Interpreting a target - 200.20x/308

Discussion in 'Big Stuff--7mm, 30 Cal, .338+' started by MikeMcCasland, Nov 25, 2019.

  1. MikeMcCasland

    MikeMcCasland Gold $$ Contributor

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    Hey Guys,

    I've posted some questions before (likely way too many) about 308s in F-T/R, and I think I'm starting to get comfortable with the cartridge....very limited experience prior.

    That said, I've had pretty good luck with this rifle in the limited time I've had it. Prior to yesterday, I'd only ever shot it at 100 yards to do preliminary load dev, and then went directly into two 1,000 yard matches back to back.

    I finally got a chance to shoot it at 300 yards (longest distance I can shoot thats not a 1.5hr drive), and here's what it did:

    308 Groups.jpg

    Overall, I'm thrilled with the groups, but I think I have some minor tweaking still left in it. I'd been running most everything at 44.7gr, because I developed the load in ~30 degree temps, but I think it's on the verge of being out of the node (more vertical than the 44.5/44.6gr groups). These groups were shot in ~55-65 degree temps.

    It's my intent to load up 44.5 (TGT 1 - B - Highlighted Red ) at .015" off the lands (TGT 5 - C - Highlighted Red) to see what it does.

    Seems to me the guns vertical shrank as I lowered the charge, and pulled the bullet back from the lands slightly.

    Anyone have any thoughts?
     
    Last edited: Nov 25, 2019
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  2. Bc'z

    Bc'z Gold $$ Contributor

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  3. Fred B.

    Fred B. Gold $$ Contributor

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    You might want to try 44.5 with .020 and .025 jump.
    Looks like it started to come together as you moved away from lands.
     
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  4. damoncali

    damoncali Bullet Maker Site $$ Sponsor

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    There's something bothering me about the seating depth - the groups are all strung one way or another. I'd retest and see if you can find a depth with round groups - keep backing off and see what happens. Might squeeze a little more out of it.
     
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  5. perazziguy

    perazziguy

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    How about wind flags? Was the wind much of a factor?
    Jonathan Taylor
     
  6. MikeMcCasland

    MikeMcCasland Gold $$ Contributor

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    No wind flags, and I wasn't even reading for it...but the wind was light. Maybe 1-3mph, hence why the side-to-side isn't bothering me all that much....although that 44.6 group was either shot during a gust or I pulled it.

    My interpretation is that 44.7 is where vertical starts to creep ever so slightly into the picture, and I agree the further back off the lands I've gone, the better it seems to shoot.

    I didn't catch it until now, because all of these look tight at 100.
     
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  7. perazziguy

    perazziguy

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    A few minor tweaks and bam! You'll have it.
     
  8. fm1947

    fm1947

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    44.7 looks like a good start , With my 308 or any round that I'm working on load I start at the lands find the load doews the bext then mess with seating depth, most of the time I'm good at lands.
     
  9. murray brook

    murray brook Silver $$ Contributor

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    @MikeMcCasland Your groups look much like mine do also at 300 yds with my 7mm/08. You seem to have one shot that open up your group. I have been trying to get that one shot in with the rest but so far have been unsuccesful. Not sure if it is me or the load. I'll have to wait till next summer to try again. Will be keeping an eye on this thread. Good luck.
     
  10. Fred B.

    Fred B. Gold $$ Contributor

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    Different primer might get read of that flyer for you. Check the ES.
     
  11. Ned Ludd

    Ned Ludd Gold $$ Contributor

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    Based on your velocity numbers (which only increase a few fps between 44.5 and 44.8 gr), it looks like you've found a good velocity window (i.e. "flat" spot in the velocity curve). At 44.6 gr, the group was tight vertically, albeit strung out horizontally similarly to the 44.5 gr group. Is it possible that the wind condition played a role in the group widths?

    With that target info, I'd probably re-test seating depth with 44.5 and 44.6 gr, using -.003", -.006", -.009, -.012", and -.015". In my hands with Varget (~43.5 gr), the 200.20Xs seem to tune in around .009" to .012" off the lands, with velocities in the 2640-2650 fps range, or a wee bit faster than the ~2630-ish fps velocities you showed above. Increasing the N150 charge weight to 44.7/44.8 gr doesn't seem like it's going to buy you much in terms of velocity at the current ambient temp, and might actually put you "out of the window" when the temp is ~80 degrees or higher. If the number of rounds you have down the pipe is less than 200-300, the number of firings on your brass is zero (virgin) or 1, etc., it wouldn't be surprising to see the velocity increase another 10 to 20 fps as you put more rounds through it. That would put you in the 2640 to 2650 fps range where I'd have guessed that load might to tune in. However, I've never worked with N150 under the 200.20X bullet, so that's merely a guess. Although I know someone running the 200.20Xs with N150 at around 2650 fps, it may generally like to tune in a bit slower than Varget in some setups. A difference of 10-20 fps really isn't worth mentioning if the precision is good.

    I've always gotten the best results loading to slightly below the middle of the window, then tuning the groups in with seating depth, especially if it was during a cooler time of year. In my hands, that practice seems to result in a load that works well in temps ranging from the mid 40s to mid 80s. If I try to load to the higher end of the window when it's cool outside, the load often performs poorly during the warmer months. Of course, when the mercury gets into the 90s (or higher), even loading slightly below the middle of the window isn't enough and you may need to back off another tenth or two to maintain the original velocity.
     
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  12. SPJ

    SPJ Whoops !! Gold $$ Contributor

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    I’m guessing that thing kicks like a mule with all that powder behind a 200 gr Bullet
     
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  13. MikeMcCasland

    MikeMcCasland Gold $$ Contributor

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    Gun weights 18lbs, has a RAD, and a 1" decelerator. Assuming you could afford to keep feeding it and barreling it, you could fire 500-1000 rounds a day without a problem.
     
  14. Bc'z

    Bc'z Gold $$ Contributor

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    My over pressure load in my 30-06 with Rl26 and 200gr bullets was a cream puff to shoot.
    It's all about the brake!!
    Preasure curve of rl26 is pleasant to shoot by itself.
     
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  15. XTR

    XTR

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    Jade and I both ran 44.3 in our rifles with similar chambers at the FCNC. (my mid range gun. My long range rifle has a very different freebore, and runs more powder for the same node) I think we both decided on 44.7 at one time or another and both later decided that it printed good 5 shot groups but in a 20 shot string we got the errant high flyer and ended up back down at 44.3. One thing that we've noticed, and that PJ has commented on is that N150 seems to have a very wide node in there, pretty much anything from 44.0 to 44.5 will shoot.
     
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  16. MikeMcCasland

    MikeMcCasland Gold $$ Contributor

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    @XTR - I *really* appreciate that kind of feedback; exactly what I was hoping to get.

    I'm going to back it down to 44.5 and test two bushings at .009 off (where I'd run it up until now), .015 off, and .018 off to see how it shoots. Whatever does best, I'll load up for a 1k match this Sunday.

    Regarding the flyer, I suspect you may be correct. I'm not an HM yet, so I'm still a much bigger factor in load dev than some of you guys. The only target I have saved from 1k was it's first match/first relay, and it's got more vertical than I'd like.
     

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  17. rardoin

    rardoin Silver $$ Contributor

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    Mike, are you shooting off a bench with a steady front rest or using your TR bipod? If the latter then consider getting a sled block you can attach to the fore end and a front rest to test using a bench set-up to minimize hold variations.

    Robin
     
  18. MikeMcCasland

    MikeMcCasland Gold $$ Contributor

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    Hey Robin,

    I've got less than ideal conditions at my local range. I have the option of 100 yard indoor range off a bar stool, or rickety wood bench (complete with the next shooter so close you could literally lean over from your stand and look down their scope) out to 300.

    Paper shooting in the Austin area doesn't leave you with a lot of good options. :(
     
  19. D-4297

    D-4297 Silver $$ Contributor

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    For what it's worth ....I load a 200.20x with 44.1gr of Varget , .020 off touch in a 30" Brux . Runs 2,625 - 2660 . And when I do my part , I can get to higher 190's . Summer load here in Phx. is 43.8 Varget .
     

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