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Suppressed vs. Unsuppressed Velocity

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    Suppressed vs. Unsuppressed Velocity

    So another thread got me interested in this topic recently and I had the opportunity to collect some data today.
    I needed to fire form 50 cases for my new APR
    6.5 Creedmoor
    20" barrel
    Barrel was brand new.

    Unfired Peterson brass full length sized, trimmed, neck turned, reamed, faced, chamfered, and deburred. The necks all seemed to have adequate tension-- I did not size them, which may add some scatter to the data. the SD is pretty high for both sets, but it also took a few rounds for the barrel to settle in, which added to the SD.

    129 gr. SST
    42 gr. of RL-17

    I didn't Q/C the charge weights like I normally do since I was just fire forming, but I dialed the first one and all were thrown with a Redding BR-30, which is very consistent normally.

    I shot groups of 5, starting unsuppressed, then adding the can, then back, through 50 rounds. Chrono'ed with a Magnetospeed. The first round with the can didn't read properly because I had too much gap. Round 40 failed to feed because I accidentally pulled a 7mm button through it after the neck got dinged and didn't resize the neck far enough down to feed.

    One small set of data and I didn't know what to expect, except that some folks on here said the can would add velocity. I grouped "shot pairs" even though they weren't shot that way because it seemed to present the comparison in the best way. Scatter plots didn't really say much.
    Attached Files
    Last edited by meltingfeather; 01-18-2020, 01:16 PM.

    #2

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      #3
      Ignoring the first 5 pairs changes the data:
      Suppressed:
      Avg. - 2,746 fps
      SD - 18 fps

      Unsuppressed:
      Avg. - 2,730 fps
      SD - 22 fps

      If anyone has ideas about different looks at the data or experiments to run, I'm all ears.

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        #4
        I was gonna be pretty surprised if there was a substantial gain-- just seems like too much volume in a can to continue to push the bullet in a meaningful way, but there does seem to be some effect... worth about 1/2" of barrel length!

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          #5
          Interesting! I did the same test with my Specwar back in the day and got 2% velocity increase. But it wasn’t as detailed of an analysis. Yours is way more legitimate

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            #6
            Very interesting study you did there. Thanks for posting it.


            Sent from my iPhone using Tapatalk Pro

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              #7
              Good test. Thanks. Pretty similar to what I typically see.

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                #8
                good info

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                  #9
                  Pretty similar to data I’ve seen in person over the years as well.


                  Sierracharlie out…

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                    #10
                    Did you notice any difference in accuracy. I know on a couple of my rifles they shoot tighter groups suppressed

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                      #11
                      Originally posted by ORIONTHEHUNTER View Post
                      Did you notice any difference in accuracy. I know on a couple of my rifles they shoot tighter groups suppressed
                      I was fire forming and had the Magnetospeed strapped to the barrel, so not really shooting for groups.

                      That's a decent idea for when I do get a load worked out though-- I'll remember that. It plays into another topic that came up recently which is the difference (if any) between brands of suppressors with respect to accuracy. Your idea adds a little different flavor.

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                        #12
                        I have always wondered this.Thanks for posting.

                        Sent from my SM-G970U1 using Tapatalk

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                          #13
                          Did you notice much change in point of impact, with / without suppressor?

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                            #14
                            Thanks for sharing! And I'll echo John316's question. I'm going to pick my suppressor up this afternoon and I want to know what I'm in for!

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                              #15
                              Originally posted by John316 View Post
                              Did you notice much change in point of impact, with / without suppressor?
                              There will be a shift in POI. How much depends on several things. Your barrel contour, length of barrel, caliber, which can you’re running, etc. Two of the same rifles with the same suppressors side by side may have differently POI changes. If you’re running a good setup, this shift should be repeatable though. I run an Omega direct thread on multiple rifles. They’re all zeroed with the suppressor, and I have no issues with POI shift when swapping the can back and forth. I can’t remember what my actual shifts were prior to zero (it’s written down somewhere), but they were all low. Roughly somewhere between 2-4”~ at 100 yds on average if I remember correctly.

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