Pressure signs/chronographing

[overbore]

Son, I suggest you have a look at how Hogdon Powder lists a max load. FYI, that is not maximum pressure nor is it max velocity; rather, it is Optimum Charge Weight. Pressure is NOT from one thing alone. for example, changing brands of cases changes volume. Going from a mild primer ( Russian and CCI 200 )to hotter primers will increase your pressures around 15%!! Using moly coated bullets will lower your pressures. Adding neck tension will increase velocities-- got the picture?? Until you grasp the variables, I respectfully suggest that you you adhere to published data then work up charges in 1% incriments until you get experience and knowledge in what you are doing and alway wear eye protection!! Cordially, Overbore

[jwp475]

You are correct Moly use does lower pressures, and with the reduced pressure also comes lower velocity. IME changeing to a hotter primer will increase pressure as well as velocity. Velocity is not a definate indication of presure as has allready been stated, but if one is useing the proper burn rate of powder and your velocity is in the stated velocity range for the cartridge then one is in safe territory IMHO. Example in the 30-06 useing H-4350 powedrr and 180 grain bullets if you are getting 2700 FPS you are in safe territory, if you are getting 2900 FPS it is safe to say that you are above SAAMI pressure specs with this powder... If one loads a faster burning powder such as BUllseye in the 30-06, then dangerous pressure will be reached long before spec velocity levels are ever reached.

[.280Rem]

Originally Posted by overbore

Son, I suggest you have a look at how Hogdon Powder lists a max load. FYI, that is not maximum pressure nor is it max velocity; rather, it is Optimum Charge Weight. Pressure is NOT from one thing alone. for example, changing brands of cases changes volume. Going from a mild primer ( Russian and CCI 200 )to hotter primers will increase your pressures around 15%!! Using moly coated bullets will lower your pressures. Adding neck tension will increase velocities-- got the picture?? Until you grasp the variables, I respectfully suggest that you you adhere to published data then work up charges in 1% incriments until you get experience and knowledge in what you are doing and alway wear eye protection!! Cordially, Overbore

Son? Got the picture? I understand how the variables can change things. It's why when you change some component you back off and start working back up. Sometimes it has an effect, sometimes not. The pressures given in loading manuals, and such start at starting loads, and work up to max safe loads. Hodgdon can't give me an optimal charge wt for my gun using their components and bbls. The Hodgdon Data max loads are loaded up to or just below SAAMI max for any given round.

Again, its not an absolute, but velocity, taken in to account with all the variables factored in, indicates pressure.

I suggest you go read Handloader Apr-May 2007, John Barsness' article on the 7x57, and how to load it to modern pressures for modern guns. He outlines it by watching velocity to know when you're at max safe pressuress. It's how I approach my load work up for all cartridges.

Cordially, .280Rem

[travelr47]

I'm in agreement with 280Rem re velocity and the use of a chronograph to aide in determining pressure without pressure testing equipment. Some of the other comments
seem a bit scary though. There are a lot of variables that need to be recognized
and taken into consideration when working up any load, starting with the specific
firearm that's going to shoot the load.

If your load is below the maximum load listed and is chonographing from your rifle
at the maximum velocity, you've got a max load!

Changing from a standard primer to a magnum primer does not automatically increase
the pressure by 15% or anything else! In a variety of primer tests over the years that
I've read, including Barsness' in Handloader Magazine, where WW magnum rifle primers increased the pressure by 20,000 psi, while there was negligible difference between some other mfr's magnum primers from their respective standard primers. Maybe the results from Barsness' test only address the lot numbers of the primers he tested, maybe not. Regardless, it's always risky to generalize when we are only reloading for our specific guns.

Ken Waters in his "Pet Loads" book describes his method for measuring pressure without
the appropriate equipment, where he measures the case head with a micrometer of new
unfired brass, then again from factory loaded after it's been fired. The case head expansion measurement from the fired factory load he sets as "maximum". (Actually Ken measured the pressure ring just above the case head that is formed on fired brass. And it requires a micrometer to accurately take this measurement.) But Ken also chronographed velocity as well to balance out other indicators.

As mentioned above, another indicator that you're at maximum load is when adding a half grain of powder doesn't increase velocity. Not always, but usually. Some other indicators include enlarged primer pockets, blackened primers, blown primers, flattened primers, excessive case stretch requiring the cases to be trimmed after firing, as well as hard to open the bolt, etc.

Re Hodgdon and their list of maximum loads with their powder: Hodgdon definitely is listing MAXIMUM LOAD DATA, ALONG WITH EITHER PSI OR CUP MEASURED PRESSURES. I'd suggest if anyone thinks otherwise, a phone call to Hodgdon will quickly clear up the confusion. But again, that's only with their test barrels and components, and every bullet & powder mfr I know of repeatedly WARNS the handloader to work up their loads carefully and only using the load data these companies provide as guides and NOT just jump in and go to their maximum load data to start with!

I don't know of any rifle cartridges that use Bullseye or any other fast shotgun powders typically used for loading some handgun cartridges, when loaded with jacket bullets. I know a fella who loves to use BlueDot and GreenDot for "reduced loads" in some rifle cartridges, but even those powders are significantly slower than Bullseye! The only rifle cartridges I can think of that might use such powders are JDJ's Whisper cartridges. To suggest velocity should be discarded as a pressure indicator is simply a fool's folly. The Bullseye example notwithstanding. Everyone needs to be aware of every component's compatibility with the other components they're using to handload for any cartridge and NOT create a dangerous situation by mixing and matching capriciously. That includes the differences between 5.56x47mm military brass and .223 Rem brass; and, simply the volume capacity difference between one brand of brass from another brand, regardless of caliber. And how the various bullets, and their design affect pressures. Such as a Berger 168-gr VLD bullet (308-cal) versus someone else's 165- 168-gr of the same caliber.

Bottom line: Without the appropriate testing equipment to measure pressure, we have to rely on a variety of information to make an informed and reasonable assessment of whether or not we've reached a maximum load. To arbitrarily dismiss one form or another of data available to us is courting disaster.

[.280Rem]

travlr47,

Good post. So many times I post about loading, velocity, max powder charge, and pressures, and most everyone that reads it focusses on one aspect or another and loses the rest.

If your load is below the maximum load listed and is chonographing from your rifle
at the maximum velocity, you've got a max load!

Exactly! When I write or talk about this stuff, everyone automatically assume I'm suggesting you can always load over max. I suggest you can safely load to max, so long as you choose the right powders and bullet combos. I'm suggesting that velocity is more reliable than merely saying "Well, I'm within book max loads". I've seen rifles, custom rifles usually, with tight chambers, that wouldn't take max powder charges. They did, however, shoot to max velocity, but with charges under the listed max powder charge. When you hit max velocity, you don't add powder. You can add powder until you hit max velocity, BUT max velocity is different with each powder/bullet combo. You can't safely get as high a velocity with R-7 and 165s in a 30-06 as you can with R-22. Still, if you have the data to reference you can know what your "max velocity" is with each powder. "Max velocity" I think is where some get confused. "Max velocity" varies, but if you read the data correctly, you can pretty well estimate what it is with a given powder.

Another example of mine: Noslers top velocity load for the .280Rem is 57grs of R-19 with 140s at 3150fps. Theirs is done in a 26" bbl, so I subtract @ 50-75fps to figure my top velocity in my 24" gun. I start loading R-19 and bump it up until I hit @3075-3100. Then I stop. If it takes me 56grs or 58grs, I'm there. I don't add more if I hit 3100 at 56grs because the book says max is 57, I stop. Likewise, if I'm at 2950 when I hit 57grs, I'll add powder. Also, knowing that SAAMI max is 60k psi for the .280, and 65K for the .270, I find it's safe to load to 65Kpsi, and I can bump it up a bit more if I want. 3100-3150 with 140s is my standard load with many 139/140 bullets, using R-22, R-19, H4831. These velocities could not be obtained using faster burning powders. With H4350, my max velocity would be @3000-3050fps. Running the data through Quickload suggest that I'm running @ 62K-63K psi. And since I've loaded these loads for years with zero signs of pressure, and good brass life, I think I have a pretty good handle on velocity vs. pressure.

[eddybo]

Good info in this thread. One thing I have wondered about that maybe some of you can answer is neck tensions effects on velocity and pressure.

Can you see a scenerio where velocity of a load is right in line with book velocities, and the load is well below max reccomended powder charge, but with above saami pressures?

I would not think that there would not be a direct correlation between velocity and a pressure spike caused by an unreasonably tight neck and that the above scenerio can and does happen even though the loader fully believes that his load is safe.

[.280Rem]

I had to go back over this again. I don't appreciate the condescending tone.

Originally Posted by overbore

Son, I suggest you have a look at how Hogdon Powder lists a max load. FYI, that is not maximum pressure nor is it max velocity; rather, it is Optimum Charge Weight.

I can't find where it says that anywhere on the Hodgdon Website, but would love it if you'd point that out to me. It does say, as all load data warnings do, "NEVER EXCEED MAXIMUM LOADS". And to further show that they are "maximum loads". The "max load" data in say for instance the .270Win runs arond 60K-63.5K psi. SAAMI max is 65K psi. Most all modern data that I read gives a little cushion, usually around 2K-3K psi from the very max pressure. These are, for all intents and purposes, max pressure loads.

Originally Posted by overbore

Pressure is NOT from one thing alone. for example, changing brands of cases changes volume. Going from a mild primer ( Russian and CCI 200 )to hotter primers will increase your pressures around 15%!! Using moly coated bullets will lower your pressures. Adding neck tension will increase velocities-- got the picture??

Yeah, I got the picture! I don't at all think any of my posts said anything to the contrary. However, I'd suggest your 15% mark for hotter primers is too hard a number. It could be more or less. In fact, many think that Winchester Large Rifle Primers are about as hot as other Magnum Primers. When I tried CCI Mag primers with a load I'd used WLR's with, the velocity changed very little. Pressure may have changed some, but not enough to notice any signs or velocity changes. But, that may be because WLR's are very hot anyway. I agree that changing the primer, next to changing powder can have a large effect on pressure.

Originally Posted by overbore

Until you grasp the variables, I respectfully suggest that you you adhere to published data then work up charges in 1% incriments until you get experience and knowledge in what you are doing and alway wear eye protection!! Cordially, Overbore

I do grasp the variables. You just don't agree with the way I load I guess. I have plenty of experience. A little over 20 years of loading and shooting. More if you count my time spent watching and learning from my father. Maybe not as much as you or some, maybe more, I don't know. If you'll talk to some in the gun and gun writing biz, you'll see that my approach to loading, velocity, and pressure, is a sound approach to safe loading.

And finally, I want to say, that I'm not suggesting that you do it my way. Im simply laying out how I approach loading. It works for me.

Best,

.280Rem