Hey all,

When working up a new load, at what point do you say, "O.K, I've reached or exceeded max for my gun" and cease further shooting of that load.

I've always thought, besides flat or loose primers, that scaring on the case head from the bolt face or extractor was also a tell tale sign of excessive pressure. Today, I was told otherwise by someone I feel to be a fairly knowledgable loader. He said scaring is a sign of pressure, but not dangerous pressure. Is this true?

I've been working up loads for my 270 Wby and have experienced scaring, but the primers and pockets look fine. Is this ok, or should I consider this over max even though the primers look normal?

Thanks.

Are you chronographing as you go along? Pressure follows velocity.

I don't think the scarring is an issue ;brass flow back into the ejector slot, or hole(shows as a shiny spot on the case head)is a sure sign you have gone too far.

In a rifle with a blue printed action, a perfectly flat boltface perfectly perpendicular to the barrel, a firing pin with a perfect fit pushed by a strong spring, and a chamber with minimum headspace, when pressure signs show up, pressures will already be too high.

In rifles with lousy fits, pressure signs will start being evident before you reach maximum recommended pressures.

That is my belief.

A very reliable indicator is velocity, like BobinNH suggests, as it ain't nothing as a free lunch.

Just my two cents.

All the pressure signs really indicate is that the brass has
begun to yeild and has little strength left. Time to back off.
Good luck!

Velocity is the best indicator that us average guys have. If you ain't running them through a screen you are flying blind.

+1... Steelhead has it right! Most modern manuals are way more conservative than the older ones..I have some older Speer/Sierra/Lyman and Hornady manuals that have loads listed that I could't even come close to approaching max loads...Chronographs are relatively inexpensive today and the very best way to monitor pressures in conjunction with NEW manuals...if you do lots of reloading they are money well spent... ....FLEM

Thanks for the reply's everyone.

I am using a chronograph. The manual shows 3414fps for a 130 grain bullet with the powder weight I used. The two rounds I fired(which left ejector marks)chronoed 3459 and 3470. So just a little above book velocity. I don't consider this to be too abnormal. I have a 25-06 that often exceeds book velocity without showing signs of pressure.

Sorry for sounding like a neophyte, but how do guys use your chronograph to determine max or above max loads?

Thanks.

+ 1

There's nothing wrong with using a chronograph, but velocity isn't the last word on pressure.

I keep a close eye on the condition of the fired primers. Reading them is an inexact science, but I don't like to push a load to the point that the radius around the edge of the primer disappears.

One well known and published load for a .243 will iron the primers flat as a pancake in one of my rifles.

I have read that while working up loads ( same components as in the loading manuals, barrel length, etc. )you should not exceed book velocities to insure safe pressure. Is this true ?
What if you use a different brand of brass or type of bullet or primer ? How do you compensate for this ?
Basic questions but something to be concerned with, IMO.
Would appreciate any advice. I watch the Oheler 35, check Quick Load, and inspect the fired brass and primers. What more should I look for ?
Thanks,
Jim

IMO here, if you're getting velocities above book max I wouldn't press on...50 -75 FPS above max isn't going to help you that much anyway and then there's case integrity and other issues you may have to address...Most modern firearms will handle stout loads many of which are not the most accurate but why push the envelope..not really necessary at all...If you get the accuracy with the velocity the manuals list then it's time to stop.... ....FLEM

It depends on which book you use.

Lots of really good advice already given.... just a couple more comments.

Different rifles will give different pressures with the same load. If your MV is above the published MV for a given load, it's a good bet that you are also above the recorded pressure for that load. 50-75 FPS doesn't seem like much, but in common hunting size cartridges it indicates about an extra 2,500-3,500 PSI.

Pressure signs tend to kick in at very roughly 70,000 PSI. As stated, much too much pressure. I've not heard the comment about them showing up earlier in less precisely made firearms, but I suppose that is possible.

SAAMI pressures are supposed to be measured at 70 F. It is normal, and apparently alright, for pressure and velocity to be higher if the barrel and ammo are at a temperature higher than this.

Hope that helps. Good luck with your project.

A big plus 1...
IIRC...& that is not always the case...I don't think there is a SAAMI spec. or standard established for Weatherby cartridges as far as pressure goes...3400 fps is what the factory rounds are published at & if you're getting 3400 + along with ejector marks I'd back off at least a grain & see how it goes...wby ammo is loaded about as hot as they can safely go.

Chronographs are a great aid, but not everyone has one or can afford the luxury.

All of us curmudgeons had to get by without chronographs and pressure testing data, and most didn't even have but one loading book..

GENERALLY SPEAKING:
1. The first sign you will see is a flat primer and it may or may not be an indication but do not ignore it and proceed carefully from that point on.

2. The next sign will be an ejector mark on the case head and it will be a small square mark.

3. Next will be a burned black ring around the primer and 1 and 2 can be reversed at times.

4. Probably a sticky bolt if your lucky

5. A blown primer and enlarged primer hole

6. stuck bolt accompanied by a missing extractor perhaps depending on the make of the gun. I will add that sometimes you will hear a crack as opposed to the usual boom, that sounds different, beware of that.

7. A loud exploscion that you may or may not hear or it may be the last thing on earth that you hear!

The order of the above can be questionable and argueable and can be out of order at times, but its close and gives you a starting point and an understanding of what your dealing with..

Whatever order it occurs be prepared to back off and always keep in mind that 100 FPS makes absolutely no difference in killing power or anything else for that matter so why try and squeeze every last drop of velocity out of any cartridge, but such advise on many ocassions lands on deaf ears..

I'll just make some comments on what Ray posted, then a couple more in general:

Flattened primers can also be caused by a slight amount of headspace. The fikring pin shoves the case as far as it will go into the chamber, so the very rear of the primer isn't supported and expands more than normal. Then the case backs up over the primer, making it look VERY flat, but the problem isn't necessarily excessive pressure.

Also, some primers flatten a lot more easily.

Ray obviously only shoots 98 Mausers, pre-'64 Model 70's and others with an ejector slot. Many of those blasted push-feed rifles leave a round mark on the case head.

Also, once in a while a rifle will have a little ridge around the ejector slot/hole that leaves an imprint on the case head even with mild loads. Usually this is with a new rifle, but I've seen it on well-used rifles.

A chronograph is indeed the best pressure-indicator for handloaders. But the most accurate results by far are when using exactly the same bullet as used in the manual, since today various bullets of the same weight and diameter create widely different amonts of pressure.

I have had more than one professional ballistician tell me this in recent year, long after I had come to the same conclusion myself. In fact I wouldn't even call a chronograph a pressure indicator, I'd call it a measurement device, because the connection between pressure and velocity is so consistent.

I'd agree the chronograph is a vital tool. But the sign I use most particularly in wildcats ... when the bolt shows a touch of resistance to closing on a fired case.
Cheers...
Con

Actually it is the primer firing that pushes the case forward.
With a light load and headspace the primer stays projecting out.
At somewhere around 40 KPSI the case comes loose and backs over
the primer. If the pressure is high enough the primer will have
bulged and when it comes back it looks like a rivet.
Good Luck!

This has been posted several times by different posters, but I don't think once more will hurt anything, and might help.

When you reach any of these high pressure signs, your are already well over safe and SAAMI pressures.

The problem is, you don't know how much over.

An additional good way to measure things...using the bolt as a "feeler gauge".I do this with M70's by pulling the firing pin assembly and chambering the fired round.There is less camming power that way and you can "feel" the resistance if brass has swelled too much and failed to "bounce back".

Steelhead got to the point in an economy of words and is spot on

With some rifles/cartridges you'll notice a trend. As you go up in powder (say .4gr) you'll see the velocity climb. It won't be linear, but you'll see say something in the vicinity of 17~25fps. All of a sudden you'll see the velicity climb by a low number, or even loose velocity.

Here's your sign...

In addition ... this point appears to be about 1.5-2gr (with large 308sized cases ... not a 22Hornet) of powder below where you'll notice sticky extraction on opening the bolt.
Cheers...
Con

I agree 100% with your posts John. I also agree that a chronograph is nothing more than another aid, its not the "where with all" or the "2nd coming", but it is an indicator. My post was a guide only based on how we did it back when there was no other way, but these steps worked even then if you were flexible and used the prime component of handloading and that is a 1000 grs. of common since..Any one componient by itself tells you little but when you start putting them together, it starts to make since.

BTW whats a push feed?

I do load for some lever guns you know, I just praised you in another thread for your contribution to my useing Varget, and your advise to me turned my 99F, .308 into a world class bench rest rifle! May Allah raise you amongst the exhaulted for that, and may the good Lord take a lik'en to you.:)

If your chamber is the least bit oily, you will have scuffed case heads and flattened primers. I use a 12ga shotgun patch with lighter fluid on it to clean the chamber, removing any oil or bore solvent that could be in there.

Another indication is the bolt hard to lift? Do you have to full length size the brass after each firing?

Brass will vary in hardness by up to 12% in the same lot, some softer, some harder.

Another issue, Weatherby brass is SOFT!

While you are getting pressure signs in soft brass, brass made from 264 Winchester (winchester brand may not give you pressure signs at all).

Good luck!

Keith,

Actually, I have had pretty good results from Weatherby brass in recent years. Just bought yet another .270 Weatherby this spring, along with new brass, and am getting 3400 fps with 130 E-Tips without the slightest sign of softness.

Have also used quite a bit of .240, .257 and .300 Weatherby brass in the past 3-4 years with no problems getting top velocities.

Ditto, I've had no issues with 'soft' Bee brass in the 257 and 300.

It's soft...I had it Rockwell'd along with Fed, Win, and Rem.

Federal is neck and neck with the bee brass.

Keith,

So what?

If Weatherby brass doesn't show expanded primer pockets (or any other sign of "excessive pressure") when shot at maximum/velocity/pressure loads, what difference does it make if it's softer than X brand brass?

Actually the case comes back with the same force with an oiled
chamber. What happens is that it comes back at a lower pressure
then stretches forward. This avoids the "stress ring".
The old timers used an oiled case as a proof because otherwise
with low pressure cartridges the locking mechanisms wern't being
tested. That is why Ackley could fire a 94 winchester without a
locking bolt. It wasn't the improved case that allowed it.
Why an oiled case would cause a flatened primer is beyond me,
I've never seen it, anyone else seen such a thing?.
Good luck!

i've read about some guys getting pressure signs up to and including blown primers from wet ammo (such as rain on exterior of cartridge). i've shot wet ammo less issue before, so i was curious and emailed Hornady, Federal, and two guys posting on the boards that work in ballistics labs asking why. the replies just acknowleged the issure and cautioned against using wet ammo, but i did not get a satisfactory explanation as to why.

Oil or grease or water if thick enough can be pushed around the neck and prevent the neck from expanding. A real "maybe".
Good Luck!

toad,

I've asked a couple of ballistic techs about the wet ammo thing myself. Basically what they said was that water on the bullet can end up inside the barrel, which creates excessive pressure due to extra friction--much like we sometimes feel when driving a pickup into a puddle.

Water can end up in the bore without ammo being wet, of course, but the problem is particularly acute when there's water right in front of the chamber, where pressure peaks. Water further down the bore doesn't affect pressure as much, both because pressures are lower and because some of it may be blown out of the muzzle by the air being pushed by the bullet.

I too believe this to be true...

In my 338WM the vel I get for the middle of the road Nolser 200g loads are much faster than the book, near Max... so I believe the pressure is Max too

Velocity ain't everything. If you get hard bolt lift, ejector marks, CHE, blown primers (black rings), OR velocity in excess of maximums listed in manuals where labratory pressure testing was used during development, it is time to back off. Velocity indicated by a chronograph alone is not a valid reason to keep adding powder if the other pressure signs are present.

The only objective measurement is a pressure transducer bonded to a test barrel and associated software to utilize it. Chronograph interpolation is only an approximation, and can exceed maximum pressure without warning.

Otherwise, just stick to published data, follow the recipe exactly - especially primers used for any given load. Do not reduce charges of slow powders below the recommended, or exceed the maximum listed. Do not swap flat based bullets of a given weight for loads published for boat tail bullets. In other words, follow all instructions in any CURRENT manual.

Do not rely on data published in obsolete manuals, powders have changed over the years, even those of the same name. You should find cartridge data on Hodgdon's (IMR-Winchester) web site, or the various powder manufacturer's web sites, or at www.loaddata.com, otherwise use extreme caution.

If more velocity is required, move to a larger cartridge, don't try to horse a few more fps out of a given cartridge. In my 50 years of reloading I have never blown a case or primer (I have had primers pin hole due to weak cups) stuck a case or seized a bolt. Accidents happen too fast to get out of the way, you'll be blinded, lacerated and bleeding before the pain reaches your brain. As the guy in the welding tank supply said, "If one of those oxygen cylinders blows, you'll never know it happened." Be careful with high pressure gas, especially when it's a few inches in front of your face.

WranglerJohn,

Actually, chronograph data is a VERY good indication of pressure. Like a strain gauge or a piezo transducer, it IS another measure of pressure.

I have visited professional pressure labs, and even helped in one. It is astonishing how closely pressure and velocity are tied together, the reason many professional ballisticians also suggest that a chronograph is the best affordable home test of pressure.

Now, you can run into trouble with a chronograph if it's giving false readings, and some do, especially under certain conditions such as bright sunlight. Which is why we should always remain cautious--and as Big Redhead pointed out, we still have to be observant of traditional signs of excessive pressure.

But I have been using a chronograph as my primary method of pressure measurement for several decades now. While I've run into signs of high pressure now and then, most were also accompanied by too-high velocities.

The exceptions that I can remember were rare instances of too-soft brass, and a few bolt-faces that had little machining ridges around the ejector hole that left a mark on the case heads even with mild loads.

As the last pressure-lab ballistician I visited (just a few months ago at the Western Powders lab) said during our afternoon: "The chronograph is the handloader's best friend!"

I've wrestled with the idea of using a chronograph to indicate pressure, and think the following is correct:

For a given bullet and powder combination, in a given rifle, peak pressure and MV are highly correlated most of the time. As long as you're in this situation, MV is an excellent indicator of relative pressure.

The problem is that for reasons I don't yet understand, some cartridges are finicky. By finicky, I mean that straightforward orderly progression of MV and pressure are not to be depended on. 7mm Mag, 243, and 338 Lapua have this reputation. Some cartridge and bullet combinations hit a point where additional powder does not add MV, but apparently does add pressure. Although I didn't measure pressure, I did find a point with my 308 and 2520 powder that more powder did not increase the MV.

So I would say that if you are working up a "book" load for a known combination of powder and bullet, and are observing orderly increases in MV as you increase powder, you're in the "well behaved" region and can use MV measurements as an indicator of pressure.

It also increases bolt thrust. Oil, resizing lube, residual cleaning solvent in the chamber, or even water prevents the brass case from "sticking" against the microscopic (and sometimes not so microscopic) tooling marks inside the chamber left over from the chambering reamer. The case is confined in the chamber at peak pressure as if it were a brake shoe expanded against a brake drum. This reduces bolt thrust and locking lug loading during the firing cycle.

As a test Ackley removed the locking bar from a Model 94 and fired it (remotely), the bolt did not fly out or the case burst because it was held in place by case "stiction."

Fire forming an improved cartridge with too light a load will cause primers to back out appearing as if there was excessive head space. Because the case swells to fill the chamber, the primer backs out as the case shortens, and there is insufficient residual pressure to force the case backward to pick up the primer. All caused by the relationship between case stiction and pressure.

Yes, I use a chronograph during every load development session. However, during my career in the water and wastewater treatment field, I installed and operated various electronic and mechanical pressure, flow, temperature, turbidity and analytical instruments. Each different type of device has a range of accuracy related to percent of scale. Many accuracy standards range between 2% to 10% of full scale value, 2% across middle half of scale, etc. Operational instruments such as bourdon tube pressure gauges are less accurate than precision calibrated electronic transducer gauges, but are sufficient for the purpose. Online real time analytical instruments are usually less accurate than laboratory instruments calibrated at time of use.

In the case of chronograph data, there are too many variables to use for other than determining trends in pressure based on velocity. While there is a interrelationship between charge density increase, percent of velocity gain and pressure, the accuracy of all instruments involved determines the result, as you point out.

My main concern is that to make the test requires discharge of a cartridge that may or may not go to failure. If this test is conducted by live firing, it exposes the shooter to a hazardous condition.

While the advanced loader can find the chronograph a useful instrument in recognizing velocity and pressure trends relative to increases in charge density, he or she is still not measuring actual pressure or pressure/time curves, but determining the point where additional powder is not producing velocity gain. Regardless of the velocity he or she is able to say that load is near maximum based on efficiency, but not the actual pressure.

So I believe the novice or disinterested loader is better served by using tested data from reliable sources.

Well, I fall in with the chrony pack. You are flying blind otherwise - no matter what data source you are using.

I will give my example of one that proves my point. Factory Dakota M97 300 Win Mag. Reaches Nosler #6 published velocity several grains before the max published charge weight...and no "signs" of pressure.

The reasonable man would look at his chrony and say...holy crap!!...I'm not even at book max and I'm 100fps faster than the book (a given we are talking the same components).

However, on this and other forums I would be led to believe I have the magical 'fast' barrel...and assured I could keep adding powder as long as I kept to the 'book' charge, and it was 'safe' in my gun.

Suddenly I would find that pressure 'sign' as my bolt locked up - being the lucky guy I am, I assume my bolt would hold. But who knows, as I'd be well over 70,000psi at that point.

WranglerJohn,

I am not (and never have) suggested that the average handloader ignore pressure-tested data and rely totally on a chronograph.

What I have always suggested is that the average handloader compare published, pressure-tested data with the chronographed results from the same bullet/powder combination in their own rifle.

Gotta say it....

+1

Having had to work up useable data where there was none available... I rely on a chrono... and I've watched the speed vs powder increases.. and it has pretty much summed it up that when the same amount of increase in powder fails to increase the MV the same amount as it was basically... IE you get less for more... then its way time to stop...

Doing it this way and then later having had things tested with a strain gauge it seemed to be that I was right where I figured...

Does a chrono lie? Nope, but then how often do you have exactly the same components to a T RE matching velocity then... There are way to many variables to say that in a certain cartridge.. IE like 130 grain in 270, that 3100 fpx is max period... and I'm not alluding to simple things like barrel length only.

I am also using a chronograph.
I usually like to shoot some factory loads first, to see what velocity that particular rifle will produce .
If velocity of my loads approaches or exceeds factory loads I will be measuring the cases very closely and comparing with the factory cases I previously shot.

I don't worry about trying to meet "Book" numbers, They weren't shooting my rifle when they clocked the numbers.

Pressure sighns?

When the barrel splits, you just exceeded max load - back off a little!

You're not serious if you don't have a chrono

I grew up reading Ken Waters' Pet Loads, where he measured case head expansion with micrometer, and I have used that approach for a number of years in judging pressure of handloads. I think in the books it is the first chapter.

On one batch of factory .25-06's I diligently loaded up and very slightly exceeded factory case expansion measurements. Then I bought a chrono and discovered the factory loads were a good 300 fps under spec! I was significantly under-loading the cartridge, based on the expansion measurement method alone.

Is the published max velocity in a manual still valid even if different primers are used. For example if the Barnes #4 manual lists a max velocity of 3003 fps with some powder and Fed215 primer. If I am using CCI 250 primers, is the 3003 fps max velocity still valid to use?

Great discussion. If pressure and velocity are tied together why do certain powders top out at a lower velocity than other powders? Aren't we forgetting another variable in the equation - such as burn rate?

"Aren't we forgetting another variable in the equation - such as burn rate?"

We might be, but burn rate is one thing that we shouldn't ignore.

A fast powder, by this I mean a faster powder than will give the most velocity, if velocity is what you are looking for.

For example, using a .300 Wby., you would be well beyond safe pressure if you tried to equal the velocity you can get with IMR 4831 if you substitute IMR 4895. Using a chronograph or not, a 180 grain bullet at 3100 FPS in front of IMR 4895 is going to give pressure out of sight, while this same velocity is feasable with IMR 4831 or H1000.

You have to match the chronograph with the powder and velocity you expect from that particular load. You cannot get max velocity and safe pressure with a fast burning pistol powder, regardless of what your chronograph is reading.

That is the point I was trying to make. I think pressure and velocity are related for an individual powder/bullet combination but they can't necessarily be compared between other powder/bullet combos in the same rifle. Just as some combos may be on the slow side for a given bullet weight, some are also on the fast side for the same bullet weight...even thought there may be a 300 fps difference the pressure may be the same.
So, do the newer powders modify the burn rate enough to give increased velocity over the old standard loads w/o exceeding pressure limits?

Any combustible fluid even water will vaporize at the chamber pressure. When you vaporize water -Oxygen and 2 parts Hydrogen are released into the burn, somewhat like adding water to a combustion engine to gain extra mileage. So you would see a pressure spike higher than a clean burn. Don't have to be Einstein to figure this out. Like throwing a cup of gas in your campfire.