Making Power Factor

[MikeBjerum]

One of the games played by handloaders when making power factor is felt recoil.  Light bullets, fast burning powder.

Increase bullet mass and you increase felt recoil, even when down loaded to same power factor;
Decrease bullet mass and you reduce felt recoil, but without increased velocity you lose power factor;
Decrease bullet mass, increase velocity, and tweak the powder burn rate, and you get power factor with less felt recoil.

This is why if you go to many of the practical shooting suppliers you will find recoil springs in all weights. As you mess with the above you also mess with the ability of a semi automatic to function reliably. 

[alfsauve]

Sorry for the delay but I've worked every day since I got back from IRC.    I did get by the indoor range and do some testing.

This is Armscor  158 TMJ .38spl.   They advertise it as being 900fps, which I feel is probably out of a locked breech barrel, not a revolver.   At least not a 5" one, like I shoot.

I tested it before IRC and was getting high 700 to low 800fps.  Easily making 120PF needed for ICORE.   Got to IRC and my ammo was just below 750fps.    I barely had one round, out of 6 that made it.  Temperature differences were nil between my testing in Oct and the FL weather at IRC.   IRC was using a LabRadar as I had been.

What I do know is the first 5 boxes I bought from Cabela's were packaged differently from the 10 boxes I got online.   They were labeled the same so I didn't give it much thought.   Evidently there is was a difference.   Sadly, to save space I had mixed all of the original ammo with the newer ammo in a baggie.

Today I took the bag and grabbing random handfuls ran a test over the LabRadar.   Now the bag was roughly half and half.   Here's what I got.   12 of the 25 rounds were below 120PF.   Of course, what I took on the range at IRC was all from the newer slower batch. 

25 Rounds    686 5"   
Stats - Average   749.7   fps
Stats - Highest   816   fps
Stats - Lowest   634   fps
Stats - Ext. Spread   182   fps
Stats - Std. Dev   43   fps
      
   Vel   PF
   702   110
   697   110
   781   123
   763   120
   810   127
   788   124
   773   122
   816   128
   733   115
   634   100
   777   122
   774   122
   753   118
   776   122
   680   107
   779   123
   725   114
   747   118
   780   123
   715   112
   774   122
   713   112
   784   123
   742   117
   727   114

[Big Frank]

That's a huge spread. I'd expect it to be a lot smaller even if they are from different lots.

[les snyder]

anecdotal... prior to shooting the my first Ft Benning 3 gun match in 2005 I purchased 1000 rounds of S&B 55 grain M193 for the match...this was NATO head stamp (cross inside circle) and tested exceptionally well at 400m, shooting several 5 shot groups under 4".... in spite of the need for good wind hold with the lighter bullet, I shot it for the 6 years I had the opportunity to shoot the match... even managed a 12th place stage finish in 2009 for the sniper stage...after the 2010 match I was getting to the bottom of the original order...I purchased an additional 1000 rounds of S&B M193 55 grain (without the NATO head stamp), and when tested, would not do better than 7" at 400m... I now rely on Australian Outback 69 Sierra Match King for anything over 200m... a lot can happen in the span of a couple of years... regards...

[alfsauve]

Finally pulled the spreadsheets from the  686 4"
A little better but that could just be the mix of old/new rounds a grabbed in the bag.
Next test is with a virgin box of the newer lot box.   Maybe be late next week.  I've got a USPSA match on Saturday.

                             Vel    PF
Stats - Average   769   121
Stats - Highest    830   131
Stats - Lowest     662   104
Stats - Ext. Sprd    168   27
Stats - Std. Dev   41   7

[Sponsor]

[alfsauve]

Went to Cabela's and found the original Armscor ammo.   Tested both this and the other lot's that I got.

The markings on the boxes are almost identical except:   (Let's call them the Fast and the Slow)

UPC:
Fast  8 12285 02004 4
Slow 4 806015 500612

The Fast box is a little taller, almost like it was made for .357 length.  It has an 1/8" piece of foam packing on the top to keep the .38spls from rattling about.

The logo on the Slow box say "precision" under the Armscore name.  The Fast box has "USA" instead.  And the Fast box also has the tag line:  "Right on target/Right on the price."    Also under the legaleze Fast say "Made in USA" and gives a MT address, while Slow says Marikina City Philippines.   That must be the difference.  Made in the USA are better.

Otherwise the ends are the same and the are both labeled.  <star>38 SPECIAL/158 GR FULL METAL JACKET

Here's today's results.  It's obvious that since I tested the FAST ones I thought no sweat making PF.  But the bulk of the boxes I bought to take were of the SLOW variety.   Quite a difference.


FAST                        FPS          PF
Stats - Average   818      129
Stats - Highest    859      135
Stats - Lowest           799      126
Stats - Ext. Spread   60      9
Stats - Std. Dev   19      3

SLOW                       FPS          PF
Stats - Average   717      113
Stats - Highest    780      123
Stats - Lowest           656      103
Stats - Ext. Spread   124      20
Stats - Std. Dev   40      6

[Big Frank]

I see the extreme spread and SD are both a hair over double on the slow rounds. That plus 100 FPS is quite a difference. I'm guessing their quality control wasn't as good.

[alfsauve]

Yep.   I'm guessing the USA are made to higher standard as well as a higher velocity

[alfsauve]

Still searching for that perfect .38 Special to compete in ICORE with a Power Factor over 120.  Forget USPSA, but then nobody should be shooting .38 Special anyway.   9mm 929 are the "in" gun there.  Or if you are shooting a 627 in .357, you're probably loading your own Short Colt ammo.

So far, Armscor USA is it.  Not only is it average about PF 125 in my gun, but the SD is tight!!! 

Here's what I've tested so far with my S&W 686 SSR 5".   I've had trouble finding Atl Arms & Ammo, but now have some rounds on order directly.  Shipping is a killer.

Weight    Brand      PF
124      Reloads       130
130      Amer Eagle  110
158      Amer Eagle  120
158      Freedom      110
158      ArmscorUSA 125
158      ArmscorPre   113
132      PMC Bronze  105
130      Fiocchi 38A   110   

There are many more brands, but most of the common ones, like Winchester white box, are commonly known to be in the PF110 range.   




I still get a chuckle out of PPC rules.

NRA Rule Book <emphasis mine>

3.17 Ammunition: No high speed or Magnum
ammunition will be allowed. Ammunition must be
loaded to produce sufficient velocity to pass
through the target AND the backer. Shots that
do not pass through the target and the backer
will be scored as misses.

[Majer]

Alf, Check out this company, They're new and look like they will work with you to get you what you want in ammo.
https://choiceammunition.com/