Great groups at 500 yds but crappy ES

Quack303Head

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I'm going to try and make this short and sweet



Facts:

Action BH
Barrel .236 bore 4G 1-7.5 chambered in 6CM @ 26in suppressed
Powder h1000
Brass Win .243 FF
Bullets 105 Berger 105 VLD
Chrono CED M2
RCBS Charge Master



I can get the things to shoot small groups at 500 yds but the SD is insane.

47G of h1000
Group size 1.821 horizontal .648 vertical @ 500yds
Velocity 3045fps
ES 42
SD 15
This was a 5 shot group

I shot several other loads, all shot pretty good but ES were about the same


I really don't want to change any of my components because I have enough to last me the shooting season and I'm feeding another rifle that's getting small ES's. I'm stuck on the seating depth of .80 thow off the lands because they group the best. I'm about to say screw it and run with it for the year but I really would like to shrink my ES by at least 20 FPS. 90% of the shots I'll be taking this year will be within 900 yds.


Thoughts?
 

TannerGun

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My 7RM posts atrocious consistency on the chrony, but I pay attention to where the splashes are on the steel more than anything.

If you can, I'd shoot it from 500-1000 in 100yd increments and see what kind of vertical is produces. ES might not matter, even though it sounds foolish to say....
 

jwp6114

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you may only see movr vericle spread at greater distances... shoot it at 600 and further and see how it does... i know that ES plays a big part at 1000 yards...

if 500 is the furthest you intend to shoot, your fine...
 

Jedi

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Dec 10, 2003
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Forget the numbers

what does the target tell ya

folk chasing ES/SD numbers instead of just shooting, if its a TAC rig it makes ZERO sense
 

InkedIan

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Is h1000 big? I know my charge master will over throw h4831 by a couple of kernels or just barely get it right on. That could be the cause. Or the chrony.... Ive shot the same load through 2 different chronies and showed 2 very different ES's. Great groups by the way!
 
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InkedIan

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Also heard that magnum primers can cause that... Idk if you're using those
 

B3dlam

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Targets don't lie but your chrono might there is a reason the way to get the most accurate results from a ballistic calculator is to true it by using your drop at near transonic ranges for your setup. Chronos are relatively accurate but I wouldn't be worrying to much you seem to have a load that performs well if you are getting the results you want on target why worry about numbers.


Sent from my iPad autocorrect at your own risk.
 

fx77

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  • Nov 29, 2005
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    Consider reshooting on a different chronograph for comparison..the accuracy is documented with your groups..the numbers either are wrong or do not matter.
     

    Quack303Head

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    In no way am I complaining abut this group. I'm worried about the ES at distance, say 900 yds. Most targets at that distance are at least a min of angle so i should be able to squeak by with a low hit on steel if my lazer is dead nuts.

    Yes CM is comp match.

    Inkedian,
    H100 is pretty big. After doing a lot of load development I can calculate that 1/10 gran is about 6fps at this charge weight. It should have to be a pretty big over/under pour to get this ES.

    Thanks for your input though.
     

    Quack303Head

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    Consider reshooting on a different chronograph for comparison..the accuracy is documented with your groups..the numbers either are wrong or do not matter.

    Did this yesterday with my buddy's CED, both chronos showed crappy ES. I should be able to shoot out to 800 on Wednesday. I'm going to load up the same charging and print on paper.
     

    XL Mammal

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    That's easy. You're shooting a quick, decent BC projectile. That vertical spread is right on with what JBM gives me at 500yds with an ES of 42.
     
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    InkedIan

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    In no way am I complaining abut this group. I'm worried about the ES at distance, say 900 yds. Most targets at that distance are at least a min of angle so i should be able to squeak by with a low hit on steel if my lazer is dead nuts.

    Yes CM is comp match.

    Inkedian,
    H100 is pretty big. After doing a lot of load development I can calculate that 1/10 gran is about 6fps at this charge weight. It should have to be a pretty big over/under pour to get this ES.

    Thanks for your input though.

    Hmmm, well even with an exact charge each time you're still going to show a deviation in velocity(10 sd, 20 es is fairly normal). If you throw in a small under and over charge it's possible that might cause that problem, but who knows some stuff is unexplainable.... I hope you can find a cause! Also, neck tension lol just throwing ideas out there...
     

    XL Mammal

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    Can't help you with the bushing question, but have you tried turning the necks? That might yield some more consistent velocities.
     

    17874

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    Hell, I would be happy with where it is if it shoots good. I would want to put it on paper at 600-1000 if I could though.
     

    TheGonz

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    You want .001-.002" of tension on the bullet. Youll have to use the same cases for each bushing. So if you have only one bushing that will give you .001" of tension then I would just stick with that one, but remember, different makes might be thicker or thinner.
     

    wvlapua

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    Try neck turning your brass and .002 neck tension. Not sure what dies you are using..but often times vld bullets require a longer seating stem for oal consistency (since the vld bullets have a longer profile they will bottom out).Essentially, the non-vld stem will seat off of the meplat instead of the ogive. Redding and Forster have stems for their dies. You may also try different primers as one will ignite certain powders better than others.
     

    John L

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    but the SD is insane.

    Group size 1.821 horizontal .648 vertical @ 500yds

    SD 15
    This was a 5 shot group

    [/QUOTE/]

    First your basing this off 1 - 5 shot string, not a very good sample size.

    Second a 15fps SD is not really all that bad, single digit SD's are nice but can you really hold and call your shots that well?

    Personally Id set the chrono aside and shoot the shit out of that rig.

    Just my thoughts.
     
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    X-fan

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    Though it is possible it is not likely that you would shoot a 1/2" vertical at 500 yards with a 40fps ES.
    JBM gave me 1.6 inches with your bullet and velocity...or about 9 inches at 1000yds.

    I have money the problem is a chrono setup issue. Beg borrow or steal a heavy duty tripod and make up a blast shield for the front screen.
    If you can see the screens move from the blast the unit will read differently.
     

    427Cobra

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    I know a couple of people who shoot 6CM, they use 49.0 of H1000, so my advice is work up slowly to max, I have found the closer you get to max the smaller the spread, as for your chrono I completely trust my M2, and have checked it against a 35p, I extend it as far as the cable will allow.
     

    jwp6114

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    If you have more than say 5 firings on your brass I would say annealing would help your neck tension consistency' neck turning is useless if you dont anneal.

    Once my friend and I started neck turning and annealing, we started to see ES,s like 12, or 7...
    and groups at 600 yards you could cover with your thumb in best conditions. We began to se 1/4 min groups out to 800. We are also sorting bullets, trimming and pointing bullets...

    A bit excessive if u ask me, but we wanted to see just how much work it is to achieve such accuracy... And let me tell ya, expensive tooling and countless hours with brass prep and bench time.
     
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    mikeltee

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    If your bullets are landing approximately the same vertical on target Out that far I'd guess it was the chrony.
     
    M

    milo 2.0

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    Qauck,
    If the gun shoots that size group at 500, I'd run with it. My most accurate gun and load had an ES of 60+, and a SD 20+, hit most every target I shot at, out to 1850 yards. Ran ti over 4 diff chrono's, same results.
    A friends 300 Norma, we were getting an ES of 9. SD around 1.7, many times, accuracy wise, the gun is one big disappointment.

    I think a guy can read, and try to put way more than neccesary into this game. Unless you're shooting 1000 yard BR, or f-class, your load should be great for banging steel targets on the weekends, comps or not.
     

    SONIC SAAMI

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    I know a couple of people who shoot 6CM, they use 49.0 of H1000, so my advice is work up slowly to max, I have found the closer you get to max the smaller the spread, as for your chrono I completely trust my M2, and have checked it against a 35p, I extend it as far as the cable will allow.

    This ^^^^^Why did you stop @47?
     

    Quack303Head

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    I appreciate everyone's input. I ended up going out again today at 500 with the chronograph., no chang in loads. Light conditions where perfect and consistent. I shot 15 and my ES was around 30 SD of 9, I had two shots that messed everything up so good enough for me.

    As for loading @ 47 grains i want to keep my barrel intact for the rest of the year. My Ai will fling DTAC's @3200 and I did for a wile, measured my throat and It's now moved 100 thow with 2k on the barrel.

    Thanks again everyone.
     

    B.Bates

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    I don't trust chronos . Own a Pvm had ohler I experience issues with them


    Shoot it. If you notice little vertical keep on shooting Trust the gun

    Good luck