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Thread: Help me with my velocities

  1. #11
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    Quote Originally Posted by ubet View Post
    The 77gr smk load when I did load development was 3/4 moa at 700 in a ladder/ocw test, the loads were 23.9, 24.1, 24.3 I settled on the 24.1.
    Quote Originally Posted by mRad View Post
    If you haven’t taken it to 700 yet, why did you say it was shooting 3/4 at 700?
    Quote Originally Posted by ubet View Post
    Since I built the load. I shot it at 700 when I built it.

    We're trying to help you, but you're not making sense...

    If this load shoots 3/4moa @ 700yds, then don't change a damned thing.

    If that's not the case, then you're right that your velocities are all over the place...



    Quote Originally Posted by ubet View Post
    It’s all cci 41, cfe223 powder, crimped, seated just below mag length with a Redding comp seating die. The cases for the 77s were lc brass from top brass.
    Any number of factors could give you inconsistent velocities...

    How sure are you about your powder charges?

    Did you trim the cases? (Don't trust that they came trimmed to a consistent length.)

    Why are you crimping?

  2. #12
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    Help me with my velocities

    Quote Originally Posted by Bimmer View Post
    We're trying to help you, but you're not making sense...

    If this load shoots 3/4moa @ 700yds, then don't change a damned thing.

    If that's not the case, then you're right that your velocities are all over the place...





    Any number of factors could give you inconsistent velocities...

    How sure are you about your powder charges?

    Did you trim the cases? (Don't trust that they came trimmed to a consistent length.)

    Why are you crimping?
    I’m confused as well, trust me.
    No, I didn’t trim. That in there is probably the culprit too.
    I’ll measure some tonight and see what the lengths are.
    I crimped because in my original load development, the crimped shot more accurate than non crimped.


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  3. #13
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    Quote Originally Posted by ubet View Post
    No, I didn’t trim. That in there is probably the culprit too.
    I’ll measure some tonight and see what the lengths are.

    I crimped because in my original load development, the crimped shot more accurate than non crimped.

    Assuming that wherever you bought your brass didn't trim it, then it needs trimming, especially if you're hoping for something consistent and accurate.


    Hopefully somebody smarter than me will chime in to confirm or correct me, but if you're not trimming your brass, and they're all different lengths (even slightly), and then you crimp the case necks, then the different length case necks will be crimped more/less based on how long they are, which will give you wildly varying neck tension, which will give you wildly varying velocities (like you're seeing).

  4. #14
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    Depends on the type of crimp. Roll crimp must be exactly the same length.

    Taper crimp it’s better if it is all the same but it doesn’t have to be exact.

    If it’s “factory crimp” a little variance doesn’t seem to make much difference.

    Anything I’m shooting for precision, I’m trimming every firing regardless.

    I’ve found crimping does make better ammo for an AR. I’ve more than once had erratic fliers. I figure out it was from rounds sometimes growing as they were slammed into the chamber. Crimping solved fliers.


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  5. #15
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    It’s all top brass. I’ll measure and report back, I have a few hundred empty cases still. Thanks for the help. I didn’t even think of the trimming being an issue.


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  6. #16
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    So I measured case lengths, the 12 I measured varied +/- 12 thousandths


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  7. #17
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    I'd like to help you out, but I'm a bit confused by what I'm reading here. For long range precision and accuracy, you need to be concerned with consistency from round to round. It doesn't matter what your muzzle velocity is as much as whether it's the same velocity from shot to shot. Check this blog and it will help tremendously:

    https://precisionrifleblog.com/2020/...-for-shooters/

  8. #18
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    Based on the numbers you provided, you're asking the wrong question. The question is why is your ES >100 and the answer is inconsistencies in your loading process. Get your ES below 10 then start looking at velocities. This assumes your magneto-speed is producing reliable results, a sanity check of that is probably warranted.

  9. #19
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    Quote Originally Posted by HKGuns View Post
    Get your ES below 10 then start looking at velocities
    I'm assuming he meant below 100 - I'm not trying to contentious here... but an ES below 10fps is really low. like REALLY LOW and really hard to achieve on a progressive press in my experience. An SD of around 10fps will probably give you about 1 moa of vertical stringing/dispersion at 700 yards. You should be able to get an SD of around 15fps without getting too fancy with handloading. I just wanted to throw that out there if you're going to set goals for yourself.

    Also, if you shoot at various ranges, you can calculate your MV to corroborate your chronograph. If you're consistently getting 1 moa at 700 yards, you know your approximate SD. Then if you observe your drop at 200, 300, 600, 700, you should be able to calculate a fairly accurate MV.

  10. #20
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    Quote Originally Posted by Bullz View Post
    I'm assuming he meant below 100 - I'm not trying to contentious here... but an ES below 10fps is really low. like REALLY LOW and really hard to achieve on a progressive press in my experience. An SD of around 10fps will probably give you about 1 moa of vertical stringing/dispersion at 700 yards. You should be able to get an SD of around 15fps without getting too fancy with handloading. I just wanted to throw that out there if you're going to set goals for yourself.

    Also, if you shoot at various ranges, you can calculate your MV to corroborate your chronograph. If you're consistently getting 1 moa at 700 yards, you know your approximate SD. Then if you observe your drop at 200, 300, 600, 700, you should be able to calculate a fairly accurate MV.
    I didn't see he was using a progressive press. I only load rifle rounds on a SS press as there is just too much variability when using a progressive to load accurate rifle rounds. My progressive is strictly for pistol cartridges.

    But that too is a place to start at refining his process.

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