what do groups mean?

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by bigsal5353, Mar 16, 2011.

  1. bigsal5353

    bigsal5353 Well-Known Member

    Messages:
    90
    Joined:
    Mar 4, 2004
    i know this has been discussed before, but i cant find it when i do a search...

    what do different group shapes mean?

    ex. if all shots are vertical, horizontal, triangle?
     
  2. royinidaho

    royinidaho Writers Guild

    Messages:
    8,853
    Joined:
    Jan 20, 2004
    Ur gonna open a can of worms with this one, I'm bettin'.:) There will be plenty of subjective responses and personal experience. All responses will be good for consideration.

    Initial considerations/assumptions upon which my "experience" is based.


    1. the right load

    • Correct combination of powder/primer/bullet/seating depth that particular rifle.

    1. Rifle is 'properly' bedded

    • action is bedded
    • barrel is bedded up the chamber (2" or so)
    • barrel is free floated from there to the end OR
    • barrel is bedded to the end of the forearm.

    1. Proper bore cleaning regimen.

    1. Scope properly mounted AND

    • Focus and parallax properly adjusted

    1. Proper shooting skill have been developed.
    THEN: Many many times I have seen '|" shaped groups turn into '--' shaped groups with the addition or subtraction of a few grains of powder. When that happens I try various powder charges somewhere around half way between these two charge weights and nearly always end up with a '.' shaped group.

    In even more :) words when I get a nice small vertical string I add powder. 2 grains or so in for an example rifle (uses 100 grain charges) if the result is a horizontal shaped group, I reduce the load by a grain and can bet that the resulting group will approach a uniform 3 shot triangle shape. This usually works.
     

  3. bigsal5353

    bigsal5353 Well-Known Member

    Messages:
    90
    Joined:
    Mar 4, 2004
    Roy, thanks for the reply and info....

    Ideally... what kind of group would be best?

    I shot a new load this week at 200yds.. (4 shots) had 3 touching vertically, and the 4th was to the right of the top of the vertical string.. all shots were touching... very happy with .7'' group at 200 yds.. just curious if i should play with anything
     
  4. royinidaho

    royinidaho Writers Guild

    Messages:
    8,853
    Joined:
    Jan 20, 2004
    Before finding LRH.com I would have suggested 'go for the one holer.':rolleyes:

    I suffer from major "tinkeritus" and have worn out perfectly good barrels playing around.:rolleyes::rolleyes:

    At this point in a long life I'd say stick with that load, don't mess with it at all!!

    The math says that you are, with that group as an example, hitting within 0.35" of POA at 200 yards or 0.175 MOA. Figure how far that will make you rifle effective. It's a right fur piece!!!

    This is where I would work up the drop chart for that load then shot in cold bore every once in awhile and go from there.

    What are the details of this rig that is being so accurate?
     
  5. boomtube

    boomtube Well-Known Member

    Messages:
    1,595
    Joined:
    Oct 8, 2007
    "Ideally... what kind of group would be best?"

    A single round hole of bullet diameter.
     
  6. bigsal5353

    bigsal5353 Well-Known Member

    Messages:
    90
    Joined:
    Mar 4, 2004
    boomtube... not really the answer I was looking for


    Roy.. this gun is a REM 700P bought back in 2003. Just got back into shooting LR last year after taking a few years off and started working on better loads for it.

    300 WM, only work done is trigger
    sightron SII 6x24
    72.4 gr of reloader 22
    190 berger VLD
    just touching lands.
    winchester brass

    have had several loads shoot at or better than .75 moa, then I shot this load mon at 200yds and it was very tight (less than.5 moa)
     
  7. cfvickers

    cfvickers Well-Known Member

    Messages:
    372
    Joined:
    Jun 18, 2010
    It depends on the rifle. My LRH shoots triangular groups with any load where my Husquvarna 6.5-284 strings loads when deviation is too much. I have a Model 100 Winchester that shoot unbelievably well, but every different bullet will group in random areas in relation to point of aim and will require adjustment for Zero. One load may be dead on and 1/2 inch dead center, switch to another bullet of the same weight and it can shoot as much as 8 inches left or right. This may not help much but the main thing I have noticed is that there is no rule that applies with EVERY rifle.
     
  8. cfvickers

    cfvickers Well-Known Member

    Messages:
    372
    Joined:
    Jun 18, 2010
    There is one thing I have noticed with every rifle. One main factor is always the amount of torque on the stock screws. I can look at that accustock and see if it is set right but with most you just have to find the sweet spot. one gun may be right when it almost feels loose, where another may feel like it needs to be torqued down with an impact driver. Just depends on the rifle. Like the first reply said, everyone here will have different experiences and opinions, but I think that speaks volumes about the different "personalities" of every rifle. Most modern bolt actions are capable of sub-moa accuracy many of them sub half, but you just have to figure out how it likes to be set up. and when you find what works you need to make note of everything and expect ALL changes to that setup to affect your groups.
     
    Last edited: Mar 17, 2011
  9. RockZ

    RockZ Well-Known Member

    Messages:
    899
    Joined:
    Mar 10, 2006
    How about a single round hole just slightly larger than bullet diameter @100yds.


    You need to shoot at long range and you want a group with very little vertical.

    If the group has vertical at 100yds it usually doesn't work out a long range.

    I shoot for 1-1.5" of vertical at 600yds for 3 shots.With not much more horizontal depending on the wind of course.
     
    Last edited: Mar 17, 2011
  10. bigsal5353

    bigsal5353 Well-Known Member

    Messages:
    90
    Joined:
    Mar 4, 2004
    rockZ, thanks for the reply....

    I'm shooting a factory gun, the tightest group I have so far at 200 yds has 3 shots vertically over lapping, and the 4th hole at the top of the string off to the right...

    The vertical string of all 4 shots measures .58''

    obviously you cant tell me what that will do at 4,5,600 yds, but do u think it will hold a descent group?
     
  11. RockZ

    RockZ Well-Known Member

    Messages:
    899
    Joined:
    Mar 10, 2006
    Bigsal,
    It shows promise with about a .5" group at 200yds.
    The only way to know is to shoot at the distance you want to hunt.

    I've shot groups that measured in the .1"'s at 100yds and had 5-6 inches of vertical at 600yds beacause of a high es/sd.
    At short ranges the velocity spread doesn't show, but as you stretch it out, it shows big time.

    Look at the sticky on the ladder testing method that Jason Baney does, that is pretty much how I fine tune my loads at long range.
    http://www.longrangehunting.com/forums/f28/ladder-testing-1k-detailed-article-video-42881/
     
    Last edited: Mar 17, 2011
  12. Don Ward

    Don Ward Well-Known Member

    Messages:
    120
    Joined:
    Jul 25, 2009
    Here's an important factor that I have found applies to every rifle & load I've ever shot...

    No matter how good or bad it shoots, or which way it strings or sends a flyer, I can make it worse.

    Point being, shoot enough with the same rest and as close to the same hold, cheek pressure, trigger squeeze, hand position, shoulder pressure, & follow through before jumping to conclusions on equipment. It takes very little wrong on the shooters part to mess up what the rifle is trying to do.
     
  13. paphil

    paphil Well-Known Member

    Messages:
    254
    Joined:
    May 14, 2009
    Bigsal, The gun is junk- sell it to me for $100 and I'll try to get it to shoot!! Awsome group and it should shoot just fine at 1000 yards.
     
  14. rscott5028

    rscott5028 Well-Known Member

    Messages:
    2,608
    Joined:
    Apr 18, 2010
    Everyone should know this. It's common knowledge...

    A group that has horizontal distribution means that some of the bullets went left or right of the intended POA/POI.

    While a group that's vertically distributed means that some went high or low of the intended POA/POI.

    Actually, I read an article once where the guy was explaining how seating depth would cause the dispersion to change from horizontal to vertical and that there was a sweet spot just in between. But, I was never able to reproduce that exactly. ...just too many variables.