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Blackout load trouble

Discussion in 'Handloading and Reloading' started by Blade&Bullet94, Mar 30, 2013.

  1. Blade&Bullet94

    Blade&Bullet94 Well-Known Member

    alright so i finally got the 300 blackout iv been dieing after ever since i read up on the caliber. i have hornady dies, a pound of h110, some converted and unconverted 223 brass, and some spare 180 grain boat tails. the problem is, i dont yet have a good reloading manual, the one iv used is outdated, and hodgdon has a gap from 135 to 200. my upper is a CMMG Wasp with a 1:8 twist. i started at 13 grains, and theyd shoot, but only cycle maybe 2 of 3 times if i was lucky. being short on bullets, i made a rookie mistake and jumped to 14.5, which blew the primer, belted the case, and locked up the bolt on the first shot. oops. my problem is i dont trust my little rcbs manual scale as far as i can throw it, as it is exceedingly hard to get level and will give me different readings when it is :( i dont want to drop $250-$300 on one of those automated measure/throw/weight machines and then have the same issue. does anyone have any load data, advice, or recommendations for equipment? sorry that this has been so long winded, but it would frustrate me to no end to have this rifle be a very expensive paperweight (gave up the 5.56 upper to get the 300>>)
  2. Walkalong

    Walkalong Moderator

    I really enjoy my .300 BLK. Yes, data isn't as prevalent as with other long established calibers. It is out there if you do some searching. H-110 is very popular for loading the .300 BLK, so you should be able to find some.

    Here is a good place to look.


    Hodgdon has .300 BLK data at its reloading center online. It shows H-110 data.



    An experienced handloader should be able to use it to work up a load with a bullet weight they skip, but it sounds like you need to stick with data they have for now.

    The RCBS scale is a good one. If you are having problems with it I suggest you call RCBS.
  3. cfullgraf

    cfullgraf Well-Known Member

    As usual, Walkalong gives good advice.

    Also look for reloading data for 300 Whisper. Starting loads will be safe for use in the 300 BLK. Adjust the overall length to fit the magazine.

    Starting 300 Whisper loads may not cycle the action of an AR-15, so work up carefully.
  4. Blade&Bullet94

    Blade&Bullet94 Well-Known Member

    the other major problem i am having is chambering. im using 180 grain sierra matchking HPBT with no cannelure, and when and if they chamber fully they require more force than should ever be needed to remove the round from the chamber. at first i thought it was my COL was too long and they were jamming in the rifling, but even when theyr 2mm short than what published COL calls for, they STILL stick. also, when i manage to get the cartridge unstuck, the neck has a scratched-shine, like its being squeezed. i just now tried reducing the weight of my buffer by removing one of the 3 weights, and with 13 grains of powder it would chamber, fire, extract and eject, but not load another round, and failed to lock back, so its shortstroking
  5. rg1

    rg1 Well-Known Member

    Hornady 9th Edition manual:
    300 BLK. 178-180 grain bullets---Hornady case---WSR primer--16" barrel
    H110--start 10.2-1300fps---11.5-1400---12.8-1500----max 14.1-1600fps
    overall length for all 178 and 180 gr. bullets tested at 2.210"
    I've only used converted LC brass to form 300 BLK and have had no problems. I've read that some brand cases have slightly thicker walls and necks can be too thick to chamber?? I use Hornady's Blackout dies also and use Hornady's Headspace gauge set to measure the shoulders of cases and to adjust my sizing die. I measured fired brass in my rifles chamber to get the shoulder dimensions.
    Last edited: Mar 31, 2013
  6. oldpapps

    oldpapps Well-Known Member


    I must assume that the only powder you have is H110 and the only bullets are 180 grainers. I have found H110/296 is very good in the 300 Blackout but the two extremes of the round is sonic and sub-sonic. Your 180 grain bullets don't do well in either of these ranges.
    That doesn't mean that they can't be used. They will most likely have less than stellar velocities for either end. Too slow, yet too fast.

    I have also found that seating depth is more important.

    The powder quantity spread isn't very expansive. My bottom to top spread for H110/296 and 110 grain V-Max is only 1.5 grains. You jumped that in you second loading.

    I use a powder measure (volume) into a scale pan and trickle to the weight that I want. If you scales are no good, get a second set. That is much less than $250.

    Both powder and bullets are becoming more available. I would look for bullets first. Ever think of Missouri Bullet's heavy lead?

    Narrowing your search down at the following link. Look for me.

  7. Lennyjoe

    Lennyjoe Well-Known Member

    I'm using 125gr TNT's for supersonics with Lilgun for mass range rounds. The load shoots good and the bullets are available for a decent price. My plan is to load 208 Amax and/or 220 Matchkings when the suppressor comes in.

    I had some 200gr Speer hot cores that I loaded to subsonic with Lilgun just to try them. They shot ok but didn't cycle the gun. They ejected fine but wouldn't feed another round. Was fun trying but a waste of bullets/powder.
  8. cfullgraf

    cfullgraf Well-Known Member

    If you are crimping your reloads, stop crimping. With proper neck tension, crimping is not necessary. (edit)--Actually, crimping will not fix improper neck tension.

    By crimping on a bullet with no cannelure, you are probably upsetting something in the mouth/neck area that is making the round too big for the chamber.

    Another trouble shooting aid is to take magic marker and blacken the bullet and case neck. Chamber and remove the round and you will see where you are getting interference.

    While I am not planning to operate my rifle subsonic, I have played a little with heavy bullets. As, LennyJoe said, interesting but a waste of powder. If you get a suppressor, the suppressor creates more port pressure with heavier bullets and will cycle the action.

    Hope this helps.
    Last edited: Mar 31, 2013
  9. Blade&Bullet94

    Blade&Bullet94 Well-Known Member

    thank you for your help guys. iv been using the 180s because they are currently the heaviest and longest .308 bullet i can get ahold of locally. when i looked up how the twist rate effects your loading i was under the impression 125s wouldnt stabilize in such a fast twist. i will try the magic marker trick and get back to you
  10. Walkalong

    Walkalong Moderator

    It is possible your chamber is tight and your necks are a bit too thick, possible. A chamber cast is the best way to find out how big your loaded round can be at the neck.

    As cfullgraf posted, if you are crimping, you could be bulging the neck, especially if your are crimping a bullet with no cannelure like the SMK. Even if you have a cannelure, if case lengths vary a lot you can still buckle a case neck even if the crimper isn't adjusted down too far.

    Some crimp pics

    I am not crimping the 110 Gr V-Max or the 125 Gr TNT bullets, as they have no cannelure.

    Get some measurements of the OD of the necks when loaded. Both pre and post crimp if you are crimping.
  11. oldpapps

    oldpapps Well-Known Member

    I agree, "If you are crimping your reloads, stop crimping." I don't/haven't done a role crimp on any 300 Blackouts. I have used the LEE Factory Crimp. I use it for another layer of uniformity.

    I have only used Remington 300 AAC Blackout head stamped and LC reformed brass. I have had no problems with thickness of brass. I did see a series of posts (another forum) discussing and listing odd ball brass and (new) neck thicknesses.

    As for stabilizing 125 grain bullets, I too have a 1 in 8 twist and have had no problems with over stabilization of any bullets down to 110 grains.
  12. Nikdfish

    Nikdfish Well-Known Member

    There have been instances of 300blk dies with issues due to not setting the shoulder back far enough or sizing oversize just below the shoulder. The best way to know if you are properly forming brass is to use gauges. The LE Wilson case length headspace gauge to check cartridge length and shoulder placement. The Sheridan ammo gauge replicates a min spec chamber to verify cartridges or finished ammo will chamber in any in-spec weapon.

  13. Lennyjoe

    Lennyjoe Well-Known Member

    The 125's are shooting fine out of my 1-7 twist 16" DPMS chrome lined barrel.
  14. Blade&Bullet94

    Blade&Bullet94 Well-Known Member

    my brass is a mixed batch. few LC that have no issues, som federal centerfire that hasnt had much issues, som aromscor precision which i havent tried. i realize now that the S&B 223 brass is what iv been using that jams. i will try making a dummy with each brass and not crimping it and see what happens. also length uniformity is not a problem as i have a lee trimmer with the 300 aac gauge

    *EDIT*just made 4 dummies, 1 LC brass, 1 FC brass, 1 AP, and 1 S&B, COL 56mm. the LC and FC chambered and unchambered with zero issues. the AP chambered fine but unchambered with alittle resistance. the S&B chambered fine but more resistance. these had no crimp at all. will definately look into lee factory crimp die
    Last edited: Mar 31, 2013
  15. Blade&Bullet94

    Blade&Bullet94 Well-Known Member

    got a box of 125s today. loaded 10 rounds. shot great! also traded off about 50 rounds of ap and s&b brass and 40 rounds of federal 45s for about 75 rounds of lake city brass
  16. Walkalong

    Walkalong Moderator

    I checked the neck thickness on some factory RP .300 brass last night with a ball micrometer, and it was in the neighborhood of .009 to .011, while the LC 08 brass I just used to make cases the necks were in the .011 to .012ish range. I wonder what the S&B brass necks are you made.

    Attached Files:

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