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Thread: Optimal Weight for supersonic 300 Blackout?

  1. #1

    Optimal Weight for supersonic 300 Blackout?

    What do you think?
    I was planning purchasing a couple lee molds to mess with and see what I liked best.
    I think the lightweights might not work too well at the higher speeds with such a fast twist.
    So im trying to find a heavier bullet that will work well within the velocity threshold for good accuracy with cast but still move pretty fast.
    My thouuts are that a 170 or so at about 2000FPS Might be a good balance.
    or maybe down to 150 moving a little faster.
    Any reason to go with the 125s or up to the 200+?

  2. #2
    Boolit Master popper's Avatar
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    I did Hornady load book values (no QL), with kinda guessed at BC. Enter into ballistic calc ( or just use muzzle fps) and calculated energy @ 100 (>1k ft/#, no requirement in Tx but margin of error?). Also calc. rpm for 1:10 twist. Decided on a 145gr. PB FN I've chronyd at 2100 fps. Actually did the same for comparison with 30/30. So I'm at starting 150gr 30/30 load that gives good trajectory. Should give me a decent 100-150 yd deer or pig load. 170 gr @ 2k fps is pretty hot.
    Whatever!

  3. #3
    Boolit Master
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    I have a 1-7" twist. 110 & 125gr jackets shoot great. I tried cast 150gr Lee at 1800 fps and at first it shot great. I dropped the powder charge 1/2gr and they would barely stay on a paper plate @ 50 yds. I checked the gun by putting 5 110grRN into 1". I had to quit at that point but what's the deal? I'm hoping I'm not high jacking here. Just wondering if I have the wrong bullet.

  4. #4
    Boolit Master 1johnlb's Avatar
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    The lee 155 has been a good performer in everything I've put it in. If your having trouble keeping it on the target, check your size to make sure it's big enough ans your alloy is hard enough.

  5. #5
    Quote Originally Posted by Texas by God View Post
    I have a 1-7" twist. 110 & 125gr jackets shoot great. I tried cast 150gr Lee at 1800 fps and at first it shot great. I dropped the powder charge 1/2gr and they would barely stay on a paper plate @ 50 yds. I checked the gun by putting 5 110grRN into 1". I had to quit at that point but what's the deal? I'm hoping I'm not high jacking here. Just wondering if I have the wrong bullet.

    Was everything else the same? Same alloy? Lube? Hardness and age on bullets?
    same setting on your dies?
    What powder?

  6. #6
    Quote Originally Posted by popper View Post
    I did Hornady load book values (no QL), with kinda guessed at BC. Enter into ballistic calc ( or just use muzzle fps) and calculated energy @ 100 (>1k ft/#, no requirement in Tx but margin of error?). Also calc. rpm for 1:10 twist. Decided on a 145gr. PB FN I've chronyd at 2100 fps. Actually did the same for comparison with 30/30. So I'm at starting 150gr 30/30 load that gives good trajectory. Should give me a decent 100-150 yd deer or pig load. 170 gr @ 2k fps is pretty hot.
    Im thinking about the same. 150 grains or so should give the best bang for the buck. Thinking the 170 might be ok too if the 150 is moving too fast for good accuracy. Better a 180 at 1800 that a 150 at 1800. That is if I can hold accuracy at a higher velocity.
    Where do you guys see for a drop off on accuracy with that twist ? Is 2000 possible. I'm hi-tek coating

  7. #7
    Boolit Master
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    Quote Originally Posted by Michael J. Spangler View Post
    Was everything else the same? Same alloy? Lube? Hardness and age on bullets?
    same setting on your dies?
    What powder?
    Hodgdon Lil Gun-15 grs instead of 15.5 is the only difference. If someone will confirm that my twist(1-7") is too fast for cast I'll quit spinning my wheels. The same bullets are fine in my 1-12" 30-30. Best, Thomas.

  8. #8
    Boolit Master


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    I'm not sure that 2000+fps is possible with a 170gr in the Blackout. I worked up the Lee 155gr standard groove for a carbine length PSA upper. Mine came out around 162gr with lube and check from what I recall. I was getting about 1950fps on the chrony. My load and my velocity were both North of anything I'd seen published online.

    I tried the same loads in an upper with a pistol length gas system, and it blew the primers out.
    ΜΟΛΩΝ ΛΑΒΕ

  9. #9
    Thomas

    if the 15.5 shot well I doubt it's the twist because 15 would be giving you less rpms and should be fine anyway. Also the 7 twist is should be enough to stabilize at those speeds. I'm trying to think of some other weird variable.
    Hmmm

  10. #10
    Boolit Master
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    lyman 311413 (169 grains w/ gas check and powder coated) sized .309 over 18.5 grain AA1680 works for me. I get baseball sized groups at 200m. estimated 1800fps (no chrony).

  11. #11
    Boolit Master
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    I have 40 more to try. Another difference is I crimped these. I'll try it again- I just wondered about the twist. It won't break my heart to not use cast in the AR. I have a 30-30 and a .358. Best, Thomas.

  12. #12
    Boolit Master popper's Avatar
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    I used 150s for the 1:7 carbine when I had it, worked fine with 4227 that was available then. 110 works fine. I was using 3% Sb WD & PCd. My experiments with hitek rifle didn't work well. 1800 is max with 170. Primers get flattened but I've not had any blown out. I've not used lilgun, heard some strange stories about it. I did pick up some BLK to try.
    Whatever!

  13. #13
    Ok so looking at some more data I think i'm going to try out some of the lee 170FP bullets. A buddy just got the PB and the GC version of this mold.
    I'm thinking 170 at 1800 FPS should be pretty nice. Should be slow enough to be accurate but heavy enough to be a hammer. Flat point is a bonus.
    has anyone run this bullet in Blackout?
    I ran a bunch of slower HiTek in the rifle... and last nigh I ran 50 rounds of the 311365 over 11 grains of H110 which depending on the load data you look at yields between 1100 and 1300. Not very hot at all really but I have run max load of H110 with a 158 grain 357 in my Marlin 1894 which should be clocking pretty darn fast. Nothing but a clean barrel when I'm done.
    That is a slower twist though.

    popper I looking to the BLK and that stuff looks awesome. Higher velocity and lower pressures that most other powders listed. No doubt there is a few other powers that will work as well in that cartridge but the manufacturers just haven't done the testing of them yet. Maybe with BLK coming out they will find the need to develop a new powder to match or just work up some data with their slower powders.
    I hope so because I'm getting frustrated with the huge discrepancies in the data for 300 blackout.

  14. #14
    Boolit Master popper's Avatar
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    I have a 10" pistol I tried my 170 gr RD PB, 1:8, worked fine need to try in rifle. Between the windy weather and a couple months of eye work ,it may be summer before I get much done.
    Whatever!

  15. #15
    Boolit Master
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    Would imagine a 150gr cast can be driven as hard as a 125gr jacketed. I have been loading PC coated 200gr in a 308 and they go just as fast as my 150gr jacketed loads.

  16. #16
    I'm not using the 300 Blackout, but my wife and I each have ARs in 7.62x39. Ballistically, both rounds are almost identical on the top end. We are using 16" barrels and in these efficient cartridges, you can easily match advertised velocity or exceed it slightly. The only practical difference between the two rounds is the barrel twist used with them. That's why I went with the 7.62x39. I've noticed that the faster twist tends to shoot slightly slower and bullets tend to come apart easier due to the added centrifugal force.

    Our barrels are 1:10 .308, but shoot .310 factory ammo just fine. I haven't noticed any pressure or velocity difference between the while reloading. While testing the different ammo, I referenced back to my 30-30 data and am only getting about 100 lbs of energy difference. When you add the ballistic coefficient of pointed bullets, you are actually at higher power by the time you get to the target in many cases.

    I'll start with my experience with the j-words.

    I think that these rounds really shine with the 30-30 designed bullets but those aren't very aerodynamic. The best are made by Speer and those IMO are the best performers on deer and hogs from the ol' lever guns. The 130 and 150 should work very well as long as the front lip of the magazine doesn't catch it. I also tried the Speer 110 gr Hotcor SP and they hold together well while giving plenty of penetration on average size deer. My most accurate handloads with this round is with the Hornady 123 SP in .310 made for the 7.62x39. Again this is out of a .308 barrel. This bullet pushed with Reloder 7 will easily shoot sub moa with an entire magazine. The others aren't that far behind in accuracy though. These also work well in deer and hogs but the best performance that I have found so far is the 123gr .310 SST Hornady. I have shot several big (250+) boars broadside and they just folded up. I've only had two animals run with a broadside behind the shoulder shot and one went 10' while the other made it about 25 yards. Oddly enough, these bullets give a bigger entrance would and deeper penetration than the regular SP. I'm planning on buying some to reload because the factory rounds are kinda pricey and not quite as accurate. I also have a box of Speer 130 gr HP but haven't had a chance to try them. I've heard that they work very well in the 300 BO. If you have trouble finding 300 specific bullets, you may try the ones designed for the 7.62x39, obviously starting low and watching for pressure signs.

    I have some Laser-Cast 170gr RNFP GCB (without a GC) at .310 that have shot well at both high and low velocity out of the 30-30 but haven't tried them in the 7.62x39. As you're probably aware, this round wasn't designed for straight magazines and I believe trying cast in it would just lead to me having to clean lead shavings out of the action. You shouldn't have that trouble with the 300 Blackout but I worry that the twist rate might give you fits. I haven't seen a benefit going above 150gr at this power level.

    Our options are increasing everyday in the way of available bullets that will work with these lower velocity rounds. I contribute that to the popularity of the 300BO. This is beneficial to both 30-30 and 7.62x39 shooters. I might even have an upper made in 300BO with a 1:10 twist one day. As much as I love my old '94s, it's hard to beat a semi-auto with the same ballistics.

    If anyone is interested in a few samples of the bullets that I have mentioned, shoot me a PM. We can trade or I can just send some to you. I hope that it helps.

  17. #17
    Boolit Master

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    Early on I tried the Lee 170fp, it is so short it did not cycle well from any of our 300BO uppers, it tended to nose down in the mags and FTF. Your mileage may vary, but probably not by much. I do have a 7.5" Encore pistol barrel it would probably work well in.

  18. #18
    Ok so here are some results with the 311365.
    As suggested I was setting them with a driving band 2/3 of the way exposed. Hoping to get close to the rifling and gain accuracy. I have had some issues with feeding which I thought was due to the gas system being carbine and the adjustable block adjusted 60% open to run smooth and flat with my J word loads.
    Well I tweeted my loads a little hotter and still had issues. Upon finally loading some mags near full I found that the cartridges were binding a bit and hard to load. After some inspection I noticed that the full diameter of the 311365 was riding on the guide grooves at the front of the magazine that would normally keep the 5.56 cartridges staggered properly to allow proper operation and advancing or double stack cartridges. Well with a damn near straight case and a 30 caliber bullet seated long they tend to rub on said grooves and drag.
    The bolt would operate and close before the next cartridge would advance in the magazine. Once I was down to 3 or 4 cartridges it would stop binding and cycle fine. Now and then the bolt would catch halfway on an advancing cartridge and jam.

    So after slowly single shotting my way through 100 rounds I quit for the night. Tonight I loaded 5 dummies to the crimp groove. I'm guessing about .100" shorter than what I was previously loading.
    I loaded them into the magazine without any drag or binding. Even when pushing them down haphazardly to simulate a fuller magazine there was binding at all.

    Good news is that this bullet is still shorter than a 208 amax which has a ton of data available. So I should be able to creep up on amax data and not be playing on the hairy end of pressures due to deeper seating bullets raising pressure.

    Lets ts see how it works next week.

    I also grabbed a lee 309-150-f in hopes of making that my go to bullet. I think the 311-155 is a better design for the short necked cartridge but it lacks the flat point which would be better on game.
    Guess we will see how the 150-f works.

  19. #19
    Boolit Master
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    the 311365 should do well, I personally like the 311041, it works well in mine feeds well and wt's 180gr's. I just need to load about a 100 or so now.

  20. #20
    Boolit Master
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    I have read some go to the polymer AR mags for the 300AAC due to the mag issue. You cant grind down that ridge in the metal ones. And they now sell 300 specific mags. Guess it depends on the bullet used as to being an issue.

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check