handload .308 subsonic tests

Discussion in 'Reloading' started by Jayne, Aug 9, 2019.

  1. Jayne

    Jayne Just here for the memes Charter Member Supporting Member

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    Finally going to try my hand at reloading 308 subsonic. I picked up some subsonic Atomic 175gr as my factory test load to compare to.

    With online loading data, I've decided to try trailboss. I've made up 9.5, 10.0, 10.5 and 11.0gr loads using 168gr SMKs, 2x fired FC cases and federal magnum primers. I read about the 220s not stabilizing well in 308s so I didn't go there.

    If all goes well I'll test them tomorrow over the chrono and look for keyholes before pushing them through the can and optimizing for accuracy.
     
  2. Average Joe

    Average Joe Just A Everyday Joe Life Member Supporting Member

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    Look forward to hearing your results.
     
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  3. InvisibleOne

    InvisibleOne a.k.a. LoboLoco Life Member

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    I get great results with 10g trailboss under 180g and 200g bullets in a Rem700 AAC 20" 1:10.
    At 100 yds they hit 20 moa below my full-speed 168g zero. sounds like a pellet gun.
    Lapua 200g subsonics are very consistent.
    I've been thinking about trying some Lehigh 194g.
     
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  4. Average Joe

    Average Joe Just A Everyday Joe Life Member Supporting Member

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    @InvisibleOne do you open the flash hole or leave it standard? I’ve read that some people feel you get more consistent results by doing so.


    Sent from my iPhone using Tapatalk
     
    Last edited: Aug 10, 2019
  5. InvisibleOne

    InvisibleOne a.k.a. LoboLoco Life Member

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    I did that on my first batch. But, after running several batches without enlarging, it doesn't seem necessary. And I don't want to accidentally reload one of those cases with a supersonic load.
     
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  6. Jayne

    Jayne Just here for the memes Charter Member Supporting Member

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    First tests done today and we're going to call it a learning experience. Out of the 20" gun even the factory subsonics were not subsonic. The 10.0gr load started keyholing and it got worse from there.

    The 9.5gr load wouldn't chrono correctly, it kept throwing errors and I was testing other (factory non-subsonic) through the chrono after each failure just to see if something was wrong with the chronograph. Those all read fine. The accuracy was crap, but we're talking 5" at 50 yards, so not enough to hit the screens on the chrono or miss... is it? Chrono was 10' in front of me so that can't be it.

    upload_2019-8-10_13-16-52.png

    I'm going to try a 10.0gr and 10.5gr charge with a 175 and a 10.0gr under a 180gr. The 180gr I have are some ugly flat nose things for my 30/30 but the target won't know. Bummer there isn't enough barrel past the sight and mag tube on the 30/30 to get that threaded, that would be fun.

    5 rounds of the 10.0gr @ 50 yards, you can see a few hitting kinda funny:

    IMG_5570.JPG
     
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  7. JimB

    JimB Picking it up slowly. Benefactor Charter Life Member

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    The keyholing means that you need more spin, and since it’s happening above the speed of sound I don’t see how you’d ever get that bullet to shoot well subsonically out of that gun.

    I would try something that stabilizes easier, something short for weight.
     
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  8. InvisibleOne

    InvisibleOne a.k.a. LoboLoco Life Member

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    Twist rate is critical to stabilize subs. I've read that 1:10 or faster is recommended.
    @Jayne, I'm all out of the Lapua 200g. But, I've got 10 Speer 200g HCSP bullets I'd be glad to send to you, if you want to try them.
    They fly almost as good as the Lapuas in my Rem. Send a PM and they're yours.

    edit to add: I also use a slight crimp with a Lee Factory Crimp die.
     
    Last edited: Aug 10, 2019
  9. Catfish

    Catfish E Pluribus Mendacium Charter Member Supporting Member

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  10. 11B CIB

    11B CIB Administrator Staff Member Charter Life Member

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    150gr FP by Xtreme makes some cheap and fun subs. I load them over Trail Boss also. Can’t recall my load offhand but it’s between 9 and 10 grains
     
  11. MacEntyre

    MacEntyre Shoot on Sight! Charter Member Supporting Member

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    Try some lighter bullets. I have a lot of 30 cal bullets of various weights, partial boxes I picked up over the years. Now and then, I make up light loads for 30-30. Not so much these days... I shoot mostly CCI Quiet-22 and Aguila Colibris, with a 24" barrel they are quieter than an air rifle.
     
  12. 7.62 Sam

    7.62 Sam Member Charter Member Supporting Member

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    the 175SMK is my choice for supersonic work, I load the same bullet with trail boss(9.9 gr) .
     
  13. Jayne

    Jayne Just here for the memes Charter Member Supporting Member

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    Back from the range, and we have stable subsonics!

    The 175gr SMK over 9.5gr of Trailboss is averaging 1055fps and isn't keyholing at 50 yards. The 9.8gr load is 1087fps but some were above that so not always, the 9.5gr seems like a better choice.

    Accuracy wise they both look promising. The two 5 round groups fired through the chrono look like this:

    IMG_5634.JPG IMG_5633.JPG

    So other than the flyer that's me, they're good enough for the test. Now that I have a load I'll see what they do at 100 yards with the can on now that I'm pretty confident I'm not going to see baffle strikes.

    The 220gr failed again, way subsonic but also not accurate:
    IMG_5635.JPG

    For this test, getting a 220gr load isn't required. There is more testing that can be done here obviously, but I don't need 220gr to punch holes quietly in paper.

    upload_2019-8-18_17-27-53.png
     
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  14. BowWow

    BowWow Happy to be here

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    The 175's came out great. Its tough to beat that with subs. For 220 grains......i would expect you would at least need a 1in8 twist barrel.
     
  15. Jayne

    Jayne Just here for the memes Charter Member Supporting Member

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    Another batch loaded tonight. Now that we know 9.5gr is good, and 9.8 is almost too fast, I'll try the variants in-between to see which gives me the best 100 yard accuracy. Then... maybe we actually try them with the can on and see if it was all worth white.

    test_batch_4.jpg
     
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  16. Jayne

    Jayne Just here for the memes Charter Member Supporting Member

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    Testing done, 9.6 had one that went supersonic out of another 20" gun (as observed by the noise even with his can on, we didn't have the chrono setup because it was raining) so it looks like 9.5gr is the final answer if you 'always' want them subsonic.

    At 100 yards with a 100 yard zero with FGMM 168gr, these are hitting 2.5-2.6 mils low.

    That's probably the end of these for now, I gave in to peer pressure and got a Ruger Ranch in 300BLK that has about a zillion option for subsonics (even with 168!) with it's faster twist barrel.
     
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  17. willpgn

    willpgn Well-Known Member Life Member

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    I’m headed that way myself and almost bought one at Academy this weekend but it wasn’t the AR mag version. Going to LGS this weekend though!
     
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  18. KnotRight

    KnotRight Well-Known Member Charter Member Benefactor Life Member

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    Jayne, what chrono are you running? And how are you getting your OAL with each bullet? When I am running a 150 FMJ and a 168 SP I usually keep the OAL the same.
     
  19. Jayne

    Jayne Just here for the memes Charter Member Supporting Member

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    Chronograph is an old "shooting chrono beta" from the early 90s. Zero features except "how fast is it"? Everything else you have to write down and do the math on.

    OAL is via a dial caliper. Once I set the dies they don't move for that bullet type so I just spot check as I go. For this and the 300BLK I've been seating the 168, 175, 220s all the same depth with the same seating die. I did try some Hornady ELD and had to change the die setting because the super pointy tip was way long and wouldn't feed in the mag.
     
  20. KnotRight

    KnotRight Well-Known Member Charter Member Benefactor Life Member

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    That is what I was thinking. Once I find an OAL, the dies do not move. What dies are you using? I have a set of RCBS Black box dies for my 300 BO. I need to check to see if the seating steam has a flat surface or very shallow concave, would you need to change the seating length using the ELD's?
     
  21. Jayne

    Jayne Just here for the memes Charter Member Supporting Member

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    RCBS comp seater (with the micrometer adjustment top). Used to be a serious 308 loader back in the day.

    Depends on where the seater impacts the bullet, if the shape is different at all then yes, you'll have to mess with the seater.

    The Lee 300BLK dies I'm using are kinda crap, they adjust too easily and move around while loading (the seater depth adjustment, not the die in the press). Not huge amounts, but noticeable. I've got a sharpie mark on the adjuster so I can see when it moves around on me.
     
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