Dumbing down of loads?

[Bullet]

I believe the way the pressures are measured has changed over the years. This dumbing down of loads or the reducing of loads I’ve seen mentioned here. Could someone explain the reason for the differences between the old data and the new? Also does the pressure limits on cartridges have to do with the strength of the guns or the strength of the brass?


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[RON in PA]

You've answered your own question with you first sentence. Folks make the claim that loads have been reduced, especially the 38 special based on changes in manufacturers' data on velocity. The testing standards were changed, especially barrel length and the use of venting. What needs to be done is to compare loads made before the 1970s and test them under current testing conditions or test current loads under the old conditions.

In regard to your second question it's both.

 

[steve4102]

Question 2, In many cases it's the rifle itself. For example the 30-06 is running at 60,000psi because there is a lot of older rifles out there that can't handle more than that. The 280 is also running at 60K for the same reason. Now the 25-06 is 63K and the 270Win is 65K. These two are relatively new as are the rifles chambered for them. All of these cartridges are based on the 30-06 case. Brass can be formed from one to the other.

 

[uneasy_rider]

Now the 25-06 is 63K and the 270Win is 65K. These two are relatively new as are the rifles chambered for them.

The 270 Winchester was introduced in 1923... Is this relatively new to you? That was 85 years ago. The cartridge is only 17 years younger than 30-06, and there are plenty of old rifles chambered in 270 win.

 

[USSR]

Could someone explain the reason for the differences between the old data and the new?

Sure. Lawyers.

Don

 

[strat81]

The 270 Winchester was introduced in 1923... Is this relatively new to you? That was 85 years ago.

Maybe he was born in 1851?

My 2 cents is that sometimes powders of the same name have changed slightly too. Furthermore, society is more litigious (interpret that as you may).

 

[rcmodel]

Another reason is that ballisticians now know things they didn't, or couldn't know 20 - 30 years ago.

All the old copper crusher (C.U.P.) method of pressure testing could tell them was the max. pressure.

It couldn't tell them "where in the chamber or barrel that max. pressure occurred, only that it had occurred.

Now, almost everyone uses pressure transducers, (PSI) and can see the pressure/time curve graphed out on a lap-top screen.

In many cases, they have found pressure spikes that went far above the max pressure of the round, for such a fleeting moment in time the copper crusher couldn't measure it.

In other cases, (.357 Mag - .44 Mag and others) SAAMI has lowered the max pressure standard in deference to lighter & smaller guns now being made for them.

rcmodel

 

[Slamfire]

I believe the way the pressures are measured has changed over the years. This dumbing down of loads or the reducing of loads I’ve seen mentioned here. Could someone explain the reason for the differences between the old data and the new?

I believe it has been dumbed down. I have very old reloading catalogs, Phil Sharpe's Reloading book, for example. Some of the powders that he lists are still around. Bullseye, Unique, 2400, maybe IMR 3031 and 4350.

Hercules was very good about supplying pressure data with their reloading data, and in Phil Sharpe's book you can look at the pressures and the powders charge, and the old loads show greater amounts of powder.

Now the old data was taken with copper crushing equipment, and that is not the same as psia.

Most of the old manuals, Lyman, Speer, Sierra, they used their barrels and actions and estimated pressures the good old fashioned way: Blown primers!

Data produced by that measuring technique does of course vary all over the place. I believe, especially in pistols and revolvers, they purchased factory ammo, shot that across the screens, and used the velocities as the upper limits for their load development. I really doubt the old pistol data had any relationship with pressure at all.

Also does the pressure limits on cartridges have to do with the strength of the guns or the strength of the brass?

For new cartridges and guns : Yes, and yes. When cartridges and firearms are designed in tandem, the thickness of the cartridge, the operating pressures are determined, the gun envelope is determined, if both prove satisfactory, then they are baselined.

For rifles, the cartridge is always the weak link. Revolvers, usually. In semiautos, it all depends. In all cases, the gun designer designs the mechanism to support the cartridge. Strong designs support the cartridge better than weak designs. If the cartridge ruptures, than you have a big problem.

 

[rcmodel]

For rifles, the cartridge is always the weak link. Revolvers, usually.

I'd have to disagree with that. Rifles, yes, but not the "Revolvers, usually" part.:

Brass strength is seldom if ever the weak link in a revolver. Or it wasn't anyway, until they started building behemoth revolvers like the S&W X-frame, etc.

In normal size guns of traditional design, the cylinder wall thickness, and bolt-cut depth, are the weakest link.
Followed closely by the top-strap strength.

Blown cases in a traditional revolver caliber just don't ever happen, until something much worse happened first.

rcmodel

 

[Rottweiler]

USSR covered it all with 1 word

 

[mkl]

If you want one of the best "old loads" books, pick up a copy of the Speer #8 loading manual. Published in 1970 and used "pressure signs" instead of instumentation.

Back off their starting load by about six percent and work up. Their maximum loads are generally very hot by today's standards. Be especially careful of thier "Defense Loads" for the 38 Special -- those little puppies will develop 357 Mag pressures at the charges suggested.

I had to get mine out last week to find a load for Reloader 21 (yes Re21) for my 6.5x55 Swede.

I've seen the Speer #8 listed now and then on Ebay.

 

[Slamfire]

Blown cases in a traditional revolver caliber just don't ever happen, until something much worse happened first.

Yes, the statement was way off the mark. I cannot remember ever seeing a blown case head in a standard rimmed revolver. Seen some blown cylinders, busted frame straps.

Seen a few blown case heads in pistols.

 

[.38 Special]

Also worth noting that some powders have changed a bit over the course of decades. 2400, for instance, is certainly a bit faster than it was in the 1950's, when so many famous loads were developed with it.

I don't doubt that liability has something to do with some of it, but I get nervous when I hear talk like "Ah, those modern manuals all list powder-puff loads because they're afraid of getting sued. You need to add 10 percent (or whatever) to get the REAL loads".

I suppose that could actually be true -- but I trust the loading manuals a lot more than I treat Bubba's guesses.

 

[USSR]

I don't doubt that liability has something to do with some of it, but I get nervous when I hear talk like "Ah, those modern manuals all list powder-puff loads because they're afraid of getting sued. You need to add 10 percent (or whatever) to get the REAL loads".

Have you looked in a Sierra reloading manual lately.

Don

 

[Clark]

CAUTION: The following post includes loading data beyond currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The High Road, nor the staff of THR assume any liability for any damage or injury resulting from use of this information.

Canister powder had better not be getting faster.
What am I paying extra for?
It is supposed to be bomb tested and blended and bomb tested again until it meets the canister specifications.

My canister IMR4895 always seems to be within 1% of all other IMR4895 canisters of the last 10 years.

I have many pounds of the same lot # of bulk surplus IMR4895 is ~10% faster. I call it H322 in Quickload to get the right velocities and pressures.

 

[Galil5.56]

Also worth noting that some powders have changed a bit over the course of decades. 2400, for instance, is certainly a bit faster than it was in the 1950's, when so many famous loads were developed with it.

I have one square can of Bullseye, and another of 2400 from the mid 60's I need to compare (chronograph) with paper cans from around 1980. Hercules used to hang their hat on the idea of keeping lot to lot variation at nearly zilch, and I want to see if we are seeing little more than lot to lot variance.

I was told when I went to Accurate Arms for a job interview almost 18 years ago, that they shoot for a lot-to-lot variance of +/- 3%... That is a lot of leeway when you put pen to paper with one bottle you bought that was -3%, and then you might get one +3. I can easily see this as the case, as it seems at some points in time a bottle of "X" AA powder might have three different "Made In ________" on it. Pays to work up loads carefully, and never treat burning rate as static.

 

[zxcvbob]

Yes, the statement was way off the mark. I cannot remember ever seeing a blown case head in a standard rimmed revolver. Seen some blown cylinders, busted frame straps.

I've blown the case heads in a revolver. None of them actually blew up in the gun, the case heads seperated next time I resized them. Some of them were cracked pretty bad before I resized them, and one of them broke in my hands when I twisted it a little when I was examining it after cleaning.

These were .38-44HV loads in normal CBC .38 Special brass. The ones that didn't actually break had bright rings above the web where they were about to fail.

Nevermind how much Blue Dot powder I was using.

 

[USSR]

I have many pounds of the same lot # of bulk surplus IMR4895 is ~10% faster. I call it H322 in Quickload to get the right velocities and pressures.

Clark,

I also have many pounds of surplus IMR4895, in 3 different lots. I don't know how they compare to commercial IMR4895, because I've never bought any. I simply label the 3 lots as fast, medium, and slow.

Don

 

[rcmodel]

I've blown the case heads in a revolver. None of them actually blew up in the gun,

A "case separation" is not the same thing as a "blown case".

Had you actually "blown" a case due to over-pressure, the gun would have also been shrapnel!

Case seperations are caused by stretching the case, and doesn't result in anything bad happening because the head is still intact and providing a gas seal.

A blown case head would release gas into the action, and in the case of most any conventional revolver, also take the cylinder & top-strap with it.

rcmodel

 

[zxcvbob]

I thought a head separation was the same thing as a "blown" case. I've also had cases split when they've been reused one too many times, and nothing bad happens because it's all still contained in the chamber.

If a case were to separate at the extractor groove, that would not be good -- especially in a rifle. But since it would probably not be catastrophic in a revolver, I'm guessing that's still not what you are talking about?

 

[rcmodel]

A blown case is the result of an over-pressure load that allows the brass itself to deform around the primer pocket, releasing high-pressure gas into the action.

Once it starts, the gas melts the brass further just like a cutting torch.

It can also occur when the case head reaches the yield strength of the brass and the case lets go out the side through the extractor cut in the bolt. (Not in revolvers though)

In normal revolvers, what happens is the cylinder lets go, along with the case, which in turn blows off the top strap.

rcmodel

 

[.38 Special]

I have one square can of Bullseye, and another of 2400 from the mid 60's I need to compare (chronograph) with paper cans from around 1980. Hercules used to hang their hat on the idea of keeping lot to lot variation at nearly zilch, and I want to see if we are seeing little more than lot to lot variance.

I hope you'll share the results with us. I'd encourage you to test some currently available Alliant Bullseye and 2400 as well.