Fast Powders Vs Slow Powders


Dear Sir:

I am trying to resolve the issue whether or not “slow” powders have less recoil than “fast” powders in shotgun shells. To illustrate the source of the difficulty I am including a few expert and non-expert quotes.

Excerpts from articles on the subject:

1) Slow powders exert less pressure than fast powders. Pressure does not enter into the recoil calculation.

2) For the same velocity one uses more slow than fast powder. The products of combustion are part of the ejecta and the more ejecta the higher the recoil.

3) Some shooters use International Powder because it shoots softer than Clays.

Non-Expert verbal communication: 700X kicks and Green Dot doesn’t.

I am looking forward to your reply.

Dieter
Dear Dieter,

This is heavy stuff and I’m not sure you should trust me where sensitivity to anything (recoil, mushy movies, babies) is concerned. I’ve covered this question before, but it doesn’t hurt to go over it again for our new readers. Besides, maybe I’ve changed my mind.

The comparison of fast and slow powders brings out the differences between “calculated” recoil and “perceived” or “subjective” recoil. As in any debate, you’ve got to define your terms to have the discussion mean anything.

I define calculated recoil as free recoil expressed in foot pounds that is calculated by the standard recoil formula. The one I use is from the SAAMI Tech Data sheet 1.0401, but there are many other sources. Basically the formula for calculated free recoil takes into account the weight of the gun, the weight and speed of the ejecta (lead shot, wad, powder) and assigns a fixed value to the speed of the exiting gasses. There is no other factor in the formula.

A standard 8# gun shooting 1-1/8 oz with a 33 grain wad and 17 grains of fast powder at 1200 3 foot velocity generates 19.73 ft/lb free recoil. A super slow powder charge of 25 grains, producing the same speed, has 20.60 ft/lb free recoil. That’s less than a 5% recoil increase for an extreme powder difference, but it does exist.

So, according to the formula, when you increase the amount of powder (usually slower powders require more grains of powder than faster powders), you increase recoil. Has to be. Got to be. Maybe not by much, but since ejecta weight increases, calculated recoil increases.

Frankly, the key to it all isn’t calculated recoil, it’s subjective recoil. It’s what you feel, not what some formula tells you. A gas operated semi-auto has exactly the same free recoil as a fixed breach gun of the same weight with the same shell, but the subjective recoil is much lower. That’s because the gas gun stretches the recoil pulse out over a longer period of time. The recoil becomes a long push instead of a sharp stab. If you graphed it, there would be exactly the same area under both curves, but the time axis of the recoil curves would differ substantially.

In theory, it’s the same with fast and slow powders. In theory, slow powders give you a push, while fast powders give you a poke. The funny thing about it though is that different people perceive it in different ways. For everyone who thinks he feels that the slow powder gives a softer push, I’ll show you someone who thinks that the faster powder is softer because it doesn’t push as long. I’ve done blind tests comparing 700X and Unique (even further apart than 700X and Green Dot)and split 50/50 with my test group as to which one kicked more. As I said, it’s real subjective.

I have found that it’s easier to get a tight patterning shell with slower powder because I think that the slower powders distort less shot at ignition. Still, the difference was slim and there are many other variables. I wouldn’t write that one in stone.

Bottom line: If you think that slower powders kick you less, then by all means use them. They only cost a little more due to the large charge weights required. But remember one thing- if you notice a lot of difference in the recoil, get out your chronograph and recheck the speeds. Slower shells definitely, positively kick less than fast ones when the payload is equal.

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 Fast Powders Vs Slow Powders

  1. Rich Dettinger says:

    The writer is concerned about powder speed, most of us are just trying to find powder!

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