More powder = less pressure

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someguy2800

someguy2800

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I was doing some load development yesterday to use up some 158 grain bullets in my ruger 357 revolver with W296.

The published data I have for this combo is

hodgdon online data = 15.0gr start, 16.7gr max
Lyman bood = 16.3 start 17.0 max
older speer book = 15.8 start 17.8 max

anyway loaded some rounds from 16.5 to 17.5 in .2 grain increments and found that the 16.5 grain loads showed more flattening of the primers and more resistance to extraction (none were what I would consider sticky) than the 17.5 grain loads.

I recall also loading some 223 rounds for a single shot once with a below starting charge of benchmark. In this case I started at the published starting load and worked down in .3 grain increments and found that a couple grains below the starting load showed extremely flattened primers and sticky extraction to the point that I decided to pull the rest of the bullets.

How often do you folks witness this were pressure actually goes down with higher charges of powder?
 
I've only withnessed it once since I generally start a little above the lower charge weight in the published data. The only time I ever had high pressure that went down with an increased powder charged was when I was working up some 454 Casull loads with a powder for which there was no data. The cylinder of the handgun was almost locked up and the problem resolved with an increased powder charge.

There is a continuum which includes squibs, hangfires and increased pressure with low powder weights in some guns with some powders. It usually happens with slower powders.
 
More powder sometimes fixes things, but it isn't going to lower pressure, unless a lab proves it to me. :)
 
Pressure doesn't go down with higher powder charges.
Those cast or jacketed bullets.
The best data to use is from the manufacturer, but there will always be slight differences between manuals because every test lab uses different powder lots and tests under different conditions. Some manufacturers, Lee in particular, test nothing themselves. Lee publishes Hodgdon data in their books. Hodgdon's site, for some daft reason, lists magnum primers with magnum named cartridges, but not for non-magnum named cartridges too. Magnum primers are about the powder, not the cartridge.
Do not worked down with any cartridge or powder. Below minimum loads can be as dangerous as over max loads. Causes weird unpredictable pressures.
 
It was a Prvi Partizan JHP that I bought a few years ago. Logic would agree with more powder must = more pressure, but the results sometimes do not bear this out. I think in some instances having a slightly fuller case load causes a slower burn.
 
Someguy2800 wrote:
I was doing some load development yesterday to use up some 158 grain bullets in my ruger 357 revolver with W296.
Click to expand...

Jacketed or cast bullets? I'm going to assume jacketed because I don't have a manual that lists W296 with cast bullets.

Consider two additional sources:
  • Hornady 4th Edition lists 14.3 gr starting (1,200 fps) to 16.4 gr (1,350 fps) developed with a S&W Model 27 pistol with 8 & 3/8 inch barrel
  • Hornday 8th Edition lists 12.4 gr starting (1,000 fps) to 16.0 gr (1,250 fps) developed with a Colt Python with an 8 inch barrel.
According to the Hornady manuals, you were near or over maximum at your 16.5 grain starting load.
  • Lyman #49 doesn't list a load for 158 grain jacketed bullets with W296.
Considering just the data listed in your post, note that your 16.5 grain starting load was near Hodgdon's maximum, above Lyman's start and a third of the way up Speer's range. Your 17.5 grain load was above max from both Hodgdon and Lyman.

I suspect you saw pressure signs on all these loads (flattening of primers, hard extraction) because all of them produced excess pressure. I can only speculate why the extreme pressures of a 17.5 grain load would lead to easier extraction than a 16.5 grain near-max load.

Proper load development involves a starting load that is at the bottom of the range (or a concensus of the starting loads if multiple sources are consulted) and then slowly (i.e. 0.1 or 0.2 grain) increasing the charge watching for anomalous behavior and pressure signs. Since all of your loads showed evidence of excessive pressure, I suggest you factor in the Hornady data above, retreat to a much lower concensus starting load, beginning again with an eye towards stopping before you reach 16.5 grains since you already know it is a load that this showing excessive pressure in your gun.
 
Someguy2800 wrote:
I think in some instances having a slightly fuller case load causes a slower burn.
Click to expand...

I suggest that may not be the explanation for why increases in powder don't produce certain obvious pressure signs. In my own experience with the 5.7mm Johnson wildcat, a load of 10.5 grains of IMR-4227 produces smooth primers. 11.5 grains produces cratered primers - an obvious pressure sign given an otherwise sound bolt. But, 12.5 grains produces smooth primers even though velocity measures and condition of the brass confirm that the 12.5 grain load is definitely over-pressure.
 
i had that happen with h110 (same as w296) and a 125gn xtp bullet in 357 magnum. at a point high up in the range, the muzzle velocity went down then back up with an increase in the powder charge. i stopped using h110 and switched to blue dot. now blue dot is a "no no" for that bullet in that gun.

i'd back off the charge, or switch to another powder.

luck,

murf
 
I've been loading for 15 years and always do it safely and sensibly. The 16.5 and 16.7 loads showed mild pressure signs. Above that showed none and could be pushed out of the chamber with 1 finger.

I am actually abandoning this combo since accuracy with this bullet is poor even at 38 +p speeds. My pet load for this gun is 18gr W296 and a 140 XTP which results in brass that will fall out of the chamber and excellent accuracy. No need to beat up on a gun if you don't have to.
 
someguy2800 said:
It was a Prvi Partizan JHP that I bought a few years ago. Logic would agree with more powder must = more pressure, but the results sometimes do not bear this out. I think in some instances having a slightly fuller case load causes a slower burn.
Click to expand...
It's more likely the data provided from different sources used a different bullet seating depth which can change the pressures, sometimes greatly in small volume cases.

Physics can't be fooled. I can't believe adding powder will lower pressures, more fuel will increase gasses in a confined space which raises pressure. Looking at primers does not prove lower pressures, it only tells you what those primers look like after firing.
 
hdwhit said:
Jacketed or cast bullets? I'm going to assume jacketed because I don't have a manual that lists W296 with cast bullets.

Consider two additional sources:
  • Hornady 4th Edition lists 14.3 gr starting (1,200 fps) to 16.4 gr (1,350 fps) developed with a S&W Model 27 pistol with 8 & 3/8 inch barrel
  • Hornday 8th Edition lists 12.4 gr starting (1,000 fps) to 16.0 gr (1,250 fps) developed with a Colt Python with an 8 inch barrel.
According to the Hornady manuals, you were near or over maximum at your 16.5 grain starting load.
  • Lyman #49 doesn't list a load for 158 grain jacketed bullets with W296.
Click to expand...
Lyman 49 sure does supply data for W296 but they label it H110. Both products are identical, a fact that has been beaten to death for years and proven to be 100% true.

I would not and have not gone over 17.0gr W296/H110 with a 158gr jacketed bullet. I have not loaded lighter than 15.4gr either. With several 158gr bullets my most accurate load seems to be right around 16.4gr and then again at 17.0gr.
 
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