9mm powder felt recoil differences?

[gregjc9]

I have two pet loads I've worked up for 9mm, both loads are in the 1050 range of velocity (second up from minimum load in Sierra's Ed 5 manual). The odd thing is the recoil from the W231 seems very soft compared to the Power Pistol. I understand the PP is a much slower burning powder than the W231. Is this the reason for the recoil difference? Both loads perform very nicely in my XDm, no problems of any kind so far. Bullets used have been Rainier and Berry's plated.

The loads were based on Sierra's Edition 5 load data:
115gr (plated TCJ RN) COL=1.100 Power Pistol 5.4gr (Lee Pro Auto disk .49)
115gr (plated TCJ RN) COL=1.100 W231 4.4gr (Lee Pro Auto disk .43)

[Unclenick]

Yup. Slower powders recoil more for a given achieved bullet velocity.

First, short of a nuclear reaction, matter cannot be destroyed, but it can change form. When you burn the powder it converts from solid to gases, but the gasses have the same total mass as the original powder charge. As the bullet accelerates, a portion of the mass stays at the breech and a portion accelerates with the bullet, adding to recoil. In the case of a big overbore magnum rifle, that mass addition can be noticeable, but in this case it's too small to feel. Just thought I'd make you aware of that factor in case you start messing with rifles?

Second, and far more significant, is what's called rocket effect. This occurs at the moment the bullet exits the muzzle. The pressure in the barrel accelerates the gas mass forward to higher velocity than the bullet. That rapid gas mass acceleration results in the equal and opposite reaction that a rocket engine depends on to work, adding to recoil. How much it adds depends not only on the gas mass, but on the pressure in the barrel at the moment the bullet uncorks it. Because a slow powder is a larger quantity of propellant it makes more total gas if it is allowed to burn completely. That can be done safely because it doesn't reach its pressure peak until after the bullet has moved far enough to create more volume for the gas to peak in, but it also means there will be more pressure behind the bullet at the moment it exits the muzzle. Greater pressure accelerating greater mass means greater rocket impulse, and that's what causes most of the difference in recoil you are feeling.

People underestimate rocket effect. In some of those overbore magnum rifles I mentioned it can be over half the total recoil. That is why muzzle brakes with holes aiming equally in all directions work. They aren't controlling the recoil with jet impulse. They simply try to relieve the muzzle pressure perpendicular to the recoil force so there won't be any pressure left to create rocket effect at bullet exit. People who use detachable muzzle brakes often observe they reduce recoil significantly with maximum loads of slow powders, but don't seem to do much more than increase noise when using lighter loads of faster powders. That's because there isn't as much muzzle pressure to relieve with those lighter, faster powder loads.

Bottom line, if you want to minimize recoil, as with youth loads, you use the fastest powder that can give you the bullet velocity you want without going over your chamber pressure maximum.

[gregjc9]

Wow! What a wealth of information. Thanks for the reply!

The noticeably softer recoil with the W231 just worried me that I may not have the load right.

Considering the information you provided, and that these loads are not youth loads, and the loads will be primarily used in my XDm, and eventually in IDPA matches, would the slower burning powder be best to use in a semi-auto (to ensure proper slide operation)? I have not had any issues with either powder, so just curious if I should stick with one vs the other. BTW, both powders seem to perform equally well in my .45 Kimber Custom Classic Target at their respective loads.

I think my new pet loads will be my .380 and 9mm with Power Pistol and my .45 with W231.

[RidgwayCO]

If you don't chronograph your loads, then you don't really know what they're doing. My lot of Power Pistol must be a little faster than average, as it requires me to reduce powder weights a little in order to keep my loads within published data specs, as well as matching what QuickLOAD predicts. Conversely, I've loaded Accurate #7 loads that performed way below what various reloading manuals and QuickLOAD predicted they should do.

If the recoil impulse you're feeling is noticeably different with W231 than with Power Pistol, then I predict that the W231 loads aren't producing near the velocity of the Power Pistol loads. The only way to know for sure is to chrono them.

But hey... I've been wrong before!

[gregjc9]

Good point on the Chrono. If the charge amounts are at or slightly higher than published data (slightly higher due to the Lee disk capacities), then shouldnt the resulting velocity be near what is published?

[RidgwayCO]

The velocity you're getting depends on all sorts of things... COL, actual case capacity, actual powder burning speed, your barrel length (and yes, there are "fast" and "slow" barrels), primer used, etc, etc. The only way to know for sure what you're getting is to chronograph YOUR loads in YOUR guns.