Question about reaching for 140 power factor on 9mm 124 grain load with Alliant Sport Pistol

[rayw1128]

Sorry for the newbie question...  

 

I am looking at purchasing a single port compensated 9mm pistol and have read that I want to be around 140 power factor for the single port comp to be effective.  

 

I am currently loading 124 grain jacketed with 4.3 grains of Alliant Sport Pistol.  With this load, I am getting about 135 power factor (average speed around 1085 to 1090).  

 

Alliant chart said I can go up to 4.7 grains for a +P load with Sport Pistol.  I am sure that if I go to +P load at 4.7 grain, I will be at or above 140 power factor.  

 

I have heard that it is not wise to use fast burning powder to achieve higher power factor as it causes too much pressure; so I am a wondering if is safe for me to try and get 140 power factor with Sport Pistol?

 

I have a lot of Sport Pistol so I would prefer not have to change to another powder if I could avoid it.  

 

Any advise would be greatly appreciated.  

 

Ray 

 

 

[Guy Neill]

The benefit of a slower powder is that it will generally give more gas volume at a given power factor, making the comp more effective.

 

Since you have the Sport Pistol, I'd try it first - especially since components are not as available as they once were.

 

Do you have a chronograph to help develop a load?  Whether or not you can feel the difference between a 135 power factor and a 140 power factor depends on your sensitivity to the recoil.  If your present 135 power factor load is doing what you want with respect to reliability and accuracy, I don't know that there's a real gain going to a 140 power factor.  I would tend to stay with the load you have.

[rayw1128]

Hi Guy, thanks for the response.  I was told by the gun maker that I should try and aim for 140 power factor to see a benefit from the comp.  I have a non-comp'd version of the same gun and it is shooting great at 135.   I think I will try the same load when the comp'd version arrives.  

 

Thanks again!

[zzt]

r, couple of things to think about.  First, a comp redirects gas up so it does not exit the muzzle.  This deprives the slide of some of the energy required to cycle.  Fast powders do not generate as much gas as slower powders, so your current load may not cycle in your comp'd gun.  It would be unwise to continue to increase the SP load to try to get the comp to 'work'.

 

Second:  there is no rule that says you have to get your comp 'working'.  I shoot minor loads through my Open major guns all the time.  I have some PCC loads that will cycle the slide and feel like mouse farts.  They don't do much in the way of 'working' the comp, but they function.  I also have 140 PF loads using lots of a slow powder that do work the comp.  That is the load I use for Steel Challenge.

 

Third:  it is gas jetting out the front of the muzzle that generates the felt recoil.  Some find that initially hard to believe.  You can prove this to yourself quite easily.  Take your current load and fire it through your comp'd gun using the same weight recoil spring as in you uncomp'd gun.  Did it cycle?  If yes, did the brass eject as far?  No, it didn't.    To get proper ejection you will have to go to a lighter spring.  The reason is the comp redirects gas up, so it is not available to jet out the front.

 

Here is what I would recommend.  All you will need is a pound of slower powder and one USPSA no-shoot target.  You do not need a chrono.  Your goal should be to optimize your load for the comp so you get the flattest and softest shooting gun.  Buy a pound of CFE, Autocomp or Silhouette powder.  Use the loading tables to make the minimum recommended load.  Then make a ladder by increasing the load by .2 gr each step.  Make ten of each.  Suppose te starting load is 5.0gr and the max load is 5.8gr.  Your ladder would consist of 5.0, 5.2, 5.4, 5.6 and 5.8gr loads.  Go out to the range.  Staple your target onto a backer and shoot each load into the white side of the target while holding the comp 2" away from the target.  It is very unlikely you will see a lot of debris on the target with the light loads.  That is because almost all of the gas is being redirected up by the comp.  Continue up the ladder until you see and appreciable amount more of debris on the target.  When that happens, the comp is not evacuating all the gas produced so some of it jets out the front.  That increases felt recoil.  For the sake of argument, let's say that happened with the 5.6gr load.  Well, that tells you that the softest shooting load in that gun using that powder is somewhere between 5.4 and 5.6gr.  You can experiment further to fine tune the load if you like.

 

Now there are two ways you can approach this.  If your goal is the softest shooting load, you will already know what that is.  However, you may decide you want flatter shooting, even though it will mean a harder hit to your hand.  So you compare the feel of the 5.6 and 5.8gr loads to see if they shoot any flatter and decide.

 

Generally speaking, for games that require a double tap you want a flatter shooting gun, because your splits will be faster.  For games requiring only a single shot like Steel Challenge, you can go either way depending on your approach to the stage.

 

Have fun and welcome to Open.

[rayw1128]

Thanks for the detailed explanation ZZT.  Great idea about checking debris on the target board.  

 

Will definitely try this out!

[zzt]

2 hours ago, rayw1128 said:

Thanks for the detailed explanation ZZT.  Great idea about checking debris on the target board.  

 

Will definitely try this out!

 

Here is some additional info on the subject.  http://www.brazoscustom.com/magart/0607.htm 

[rayw1128]

31 minutes ago, zzt said:

 

Here is some additional info on the subject.  http://www.brazoscustom.com/magart/0607.htm 

Sweet, thank you!  Will be reading that article over lunch. 

[SteelCityShooter]

On 1/18/2021 at 9:44 AM, zzt said:

Third:  it is gas jetting out the front of the muzzle that generates the felt recoil.  

 

 

Gas jetting out the front of the muzzle generates SOME of the recoil.  Recoil is the reaction to all of the "ejecta", i.e. the bullet and the powder gas so recoil is not generated solely by the gas jet.   Redirecting the gas jet with a comp will reduce felt recoil somewhat but by no means eliminate it.

[zzt]

3 hours ago, SteelCityShooter said:

Gas jetting out the front of the muzzle generates SOME of the recoil.  Recoil is the reaction to all of the "ejecta", i.e. the bullet and the powder gas so recoil is not generated solely by the gas jet.   Redirecting the gas jet with a comp will reduce felt recoil somewhat but by no means eliminate it.

 

You must not be an Open shooter.  With a comp'd gun it is entirely possible to create a load that goes bang, sends the bullet down range and produces no, or a very slight recoil sensation.  The gun will not move.  The slide will not operate.  All the gasses were vented upwards by the comp.  I was astonished to learn this (by accident) with my old compensated 45 gun.  That is not possible in a gun without a comp.

 

The rules are a little different in Open.  It is possible to construct a comp with many chambers such that the correct amount of gas pulls the gun forward as much as recoil is forcing it back.  However, it will be a one shot gun, because there is no energy left to operate the slide.  Since most Open guns are semi-auto, that won't do.  So we limit the number of baffles to retain enough energy to cycle the slide, eject the case and feed a new round.

 

The point I was making above was that as you go up the powder ladder the gun shoots flatter and softer right up until you start jetting appreciable gasses out the front.  Then recoil increases.