Inconsistent Max Load Recommendations

[Mark K]

I asked this in passing in another thread, but never got an answer...

Why is there sometimes a significant difference in load data between one vendor and another, with the same powder and same weight and type bullet?

One instance I'm seeing shows a 6% difference in maximum recommended powder load between two reputable sources, and a third...

 

[DutchV]

Different case maybe? The book should list the one they used. Some brands have different internal volume due to thicker or thinner walls. That would affect pressure.

 

[Mark K]

Different case maybe?

Hmmm... maybe. I hadn't thought of that.

The case in point is .380 ACP, with 100-grain FMJ bullets, and HP-38 powder.

Hodgdon specifies 3.1 grains of HP-38 maximum, and notes it's with a Remington case.

The data with my Lee dies also show 3.1 grains of HP-38 max, without specifying what brand case.

But My Hornady reloading book shows 3.3 grain of HP-38 max, with a Hornady/Frontier case.

That seems like a huge difference for .380 ACP -- I wouldn't think case volume would make that much difference.

Also, who reloads just one specific brand of case? I think most of us reload mixed range brass, or order mixed brass.

My feeling is to treat Hornady as the outlier, and use 3.1 grains as the max...

 

[DutchV]

I agree with going with the lower charge weight. I tend to stay a little back from maximum anyway.

 

[trickg]

Welcome to the world of reloading. If you have multiple manuals, it seems that there is more often than not a discrepancy between them. My rule of thumb is to lean conservative - i almost never load max loads and when I’m getting up there, I make sure that if my powder throw is going to err, it errs a tenth of a grain or so low.

 

[Mark K]

Well, for that bullet and powder, I found the starting powder charge -- 2.9 grains of HP-38 -- was very weak and unreliable, particularly in my wife's Glock 42.

So now I'm loading at 3.1 grains.

But that brings up another concern that you guys touched on. I can start out with a powder throw of 3.1 grains, but find that over a run it can vary by a tenth of a grain or so -- up or down (Hornady Lock-N-Load powder measure). I hope that variance isn't critical...

 

[Biggfoot44]

( The brass question) depends upon the caliber and the catagory or loads .

For the short and simple answer , it is a staple of handloading journalism to do comparison of mixed brass vs single lot, single head stamp . The answer is almost always no difference to negligible difference , with the usual caveats that all brass in question is generally decent & suitable .

Actual US Mil surplus .30-06 and .38spl is indeed significantly thicker than most commercial . Not inherently a bad thing , as they are thusly more durable and long lasting , but to be aware of for top end loads with high load density .

9x19 has been mfg in huge numbers for over 100yrs , under specs from different millitaries, and different standards organizations worldwide . So other than relatively modern commercial brass , it warrants inspection for thickness , and internal dimensions .

In revolvers generally , no cannalure vs cannalure, vs cannalure in various locations for specific bullet weight ( think .38spl Waddcutter vs 158 RN ).

In .45 Colt specifically , for different load levels particularly , there are important differences in thickness and hardness . R-P is thinnest and softest . No issue at SAAMI level , and actually prefered for black powder . W-W is inbetween . Federal and Starline hold up best for top end " Ruger Only " up through " Custom 5 Shot Conversions " ( think near Casull presures ) .

As to .380acp published load variations ? No personal experience with developing max .380 loads . But the usual explanations is that each source is accurately reporting Their results , with Their Exact components , in Their Test Bbl , on that day ( filtered through how close their lawyers let them get to Max average pressure , with how much standard deviation ).

I have coresponded with a shooter in ( redacted country ) , and due to their firearms laws , they do some very * Interesting * things with .380acp that would make USA handloaders faint , but with their specific guns , in their legal parameters , it works for them .

In our conventional context ? Both illadvised and pointless to hot rod the .380 . Strive for reliability in Your Gun ( and pressure Curve can matter as much as peak pressure ) , and accuracy .

 

[K31]

Well, for that bullet and powder, I found the starting powder charge -- 2.9 grains of HP-38 -- was very weak and unreliable, particularly in my wife's Glock 42.

So now I'm loading at 3.1 grains.

But that brings up another concern that you guys touched on. I can start out with a powder throw of 3.1 grains, but find that over a run it can vary by a tenth of a grain or so -- up or down (Hornady Lock-N-Load powder measure). I hope that variance isn't critical...

.1 grains is the accuracy of most reloading scales, so if I vary by +- .1 , I don't sweat it.

 

[erwos]

Yeah, tenth of a grain (or even .2) is not gonna explode your gun unless you're running way over the red line already. It could potentially lead to earlier failures, but anyone running hot loads is going to get into that.

Different barrels also have different rifling characteristics, and this can influence pressures. COAL also makes a substantial difference, and we've also discussed case and primer differences.

My biggest beef with reloading guides is not the inconsistency, it's the refusal to list out full-pressure 5.56 and 308 loads, and not give data for common tactical bullets. I get it, you don't want Cletus the Slackjawed Yokel to blow up pappy's 50 year old hunting rifle because he felt like he could go 10% over max 5.56 load on his first batch, but I'd LOVE a "Tactical Reloader Handbook" that gave you big boy loads for social work.

 

[JB01]

Inconsistent 380 AXP Max Load Recommendations

Would variation in temperature during testing be sufficient to cause such differences?
JB

 

[Pinecone]

1) Different cases

2) Different primers

3) Different firearms

All those have an effect.

Max load is not the max load in EVERY case. The published max load may be too hot for YOUR firearm. Or, your firearm may be fine with a higher powder charge load.

That is why EVERY loading manual says to start low and work up.

 

[Doco Overboard]

PC gets it. Different flash hole diameters will produce different pressures. Same as a variance in bullet force-ment or angle of the leade in.
It's one of the reasons when you change components you start low and work up.Batching cases, same head-stamp, primer selection etc. etc. just like he says.
Most published loads I see for 223 556 are big boy loads, most of them start out around 50 some odd thousand lbs.

I see publishers with 40 g hollow points approaching 55 k. with some powders in 223.

 

[Mark K]

Thank you, Gentlemen. That makes me confident in 3.1 grains, the max recommended load from most of the sources I've looked at.

I haven't gone out and chronographed the 3.1 grain loads yet -- it's a hassle on an indoor range.

But I did chronograph some 3.2-grain loads (same bullet) a couple months ago from my Bersa Thunder 380CC (3.2" barrel). Came up with an average of 1001 fps at the muzzle, and 222 ft-lb of energy. I think that was too hot...

 

[lazarus]

PC gets it. Different flash hole diameters will produce different pressures. Same as a variance in bullet force-ment or angle of the leade in.
It's one of the reasons when you change components you start low and work up.Batching cases, same head-stamp, primer selection etc. etc. just like he says.
Most published loads I see for 223 556 are big boy loads, most of them start out around 50 some odd thousand lbs.

I see publishers with 40 g hollow points approaching 55 k. with some powders in 223.

Yes. My only “well actually” would just be if you are running plinking loads well below max pressures you probably don’t need to worry about it too much for minor changes. Like loading someone else’s 115gr RN in 9mm, if you are at like 90% max, you probably aren’t going to start blowing up your gun. Same with different brass in that respect.

If you were approaching max, start over and work your way up always. Same with a new powder.

 

[Doco Overboard]

Yes. My only “well actually” would just be if you are running plinking loads well below max pressures you probably don’t need to worry about it too much for minor changes. Like loading someone else’s 115gr RN in 9mm, if you are at like 90% max, you probably aren’t going to start blowing up your gun. Same with different brass in that respect.

If you were approaching max, start over and work your way up always. Same with a new powder.

You'll see more pistols blown up or damaged than rifles because of the lack of available space in a pistol cartridge.
One of the reasons is because the quickness of the powder and the pistol frame not having the strength or design to adequately control the rapid rise in pressure.

Usually, every loading manual will have some sort of language or words to the effect, something like- "To develop loads in the firearm they were intended to be used with."

They never say, "Safe for use in any firearm designed for the same cartridge or your buddies new Rosco"

It could be something as mundane as a bullet jammed into the rifling, a near interference fit with the chamber or even a heavily crimped load and a combination of any mechanical interference or other anomaly.

Even with a plinking load or that one piece of oddball brass.
The effects of uncontrolled rapidly expanding gases are usually cumulative in effect or what could be considered a light or plinking load and wind up being harmful to the shooter or the gun, especially so in pistols.

 

[Muleskinner]

Make sure the barrel length they are recommending are the same...longer barrel, higher pressure...so the max load in a 3 inch barrel would be potentially dangerous in a 6 inch barrel...there are a ton of variables...that's why working up a round for YOUR particular firearm is important. Start with minimum loads and work up. Inspect every case for signs of over pressure...Flat or bulging (or even missing) primers, splits in the case...sometimes you might not see any but you can feel it in the snap of the recoil or if you consistently get FTF or FTE because it can cause your action to cycle faster than the mag can feed the next round.

Also there is a TON of good info on reloaders forums online...read read read..

 

[Park ranger]

Not sure I agree with barrel length and pressure per se. Chamber pressure is what it is, exit pressures will be lower with longer barrels. That's why a 10" AR is blasty compared to a 24". But the chamber pressure is the same.

 

[Doco Overboard]

One other thing is the tendency for compressed powders to increase pressure somewhat. 10 or more percent in some applications.
Loaded rounds rolling around in the cup holder or console for a while, powder coatings that have become degraded, powder laying up to the front of a case or in a certain position bullets getting pushed deeper in the case and so on.

 

[Mark K]

OK, so, I understand how various sources can have different results and recommendations -- based on different brass, etc.

But most of us don't use the specific-brand brass (or primers, etc.) that the sources used. In fact, we use mixed brass and various primers. How are we supposed to interpret data that's not consistent?

I think the answer is look at a variety of sources; throw out the outliers; and be conservative.

Inspect every case for signs of over pressure...Flat or bulging (or even missing) primers, splits in the case...

Well, those apparently aren't always reliable indicators. I recently destroyed my Bersa Thunder 380CC. apparently by using really hot commercial Underwood ammunition -- well over 200 ft-lb using, I assume, SAAMI standards.

I always collect my range brass for reloading, and didn't noticed any damaged cases... I do seem to remember those shots were really snappy, but no other indicators...

 

[K31]

OK, so, I understand how various sources can have different results and recommendations -- based on different brass, etc.

But most of us don't use the specific-brand brass (or primers, etc.) that the sources used. In fact, we use mixed brass and various primers. How are we supposed to interpret data that's not consistent?

I think the answer is look at a variety of sources; throw out the outliers; and be conservative.

Always start at the minimum load and work up your own load for your own firearm and components. If you vary any, start again.