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Thread: .338 RUM reloads erratic at 300yds.

  1. #1
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    Default .338 RUM reloads erratic at 300yds.

    Ive been reloading diferent loads w different powders(due to availability!). I have good results w certain recipes at 25 and 100 yds. Then if they are good performers I go out to 200 yds., Then to 300 yds. w/ 5-10 shots. Im having weird results at my 300 yds on more than one load. Shots are going erratic 12" scattered and dropping from 6-10". I run a wire brush through barrel after 5-10 shots and let the barrel cool down after 2-3 shots once its hot to touch. I try to keep things consistent. I weigh ea load seperately into indentically trimmed cases. I back off the case neck 1/2 turn from touching. My groupings are within a 3" circle at 100 and within 5" at 200yds. Im getting chrono speeds of 2850-3200 fps. Using Accubonds and Hornady sst boat tails w/ H4831sc, RL25, H1000, Retumbo and Magnum. Just cant figure why my loads are falling away at 300yds.

  2. #2

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    If you're getting 5" at 200, expect to get around 10" at 300 with no erratic stuff going on at all. Just the nature of bullets flying further and further away. If you want to be getting less than 6" at 300, better find loads that are giving you less than 2" at 100. Add in sighting errors, wind, mirage and more stuff going on, and groups can grow even further.
    "Lay in the weeds and wait, and when you get your chance to say something, say something good."
    Merle Haggard

  3. #3
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    If your only running a wire brush through you may have copper fouling and will need a copper cleaner to clean that out. What weight bullets are you using?

    Sent from my SM-G920I using Tapatalk

  4. #4

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    Yes.....all of that and the rate of twist, the bullet may be stable at 100 and 200 and be wonkie at 300 and Parallax can be a factor, and often the highest probability is how the rifle is mounted by the operator, this meaning perfect cheek weld, and eye ball looking straight down the center of the axis of the optic. It seems that people when shooting at longer ranges are inconsistent about looking down the center of the optic. Which being hunched over when shooting off a bench, with head down, and eyeball rolled up towards your hair line, it is easy to be off center. where as shooting off hand your looking straight with head up.

    If I understand this parallax it has to do with the target enters the scope upside down and is righted behind the reticle, and the parallax adjusts so the two are in alignment.

    I never shoot at long range......and I have never read the operators manual for an optic, assuming how hard can it be. Yesterday my New Leupold VX-6 tactical super-duper scope arrived. And being it was rainy, and because this was a $1,600.00 optic, I figured just for giggles I will read both of the manuals that came with the scope. I learned a lot, Especially about parallax and viewing down the center. Then add in if the rifle is tipped a few degrees left or right off of straight vertical axis


    Quote Originally Posted by BrownBear View Post
    If you're getting 5" at 200, expect to get around 10" at 300 with no erratic stuff going on at all. Just the nature of bullets flying further and further away. If you want to be getting less than 6" at 300, better find loads that are giving you less than 2" at 100. Add in sighting errors, wind, mirage and more stuff going on, and groups can grow even further.

  5. #5
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    The other posters already addressed the group size issue, barrel cleaning and shooting technique. So, I'll mention the reason your bullets are dropping 6-10 inches at 300 yards. Each bullet has its own ballistic coefficient (B.C.) which is the mathematical representation of how well it moves through the atmosphere. Hornady won't shoot to the same point of impact as Accubonds because they have different nose profiles which affect their ballistic coefficients.

    I'll give you an example of how I recently sighted in two of my 30-06s using an online calculator of sorts to plot the trajectory. This happens to be from Hornady's web site and there is a lot of info you can plug in but I'll simply list out the trajectory I'm using out to 300 yards.

    168 TTSX 2857 FPS

    100 yards 3.2 inches high
    200 yards 2.9 inches high
    300 yards 3.2 inches low

    Velocity plays a huge role in bullet drop too and I hope this helps clarify why your bullets are dropping so much at 300 yards.

  6. #6
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    Quote Originally Posted by sep View Post
    The other posters already addressed the group size issue, barrel cleaning and shooting technique. So, I'll mention the reason your bullets are dropping 6-10 inches at 300 yards. Each bullet has its own ballistic coefficient (B.C.) which is the mathematical representation of how well it moves through the atmosphere. Hornady won't shoot to the same point of impact as Accubonds because they have different nose profiles which affect their ballistic coefficients.

    I'll give you an example of how I recently sighted in two of my 30-06s using an online calculator of sorts to plot the trajectory. This happens to be from Hornady's web site and there is a lot of info you can plug in but I'll simply list out the trajectory I'm using out to 300 yards.

    168 TTSX 2857 FPS

    100 yards 3.2 inches high
    200 yards 2.9 inches high
    300 yards 3.2 inches low

    Velocity plays a huge role in bullet drop too and I hope this helps clarify why your bullets are dropping so much at 300 yards.
    Tried to edit this post to add this but apparently too late. The above trajectory is with a 260 yard zero. Here's how the trajectory changes if I instead zero the rifle at 100 yards.

    168 TTSX 2857 FPS
    100 yards 0
    200 yards 3.5 inches low
    300 yards 12.7 inches low

    Hope this helps illustrate the trajectory difference based on the distance you zero the rifle.

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