Charge Selection and Barrel Harmonics

Discussion in 'Reloading Forum (All Calibers)' started by 6ShotsOr5?, Jul 14, 2019.

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  1. 6ShotsOr5?

    6ShotsOr5? Gold $$ Contributor

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    Free advice is always welcomed, and if it’s bad advice, well I probably won’t know. :confused:

    I’m developing 338 LM loads for long range fun shooting at an upcoming LRP course at ~ 1 mile elevation. This load is for out to around 2000 yds or so. I’m also working on another load with Warner Tool Flat Line 255.5 gr bullets that have a slightly higher BC and will have an extra 100-200 fps that I will use for anything longer — again all for fun, not competition.

    Rifle: Factory Savage action in 338 LM, 24” 9.3 twist fluted light/medium profile barrel with SilencerCo Harvester BB suppressor.
    Bullets: Berger 300 Hybrid OTM Tactical
    Cases: Peterson (1st Firing)
    Powder: RL-33
    Primers: Federal 215M
    Seating: ~ 3.72” COAL varies a little with the meplats, did not measure the CBTO.

    I’ve also tried Lapua cases and the RL-33 load looked pretty good at 97.5 gr. I tried several other powders with the Lapua cases before I got the suppressor, and RL-33 was easily the best for this rifle and bullet. I’ve already stocked up on RL-33 and the Berger 300s. I may still use the Lapua cases. I’m just trying different stuff and having fun doing it.

    The photos are some 100 yd groups I shot today with the Peterson cases. None of these groups are great, but the rifle is nothing special, plus I’m highly allergic to the recoil. The only things that are still Savage on this rifle are the receiver, the bolt, and the barrel, and the barrel is on probation.

    The first group is only two shots because I used the first three shots to get back on target after bedding my rail. The other four are 5-shot groups. Point of aim on the centered on the red diamond for all groups with no scope dial changes. Did not chrono, saw no pressure signs. I won’t go any higher on the powder charges without measuring velocities. Since I use a Magnetospeed, I just try to find a pretty conservative load that will shoot first by checking several reloading manuals and staying within the safe ranges and checking for pressure signs, then I chrono any loads that looked promising. If the velocities end up at the low end compared to what the manuals show, I may go up a little from there, but very cautiously and with more velocity measurements along the way.

    My understanding is that the reason the higher charge weight shot lower on the target is probably because the barrel is flexing down at the 98.5 gr loading and by the same logic it appears that it’s flexing up at the 97.0 gr loading, and these high or low points are where the barrel vertical velocity is slowing to zero and changing direction. It seems like you can really see the barrel harmonics in these groups with the lightish profile barrel and the largish can.

    Without any advice from y’all to the contrary, I would probably focus on the 98.5 gr load because the vertical was so consistent — I’m taking “credit” for all that horizontal. On the other hand the vertical component wasn’t that tight at the “top” on the 97.0 charge, so I think some of what I’m seeing is just normal variation due to the weapon system and the shooter. So if all other things are equal is there an advantage to choosing the high point or the low point of the barrel oscillation, and what is the reason? What do all of your more experienced eyes see that I’m missing?
    E5C761A7-2232-43BF-9007-BE1449BD30CB.jpeg 02B4E537-1C56-43F5-A2A3-C2E4387C71ED.jpeg
     
    Last edited: Jul 14, 2019
  2. Bc'z

    Bc'z Gold $$ Contributor

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    Seating depth test on your 98.5 charge.
    But you probably already knew that.
    Nice!
     
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  3. 6ShotsOr5?

    6ShotsOr5? Gold $$ Contributor

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    Thanks. I realized I left out the seating depth and was adding that, man you’re fast!
     
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  4. mikecr

    mikecr

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    He suggested a seating depth TEST.

    ELR is confusing to me. Shotgun pattern @ 100,, gotta be worse by 500, but you're going right to 2,000...
    What would you try to hit at 2Kyds? A Toyota?
     
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  5. 6ShotsOr5?

    6ShotsOr5? Gold $$ Contributor

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    Sure. Can I use yours?
     
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  6. Texas10

    Texas10 Gold $$ Contributor

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    Thanks! Just sprayed my computer with coffee :p
     
  7. hambone1971

    hambone1971 Silver $$ Contributor

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    Something's wrong here 6shot at 100 they should all be about in the same hole. I had to move my 338L out to 400 yards to do my testing. Just to see what the different powder charges and seating depths did.
    This was with with a 112 Savage RL33 and SMK 300. I got it to under 1/2 MOA and called it good for my purposes....Good luck.
     
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  8. 6ShotsOr5?

    6ShotsOr5? Gold $$ Contributor

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    I’m not opposed to trying some SMKs. Definitely somethings not up to snuff. I have been able to develop some good loads and shoot some respectable groups for another rifle. Hearing that you got your factory Savage action and barrel down to 1/2 MOA is encouraging. I want to be able to hit a small Toyota, not like a minivan or something. Thanks.
     
  9. Howland

    Howland

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    Seating depth testing at 98.5 and measure to CBTO. Giraud makes a nice comparator for .338LM for about $33 shipped. I would attribute location to harmonics and if you aren't running a brake, get one. A good brake will tame recoil and reduce variation attributable to the shooter. I would stick to the heavier bullets for 2,000 and work on one load at a time.
     
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  10. CharlieNC

    CharlieNC Gold $$ Contributor

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    Since you stopped at 98.5 you do not know if it is at the bottom, or just at a steep incline and still headed down. If you safely have room I would start at 98.0 and go up in 0.2 increments to at least 99.0 to clearly refine the node definition.
     
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  11. 6ShotsOr5?

    6ShotsOr5? Gold $$ Contributor

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    Thanks @Howland. I’ve got the Redding Instant Indicator so I can check that I’m getting consistent CBTOs and I have the Hornady comparator that attaches to my caliper so I can calibrate and get the actual measurement. I’m using the Redding Competition seating die to seat the bullets. I’m using a SilencerCo Harvester Big Bore suppressor which also includes an omnidirectional muzzle brake at the exit of the can. I think the recoil is pretty comparable to when I had the APA Fat Bastard brake on it, and the concussion seems to be way less. I haven’t shot this prone with the suppressor yet, but I expect it will kick up a lot of dust.
     
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  12. hambone1971

    hambone1971 Silver $$ Contributor

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    6shot with Lapua brass, RL-33, 300g SMK my 112 liked 96.7g of powder with speeds around 2730 or so.
    Working up to the next node I ran into hard bolt lift and swipe marks on the brass and backed up and called it good at 96.7
    You can get no where fast changing brass, bullets, powder, etc. Pick a good heavy long distance bullet, known powder and brass and keep it simple. Find your node for your gun and that combo, it's there.
    I like the longer test range (400Y) it really shows up when approaching the nodes. HB
     
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  13. 6ShotsOr5?

    6ShotsOr5? Gold $$ Contributor

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    I like the suggestion to test at longer range. I’m going to do that soon on a day when I don’t have much crosswind to muddy the waters. Thanks.
     
  14. 6ShotsOr5?

    6ShotsOr5? Gold $$ Contributor

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    @hambone1971 just curious where you landed on seating depth with the load you described above?
     
  15. hambone1971

    hambone1971 Silver $$ Contributor

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    For OAL with average of 5 loads it's 3.695 or Sinclair's 338 measuring tool similar to Hornady's it came to
    2.900 . I haven't done a lot of seating depth testing, mostly powder charge testing with RL-33 , 300 SMK and the Lapua Brass. I don't think the wind has much affect on this bullet at these close ranges, unless it is really howling. HB
     
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  16. Zero333

    Zero333 Silver $$ Contributor

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    With decent recoil I'd always test 2+ different scopes to rule out the scope as a problem.
     
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  17. 6ShotsOr5?

    6ShotsOr5? Gold $$ Contributor

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    That’s always a possibility. Some of the groups I’ve shot are around 1.25 MOA which could be related to a very small scope wiggle. I was having trouble with a chronically loosening rail on this rifle but I bedded it with JB Weld so it’s pretty snug for now. I use a QD LaRue mount with the ATACR and I used the same mount and scope to shoot several 5-shot groups less than 0.3” at 100 yds recently on a very heavy, suppressed 6mm rifle - it’s closer to no recoil at all. When I mentioned the recoil for the LM, I was thinking more about me flinching than equipment issues. I’m still trying to figure out how I can make a good trigger pull and then be somewhere else before the rifle fires.
     
  18. Zero333

    Zero333 Silver $$ Contributor

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    Maybe trying a little less powder might result in tighter groups ?

    If it was me, I would work around 95 gr of RL-33.
    94 - 94.5 - 95 - 95.5 - 96
     

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