Power Factor Variation in Stock 2s

[B21]

Wondering if anyone else noticed this, I have 3 stock 2s.  I just shot a major match and a few weeks out decided to chrono my match ammo in my practice gun, and my main match gun.  Surprised to observe about a 125fps variation in the two guns. My match gun came in a lot slower then my practice gun.  I was initially assuming it was because my practice gun has around 40k rounds through it, however it has been consistent on the chrono since it was new.  For giggles I busted out my 3rd stock 2 and it landed somewhere in the middle of the other two in terms of power factor.  The only test sample is my regular ammo, which is 125g blue bullets with 4.0 grains of titegroup at 1.250

[Fasthenk65]

22 hours ago, B21 said:

Wondering if anyone else noticed this, I have 3 stock 2s.  I just shot a major match and a few weeks out decided to chrono my match ammo in my practice gun, and my main match gun.  Surprised to observe about a 125fps variation in the two guns. My match gun came in a lot slower then my practice gun.  I was initially assuming it was because my practice gun has around 40k rounds through it, however it has been consistent on the chrono since it was new.  For giggles I busted out my 3rd stock 2 and it landed somewhere in the middle of the other two in terms of power factor.  The only test sample is my regular ammo, which is 125g blue bullets with 4.0 grains of titegroup at 1.250

I have the same with my Shadow 2's, so seems normal? I have 129 PF out of one and the other, same ammo, same day, makes hardly 125.....

[B21]

I figured there would be a deviation, I was just surprised to see how large of a spread three of the "same" guns would have.  Good to know it's normal in the shadow's as well, I kind of figured it was attributed to the poor QC of the tanfos.  Guess I'll have to adjust my match ammo a tad to ensure all my guns meet PF with some room to spare  

[zombywoof]

I have 3 Stock ll's and a Witness Steel, they are all close.

[V2plus25]

It could also be the variation in your powder drops too, or OAL perhaps.

 

That does seem to be a bit much of a spread of fps.  I had that variation once when I forgot to attach the powder return rod on the press.

[Hi-Power Jack]

How many rounds did you test in each gun ?

 

That's a large deviation - wonder if it could be because of

a very low sample ?   Did you fir 10 -20 rounds in each gun ?

[tdp88]

125 fps seems like a lot. Did you have one chamber reamed and leave one factory?

[B21]

On 9/15/2019 at 5:53 AM, Hi-Power Jack said:

How many rounds did you test in each gun ?

 

That's a large deviation - wonder if it could be because of

a very low sample ?   Did you fir 10 -20 rounds in each gun ?

 

I only fired 10 rounds through each gun.  I don't think it's a ammo quality control issue, because the deviation in each gun was within 20 fps.  Next time I go drag my chrono out, I'll try a larger sample 

[B21]

On 9/16/2019 at 9:21 AM, tdp88 said:

125 fps seems like a lot. Did you have one chamber reamed and leave one factory?

This may be a contributing factor.  All of the chambers have been reamed, however two of them were done by one company, and my third stock 2 was done by a different company.  All of the barrels allow my ammo to plunk and spin freely.  

[MacLethal]

I only have 1 stock2 so I’m not much help, but it has been very consistent through multiple bullets and powders.


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