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Is it Really all about consistent MV?

Discussion in 'Handloading and Reloading' started by Bitswap, Jul 31, 2007.

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  1. Bitswap

    Bitswap Member

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    Irregardless of powders, primers, brass (match) prep, when the bullet meets the landings, is it really all about consistent muzzle velocity?

    If I have 200 brass cases of this and 200 of that, with IMR powder for this and Varget for that. If I load for 2700 fps for both, will it make any difference when taking case weight and neck thickness into consideration?

    I'm not looking for anything special, one moa is fine, half better.

    Thanks,
    Bit
     
  2. OKIE2

    OKIE2 Member

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    Beings no one answered your question here is my experience with 308 win.
    my load of
    168 sierra smk's
    imr 3031 ---39.5 grains
    &
    imr 4895----39.5 grains
    although have less than 50 fps differance
    they both shoot the same size 1/2" group but a little different poi so your thoughts may be right.
     
  3. Grumulkin

    Grumulkin Member

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    My experience with various cartridges is that decidedly better accuracy is obtained by using one brand of case. Whether or not you'll do one MOA or better, depends on the gun and the cartridge. If you have an accurate gun and a powder where half a grain or a grain one way or other doesn't make much difference in pressure, then maybe 1 MOA would be possible. I not uncommonly load mixed brass but I don't expect and I don't get the optimum accuracy from that technique.

    On the other hand, I don't know that the deciding factor is muzzle velocity consistency. Things like different recoil or who knows what else may be influencing factors. A reputable writer in Handloader Magazine recently made the point that he had experienced quite accurate loads with fairly large variations in muzzle velocity. Since I work up loads for accuracy and don't general use a chronometer in working them up, I wouldn't know (once I get an accurate load, I use a chronometer to satisfy my curiosity as to how fast my bullets are going).
     
  4. Bullet

    Bullet Member

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    Your ammo needs to be consistent but if it is a load that is not tuned to your barrel it still won’t shoot good. Something to do with barrel harmonics, about when the bullet leaves the barrel in relation to the barrels vibration or oscillation. Changing components will effect this.

    If your rifle could shoot ½ MOA with the right load, then many loads might give you 1 MOA.
     
    Last edited: Aug 15, 2007
  5. Ranger61

    Ranger61 Member

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    In my experience velocity consistency is a more helpful gauge of accuracy for hand guns with their short ( relatively) stiff barrels than for rifles with their long more flexible barrels. Acuracy in rifles is much more about getting the bullet to exit at the same place in the barrel vibrations. A rifle barrel vibrates like a tuning fork from the force of the gas pressure shoving the bullet down the barrel. I've had some 7mm Remington Mag loads that had velocity variations of plus or minus 25 fps that always shot 1 inch groups at 200 meters and yet the same rifle with the same bullets and cases but different powder and primers had velocity variations of 7 fps yet grouped just over an inch at 100 meters and about 2.25" at 200 meters. The key is finding the sweet spot for your gun, which is why handloading for accuracy in rifles can be so rewarding.
     
  6. Mark whiz

    Mark whiz Member

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    Not sure how well this will apply to cartridge shooting, but I spent a whole lot of time measuring my black powder loads once I found loads that I was statisfied with. I had the theory that all of my good accurate loads had similiar muzzle velocities. After running several series of around 15 different loads out of my rifle with my chrony - I proved to my satisfaction that this was right. All of my most accurate loads with bullet-type projectiles (sabots and conicals) all had muzzle velocities within 10% of each other and most were within 5%. POI was similiar with them as well - at least out to 50yds, as I cut a 2" hole out of the target with 50 rounds fired................and I was NOT concentrating on accuracy that day - just the CHrony results.
     
  7. griz

    griz Member

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    FWIW, in the current issue of Handloader magazine, there is an article about primers and how they affect accuracy. The author noted that the smallest group fired had the highest extreme spread in velocity, and the largest group fired had the lowest. Both were with the same load. That is only one example, but he concludes that consistent MV has no bearing on accuracy.
     
  8. GRIZ22

    GRIZ22 Member

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    I worked up many accurate loads before I got a chrongraph. I chronographed my pet loads and while I found any load with a small ES and SD were accurate I have some loads with what one might consider too large an ES and SD that are very accurate.
     
  9. peterotte

    peterotte Member

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    My Lee Enfield in 303Brit will shoot higher or lower depending on powder charge. (The higher the charge, the lower it prints). But within one powder charge, I seem to get a slightly sideways oval group. That could be me.:(

    My hornet on the other hand, shifts it's POI sideways with differing powder charges.:confused:

    I have not chronograghed my loads. (Yet!)

    Peter
     
  10. USSR

    USSR Member

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    Depends upon the distance. Shooting at 1k as I do, it means everything.

    Don
     
  11. caz223

    caz223 Member

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    If you plink at 100 yards, absolutely no difference.
    Once you make to out past 300 yards, it starts to show up.
    At 600 yards it will be very pronounced.
     
  12. DogBonz

    DogBonz Member

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    No... Not really... well sort of...

    Accuracy is shooting right where you are aiming… and then repeating it over and over again.

    MV is one of the many variables in shooting. The more variables that you remove (or minimize) the easier it becomes to repeat your previous shot. Case wall thickness can play a roll in presser variance, which could cause velocity fluctuations. Neck tension is another area where consistency is important.
     
  13. Walkalong

    Walkalong Moderator

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    It sure helps up close, and as the distance gets further it gets more near critical. :)
     
  14. Mark whiz

    Mark whiz Member

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    I really think there are 2 ways at looking at MV.

    First, as in what I posted earlier, you have to look at a general velocity your firearm responds well too - such as 2500fps, 2700fps, etc.

    Secondly, you have to look to your extreme spread numbers themselves. These are indicative of your loading Process itself - i.e. the quality and consistency of your components, loading practices, etc.

    In practice, you could have an ES of 1fps with a load and shoot crappy groups simply because it isn't at the velocity that particular arm prefers. And conversely, if you are in the right velocity range, a load with an ES approaching 100fps could shoot nice groups at least out to 100yds or so - but out to more extreme ranges you would see a degredation in accuracy with a wide ES.
     
  15. peterotte

    peterotte Member

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    Mark has summed it up very nicely!

    An additional point, using a powder that very nearly fills your case can reduce some of the variables too. For a start, the bulkier the powder, the less sensitive it becomes to tiny charge variations.

    I can't help wondering whether a heavier bullet helps reduce variables by being less dependant on consistent neck tension? That is definitely important as I have demonstrated to myself. I fired a group of new-case loads alongside a group of paper-sabot loads. There was no change in group size but the POI shifted. (To the left???:confused:)

    Peter
     
  16. the new guy

    the new guy Member

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    The way I understand it, consistant MV, ES are more of an indicator. If you load 20 rounds by just feeding the press cases and bullets, you might get decent consistancy, but probably not good consistancy. However, if you prep the primer pockets, de-burr the flash holes, turn the necks of the same brand of cases from the same mfg lot, your consistancy will improve. This will not (more than likely) turn a 1.5moa load into a tac driver load but will (almost always) make a pretty accurate load even better. One thing I just did for my rifle(fat barrel) is picked a clean burning powder, chose a target velocity that I wanted to shoot at, and started loading 5 rounds each at a specific bullet steating depth, and seating .005" deeper with each group of five (I started at .010" shorter than what the bullet would touch the lands at). After loading 8 groups of 5, I went to the range. My groups were: 1 1/4", 1 1/4", 1 1/16", 7/8", 1", 3/8", 1/4", 5/8", all at 100 yards, no wind. I've done this with 2 different powders at 2 different velocities, one hot, one mild. The first load of 40, I had a 5 shot group that measured 1/10" and I'm fairly sure I can get that out of the 2nd load with a bit more tinkering. Up to now I have done no case prep work other than trimming to length. This, to me, proves Ranger61's bit about harmonics... every rifle (from what I hear) has a sweet spot FOR THAT PARTICULAR LOAD, you just have to find it. After having done this I'm now trying the case prep thing to see if the groups improve more... I'm getting almost 40 fps ES hand weighing every powder charge exactly. Bottom line: I think seating depth changes can give you more bang for the buck loading for accuracy... but all the other stuff can never hurt, and velocity fluctuations will tell you that an accurate load can still be a little better. If you want to go that far...
     
  17. peterotte

    peterotte Member

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    Interesting post the new guy . Have any idea why a POI would shift horizontally? This rifle has a mount on a barrel post. Regarding clean burning powders - I have been told that my powder is not particularly clean but in my rifle with my loads, it leaves the bore pretty clean. I had a powder that I used in my 303Brit that gave me as little as 1 m/sec variation without any case prep at all. My groups were not that great (1 MOA) but the muzzle crown was cr*p.

    Regards
    Peter
     
    Last edited: Aug 17, 2007
  18. the new guy

    the new guy Member

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    Peterotte,
    Everything I've heard about wandering groups in a linear direction points to barrel/stock contact 180 degrees from the direction of stringing. I have no experience with this problem myself though. I wouldn't think a barrel mount would cause linear stringing unless it's a sling mount and you fired shots with and without using the sling for support... but still I think the poi movement would be verticle in this case.

    A bad crown can really mess with you! A friend of mine shortened his own barrel... once... and never did get the crown square. He used lapping compound and hand lapped the crown while shooting test groups at times. He had very erratic group sizes as he did this. One thing he noticed was that when he got smaller groups the fouling left on the crown was very near concentric with the bore. With the larger groups, the fouling was more ovaled. I suppose it's possible that your stringing might be caused by an irregular crown. If so I'll bet the blast pattern on your crown will tell you... it will probably be wider horizontally than it is vertically or may just not be concentric.
     
  19. peterotte

    peterotte Member

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    Hi the new guy
    Thanks for the tip. I have inspected the crown on my hornet but it seemed OK. Will go take another look with a magnifying glass. I had noticed this horizontal shift with change of powder charge. Actually, I don't know why this rifle even shoots straight at all. It has corrosion damage in the first 1/3 of the bore and the rest is less than mint! :barf:

    I re-crowned my nephew's 22lr anny. Someone had messed with it with a chamfering tool :confused: - go figure! Left a nice burr as well as an uneven chamfer. Anyway, because the bore was not concentric to the barrel, I gave it a recessed 90° crown. The muzzle pattern matched the rifling in a flower like petal pattern. (And produced tiny groups)!:)

    Regards
    Peter
     
  20. DBR

    DBR Member

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    I saw on a recent post that one can use "typewriter white out" on the face of the muzzle to visualize the blast pattern and determine if it is symmetrical.
     
  21. the new guy

    the new guy Member

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    White out...... I never would've thought of that. Nice!
     
  22. peterotte

    peterotte Member

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    I re-checked my crown but no visible pattern - white out - I never thought of that either!:)

    Peter
     
  23. the new guy

    the new guy Member

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    OK. Went to the gravel pit today and punched some paper, recorded some numbers... and sweat gallons of water out of my leaky poors. Come on winter! First, all loads are in Win. cases trimmed but otherwise not prepped, .243 cal, Wlr primers, 75 gr Hornady V-Max bullets. Groups are @ 100 yds, all powder charges are weighed on mechanical scale (I don't trust digital) as close as humanly possible.

    The first load was with 36.2 gr of Hogdon BL-C(2). the best I EVER did with this load @ .030" off the lands was a 4 shot group @ 0.2" no wind w/ bipod and bench. Today was a little different... still shot just under 1/2" 5 shot group but this time I chronographed it. Shall we say :eek:. The extreme spread was 129 fps! Holey *@#$!!! I've never seen that before. My point is that it shot well @ 100 (at 600 I would probably have shot an 18" group). One more thing, this is a fairly mild load for my gun and averaged a modest 3150 fps.

    The next load was 37.5 gr of H4895 @ 3368 fps. This one is hot, but not over pressured for me. I loaded this some time ago in search of a clean burn as I was having issues with that. I printed 3 shots @ .6" with the bullet seated .044" off the lands wich was by far the best this ever did. All past groups were over 1". The extreme spread on this load was a mere 14 fps but it shot slightly worse. Could've been me too.

    Now, with both of these loads I worked up the powder charge in 1/2 grain increments until I got what looked and felt right for pressure without paying any attention to seating depth. The best group was just under 1" with most of them being in the 1.25" to 1.5" range. I'm assuming the ES was at least close on these early groups but don't know for sure. If so, consistant velocity mattered squat while seat depth gave better results @ short yardage. Long yardage... everything matters.

    Case prep is in the near future. I thought these results were interesting though.

    tng
     
  24. OKIE2

    OKIE2 Member

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    THE NEW GUY
    Try 42 grains of IMR 4064 with 70 gr. smk's.
    this shot a .5 10 shot group in my Ruger 77 mk11
     
  25. RobZ71LM7

    RobZ71LM7 Member

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    FWIW,

    In my AR15's using H4895, H335, and RL-15 I've always (9/10) had the tightest groups with the loads that produced the lowest ES and SD.
     
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