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Thread: SP101 not shooting to POA

  1. #1
    Boolit Master

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    SP101 not shooting to POA

    ok guys need a little help with this I'm looking for a load that will shoot to point of aim In my Ruger sp101
    so far I only had luck with 148gr DEWC I have been trying to get some 158gr bullets to work so
    far not so good all the loads that I tried still shoot about 3" low so before I look for a different front sight or file it down any suggestions I have tried Bullseye / RedDot / Unique what I'm looking for is a 38 load in 357 brass that shoots to POA
    kids that hunt and fish dont mug old ladies

  2. #2
    Boolit Grand Master


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    If the windgage is all right I would just leave it. You can try the 158 with a lighter charge (should raise your POI) or just hold the front sight high. One of my S&W 36's shoots 5" low & 15 yds and my newest S&W 642 shoots 3" low and 3" left at the same distance. Considering these guns were made for minute of man at spitting distances I won't worry about it.
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  3. #3
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    If your revolver has fixed sights, all you can do is keep looking until you find a load that shoots to the sights. That is the reason I get adjustable sights whenever possible. Happily, my M1911 shoots to the sights at 25 yards with my favorite handload.

    Adam

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    Boolit Master

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    I was using 6.5gr of Unique I'll drop it down to 6.gr if that don't do the trick I will just adjust my hold then
    kids that hunt and fish dont mug old ladies

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    Boolit Grand Master Outpost75's Avatar
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    I would bet dollars to doughnuts that Ruger uses wadcutters to zero them at the factory. At least they did when I went through police armorer's school in 1984.
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  6. #6
    Boolit Master

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    Quote Originally Posted by Outpost75 View Post
    I would bet dollars to doughnuts that Ruger uses wadcutters to zero them at the factory. At least they did when I went through police armorer's school in 1984.
    Funny you would say that my DEWC shoot to POA Click image for larger version. 

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    kids that hunt and fish dont mug old ladies

  7. #7
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    My 357 SP101 has it etched on the barrel. 125g bullets.

  8. #8
    Boolit Master

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    Quote Originally Posted by Outer Rondacker View Post
    My 357 SP101 has it etched on the barrel. 125g bullets.
    So a 125gr bullet will shoot higher
    kids that hunt and fish dont mug old ladies

  9. #9
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    No. I was just making a statement. Mine has the correct windgage but shoots low as well with 38 speeds. I move it up to a hot 158 bullet and its right on. Kicks like a mule for a small gun.

  10. #10
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    Put a tritium night sight on the gun and get the smaller dot size (sits lower). Between that and using a heavier bullet (not a lighter one) you'll get it pretty close to POA. I played with mine a while before I got it right. Ten shots double action at 25 yards 3.8".

    Attachment 215643

  11. #11
    Boolit Grand Master Outpost75's Avatar
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    Quote Originally Posted by LUCKYDAWG13 View Post
    So a 125gr bullet will shoot higher
    No... A revolver is pendulum in motion so lighter bullets with less recoil impulse and higher velocity will shoot low. Heavier bullets with greater recoil impulse and longer bore time shoot high.

    Back in the day (1980s) fixed sight revolvers produced for government contract orders were zeroed using the specified ammunition provided as government furnished material. With the US Customs and Border Patrol, French Gendarmarie and India police I am familiar with the exact specs varied in accordance with the contract specifics. A .38 Special or .357 revolver such as produced for USBP would commonly be shot off sandbags at 20 yards, aiming at a 2-inch bull, or the aiming point being scaled to one inch per ten yards.

    A 3" circle was printed on the target rolls, surrounding the aiming point with the circle tangent to the aiming point at 6:00. Five out of six rounds were usually required in most contracts to strike within the 3" circle. The correct front sight height would be determined by firing a ten-board sample of revolvers with the contract ammunition to obtain the correct elevation and then all guns being assembled would be fitted with the same height front sight for that ammo. Windage adjustments would be made in the range when necessary by rotating the barrel in the frame using directed strikes with a babbit bar.

    With revolvers point of impact for elevation is determined more by bullet weight than velocity. Bullets of the same weight and type will shoot close to the same point of impact in either standard or +P loads. Getting .357s to shoot to point of aim is different, due to greater recoil impulse, but generalities of bullet weight influence hold true. In ordinary production intended for civilian retail sales it was common to use .38 Special 148-grain wadcutter ammunition for both .38 Specials and .357s because zeroing with this ammo provided a point of impact which was useful for most commonly used ammunition. The lead wadcutter bullet also provides a better functional test to detect "spitters" in which a new fit-up might over-rotate the cylinder (OK up to about 5 degrees to compensate for service wear).

    To determine how much to adjustment is needed to rezero fixed sights use the formula X=RE/D where X is the amount of correction needed.

    Reducing height of the front sight to moves the impact up.
    Installing a higher front sight lowers point of impact.
    Rotating the barrel tighter in the frame moves the front sight left to move impact to the right, etc.
    Barrel threads are timed and the fit-up checked with a gage so that barrels can be hand-tightened within 7-1/2 degrees of top-dead-center so avoid collapsing the root of the thread and causing "thread choke" from over-torqueing. The barrel thread spec was UNF-2A.

    R is the sight radius in inches.
    E is the error correction needed between point of aim and point of impact, and
    D is the target distance.
    ALL dimensions are in inches.

    In extreme cases a used old cop gun may have a bent frame from being used as an impact weapon, and/or the crane is bent out of alignment. A competent gunsmith can fix these. There is absolutely no reason why a 2-inch .38 snubby cannot be zeroed precisely and shoot accurately. My own S&W Model 36 former basket case reworked by Sandy Garrett of NoVa Gun Works now shoots ten-ring, 25-yard groups with wadcutters, and quality defense or service loads should do likewise in a mechanically correct gun.

    Attachment 215648

    Attachment 215649Attachment 215650
    Last edited by Outpost75; 03-04-2018 at 02:51 PM.
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  12. #12
    Boolit Grand Master
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    This post ^^^ needs to be "stickied". Thank you, Outpost 75.
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    yes thank you Outpost 75
    And NSB what front sight did you get
    and thanks to all
    kids that hunt and fish dont mug old ladies

  14. #14
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    I have a 2.25” barreled SP101 in .357. It shoots low with 158 gr boolits. I went to the NOE mould 360180 a wide flat nosed boolit at 180 grains and pushed the velocity to 1300 fps. That shoots to point of aim. It’s pretty wicked on both ends of the gun with that load.

    Often I run a 160 grain double ended wadcutter in it at about 1100 fps. It goes a little low, but for a defensive gun that might be a good thing as most misses in gun fights tend to be high misses.

    My 4.2” SP101 in .327 shoots to the sights with 105 grain to 115 grain boolits.
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  15. #15
    Boolit Grand Master FergusonTO35's Avatar
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    I had a 3" SP for awhile. It shot low with everything I tried. Fortunately the front blade is soft aluminum and replaceable, so I just filed it down until it shot like I wanted. That particular SP had a dreadful trigger pull, I ended up getting my money back out of it as a trade-in on a LNIB Marlin 1895.

    How do the late model SP's tend to do? The Ruger forum has a real love-hate relationship with them.
    Currently casting and loading: .32 Auto, .380 Auto, .38 Special, 9X19, .357 Magnum, .257 Roberts, 6.5 Creedmoor, .30 WCF, .308 WCF, .45-70.

  16. #16
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    Quote Originally Posted by FergusonTO35 View Post
    I had a 3" SP for awhile. It shot low with everything I tried. Fortunately the front blade is soft aluminum and replaceable, so I just filed it down until it shot like I wanted. That particular SP had a dreadful trigger pull, I ended up getting my money back out of it as a trade-in on a LNIB Marlin 1895.

    How do the late model SP's tend to do? The Ruger forum has a real love-hate relationship with them.
    Put a Wolf spring kit in the gun and fix the trigger. Even Bubba can do it right it's that easy. Cheap too.

  17. #17
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    Quote Originally Posted by Outer Rondacker View Post
    My 357 SP101 has it etched on the barrel. 125g bullets.
    That is likely one of the early "Short Frame" .357 mag SP101's. When the SP101 was introduced it was chambered in 38 Special. Ruger made some early SP101's chambered in .357 magnum and marked the barrels ".357 Magnum 125-grain ammo only"". Shortly after that, Ruger lengthened the frame and cylinder of the SP101 to accommodate any factory spec .357 mag cartridges. Ruger only made about 3000 of the short frame .357 mag models so they are a bit rare these days.

  18. #18
    Boolit Master

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    Quote Originally Posted by NSB View Post
    Put a Wolf spring kit in the gun and fix the trigger. Even Bubba can do it right it's that easy. Cheap too.
    I did that too and yes easy to do and helped a lot
    kids that hunt and fish dont mug old ladies

  19. #19
    Boolit Master
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    I had a wolf spring in mine until I had to send it back to ruger for a timing issue. They took it out and put a 10 pounder back in. :{ I guess I should order another one now that you have reminded me. :}

  20. #20
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    Try putting the top of the front blade in the center of the Bullseye.
    Put the 'shoulders' of the rear sight down at 6:00.

    Find the distance that this sight picture and your load impacts the Bullseye / Black of your target.
    This would be your 'Max' range.

    Bring your target in until the 'normal' sight picture hits so POA = POI.

    Now hitting between these two distances and figuring out the sight picture is practice.
    Try painting your front sight in two colours so you have a center line to use as reference.

    Good luck.

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