Caught the 300BLK Bug

I don’t know if anything new has come up recently, but at least a year or two ago the list of “good” subsonics was basically Lehigh 194gr and Hornady SubX 190gr, with the Lehigh basically head and shoulders above anything else terminally, and that was pretty much it. There should be some gel tests available on youtube for both of those. Hard to find on shelves though…

For plinking/range ammo currently SGAmmo, PSA, TargetSports all have Magtech 123gr OTM in stock and all ~$0.90/rnd. Pre-COVID this was around $0.50/rnd. Like all Magtech ammo I’ve used, it is nice and clean, reliable and pretty accurate. SGAmmo also has winchester and S&B but both of those are well over $1/rnd and the winchester was pretty mediocre when I overpaid greatly for a few boxes in the middle of COVID.

GorillaAmmo is a small ammo maker that makes good quality stuff, and they have several choices in 300BO (including a loading of Barnes TAC-TX and Hornady V-MAX), and some subsonic rounds but I’m unfamiliar with those projectiles.

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The V max bullets loaded in the 300blk apparently have some potential as a SD round. They expand in a more controlled manner than when shot at 308 velocities. I picked up some made by ammo Inc for less than $1/round shipped to use as practice ammo. Haven’t had time to finish my build yet so can’t speak to Ammo Incs quality yet.

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I was lucky to get a good bunch of the V-MAX back when they were selling the 200rnd loose boxes for $100 (preCOVID). In 308 its a varmint projectile, but seem to perform pretty well at slower 300BO velocities. I’d be curious to hear your experience about AmmoInc as I see them everywhere but no one I know has ever fired it.

EDITED TO ADD: GorillaAmmo currently has 25% off with coupon code GORILLA25

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Finally got all the parts put together and to the range. Fired two boxes of the Ammo Inc 110gr VMax without a hitch. They seem to hit maybe a 1/4 inch lower on average and don’t group quite as tightly as the Barnes TAC-TX. But they are 1/2 the price and I suspect they’ll do the job out to at least 150 yards. Might use them as an in the home option due to less chance of penetrating walls than the Barnes.

Very happy with the accuracy and handling of my new tool. Only disappointment is that the point of impact with SD subsonic rounds is 3 inches lower than the Barnes at 25 yards so mixing and matching without adjusting the optic isn’t a great option.

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I love hearing about others success with 300! Thanks for sharing your progress.


I harvested a wild boar in TX with one of those before aac claimed the cartridge. I haven’t tried them yet feeding from a magazine.

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I bought this primarily for in and around the home defense. But given how accurate it is with just a generic trigger and red dot, I think I’m gonna have to save up for a 3x magnifier and maybe put on a better trigger to see just how accurate it really is. I think it will make a very good 100 yard deer rifle.

I had no issues with the 110s feeding through a standard ar mag but with the 190 subsonics the bolt kept locking back after every shot. I forgot to throw 1 of the 300blk specific mags I picked up into my range bag but suspect the the heavier rounder nosed bullets will work fine out of them.

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Hopefully you have a pistol length gas system, as all should even with rifle length barrels. And hopefully your barrel is 8.5” or longer…
It’s probably not a magazine issue, but lack of gas and dwell time from the gas port to the muzzle with subs.

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I built it as a pistol with a brace. 10” aero precision upper with pistol length gas system. I did put a heavy buffer in it to try to mitigate some of the recoil with the supers.

I only fired a couple of subs and they ejected fine but now that I think about it the bolt was actually closing without picking up the next round, not locking open. So maybe the heavy buffer is the culprit. I’d love to get a suppressor for it some day which would likely resolve the issue. Or I can just try a standard weight buffer. Though I doubt I will be using the subs much since I would have to keep rezeroing the optic to go back and forth with the supers.

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I was gonna suggest this for subsonic loads if you had a shorter barrel. But since you are using a heavy buffer with supers, a standard weight might work with subs. And it’s cheap enough to remove the weights in your buffer for testing purposes.

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It is probably not locking back on an empty magazine either if it’s not picking up a new round. You can test with one round in the magazine for lrbho as you are getting it dialed in.

I ended up opening the gas port to 1/8” and it got better but was not close to 100 percent with a 7.5” barrel. One day I might try to load subs with a powder slightly too slow for 300 and see if it will make more gas and cycle properly and remain subsonic. But it’s definitely a back burner project.

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I was in a rush with the subs because I needed to get back to work so I wasn’t paying close enough attention. But bet you are right that the bolt just wasn’t quite making it far enough back. Will have to try the standard buffer to see if that does the trick.

I’m mostly interested in the subs as an ear safe indoors defense option with a suppressor. But my pistol is my in home primary anyways and the suppressor is a bit too much of a hit for the budget at the moment. I’m just happy it did so well with the 110s.

Thanks for your input! You saved me the ammo I would have waisted figuring out it wasn’t the magazine:)

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It may still be the magazine on LRHO. My 300bo had some issues with std AR mags and higher grain weight rounds. Have acquired 300bo dedicated magpul & lancer mags and feeding/LRHO issues have disappeared. I guess there’s a little more space, so projectile tips aren’t toed in.

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