Overpressure Signs ?

[thekyrifleman]

To paraphrase Bob Hagel in his book "Game Loads and Ballistics for the North American Hunter", increase your charge until you get a sticky bolt lift and then back off one or two grains....it is quite an interesting read from a man with a tremendous amount of practical experience......having said that some of his load data is really ambitious....after well over 40 years reloading I have found that most often best accuracy is obtained at that one to two grains under max.....which in turn gives excellent case life, etc., etc.,

 

[Barrelnut]

Although your not trying to be rude, you were by assuming I haven't read reloading manuals, just finished the Berger one last weekend. Lets see if you like your own medicine: Not trying to be rude but it's highly unlikely you have the experience and background that I possess. That being said I normally don't say that to others being that is simply not humble and a very assuming thing to say. Back to gun stuff, I know of the signs of overpressure but I wanted to get peoples opinions, reloading manuals always error on the safe side and forums can't always be trusted, I like to find a middle ground. Now why don't you play friendly and be a mature adult and tell me what the Hornady manual says, since again, you assume I have a Hornady manual; after all, this is why were on forums, to talk.

Joden

Oops sorry, if I was assuming anything. From your reply it is now obvious the issue is that you haven't read enough reloading manuals.

The Berger manual does not cover pressure signs much at all. The Hornady manual does, in detail, on page 70. Also on page 23 they show a pic and explain how to measure case head (web) expansion. Hornady states that even ".0005" expansion in the area can be a sign of high pressure. They also state that a very accurate micrometer should be used for this measurement.

A previous poster on this thread indicated that they measure the web for signs of pressure. From your reply, for more detail, from that poster, From your reply, I perceived that you did not know what a web was. And I don't think you did. So I suggested that you read more manuals. It is recommended by many that you read more than one reloading manual. I have several. Also I was not assuming that you had a Hornady manual. I was assuming, that if you didn't you would purchase and read it as I told you the instructions for what you were asking were in there.

Good luck with your reloading.

 

[thekyrifleman]

+1 BarrelNut.. Would also strongly suggest a copy of Sierra's manual. IMO probably one the most in depth technical sources of information available. I have Sierra, Hodgon, Speer, Nosler, Barnes, A Square, etc. some going back to the '60's. It is an interesting exercise to take a given manufacturer, and read the various editions from oldest to current. I frequently do this......excellent source of perspective.....lightbulb

 

[seidersjoden]

Oops sorry, if I was assuming anything. From your reply it is now obvious the issue is that you haven't read enough reloading manuals.

The Berger manual does not cover pressure signs much at all. The Hornady manual does, in detail, on page 70. Also on page 23 they show a pic and explain how to measure case head (web) expansion. Hornady states that even ".0005" expansion in the area can be a sign of high pressure. They also state that a very accurate micrometer should be used for this measurement.

A previous poster on this thread indicated that they measure the web for signs of pressure. From your reply, for more detail, from that poster, From your reply, I perceived that you did not know what a web was. And I don't think you did. So I suggested that you read more manuals. It is recommended by many that you read more than one reloading manual. I have several. Also I was not assuming that you had a Hornady manual. I was assuming, that if you didn't you would purchase and read it as I told you the instructions for what you were asking were in there.

Good luck with your reloading.

Yeah, your right, I need to purchase another manual, I was surprised Berger didn't cover over pressure but I was hoping from the internet I'd fill that void.

And to be honest I didn't know what a web was, but will continue to get more opinions while I order a manual from another company.

Thanks
Joden

 

[seidersjoden]

To paraphrase Bob Hagel in his book "Game Loads and Ballistics for the North American Hunter", increase your charge until you get a sticky bolt lift and then back off one or two grains....it is quite an interesting read from a man with a tremendous amount of practical experience......having said that some of his load data is really ambitious....after well over 40 years reloading I have found that most often best accuracy is obtained at that one to two grains under max.....which in turn gives excellent case life, etc., etc.,

Iv'e heard that just under max is accurate quite a bit. Just to be clear, when you say 1-2g under max you mean for example max for my caliber, for Retumbo is 99g, so 98 or 97 is what you mean, as in 2.0g or 98.9 or 98.8 as in .1 or .2?

I ask because some long range competitors use different terminology.

Thanks
Joden

 

[seidersjoden]

Reading pressure signs from cases and primers is somewhat of the black arts. If you load long enough you get a feel for high pressure. I personally feel if the bolt handle starts binding you are probably too hot. One of my tests using a bolt action is to point the muzzle straight up after firing and unlock the bolt. Without pulling back even the slightest amount I release the bolt handle and see if the bolt will extract the case fall from it's own weight.
Yes, I know there are variables even with this to include chamber dry or lubed, FL sized cases or neck only, etc. But my reasoning is:
The force to extract is pretty consistent compared to my subjective "feel".
If the case is binding enough to resist the bolt's weight then I should check things out.
If I am hunting I want the gun to work no matter what, etc.

I do not measure case head expansion because of the great variation of brass hardness between makers and, in some instances, differing lots from the same maker. That being said, too much head expansion across the web is bad ju ju. If I find it I back the load down.

I have always read primers because they have been the first thing to let go. A system fails at the weakest link and overloads have always hammered the primer first for me.
View attachment 34697
In the photo above are two Federal #215 primers that are known to have hard and thick cups. If the #215 is showing pressure you got issues. The left is an unfired primer seated in a 375 Ruger case. Two things to notice:
1) The radius at the perimeter of the primer is pronounced. That is, it is a larger radius than the other fired primer.
2) you can make out the seating punch indent in the surface. Primer surface condition can tell you a lot, including how rough the machining is on the bolt face. These primers measure 0.210" to the nearest 0.0005".
The right primer is from a 300 WinMag load of 150gr TTSX/ 79gr RL 19/ Fed #215/ 3.500" COAL. Velocity = 3349fps, SD= 9fps.
If you click on the photo and look at the radius of the outer edge of the primer it has sharpened up a lot. The slight cratering is from a light firing pin spring because every load in this Rem 700 craters to that amount, even the light development loads. Note the imprint of the bolt face on the primer surface. This gun has a rough bolt face and it makes reading the primer easier because the imprint sharpens up very progressively with increasing pressure. The tool marks are very well defined.

Back to the primer edge radius. If your head space is pretty tight this only occurs with high pressure. It is progressive. When punched out carefully the primers show a mushroom shape with the diameter at the radius measuring 0.212". 0.002" increase is the max I will allow with the #215. But if the radius forms a sharp 90 degree edge I take that as a touch too much. Usually at that point the bolt will not extract freely when the muzzle is pointed straight up.

This rifle is equipped with a PT II strain gauge and that load tests to 62Kpsi. The primer appearance is consistent with the "feel" I have developed over a 40+ year reloading career.

Just my two cents and a picture.

KB

Thanks a lot Kennibear, that was some great gouge, going to do a ladder test today. Until now one thing I haven't looked for is flattened primer edges; I've read that before but forgot about that particular sign, I'll keep an eye out.

Thanks
Joden

 

[semtex]

Reading the books is always a good place to start in my opinion. Then read them again.
One thing I have noticed over the years is the brass is the weakest link. I read that somewhere. Also many hand loaders have mentioned the number of times their brass for certain cartridges has been reloaded.
I guess it all depends upon what caliper you are loading for and how hot you are loading, but I have noticed sometimes that the primer pockets tend to get a little loose when the primer is seated. To me that is usually a good indicator that the pressure is up and the cartridge you are loading for is a little on the hot side.
Again, I have seen some reloads with new brass trashed after the first round, sticky bolts, and burn rings from where the gas escapes around primer. This usually tends to cut a little ring around the firing pin in the bolt.

I guess I am going to go out on a limb here and say this...if you look at just about any reloading manual notice that most calipers tend to start decreasing drastically after 200 yards...you can't beat gravity its just something you have to live with.

 

[Lefty7mmstw]

An interesting thing that I've heard of locally is the shoe test. It's probably more accurate than any primer or case reading as those are influenced by headspace and chamber dimensions and/ or brass softness. Take off your loafer (not a heavy work boot mind you) and tap the bolt open with it. If it doesn't easily open with a tap up and a tap back; you are likely too high and cruising for trouble.
Chronographs aren't perfect but they do give you a general idea what's happening as it takes a certain amount of pressure to do the work required to move a bullet to a certain velocity in a certain chambering with a certain powder. The more variables you introduce the less valid this premise is though.

 

[Kennibear]

Semtex
"I guess I am going to go out on a limb here and say this...if you look at just about any reloading manual notice that most calipers tend to start decreasing drastically after 200 yards...you can't beat gravity its just something you have to live with."

Let me introduce you to the 22-250. 3600fps with a 55gr 22 cal. bullet is laser flat to 400 yards. Try the Hornady 53gr V-Max pushed to 3900fps by a max load of CFE223. Sighted at 300 yards it does not rise more than 3" (2.9" 2 175yds) and drops only 7.2" at 400 yards. At a quarter of a mile (440 yds) it is down 12"/1'. How flat is your flat?

Back to pressure. When Oehler came out with the M43 PBL (Personal Ballistics Laboratory) I though Heaven had kissed the earth. At least for a couple of thousand dollars you could get a peck on the cheek. Pressure was by guess and by golly prior to that. The Pressure Trace II has moved the cost down another notch or two as the complete set with a CED M2 chronograph ships for around $1k. These two instruments move pressure from a good guess from visuals of a fired case to solid data on the computer screen. $1k is the price of a quality scope.

I am as good as anyone at reading pressure from a case and primer. Two years ago I went digital.

KB

 

[Lefty7mmstw]

Semtex
"I guess I am going to go out on a limb here and say this...if you look at just about any reloading manual notice that most calipers tend to start decreasing drastically after 200 yards...you can't beat gravity its just something you have to live with."

Let me introduce you to the 22-250. 3600fps with a 55gr 22 cal. bullet is laser flat to 400 yards. Try the Hornady 53gr V-Max pushed to 3900fps by a max load of CFE223. Sighted at 300 yards it does not rise more than 3" (2.9" 2 175yds) and drops only 7.2" at 400 yards. At a quarter of a mile (440 yds) it is down 12"/1'. How flat is your flat?

Back to pressure. When Oehler came out with the M43 PBL (Personal Ballistics Laboratory) I though Heaven had kissed the earth. At least for a couple of thousand dollars you could get a peck on the cheek. Pressure was by guess and by golly prior to that. The Pressure Trace II has moved the cost down another notch or two as the complete set with a CED M2 chronograph ships for around $1k. These two instruments move pressure from a good guess from visuals of a fired case to solid data on the computer screen. $1k is the price of a quality scope.

I am as good as anyone at reading pressure from a case and primer. Two years ago I went digital.

KB

Pressure Trace is decent... I've had it on a rifle before. It was an older iteration of the system sold in the mid 2000's and while it worked the gauge would come loose from the barrel rather quickly... sub 50 shots if I remember right. If they can overcome that issue I might go back but you were installing a new gauge every time you wanted to pressure test on a rifle you shot a lot. Have the gauges gotten more robust or are they still rather fragile?

 

[1100 Remington Man]

I have been a Fan of Bob Hagel also & that is a great Book. I do the same & follow his advice.

 

[Clark]

... brass is the weakest link. I read that somewhere.

P.O. Ackley "Volume I Handbook for Shooters & Reloaders" 1962 Quotes Vernon Speer on page 148 and 149:

"There is a tremendous difference in the way different rifles handle pressure and it is entirely possible that a rifle used in one test was different in this respect than another one we used. We do not have a pressure gun in our laboratory, because it is in my opinion, backed up by quite a few years experience, as well as firing data from various laboratories pressure guns that data received from them is exceedingly unreliable. For a company such as Remington or Winchester having the same gun and operator comparable results to check on production problems are no doubt sufficiently accurate for the purpose for which they are used.

We use the head expansion method in determining the pressure at which a cartridge case was fired. It is our belief that the cartridge is the weakest link in the modern bolt action rifle. If the pressures at which the cartridge cases are fired do not exceed the elastic limit of the unsupported rim of the cartridge case, then we consider that the pressures are entirely usable, regardless of what they might be. We fire increased loads, increasing the charge at about a grain at time, checking the rim diameter of the cartridge case with sensitive measuring instruments, both before and after firing. If any measurable increase in the diameter of the rim of the case is noted, we consider that pressure excessive and reduce the charge about 6% and list it as a maximum load in our loading table. There is no reason why the handloader cannot use this same procedure himself and determine whether or not the loads he is using are safe and practical for use in his rifle.

In our laboratory we look for all signs of pressure such as sticky cases, tough extraction, flattened or cratered primers, as well as the rim expansion method noted above. Some cartridge cases are softer than others, notably Norma cases, and will not stand the higher pressure loadings possible in Remington and Winchester cases. This tends to bear out our contention that as long as the brass cartridge case is worked within the elastic range of the brass, then the pressure in the pounds per square inch, whatever it might be, is safe and practical for use in that particular cartridge. I hope I have been able to explain this pressure problem to your satisfaction.

Vernon D. Speer, February 6, 1958"

 

[Kennibear]

Clark
Read P.O. Ackley's V I & V II at least twenty times. A must read for every shooter. V. Speer's comment on Norma brass was decades age and does not apply today. The sections on barrel steels and case shape/capacity are eye opening. 100+ recommended read.
Lefty
The new setup from RSI includes a gel superglue that works fine. Major key to a successful strain gauge install is a surgically clean surface and LOTS of pressure for 24 hours. I use a SS hose clamp over plastic shim stock but cut up old squeeze bottles works too. Tried LockTite HyPo E-120 epoxy w/ cure @ 150F and post cure @ 250F but the epoxy shrank so much the gauge was off by 40Kpsi.
I also paint the gauge and leads over with varnish (not lacquer) as it keeps atmospherics from attacking the cyanoacrylic bond.
The cleaning for me is; nitromethane, citrus stripper wash, laquer thinner series. Not to offend the RSI folks (they are great!) but I buy my strain gauges from the maker 8 at a whack. I could do an article about strain gauge installs for LRH if Len wants and enough members would be interested.

The biggest warning I have for members is watch closely for sign of high pressure as they are subtle and pressure spikes fast!

KB

 

[Clark]

I do not use strain gauges on rifles.
My father used one on the M107 artillery design, not for pressure during firing, but to tell if the round was loaded properly.

I have plenty of CEA-O6-250UW-350 strain gauges and I have designed much better instrument amplifiers than the ones Oehler sold. But that is not to say I waste my time reading my storage scope instead of my brass.

The problems that are insurmountable with strain gauges are:
1) The absolute pressure does not matter in the quest for finding the limit of the weak link, brass.
2) The absolute pressure is hard to measure
...a) We cannot mount the strain gauge accurately
...b) The Roark equations for stress vs strain in the complex shape of an open ended tube are almost insurmountable
...c) The error calculation in traceability to NIST is nearly impossible, making absolute measurements meaningless.