Powder Charge Reminder

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I received my new Magnetospeed a week or so ago and decided to chronograph the most accurate loads I use in my .17 Remington, .223, .22/250 and .243 Winchester. All are loads that I have safely used for quite some time but had issues getting true velocities with my Chrony unit. Erratic readings, failure to read .17s regardless of all the tricks for that tiny bullet, and just plain got tired of trying to get the darned thing lined up, level and at the right height and distance and gave up on it. Happily, nearly all of my loads run through the Magnetospeed fell statistically very close to the "guestimates" I had been using and now I have them logged accurately.

All, that is, but one.

The big surprise came when testing my .243 loads. The load I have been using (44.0 grains) falls 2.5 grains below the listed maximum (46.5 grains). I had worked up to it carefully (from a full grain less than the book's start of 41.8 grains) and stopped when I hit the best accuracy load without pressure warnings. I really wasn't interested in top speed, just accuracy. Brass lasts well and extracts easily without unusual measurements, primers look good, no sticky bolt lift and accuracy that hovers between .25" and .5" consistently. Magnetospeed reads almost exactly the velocity of the listed maximum charge (2.5 grains higher than my load, remember) with an SD of 12. Now some of that may be due to my barrel being 2 inches longer than the manual's test rifle, but that should only account for maybe 50 fps or so. 150 fps is unreasonable, and I shudder to think what pressure might be like if I chose to load to the "book" maximum, or worse yet, started there as we all know some reckless people do. I'm using the same primer but Nosler brass rather than the listed Winchester and know it is heavier, which is another reason I started even lower than normal when developing the load. All charges were run from my Chargemaster and then weighed on a tuned scale for verification. Bullet is even seated a bit longer than 'spec' but not touching the lands, let alone 'jammed'. Brass is trimmed to minimum length and necks are 'skim' turned and the chamber is in a commercial barrel, not a tight custom dimension.

After all that boring detail, the bottom line is that this is a graphic reminder of why one should always start low when developing loads. Maybe this is a fast lot of powder, but it performs as expected in other calibers I use it in. Hard to say, but the lesson still remains: START LOW AND SLOWLY WORK UP!

 

[divingin]

Brass lasts well and extracts easily without unusual measurements, primers look good, no sticky bolt lift and accuracy that hovers between .25" and .5" consistently. Magnetospeed reads almost exactly the velocity of the listed maximum charge (2.5 grains higher than my load, remember) with an SD of 12. Now some of that may be due to my barrel being 2 inches longer than the manual's test rifle, but that should only account for maybe 50 fps or so. 150 fps is unreasonable, and I shudder to think what pressure might be like if I chose to load to the "book" maximum, or worse yet, started there as we all know some reckless people do.

Max safe load in your rifle may well be different (lower or higher) than what's in the book. You're inferring your rifle tracks what the published data does; but you're missing one data point: pressure (unless you have a sensor in your chamber.)

Part of working up from low towards max is to make sure you don't exceed max pressure for your rifle earlier than published data (i.e. staying safe.) The opposite is true as well (except you didn't get there): Working up to where you do get pressure signs will tell you whether or not the published max load data applies to your rifle or not.

 

[SSL]

Max safe load in your rifle may well be different (lower or higher) than what's in the book. You're inferring your rifle tracks what the published data does; but you're missing one data point: pressure (unless you have a sensor in your chamber.)

Part of working up from low towards max is to make sure you don't exceed max pressure for your rifle earlier than published data (i.e. staying safe.) The opposite is true as well (except you didn't get there): Working up to where you do get pressure signs will tell you whether or not the published max load data applies to your rifle or not.

I'm not inferring that the rifle tracks the data - rather that it does not. Pretty much my point is that book velocities, and especially maximums, can not be taken as gospel for every rifle. Only by starting low and working up can you find what each firearm's characteristics are. It isn't all that unusual to reach pressure signs before hitting maximum listed loads - I find that often when working with CFE223 (NOT the powder used in this case) in various cartridges for other rifles - but reaching the velocity range of the 'max' load at 2.5 grains less powder without any pressure signs of any kind is startling. I use the same powder in three different cartridges and I see no statistical anomalies across the range of load/velocity results. Kind of a head-scratcher.
Add an additional bit of info; a different powder tracks almost perfectly between load/velocity listed data in this rifle with all other components and conditions being the same. Just because one powder/cartridge/rifle combo mimics the 'book' values is no indication that another one will. Book values are only a guide at best. Pressure and velocity go hand in hand in most cases. If you see velocity rising at an unusual rate, beware, pressure is too. Safety first.

 

[Orr89rocz]

Try it again with the book listed brass. You change components you can expect to see differences. Nosler brass vs winchester is a change if they definitely show much different weights

seen the same thing in my 300 wsm with rem brass and norma brass. Tried my rem brass load that was under max and in a node, in my norma brass and immediately had heavy bolt lift and ejector mark. Had to drop down a good bit to maintain node and speed.
Thats why you are suppose to follow recipes exactly to expect the right results

 

[Jager]

The singular benefit of a good chronograph - over and above everything else it might do for us - is it gives us instant, actionable data... from the very first shot. Marry it to QuickLoad and you even have a view of the actual chamber pressures you're running.

Following load recipes exactly is certainly no guarantee that you're going to get the same results as whoever came up with the recipe.

And waiting for metal failure - which essentially is what classic "pressure signs" amount to - is pretty a pretty crude way to operate, when you think about it. Despite that being all we had to go on for a long, long time.

A good chrono changes everything.

 

[Laurie]

Thats why you are suppose to follow recipes exactly to expect the right results

Just so - a fact that most handloaders are either unaware of, or if they do know about this, prefer to ignore as unimportant or inconvenient. As time goes by and we have more and more brass options, I've become increasingly aware of how much this matters. It's interesting to measure the 'water overflow capacities' of different case makes and to model the pressure changes in QuickLOAD. People might get a nasty surprise with some combinations.

In the UK we cannot own semi-autos other than in .22 rimfires, but we have a large choice of full-custom AR-15s redesigned and fully adapted to manual operation with sturdy side handles. They are very effective rifles indeed, and are generally capable of considerably better precision than the genuine gas-powered originals. BUT ......... they also do tell you a lot about chamber pressures. Radway Green L2A2 (62gn SS109 type) 5.56mm Nato as supplied to the British Army takes one really hard tug to get the bolt moving for instance.

When I had one such rifle, I could clearly judge each step in pressure increase above loads that QuickLOAD computed as around 53/54,000 psi. One day I paid a visit to an outfit that loads match grade ammo on a small workshop scale and ended up buying 200 new German MEN 5.56 cases which it used for its 223 ammo. I loaded up a box with a favourite combination that worked very well and gave sweet extraction with what would have been either Winchester or Lapua 'Match' brass - probably with the 69gn SMK. Nothing exploded or broke, but after firing the first round, the bolt was locked up really tight and I had to struggle to break the case seal in the chamber and let me open the bolt. They went home and were pulled. These cases weigh 13% more than current 'Blue Box' Lapua, therefore even more than the Winchester brass of 15-20 years ago. I found them only recently, still unused. I ought to fire a couple in my 223 F minimum SAAMI chamber rifle to fireform them and see just what water weight they hold in comparison with commercial brass.

 

[Laurie]

The singular benefit of a good chronograph - over and above everything else it might do for us - is it gives us instant, actionable data... from the very first shot. Marry it to QuickLoad and you even have a view of the actual chamber pressures you're running.

Yes, I couldn't agree more. Anybody doing load development with loads that even approach top pressures should have and use this pair.