Slow Powders


Bruce,

I have become to believe that we must all see recoil in a different manner–where I can use a slow-progressive burn powder with a less-robust primer–and be completely sure that it is different than a load with a fast rate powder and 209A primer—but all of the so-called experts on the SS site think I am crazy—my wife does to but that is a different story.

I have loads that will pick up 55fps from a 26 inch barrel to a 34–assuming the speed is gained by the progressive burn powder still pushing the load.

I was intrigued when Longshot was introduced just because these speeds had not been able to be used—not that they were needed.

So I came up with my own little test using AA’s–once fired— one load with max pressures but with less speed, using a fast rate powder (clays) and a nasty one with Longshot that had three thousand psi less pressure—both shot through an auto–the retrieved hull from the fast rate powder was completely unscathed—but the hull from the Longshot load was bowed out at the back .105 of an inch to the top of the primer—my only explanation is that the Longshot load pushed so long for the bolt to lift off the case and the extractor being the limiting factor in how much damage would occur—-and the load still had enough pressure to bow the hull out after the bolt lifted. This was done repeatedly with the same results–with an SX-1.

I was just wanting to know if I really needed a therapist or is there anything to my beliefs.

Regards,

Steve

Good Morning Steve,

Your email caught me mid-way through my second cup of coffee- generally a good time. The caffeine hasn’t worn off and the reality of meeting today’s deadlines hasn’t yet dawned on me.

Usually the slow/fast powder argument centers about recoil. I have no argument with people who say that they feel less perceived recoil when using slow powders. I did some tests on LongShot too, but being a blunt trauma kind of guy, went directly to el maximo hyper velocity load. Geez, what a rocker! I never got into the 1,500 fps area they promised, but I did see the 1,400s.

Here’s the deal on slow powders as I see it. I use the standard SAAMI formula for free recoil. The only input involves the weight of the gun, the weight and speed of the ejecta and a constant for the jeto effect of the gas. Obviously there is no provision to differentiate between a slow powder or fast powder, not between a gas gun and a fixed breech gun. Time duration of the recoil pulse is not included in this free recoil formula.

Yet we all know that time is a factor in perceived recoil. That’s why gas gun kick less and why recoil pads work. The area under the recoil curve remains the same (free recoil formula), but the height and width of the curve changes (perceived recoil). The whole question boils down to perception. How much can an individual shooter perceive? This is where it gets subjective.

With the slow powders, I don’t think that it is so much a low pressure thing. Low pressure is more of a result than a cause. I think it’s a time duration thing. A slow powder burns longer, thus stretching out the recoil pulse when compared to a fast powder. This is the gas gun vs O/U analogy. It all becomes a question of how much is enough to notice. Anyone can assess the recoil attenuation of the gas gun vs the O/U, but the difference in recoil pulse rate of a powder that burns in 14″ of barrel vs one that burns in 8″ of barrel may not be as easy for everyone to discern.

It’s like a lot of barrel modifications. Take porting. I’d never argue that properly placed porting doesn’t work. But I would argue that it doesn’t work enough to matter for many shooters. Ditto slow powders. The difference between the “push” of the slow powder and the “poke” of the fast one, when used to push the same ejecta at the same speed, has never been something that I could notice over time. That doesn’t mean someone else who is less Neanderthal might not notice it, but I don’t.

I once did a blind study using 3 dram 1-1/8 oz loads with 700X and PB. Of the six shooters I tested these shell on, three thought that the PB load was softer, three though that the 700X load was softer. Go figure.

As you point out comparing velocities achieved in 26″ vs 34″ barrels, you have to be careful in your testing. I have a guy who absolutely swore to me that extra long forcing cones and 3″ chambers made his gun kick less. I asked him if he had chronographed the barrel before and after the alterations. He said no, he didn’t have to. He just knew that the barrel kicked less after modification. I don’t doubt that it did, but I also don’t doubt that the barrels lost velocity now that they effectively had larger chambers and lower pressures when using the same shell. Ain’t no free lunch.

Two things to remember when using slow powders: 1) economy. If 18 grains of fast stuff will do the job and it takes 23 grains of slow stuff to equal it, if your jug of fast powder costs $100, your slow powder costs the equivalent of $128. 2) Powder weight is a part of the eject weight in the free recoil formula. More powder means more eject means more recoil. It isn’t much, but it’s there.

I think that you made an excellent observation as to the bulging of the brass when using slow powders in your auto. It would certainly seem that the timing of that SX1 wasn’t optimized for that slow powder. I wonder if the new Berettas with their secondary gas valves would do the same thing? At any rate, I definitely would not be comfortable with those high pressure indications when the bolt is open. What if you inadvertently reloaded a hull with flawed brass?

Best regards,

Bruce Buck
The Technoid writing for Shotgun Report, LLC
(Often in error. Never in doubt.)
http://www.ShotgunReport.com

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One Response to Slow Powders

  1. Jeffrey DeSantis says:

    I feel compelled to add that I had a set of Remington 1148 skeet guns. The 12, 20 and 28 gauge guns noticeably were more reliable with slower powders. It seemed tom me that these recoil operated actions just needed a little bit more time to cycle.

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