Home Forums Hunting & Shooting Ask The Gunwriters MARCH column: Primer Flattening

Steve692


Forgot to take your meds again...…………….


Lefty

MD, I have always enjoyed reading your articles and consider you to be the best common-sense gun writer since JOC.
Your latest article on primers is no exception.
I would like to ask you a few questions. I have been reloading my own ammo for roughly 40 years. I too have found that primers are a very poor method for determining pressure and for all the reasons you stated.
First, I would like to ask you or anyone else here if you have ever seen an example of excessive chamber pressure WITHOUT having a flattened or blown primer? Personally, I have not or at least not ever thought so.
Second, what are the signs that you personally look for to determine if you are at the high or top end of your powder loads?
The reason I am asking this is just this week, I am working up a load for a 270 Win. with a custom barrel. I am using an 8# keg of H-4831SC which I have not used much of. I have worked up to 58 grains of the H-4831SC under 150 grain Nosler partitions with CCI 200 primers along with Lee Collet sized Winchester cases that were fired in the same rifle but with Accurate 4350.
With the H-4831SC, I have already exceeded any book loadings by at least 2 grains and the velocity over my Chrono is still somewhat anemic and far below book velocities.
As of yet, there are no flattened primers. By that I mean the primers are not filling the primer pocket up as is the norm in a high pressure load. There is some primer cup flowing in to the firing pin hole of the bolt face. But there is NO hard bolt lift and the cases extract easily.
For me, bolt lift AND ease of case extraction are the “go-to” indicators for excessive pressure, which is always accompanied by flattened primers at this point.
What are your thoughts on this?

Sorry I haven't responded! Tend to miss the questions on the specific columns, because there usually aren't many after a week or two.

I have had the same experience with recent manufacturing lots of H4831SC, with both a total lack of "pressure signs" and low muzzle velocities. Consequently I've been pushing the published muzzle velocities by 100 fps or so, and usually get better accuracy as well.

But these days there are also other good powders for the .270 with 150-grain bullets, including Alliant Reloder 26, IMR 4955 and 7977, and Ramshot Magnum.

excellent article!
thank you

makes us pause again when someone writes about their particular load, often over those published in manuals, showing "no signs of excess pressure"

/Good article but when I reloaded I used the primer flattening method. For me they only flattened when I was close too, at or above the maximum recommended loads. I liked ball powders because they worked so well in my powder measure but you have to run them at higher pressures or they don't burn clean. The primers started flattening and I'd back down from that until they didn't It seemed to make sense to me. Especially since I never had factory ammo primers flatten.

Just enjoying some pre-Thanksgiving pumpkin pie. Hope all of you are having an equally enjoyable evening.

Two comments:

MD is correct in recalling my test of pressure vs. flatness. A few years ago, I had a fit of ambition and started an article on evaluating pressure by looking at primers. So I loaded a couple of dozen cartridges ranging from mild to maximum, and touched them all off. Then I extracted the primers, marked them, and put them under a bench microscope. I arranged them from roundest to flatest, and found no correlation between powder charge and position in the arrangement. That article never saw the light of day. Bummer.

Again a few years ago Ken Oehler instrumented a pressure barrel with two piezo transducers, each feeding identical electronic channels. He also instrumented the same barrel with two strain gauge channels. Then he fired a series of shots ranging from pea shooter to bazooka. Given that data set, it was not a great task to derive the fundamental precision of both systems, as well as their accuracy. It turns out that each is as good as the other. Neither has a theoretical advantage. Which you use is simply a matter of convenience. The strain gauge system has the advantage of not requiring a hole in your chamber, and the physical quantity conversion chain is a little shorter than that of the piezo system.

Many people get hung up on the notion that they can't very well check the strain gauge against a known standard artifact. That's really not the problem they think it is. We know the rest mass of an electron to great precision, yet no one has ever built a suitable scale and wrestled a single electron into the weighing pan. We know the distances to the stars, but no one has ever laid a ruler along the path to one. There is no standard velocity artifact you can use to calibrate your chronograph. (Rumor has it that NIST did have some at one time, but someone peeked into the containers, and the standards all disappeared into the bush at highly accurate velocity.) There are no standard weight artifacts. What we think of as weight standards are really mass standards. Many of the measurements we confidently deal with on a day to day basis have no directly comparable calibration artifact, and we still get along just fine.

denton,

Always appreciate your observations. Thanks once again!

But would also have to comment that the head of a major powder company's ballistic department disagrees with the strain/piezo results. But that's not unusual in such, uh, sensitive topics.

Might also note that have talked to a couple of long-time heads of major pressure labs. One recommened two specific brands of primers (one SR and one LR) as the most consistent in their tests. The other guy also recommended two specific brands. Neither man's recommendations matched the other--and both had been in their job for decades.

great stuff
thanx

OMG! I'm getting a head ache reading this. I can see the merit in MD's writings. I admit I have been of the opinion that a flat primer meant it was time to back off. But reading this thread is enlightening me. I may be getting ahead of myself here but i'll make this statement. I believe that if you have a real case of high pressure that you will ;probably see a flat primer. But you will see other tell tale signs as well because after reading MDs post I believe that there are at least a couple different things other than pressure that can cause a flattened primer and that if you have a flatten primer and no other signs of high pressure you probably haven't experienced high pressure. The few times I've experienced real high pressure there were several signs of it. One, and the first thing I noticed was a sticky case and hard opening bolt. Another big one that will go along with that is wildly fluctuating velocity and accuracy or just abnormally high velocity. And the biggy, the one that's not readily noticed is an excessively expanded cartridge case base which is determined with the use of a micrometer. Of all the signs I've ever heard of that one is my main one that makes me believe I've experienced excessive, potentially harmful pressure. But I also think that you'll see more than one sign if it's really high pressure. Like I said. correct me if I'm wrong because these are just my opinions.

I would simply say this about excessive pressure. For me, these three happening together give me pause.

1. Felt recoil increases.
2. Chrono display is higher than normal.
3. Primer looks unusual.

Stop.

Don't worry about what was written in this thread. If you follow a manual, and your scale is okay, you are good to go.

article is a joke

About primers. pressures and powders: First, an anecdote about primers in two different .35 Whelens, both single-shots; and then a third .35 Whelen is involved.

The first .35 Whelen was an M7400 (semi). Everything worked well... never a problem, though some handloads were likely over pressure, yet I never used "small base" dies. That 7400 was as tough as any bolt action in ejecting fired cases. Though one load - a book load - did blow a couple of primers. It was a tough, accurate rifle that eventually got sold. A few years later, I went looking for another .35 Whelen and came home with a single-shot NEF. I also bought 50 new Rem cases in .35 Whelen. Loaded up some of the old brass used in the 7400, and some of the new brass, both with WLRM primers. The NEF would not fire the loads with the new brass but would with the old brass used in the 7400. I thought there was a head space problem so took the rifle to my smith who said the chamber checked out. Also, when returned to the place where purchased it would fire Rem factory ammo. I was then stuck with 50 new cases that needed fire-forming. That was my thinking so exchanged the rifle where purchased for one in .45-70. Sometime later, I went looking for another .35 Whelen, couldn't find one so came home with a 9.3 x 62 - no regrets there.

Recently, on an impulse, I purchased a Traditions OUTFITTER G3 single-shot in .35 Whelen with a 22" barrel and brake... It fires those same new Rem .35 Whelen cases primed with the WLRM primers! The apparent real problem with the former NEF was the hammer spring was relatively weak compared to this Traditions that whacks them like a sledge hammer!

Plus... as MD has talked about, there was a slight difference (within specs) for the head-space in favor of the TRADITIONS that has a very tight chamber!

And Steve R., new powders have made a great difference for handloaders of the .35 Whelen... in a positive sense. Plus 200 fps within SAAMI specs for a 250gr. And that's not 2600 fps but 2700 fps from a 24". So technology continues to improve matters over traditional concepts. Check Speer's Manual #14. I've recently been testing the 225gr NAB using CEF223 with excellent results that tradition would have expected from a .338 Win with a 22" barrel.Of course... it too has been "improved" by better propellants.

Bob
www.bigbores.ca

I agree, Bob. Propellant technology continues to evolve.

For me, when these three things occur at the same time, it’s time to double check things.

1. Felt recoil increases.
2. Chrono display is higher than normal.
3. Primer looks unusual.

MD remembers correctly.

I wanted to do an article on flatness vs pressure. So I carefully prepped and fired a batch of ammunition with various powder charges, using primers from the same box. Under a microscope, I arranged them from roundest to flattest. I could see no detectable correlation between flatness and powder charge.