RPR Rimfire Torque Tuning DOES work!

Subwrx300

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I tested effect of different torque values in the RPRF over the weekend. I read some other post (not sure if on here or elsewhere) that found no appreciable difference in torque tuning, but my test seemed to indicate otherwise.

Setup:
  • ER Shaw Barrel - ~600 Rounds prior to test.
  • Action Block has "Foil Tape" bedding
  • Harris bipod
  • Trigger at lightest setting 1.5-1.75lbs
  • Shot from prone with rear bag at 50yds
  • Average of (3) 5-shot groups
  • All shot with CCI Standard Velocity
TEST: Change torque of FRONT action screw only. Rear action screw set to 35lbs (factory) throughout test.

Barrel was cleaned thoroughly prior to test and 50 rounds fired to settle in barrel before shooting groups and torque tuning. Results below, picture at bottom. Shot from right to left (10inlb to 50inlb).

Note that I pulled the first shot from most groups as it drops 1-2MOA low virtually every new mag loaded, regardless of number of rounds loaded. Not sure why but this would skew results significantly so I pulled them out. My theory is that barrel cools down slightly between loadings, so wax hardens and slows bullet.

IMG_20180909_110924.jpg
  • 10in/lb .38"
  • 15in/lb .38"
  • 20in/lb .45"
  • 25in/lb .62"
  • 30in/lb .35"
  • 35in/lb .36" (factory setting)
  • 40in/lb .53"
  • 45in/lb .57"
  • 50in/lb .37"
To confirm two settings, I fired 15 shot groups @ the two best settings (35 and 50inlbs).
  • 35 in lbs - first round low still present and second shot low left. Excluding first round, group measured .68" including last 14 shots but .48" for last 12 shots.
  • 50inlbs - .49" 15 shot including all and .36" tossing first round (lowest round in left group). A second 15 shot group produced .49"/.72" group. Again tossed the first and, one called pull opened group full bullet diameter. Velocity was 1103 avg with SD of 12.
  • 50inlbs with Federal Gold Medal Target: 3 15-shot groups with FGM Target produced .55" avg group. Not likely to get any better as they are traveling at 1120fps so a few rounds crack sound barriers and produced weird flyers. SD was 7.8.
Not sure if others will see the same results but it was interesting. I'm going to run the same test with rear leaving the front at 50inlbs to see if I can get any better results but it's a low priority. Rifle is shooting pretty well and not sure any tighter groups will help vs learning wind calls beyond 50yds. Plus ammo is going to start limiting precision and I prefer to shoot least expensive ammo I can. ~.5" 15 shot groups and .3-.4" 5 shot groups are fine given cost of rifle.

Please post results if you run this test yourself.
 
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Steelhead

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Thanks for taking the time to do this and for sharing your results! When I find some time, I'll give it a try too.
 

straightshooter1

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Should be getting my Shaw barrel this afternoon and after getting it installed and broken in, I'll run a similar test using some high grade ammo to mitigate shooter error and standard deviations.
 

bmicek

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I also tried this and saw similar results. But when I went back to test my best group again, my results changed :/ so it was somewhat inconclusive for me.
 
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Boxerglocker

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I'm looking at your numbers and correct me if I'm wrong. between the 15 inch lbs and 50 inch lbs you went from an average group of
0.38" to 0.37" but increased the maximum recommended torque value by 42%?
 

Subwrx300

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I'm looking at your numbers and correct me if I'm wrong. between the 15 inch lbs and 50 inch lbs you went from an average group of
0.38" to 0.37" but increased the maximum recommended torque value by 42%?
Your math is certainly correct (42.8% to be precise). However, I'm not certain that Ruger lists 35 as a MAXIMUM but as recommended. I don't have the manual in front of me, so it very well could be a max. Please refer to your owners manual.

While some torque settings did produce measurable difference in group size, it might be more accurate to say that certain values hurt group size more than help. Again, sample of only one rifle, but 20-25 and 40-45 inlbs made groups worse than factory value.

For the purpose of the test, I could have just as easily chose 35inlbs on the basis of the 5 shot groups (statistically speaking identical to 50inlb groups and a few others). However, the subsequent 15 shot groups shows better consistency at 50inlbs than it did at 35.

If the concern is that others here may replicate and damage their chassis/rifle, I would suggest that the YMMV and try at your own risk are warranted.

But since the front screw bed is solid polymer, there is likely a low chance of any issues. More likely is stripping the bolt head (small hex) which I am planning to replace for a socket head variety.

So, yes, I exceed the recommended torque spec by 42.8% and am happy with results. If someone reading this thread is worried about damaging something, leave it alone. Otherwise, it's a $.20 screw feom the local hardware store or a call to Ruger of something goes wrong.