one!

The use of a dial type caliper would be similar to a dial indicator used in machining metal in lathes and milling machines. The amount of differences in the outside diameter of the bottom of the extractor groove will be tiny, but should show up when done before and after with the same case. Expansion in this area shows pressure.

In my above comments, using a knife edge micrometer, The difference from factory new cases to excessive expansion is around .0003 and no more. That should show up with a quality dial caliper as a slight increase of the needles travel between a single .001 mark on the dial. Visually splitting a .001 increment.

[Clark]

snuffy
..The difference from factory new cases to excessive expansion is around .0003 and no more. That should show up with a quality dial caliper as a slight increase of the needles travel between a single .001 mark on the dial. Visually splitting a .001 increment.

Micrometers may be way better than dial calipers for absolute measurement, but in skilled hands, the dial calipers can make very good relative measurements.

The key for me was getting the repeatable measurements with dial calipers was practicing measuring pin gauges and interpolating between the .001" marks on the dial.

That is not really that important for extractor groove measurements in work ups.
Typically, it is something like:
7) 49 gr. extractor groove expands .0000"
8) 50 gr. extractor groove expands .0020"
9) 51 gr. extractor groove expands .0020"
10) 52 gr. extractor groove expands .0110", primer fell out

One only needs .001" resolution to find the change.
The max practical load is going to be 47 or 48 gr for hunting big game long range, and 46 gr for zillions of shots at varmints.