I have understood that you should never load a less than minimum load and never exceed the max load. But I see some guys load less than minimum loads for target shooting. Is it a safe practice or not to load less than minimum loads ?
I see this mainly with bullseye shooters in competition.
I regularly load my 45 ACP loads below recommended levels, such as 3.5 grains Bullseye with a 200 LSWC, for 25 yard rapid fire loads, and 4.0 grains Bullseye with a 200 LSWC for 50 yard loads. These are published loads that I have found in the American Rifleman from the mid 1950's. These load levels are very common with Bullseye shooters so they are very well understood.
Propellants vary by burn rate. Slow burning powders do not do well downloaded, so downloading Blue Dot in 44 Special, 38 Special, 45 L Colt worked, but the extreme velocity spreads were in terms of hundreds of feet per second. This indicates to me that the powder is burning erratically. This could be dangerous as consistent burning produces consistent pressure waves. Powder does not burn like a candle, and the further you get from nice, smooth, pressure waves, the riskier things get. Perturbations in the pressure wave do cause over pressure conditions. In fact, we see this all the time with old deteriorated gunpowder in old surplus ammunition. Lots of guns have blown up with old military surplus ammunition. Pressures increase when powder deteriorates due to "burn rate instability". Basically that means the powder granule is producing unpredictable pressures waves which conflict with the other pressure waves being produced as the propellant burns.
For my autopistols, I can download fast burning powders and as long as the bullet leaves the barrel, and the autopistol functions, things have been OK. One risk with low pressure loads is that occasionally, a bullet does not leave the barrel. I had that happen in cold weather and a weak mainspring and AA#9, a magnum pistol ball powder. I was lucky the bullet lodged between the cylinder and barrel, so it was obvious the bullet had not left the S&W M586. If however, the bullet had been lodged half way up the barrel, who knows what would have happened next round.
I have loaded below recommended levels for a number of rifle cartridges, the 308 Win the cartridge I have most experimented with. I have shot thousands of 168 SMK's with 39 grains IMR 4895. This is below most manuals but it is a very low recoiling load, and very accurate at 200 yards. Another great load is 42.0 grains IMR 4895 with a 168 grain bullet in the 30-06. I would not use either in a gas gun, but both shoot great in a bolt rifle.
I talked to Alliant, and the technicians there told me that with piezo electric pressure gages, they can see the pressure curves, and they make decisions based on what they see. If small component changes cause huge pressure curve changes, they don't recommend those loads. The specific example discussed was the use of Blue Dot in rifle cartridges. A poster named Seafire has been promoting the use of Blue Dot in 223, and other cartridges, others have copied, and it does not take much effort to find rifles that have Kaboomed with Blue Dot loads. Here is one:
Catastrophic Failure of Rifle Due To Double Charge of Blue Dot The poor poster thought he double charged the case. These Blue Dot kabooms have occurred frequently enough that it should be obvious that small loads of Blue Dot in rifle cartridges is risky. However, those promoting the practice are adamant that nothing bad has happened to them. Actually they have been lucky, there is no skill involved, just luck, and given enough rounds downrange, their luck will run out. Call it Normalizing Risk. If you watch the movie Deepwater Horizon, you will see lots of
risk Normalization, at some point, the luck runs out. Alliant did not recommend any of these Blue Dot loads, warning that the pressure curve changed too quickly with component changes. I have no doubt Alliant has also looked at the pressure curves of many light loads, cartridge case and bullet combinations, and decided to publish based on consistency. The loads that show irregularities have been deleted from their most current reloading manuals.
So, if the manuals are using pressure instrumentation to develop loads, than following their recommendations is the simplest and safest procedure. However there are well characterized loads that don't appear in the manuals, and while there is risk in using them, it seems the risk is small.
Maximum loads are the most dangerous. Reloaders blow up guns all the time with "maximum" loads. Because the slope of the pressure curve is exponential, pressures can zoom up very quickly. Pressure is not your friend. Pressure may give you the performance you want, but is that the performance you need?
