Determining Max Loads

[Yosemite Steve]

I have watched quite a few videos and read all of my reloading handbooks and still do not feel like I have a definitive grasp on where to call it quits when working up loads to find a max load. I will be heading to the range later today to get a fresh start on working up loads for my Savage 30-06 after fixing some headspace issues from installing a new bolt head.

Aside from observing the flatness of primers and case head markings and hoping to never get a stiff bolt lift, I would like to know if there are other ways to test this that are more reliable. The only micrometer or caliper testing I have seen is comparing to factory ammo which, to me, is not a reliable method. Is there a good line to draw anywhere in how much brass expands or craters form or primers flow that is definitive?

[reddog81]

I'd say Following reloading manuals should come first. Then the steps you mention. The next level of testing would be using a chronograph. After that you can find some specialized equipment like strain gauges.

Typically the best accuracy will happen somewhere below the book max load. Most people prefer to focus on accuracy rather than pushing the edge of the pressure envelope. A bullet going 2700 FPS and hitting exactly where you want it to is more useful than a bullet going 2900 FPS and hitting 5 inches off the mark.

[std7mag]

Steve,

Start low and do a ladder test. Going up 0.3gr of powder per round. I shoot no more than 3 rounds at a time, noting where each round landed, and numbering each hole.
Look for 3 closest verticle holes in the target. This will be an accuracy node.

If rounds 6,7,8 gave you closest verticle spread use powder charge weight for round 7.
As you mentioned check each round for bolt lift, excess powder around neck, condition of base.

Don't worry about getting the last fps out of it.

Also don't load to the lands. For most bullets i seat about 0.02" off of the lands.

Good luck, be safe.

Std7mag

[Slamfire]

Unless you have a pressure gauge, the physical over pressure signs we observe are in fact indications of gross over pressure.

Ken Warner popularized measuring the case head for expansion. Ken never actually tested his theories, as is typical of in print gunwriters, but the 46th edition of the Lyman reloading manual did. There is no direct correlation between case head expansion and chamber pressures. Measuring case head expansion is meaningless, whatever Ken Warner saw, were patterns that did not exist. He might as well have been reading tea leaves. Based on all the pseudo science nonsense that Ken Warner codified over his decades of being an in-print gunwriter, I have always wondered what was in the pipe that he was smoking.

Whenever you have blown or leaking primers, this is 100% proof that you have grossly exceeded pressures, regardless of what the manuals say. Barrels, chambers, bullets vary considerably and I have walked away from threads where the original poster is absolutely adamant that, even though he is having sticking cases and blown primers, that his loads cannot be overpressure because they are below manual maximum loads. This is an example of confirmation bias and the Kruger Dunning effect.

These are overpressure loads showing leaking primers, blown primers, and case head flow back into the ejector hole of a M16. I picked these up from the AMU shooter on the point next to me at Camp Perry.



This is 100% proof of excessive pressures:



Bolt guns, you can feel bolt stick ness. However even though I grease my cases to fireform and load test, and I chronograph when possible, loads developed in cool weather having all the velocity and gross pressure indications of safe pressures, have in hot weather, or rapid fire, blown primers. Whenever you have blown or leaking primers, cut the loads. Bottom line, any pressure indications, cut the load.

I have been making a practice lubricate my cases, for several reasons. The first of which is that I want full case head thrust against the bolt face so I can detect as soon as possible over pressure conditions. Specifically I want to feel a sticky bolt when I hit a maximum load. Even this is unreliable as the pre load of the mainspring and the leverage of the cocking cams will disguise sticking bolt signs of over pressure. I have blown primers before the bolt was sticky. I have had sticky bolts before primers are blown. But, have a sticky bolt lift, that is 100% positive proof of over pressure loads, regardless of what the manuals say.

Another reason for case lubrication is that I want to see the transition from rounded primers to flat primers. While this is an unreliable indication of over pressure, it is at least, an indication of something going on. I found that dry cases in dry M1a 308 Win chambers gave spurious flat primer indications. However once I started firing lubricated cases, to extend case life, the same loads gave rounded primers. It took a little time to figure out what was going on. Now, I lubricate my cases and examine them, and once the primers flatten out on lubricated cases, I know I am at, or have exceeded, a maximum load.

Also I don't want case head separations caused by the front of the case sticking to the chamber, with the subsequent sidewall stretch that occurs as pressures build








You cannot feel bolt stickness in gas guns. Indications of over pressure conditions are blown primers, leaking primers, brass flow into the ejector/extractor holes in the bolt face, ripped rims, and malfunctions due to too high of gas port pressure.

If your primer holes open up in a couple of reloads to the point that a primer won't stay seated, your loads are too hot.

I believe that if my loads are exceeding reloading manual velocities than I have over pressure loads. I can't prove this one way or another, because I don't have a pressure gage, but I do believe this. I can say, I have had sticking bolts, blown primers, leaking primers, at velocities below manual maximums. And, I have had zero pressure indications at velocities above manual maximums.

Physical indications of pressure are unreliable but they are all we have.

I do have one final bit of advice. If you are concerned with pressure, over pressure, bolt thrust, whatever, there is one procedure that will always, 100% of the time, reduce pressures, and that is cutting your loads. Reducing the amount of powder in the case will always reduce chamber pressures. Just don't go below what the manuals recommend until you have confidence in why you are reducing your loads. Some loads are just fine below manual levels, others have blown up guns.

[Yosemite Steve]

std7mag, I plan to do exactly that. But First I want to establish my load range. I have not fired it since my last alteration and want a baseline.

[reddog81]

Factory ammo would probably be the best baseline. They've got reduced power M-1 Garand loads if you want to start out light or full strength hunting loads if you want to push the limits.

For a baseline using reloads, after having the work you've done, I'd try a starting load and go up from there. There'e no need to push the limits on the first trip to the range.

[T. O'Heir]

There is no "Determining Max Loads". There is only following your manual.
"...reduced power M-1 Garand loads..." There's nothing 'reduced' about those. The Federal AE brand stuff is standard M1906 150 grain 2740 FPS(close enough.) ammo. That is not .30 M1 Rifle ammo though. It's Federal's idea of what that ammo was. It's really for 1903 rifles.
Anyway, the M1 Rifle wasn't designed to use that ammo anyway. It was designed to use and tested with .30 M1 ammo. A 174.5 grain bullet at 2640 FPS. That had too much rage for NG ranges, so it was reduced to 152 grains at 2700 FPS, then upped to 2800 FPS to match the .30 AP ammo ballistics
https://m1-garand-rifle.com/30-06/

[reddog81]

Originally Posted by T. O'Heir

T
"...reduced power M-1 Garand loads..." There's nothing 'reduced' about those. The Federal AE brand stuff is standard M1906 150 grain 2740 FPS(close enough.) ammo.
https://m1-garand-rifle.com/30-06/

If you think Federal designed the ammo so that the 150 grain bullet doing 2740 FPS has the same pressure as a 150 grain bullet doing 3000 FPS, I guess that's your prerogative.

[Yosemite Steve]

Yes, for me there is determining max loads for each gun. If pressures or velocities are looking to be much my max load is .5 to 1.0 grains less. Follow which manual? They are all different. The max loads in certain manuals have proven to be too hot in some instances and wussy loads in others. Isn't that why we work up?

[hdwhit]

std7mag wrote:
Start low and do a ladder test. Going up 0.3gr of powder per round. I shoot no more than 3 rounds at a time, noting where each round landed, and numbering each hole.

Agreed.

It's called a "Starting Load" for a reason.

For most rifle calibers, 0.3 grain is a reasonable increment. But use common sense. If the difference between Starting Load and Max Load in the published data is 1.1 grains, you might want to drop back to 0.2 or even 0.1 grain increments.

Because I have to travel to my rifle range, I load 10 rounds at each increment. I fire five through a chronograph and five are fired without the chronograph for an accuracy group. Any consistently followed, reasonable plan should produce data that you can analyze later.

[hdwhit]

Yosemite Steve wrote:
Yes, for me there is determining max loads for each gun.

I have about a dozen reloading manuals that I have acquired since the early 1980's (before that I was so poor that I went into the gun store, read their sample copy and memorized the loads). I take a consensus of Starting Loads and a consensus of Maximum loads and then load 10 rounds at each "rung" on the "ladder" all the way up to Maximum. I store each 10 round group so that I can identify each one. When I get to the range, I start with the Starting Load group. I fire 5 rounds through a chronograph (without much regard to accuracy) and then 5 rounds without the chronograph for accuracy.

I repeat this for each group. After firing the first five rounds, I inspect the brass looking for smashed primers, primers extruding into the firing pin hole, distorted case heads, missing primers, ejector marks, extractor marks, and the like. If I don't see these, I continue to the next group. As soon as I see pressure signs, I stop.

I will return home and 1) disassemble any unfired rounds to salvage the components, 2) to evaluate the data I gathered and 3) IF I didn't find a load I liked, try loading some more groups starting by dropping back from the over-pressure load by 0.1 grain each increment and then testing them on my next range trip.

Max load for any particular gun is the load at which it starts showing the classic pressure signs (mentioned above) or reaches the maximum load per the published data - and if you are using multiple manuals, the consensus of the various manuals; being aware that you may hit Maximum sooner than predicted.

[hdwhit]

Slamfire wrote:
Look Ma! No extractor groove!

I know that to be a theoretical possibility given the way cases are drawn, but I had never seen a picture of it before.

Thanks for the "gut check".

[mkl]

Is there a good line to draw anywhere in how much brass expands or craters form or primers flow that is definitive?

The only other advice I can suggest is case head expansion (measured at the cartridge rim). Before Speer had pressure guns, they used case head expansion (along with the other pressure signs you mentioned) as a criteria for over pressure loads in developing their loading manual #8. On page 109 they state "An increase in head diameter of .001" would more than indicate excessive pressure."

Remember this was before they had any better way to measure pressure. They also discuss the other signs you and others have already alluded to.

They then state that when any pressure signs appeared, they reduced the load by 6 percent and called that the maximum for their manual.

To be safe, use the current loading manuals which do have accurate pressure measurement instruments and do not exceed the maximum loads.

[Unclenick]

I have kept a list of pressure signs on another forum for some time. It is here.

If you want to get a sense of the limitations of pressure signs, read this article.

Understand that pressure signs depend on deforming brass cases or brass primer cups. The old copper crusher system depends on deforming copper. That system calibrates the brass slugs by stacking known weights onto a piston that crushes them and then measuring how far they've been crushed with a micrometer. SAAMI has shown a 23% span of variation in results from 9 labs using a copper crusher, which means that ±11.5% is about as accurate as you can expect a copper crusher to be. Now come back to using cases and primer cups made of various alloys, with various design thicknesses in some parts and with absolutely no calibration done to them at all. Ken Waters followers asserted you could estimate pressure by deforming these uncalibrated parts. The article I linked to proves quite conclusively that it would be kind to call this wishful thinking.

What you can conclude is that the deformation of a piece of brass will tell you that piece of brass didn't like what you did to it. That's about it.

Incidentally, sticky bolt lift is another variation on brass deformation. It occurs when the chamber stretched beyond the elastic limit of the brass and returns to shape over top of the brass trapping it like a sizing die with no lube, though usually not quite as hard. The result is the brass doesn't turn freely in the chamber and any impressions made on it by features on the bolt face then try to lock the bolt from turning. When you force it, the impressions smear. That's one sure sign the pressure was too high for that brass, and probably will be for other brass, too, if it isn't a lot harder. Steel can stretch further than brass can and still return to shape, making this possible.

As far as measuring, you can get a Pressure Trace and do it. Understand, though, that such measurements typically are made by manufacturers because they want their ammo safe in all guns that have the same chambering. You might want to make such measurements to learn more about what your gun likes and what the load is doing in your gun, but usually, this is optional information and not required.

Incidentally, so-called Garand loads are all over the map. Hornady's sends a 150 grains bullet out at 2710 fps muzzle velocity. Sellier & Bellot fires its 150 at 2887 fps. Others are in between. The military specification was 2740 fps at 78 feet from the muzzle, by which time it had lost nearly 60 fps. Following SAAMI standards, muzzle velocity is measured at 15 feet from the muzzle. An actual M2 ball bullet at the nominal MV would have has an equivalent muzzle velocity of 2801 fps, dropping to 2794 fps at 15 feet, dropping to 2740 fps at 78 feet. The military spec is ±30 fps from a tight chambered test barrel. Actual field performance would vary by the gun, of course.

[Yosemite Steve]

Today I was going to just do a quick work up of IMR4350 behind Hornady's 180 gr. SST. I decided to kill two birds with one stone and got three as a bonus.

I was shooting my Savage 30-06.
I decided to try three seating depths to see what differences they would bring.
Because I had some big pressure issues the last time I did this with my shorter chamber and cartridges I started low and finished upper mid range.

The loads were as follows: IMR 4350 - 180 grain SST - CCI 200
Winchester brass weight sorted within .2 grains, 69.2 grains H2O
3 seating depths: 3.310", 3.320" and 3.330" - lands at 3.338"
Charges: 49.0, 50.0, 51.0, 51.5, 52.0, 52.5, 53.0, 53.5, 54.0, 54.5 for each seating depth.

In the images of the brass the longer COL are on the left.
I found no substantial pressure issues and my primers did not flatten enough to make me too worried. A few were getting flat but not flowing into the pocket bevels.

Here is the low end of the loads:

Here are the hotter loads:

On the loads with the longer COL of 3.330 I am at my maximum as the primer was close to the edge of it's bevel. The center COL of 3.320 could probably go another grain and the COL of 3.310 on the right possibly 2 grains. I will post my target results separately.

[3Crows]

No expert here but I do not think you can determine a maximum pressure load without a strain gage or some other calibrated pressure measuring tool. That is why they give us tables with a start load and a maximum load. Generally somewhere between the two you can find a sweet spot or two for your gun/guns and be happy. A chrono is one good tool for sure and a good powder measure so you can duplicate the load tables.

If you are loading beyond the maximum in a recognized and accepted industry table you better know a whole lot more about this stuff than might be evident by asking the question to begin with. Your maximum load is the maximum load in the table. Realizing that some deviation can occur if you choose another brass or primer or even between rifles but for the most part that should be absorbed by at least some conservatism by the loadee (you) and the table author.

3C

[Yosemite Steve]

Incidentally, sticky bolt lift is another variation on brass deformation. It occurs when the chamber stretched beyond the elastic limit of the brass and returns to shape over top of the brass trapping it like a sizing die with no lube, though usually not quite as hard. The result is the brass doesn't turn freely in the chamber and any impressions made on it by features on the bolt face then try to lock the bolt from turning. When you force it, the impressions smear. That's one sure sign the pressure was too high for that brass, and probably will be for other brass, too, if it isn't a lot harder. Steel can stretch further than brass can and still return to shape, making this possible.

That is what happened to my last work up with the short chamber. How come when I said it people though I was nuts? Maybe my words were not clear.

[HiBC]

There are some situations,like a wildcat,where reliable published data is
scarce or unavailable.In those cases,I have my processes I use when it is my face on the line.Along with watching for any indicators,the usual "pressure signs",I use my chronograph.

But that process is rather pointless with a cartridge as well documented as the 30-06.Hogdon,Nosler,Sierra,etc did that work already.
I do suggest watching for anything that suggests "enough".
But its NOT the same as adding more charge till I get pressure signs somewhere past published Max. Pressure signs are not the goal.(In fairness to the OP,he was loading a 180 gr bullet to 2610 with IMR4350. That's,IMO,quite reasonable)


For a number of very good reasons,we need a substantial margin of safety in our loads.

Name some? Lot to lot variation. Do you buy powder in 8 lb jugs? Or do you back off and work up every time you buy a lb of powder?

How about temperature? The temp of the ammo the day you "work up" vs the temp of the ammo from a hot pickup,in the sun,or sitting in a hot chamber? Fouled bore? Charge variation? A weaker piece of brass from age and stretch?

You find "Your Max" one day ,then another day you have a hot lot of powder,a little "crunch" at the powder measure and you drop a +.4 gr charge,you substitute a a primer that's a bit hotter,the ammo dwells in a hot chamber....

And the 30 year old Savage has a new bolt head because the last bolt face went concave.

OK. I AM NOT trying to bust your chops. As I recall,you were loading 180 gr bullets up to just over 2600 fps with IMR4350.

That is certainly not "pushing the limits" Its well within reason .I think you have been advised to back off the lands just a touch.

You stopped and decided to see what was going on because you had hard bolt lift . Very good!

It seemed we had the problem solved. Your rifle works.

Lets not play "Star Trek" looking for new frontiers.

[Yosemite Steve]

Lets not play "Star Trek" looking for new frontiers.

I am actually doing the opposite. I was looking for ideas and experience in maintaining a more conservative method of working up loads. I am not a veteran as many of the members are. I am, however, plagued with OCD and won't stop short of finding the best method of whatever to do whatever. The high pressure I had 9 days ago was scary. I want to make the best ammo I can for my rifle without putting myself or my gun in danger. My max is, at the moment, well below my handbooks.

[HiBC]

FWIW,I saw nothing of concern on your primers except maybe the firing pin protrusion that you have addressed.
Were those 53 gr IMR 4350 with a 180?
I just went here:
http://www.hodgdonreloading.com/data/rifle

53 gr is the recommended start load. 48300 PSI (not cup) was the pressure.

The MAX load shown was 56.5 and it was compressed. 57,200 PSI was the pressure

The COL was 3.300.

Hogdon publishes other powders with a max load up to 60,000 PSI

Which suggests to me ,per Hogdon,the Max was determined as much by case capacity as it was pressure.

I'm not suggesting you throw caution to the wind,but IMR 4350 is such a balanced match to the 30-06 with a 180 gr bullet,it would be difficult to get enough powder in the case to reach dangerous pressures in most rifles.

Of course,we can't rule out yours is somehow the reason there is a "start" load.

Try seating to a COL of 3.300. If you were looking for a benchrest championsip,it might matter. Give that bullet the .030 jump. See what happens

[Yosemite Steve]

Yes. I read that. The images were from today. The firing pin is set at .055 currently. The load I was having the high pressure with completely covered the primer pocket bevel. That was 53 grains.... with a short chamber and shooting on the lands. Today's test was further on the side of caution. Part of the test was carefully observing how seating depth is affecting the pressures because I am always searching for the "why". I am persistent about seating longer because this rifle has proven to shoot this bullet more accurately closer to the lands. This test was trying to get a feel for how close I can get safely.

If you go here,(https://thefiringline.com/forums/sho...d.php?t=593419) you can see the work up. I started at the lowest starting load of all of my handbooks. At 51.0(#3) and 51.5(#4) grains I found a node and also at 53 grains(#7). The COL of 3.320 is .020 off the lands. Next trip to the range I will be testing up to 56 grains. I am betting that 55.5 will be "my max" for this seating depth. I want to see if another node shows up above 53 grains.

[HiBC]

Good idea. You might be right about 3.320.

My way of looking at it: try (safely) 54 up to published max 56.5.Well,I'd not compress more than just a little.
I get your ladder and node test. If it seems safe,try a 5 shot group in the 55 to 56 gr range. See what it does.

IMO,its a hunting 30-06,not a 100 yd bench gun.If the "nodes" tell me to load to 2235 fps...well,I might step up to a 30-40 Krag at 2400.
Or I might try H-4350,or 4064,or RE-19.

Or I might say to heck with the ladder if I got an acceptable group .
FWIW,H-4350 is a Hogdon Extreme(temperature stable) powder.Hogdon says max is 57.5 grains,no compression,2798 fps,49300 CUP.(CUP is a different scale than PSI.)
I have tried really hard to make a powder work when I found another powder worked better.

I'll give up SOME velocity to accuracy,but I have my priorities and limits.

[Stats Shooter]

To determine max loads I keep adding powder until the case has to be pounded out with a dowel and mallet, or chamber cracks down the side and then back off a tenth or two.

Kidding....

[reddog81]

Originally Posted by Yosemite Steve

That is what happened to my last work up with the short chamber. How come when I said it people though I was nuts? Maybe my words were not clear.

I thought your prior problems were the result of bad gunsmithing. The symptoms looked like over pressure, but the sticky bolt was because the lugs weren't cut straight.

[GeauxTide]

Back in the 80s, Ken Waters used a base expansion method to determine maximum loads. He measured a factory or full length sized case just above the web. If loads expanded .0005 over, it was max. In six 30-06 rifles over the years, 52gr of 4064 under 150 Hornady measured .470 at 2910. 53gr of 4064 measured .4705 at 2950 with primer flow. It has worked for all my rifles, 223, 243, 260, 6.5-06, 280, 7mmRM, 308, 30-06, and 338-06. I didn't include my ARs in 223, Grendel, and 450BM because I'm not going to load them hot.