OAL or powder charge

[jimbullet]

I am trying to determine which is a preferred manner of increasing power factor just a tad.

I am loading 40 S&W and wanting to make sure that I will consistently pass any chrono and for that I have always wanted to have that extra margin above the specified pf, which in this case is 170 for IPSC standard division.

My current load is achieving a pf171 and since that for me is too close to the minimum major pf, I am wanting to at least reach a pf173'ish to maybe somewhere in the pf175's ensure that I pass no matter what chrono is used.

My OAL is longer for 2011 pistols which is currently at 1.170. The powder charge I use is above SAAMI specs already using win231 5.4; 180gr CMJ. A different load of 5.2 at 180gr lead gives a pf180 at OAL 1.156.

My question is should I consider reducing OAL which will increase pressure and perhaps give me that extra lift in pf or would you just stick to the OAL that you have and simple add another 0.1grain which will still take you farther out of SAAMI specs.

Both OAL's feed properly on my 2011 pistol.

Any thoughts appreciated.

[Justsomeguy]

Not that 231 would be my first choice for major, but with your long OAL pressure may still be within due SAAMI bounds even though you are over the recommended charge weight. Since it feeds nicely at that length, and you seem to be determined to use 231, I would keep the OAL and try increasing the powder charge a bit until you are satisfied with the results. There are, of course, a lot of other powders that would easily make the PF you are looking for without any drama as far as pressure is concerned. WSF, Silhouette, AutoComp, HS6, AA7, Longshot... the list goes on.

[Hi-Power Jack]

Why not try both, and see what the chrono and the accuracy tells you - you might prefer one or the other?

[jimbullet]

I have had very good success with 231 since loading 45's and now loading 40's I have decided to stay with this powder. The accuracy I am getting with this has been very good. HS6 as I thought is a slow burner and as such I have only used that for 9mm major.

[Rob01]

With my 180 HAP bullets I make 175 PF with 7grns of HS-6 at 1.155" OAL in my STI. It's my back up load as I use Titegroup at 4.6grns to make the same PF.

[jimbullet]

Anyone know which is better, a longer OAL so that the projectile is closer to engage the rifling or shorter OAL which means there is a gap and the projectile will have to "jump" before engaging the rifling of the pistol.

With all things equal, meaning it fits in the mag, functionality it works, feeds reliably, which OAL will produce a better accuracy?

[Justsomeguy]

Though excessive "free bore" in rifles can cause a drop in accuracy, the same does not always apply to pistol rounds. Rifle bullets are under a different set of parameters than pistol bullets given the pressures and velocities of the two. Pistol chambers will almost always allow for a pistol bullet to still be in the case (when touched off) as the bullet hits the rifling no matter what you set the OAL at. One thing you don't want is for a pistol bullet to actually be touching the rifling during the chambering process as this can spike pressures as you probably already know. OAL is pretty much gun and bullet specific though, and so only experiments with YOUR pistol with the bullet and powder you are currently using can tell you what is the most accurate. I grant that free bore will have some effect, but suspect it will be less than the powder choice and load volume will make.

[jimbullet]

What is an acceptable accuracy on a 40cal out at 20 meters? Should it be less than an inch group? What would make it unacceptable?

Reason I am asking is the load I have developed so far with a longer OAL appears loose but not sure if I am just too pedantic about it. The grouping I am getting is 2 - 2 1/2 inches at 20 meters.

[Hi-Power Jack]

What is acceptable accuracy on a .40 cal at 20 meters?

Acceptable is personal - up to you.

Depends on how much money you have, and what you're doing with the gun ...

Yes, usually in the action matches 2-2.5" at 20 meters is "acceptable", but you

can get better - but it's expensive.

[jimbullet]

What is acceptable accuracy on a .40 cal at 20 meters?

Acceptable is personal - up to you.

Depends on how much money you have, and what you're doing with the gun ...

Yes, usually in the action matches 2-2.5" at 20 meters is "acceptable", but you

can get better - but it's expensive.

I actually thought that improved accuracy can be achieved with a variation of a load. As an example, I previously loaded 45acp and the lyman reloading manual indicated a maximum charge and it had a designated the said load as potentially the most accurate.

I used the recipe and they were correct as I achieved 1/2 inch groups out at 20 meters with it.

Unfortunately, reloading the 40, unlike the 45, throws OAL into the mix and so I am having to throw the reloading book away and experiment.

I suppose what I am trying to find is that sweet spot using TMJ projectiles.

I previously used lead projectiles with a lower OAL of 1.158 with a pf180 and my pistol was doing 1 inch groups at 20 meters. I am trying to replicate this using TMJ projectiles and had thought that it was as easy as using the same powder charge.

[Hi-Power Jack]

You're right - if you have a gun capable of shooting 1" groups at 20 meters, you should have the potential to

find a load that will do it again. IMHO, most handguns are NOT capable of shooting that well -

But, as you mentioned, the bullet you select, the OAL, the powder and the powder charge are all variables

that you'll have to play with - that's the beauty of reloading. It's possible that YOUR gun may not like a

particular bullet, at all. Or a powder.

Good luck trying to get another 1" group load. I'd love it too.

[jimbullet]

After several test with my current OAL, it appears that it is sometimes hitting the slide stop causing a premature slide lock. I might have to shorten it apparently.

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[jimbullet]

Ok so I have now extensively tested ammo. I loaded ammo at 1.168 oal and another batch at 1.158 oal. Same projectile at 180 and same powder and powder charge.

I initially thought by changing oal the velocity will either increase or decrease however to my surprise there is no change at all. Is it just me or is this normal?

I'm thinking of trying 1.190 oal and having the same powder charge and see if there is any change in velocity.

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[mjohn]

^^^^^^^^^^^^^

Thanks for the reports(s). I too thought that velocity would change with different OALs. However, I do not have any experience in testing. I look forward to seeing your future results.

[AlphaSeeker]

I have tested 200gr and 180gr fp plated heads with SR7625.

OAL of 1.190 ; 1.165; 1.130. Groups of 10rds tested. Using 4.0, 4.5, 5.0, 5.3 gr.

Reducing OAL resulted in 35 to 50fps increase for every .03"

[jimbullet]

Perhaps my change in OAL of 0.01 was insignificant.

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[jimbullet]

Ok, so tried the OAL 1.190 with the same powder charge at 5.5, and as expected, there was a significant reduction in velocity. The change was about 50 fps from ammo that was an OAL 1.158

Edited June 15, 2014 by jimbullet

[AlphaSeeker]

Unless you are looking for the last bit of accuracy [bulls eye], loading shorter allows you to use less powder.

Loading longer is great if you are running open class and want to stuff more gas producing charge into the shell, to work the comp.

As far as feed reliability - if it fits in your mag tube, you should be able to tune the gun to eat the ammo without problems.