Loading sub-sonic 300 Blackout for a 16-inch barrel.

[mcb]

First time out with my AAC SDN-6 on my home built 16-inch AR in 300BO. Yes I should have built a 9-10-inch pistol/SBR., but when I built this they were still arguing about the legality of pistol braces and I did not want to mess with or spend the money for an SBR. So I went the safe/easy route and did a 16-inch carbine.



The suppressor and gun ran and shot well but I was disappointed with my subsonic ammo. I tried two sub-sonic loads. Some cheap Remington 220gr OT-FB (L300AAC4) and the new Hornady Sub-X 190gr . Both were super sonic from my 16-inch barrel. The Remington Chrono'ed an average velocity of 1144fps. The Hornady average 1117 fps. A few of the Hornady would dip below 1100fps and not crack. It sounded pretty good then but 85% of the bullets were super sonic.

So for now I think my best option is going to be to hand-load some subsonic loads. I have everything to load 300BO as I have been hand loading Barnes 110gr TAC-TX for hunting loads. I was hoping you guys had some load data that had been chrono'ed in 16-inch barrels to help me find a good powder and starting load to work up from. I am looking at using some 200gr or 220gr Berry's for plinking ammo and some 200gr or 220gr Makers bullets for a sub-sonic hunting bullet. Any data would be greatly appreciated.

 

[greyling22]

tagged for watching. my 9mm suppressor is in jail and I'm going to need loads as well.

 

[berettaprofessor]

CFEBLK 11.6 grains behind a Hornady 208 Match bullet OAL 2.250, goes 1099fps average out of an 18 inch barrel. It’ll probably be routinely sub in a 16.

 

[beeenbag]

Berry’s 220 grain plated with 7.5g lil gun, cci magnum primer, chrono’d a 5 shot average of 1057 fps out of my 16” barrel. Fairly accurate load to boot. YMMV

 

[mcb]

I finally got everything together this week and tested some loads today.

First was not a reload but a factory ammo. Sellier & Bellot sells a 200gr sub-sonic load (ASB300FMJ220 ) This load was super accurate for a subsonic load. Four rounds in one ragged and a fifth round open the group up to ~.7 inch at 50 yards. It was subsonic in my 16-inch carbine with the average of five shots at 1062 fps.


Next were my reloads.

Load #1
Bullet: 220gr Berry's plated
OAL: 2.190, very little crimp
Primer: Winchester Small Rifle
Powder: Accurate 1680
Charge: 11.2 gr
5-shot Average: 1068 fps (SD: 45.92)
Charge: 10.9 gr
5-shot Average: 1008 fps (SD: 26.66)
Charge: 10.6 gr
5-shot Average: 963 fps (SD: 25.55)

Load #2
Bullet: 220gr Berry's plated
OAL: 2.190, very little crimp
Primer: Winchester Small Rifle
Powder: IMR 4227
Charge: 10.4 gr
4-shot Average: 1082 fps (SD: 10.77)
Charge: 10.1 gr
5-shot Average: 1040 fps (SD: 10.90)
Charge: 9.8 gr
5-shot Average: 1006 fps (SD: 13.49)

I did not have the best rest for this testing and was more focused on getting the velocity data. That said the accuracy was acceptable for all the loads. They all produced groups of about 1 inch at 50 yards. I think if I had been over sand bags front and rear that the groups would have been a little bit better. All of the loads functioned without issue in my 16 inch rifle with pistol length gas system and through my SND-6 suppressor.

I think the 10.1gr of IMR 4227 is going to be my winner. The velocity was very consistent and the groups were a touch better than the 1680 loads and all the 4227 loads were noticeably quieter than the two heavier 1680 loads and on par with the lightest 1680 load.

Now to get the parts to load that load on my Dillon 650 instead of on my three die manual press. That was too slow. Next carbine match will be shot suppressed!

 

[mcb]

Thread update, its going to be a long one.

Finally got out today and and tested some Maker bullets. Things are not going as great with that bullet as I would like. The Barry's 220gr are still working like a champ.

Re-chrono'ed the 220 Barry's. These where loaded on the XL650 not on my single stage press with each charge weighed. First rounds through the gun, clean barrel, making sure the chrono was working.

Bullet: 220gr Berry's plated
OAL: 2.190, very little crimp
Primer: Winchester Small Rifle
Powder: IMR 4227
Charge: 10.1 gr using Dillon XL650 powder dispenser
5-shot Average: 1066 fps (SD: 17.19)

The last five round after shooting the Makers and few other shots.
Charge: 10.1 gr using Dillon XL650 powder dispenser
5-shot Average: 1049 fps (SD: 11.04)

With a dirty gun that is pretty close to what I had with the loads off the single stage press. Accuracy is pretty good too.

.7 inch group @ 50 yards

Now the Maker Bullets are not working out so well so far. I started with the 200gr bullets. Much of the 200gr bullet work was actually done before deer season late last year but I was not happy with it so I did not hunt with it. Hunted this year (unsuccessfully) with my 450 Bushmaster.

First attempts with the 200gr bullets:

Bullet: 200gr Maker REX
OAL: 2.105, very little crimp
Primer: Winchester Small Rifle
Powder: IMR4227
Charge: 9.3 gr
5-shot Average: 1024 fps (SD: 12.6)
Charge: 9.6 gr
5-shot Average: 1053 fps (SD: 10.8)
Charge: 9.9 gr
5-shot Average: 1104 fps (SD: 21.16)

The 9.3 gr load failed to eject once or twice, no lock open. The 9.6gr load failed to lock open on the last round. The fastest load (9.9gr) cycled well but was super sonic. Given how well the 4227 worked under the Barry's I was bummed it did not work terrible well under this bullet. Accuracy was OK but not great, groups where all well over an inch at 50 yards.

Bullet: 200gr Maker REX
OAL: 2.105, very little crimp
Primer: Winchester Small Rifle
Powder: Accurate 1680
Charge: 9.5 gr
5-shot Average: 879.6 fps (SD: 39.8)
Charge: 9.8 gr
5-shot Average: 931.2 fps (SD: 17.5)
Charge: 10.2 gr
4-shot Average: 979.2 fps (SD: 9.21)

The first two load were really low velocity and had cycle issues. The last load is OK. It still a touch slower than I wanted but it does cycle well and the accuracy is good, about the same as the Barry's. The point of impact is about 2-inches lower than the Barry's.


Left: Maker REX 220gr Right: Barry's 220gr

I finally got a box of the 220gr bullets. They are really long as you can see in the above picture. So long and with such a short ogive that I had to get 300 BO specific magazine to even get them to load into the magazine. I loaded these first two load at nearly max OAL of 2.25 since that put the case mouth in the last grove in the bullet. That fits nicely in the magazine but it will not feed. I had to single feed these direct to chamber. I am clearly going to have to short OAL and try again with this but here is what I got from the loads.

Bullet: 220gr Maker REX
OAL: 2.250, very little crimp
Primer: Winchester Small Rifle
Powder: IMR 4227
Charge: 9.4 gr
5-shot Average: 1054 fps (SD: 18.97)
Charge: 9.7 gr
5-shot Average: 1097 fps (SD: 2.23)

That 9.7 gr load is the lowest Standard Deviation I have ever seen in a five shot group for any load I have ever loaded. The Extreme Spread was only 6.18. Too bad it was super sonic. The Accuracy for both of these loads was very nice and the point of impact was basically the same as the 220gr Barry's maybe a half inch higher. Had to single feed them, they ejected but would not lock the bolt back. Going to have to go to 1680 to make this one work to I suspect.

Deer season starts in November, I still got time...

 

[Wreck-n-Crew]

MCB you may be leaking gas, Check your gas key and make sure it is staked and tight. Then check the Gas block to make sure it's not leaking.

 

[greyling22]

Cut a couple coils off your buffer spring. It fixed my short stroking problem, and if not, springs are cheap.

Also, my can is still in jail.......... Even though I decided to sbr the blackout via efile and it only took 18 days......

 

[mcb]

I will definitely double check for gas system leaks when I clean it. That said so far only my reloads with the Maker Bullets have given my cycle issues. It runs with just about every other commercial ammo on the market and all my reloads. Being a 16-inch barrel with a pistol length gas system it runs just about every load I have tried in it, super or sub and with or without the suppressor. The problem it that nearly all of the commercial sub-sonics I have tried are super sonic in this particular barrel.

Before I go clipping coils of the recoil spring I think I would rather open the gas port up a few thousands of an inch. I am running a standard buffer so I can't really go much lighter there.

I have a 9-inch pistol that will use the same can that is nearly complete, only a last few parts to acquire before I assemble it.

 

[greyling22]

You can take the buffer apart and remove 1 or 2 of the 3 weights. It's not real easy, but it can be done.

 

[mcb]

Late thread update: Well... way to late for 2018/19 deer season but plenty early for next season. I think I finally have my hunting sub-sonic loads set. I also finally shot and tested out my new 300 Blackout pistol.

Despite how well the IMR 4227 worked with the 220 gr Barry bullets it did not work with the Maker 220gr bullets. Despite cycling great under the 220gr Barry's 4227 would not cycle the gun under the Maker. I went back to Accurate 1680 and shortened the overall length. Basically went back to the recommended load from Maker Bullets.

Bullet: 220gr Maker REX
OAL: 2.150, very little crimp
Primer: Winchester Small Rifle
Powder: Accurate 1680
Charge: 10.4 gr
5-shot Average: 1066 fps (SD: 8.83) 16-inch barrel
5-shot Average: 977.2 fps (SD: 12.48) 9.5-inch barrel

Shot to the same point of impact as the cheap Barry's plinking load, at least at 50 yards. And it cycled the gun well locking back on the last shot. I am using some using some D&H Industry 300 BO specific magazines and they worked very well with the short ogive Maker bullets.

I did do a quick low-tech terminal ballistic test with the 220gr Maker bullet also. Filled and lined up five 1-gallon milk jugs and shot them at 50 yards from the the 16-inch gun. The bullet performed very well IMHO.







The expanded bullet was found in the fourth jug. It split the first two jugs wide open. It was evident by the exit hole in the first jug that most of the expansion had happened in the first jug. The third jug did not split but had holes in both sides that look like a hole from a very dull three bladed broad-head. The fourth jug had a similar entrance hole but no exit.



This last picture of three recovered bullets from yesterday testing, the left bullet is another picture of the bullet fired into the water jugs. It had 100% weight retention.

The middle bullet was one of the bullet fired during chrono and went through the target and cardboard backer and into the rocky dirt pile (Lots of gravel size chert r0ck) that is my backstop. It still opened, badly, but retained 100% weight.

The last, right most, bullet is interesting. I shot a 12oz Powerade bottle full of water sitting right on the backstop. The bullet appears to have expanded fully in the little 12oz bottle and then lost two of it three petals in the rocky backstop. Still weighted 171 gr (78% retention).

Now I need to shoot a few Coyotes and other varmints this summer for some real terminal testing before next deer season.

 

[CANNONMAN]

Hey fun post! Thanks, Would you mine a pic of what you ammo looks like in the mag after a few rounds? I might have missed it but I didn't see your calculation for barrel length, gas block, ammo and suppressor. I agree with WnC to check. Dirty ammo is a pretty good indicator of too much gas. My block can be switched for subs to supers. Not much $$$. Regardless, thanks for post!

 

[mcb]

Hey fun post! Thanks, Would you mine a pic of what you ammo looks like in the mag after a few rounds? I might have missed it but I didn't see your calculation for barrel length, gas block, ammo and suppressor. I agree with WnC to check. Dirty ammo is a pretty good indicator of too much gas. My block can be switched for subs to supers. Not much $$$. Regardless, thanks for post!

I don't have a picture of a partial magazine after shooting but it gets fairly dirty. But I am pretty sure that is mostly from back pressure from the suppressor (AAC SDN-6). I will take a picture of the follower and a few rounds that were in a magazines this evening, the red followers are very dirty. That said the 1680 load ran in both guns and locked back in both guns.

At this point I seem to have the cycling issue overcome in the 16 inch gun. Both of my sub-sonic loads function well, accurate and lock the action back on the last shot. The D&H magazine certainly helped feeding issues with the Maker bullets. My 300 BO pistol probably needs a touch more bolt velocity. I started with an H1 buffer and will first try a standard buffer before I try to increase gas. It ran perfectly yesterday but failed to lock back with several different loads I shots (my Maker reloads and a few factory loads). The pistol ran the Barry's loads very nicely.

What calculations are you referencing? I would be happy to share them if I have them.

 

[mcb]

The round in the magazine is the round I ejected out of the gun at the end of the day. It had four rounds fired from a full magazine above it. The round in my hand was never in the magazine/gun. The followers are pretty dirty though the magazines feed about forty rounds each loading only 5 round at a time in the magazine shooting groups and chrono, all suppressed

Quick summary of my velocity data comparing the 16-inch Ballistic Advantage barrel to the 9-inch AAC barrel

My reloads:
Barry 220 gr (10.1 gr IMR 4227) 1040/983.8 fps
Maker 200 gr (10.2 gr A-1680) 999.6/907.8 fps
Maker 220 gr( 10.4 gr A-1680) 1066/977.2 fps
Factory:
Rem L300AAC4 220 gr 1144/1057 fps
Hornady Sub-X 190 gr 1117/1056 fps

 

[CANNONMAN]

Do you know the size of your gas port? Might not really matter cuz I doubt you want to replace it. It looks like your supersonic with subsonic ammo? Gas blocks are cheep and as mentioned so are buffer springs. JP has kool adjustable buffers. That gets into $$$. The pics are pretty dirty. I've done way worse. A.95 gas port is my guess. 16" carbine. For about a C-note you might try a 10.5" 1/8 twist. Adjustable gas block. You should find you need to turn the bock for the supers and back for the subs. I think your ammo will slow for the length. You suppressor will er, I think should, work better. Oh the buffer spring, Greyling22 is probably right. To know you Db's now and with adjustment would be interesting. Basic thought with sub .300's is to run with can. However with no adjustment dirty and cycling are the most common problems. BTW, what's your twist? Or am I really off here. Are you trying to quite a supersonic round? Going for ear safe and more pleasant to shoot sort of thing? That's fine of course but then My .2 would be a different can. Either way. Fun project. I'm still playing with these same issues. Just when I think it's all me I find it's a common set of problems. The brotherhood of errors. First we shall unite then total world domination!

 

[mcb]

At this point I am mostly just rambling and documenting my progress. I am currently fairly happy with my reloads they are all sub-sonic in my two guns, run fairly well and are fairly accurate (sub 2-MOA at 50 yards so far but I have not go serious about shooting groups yet). Well see how dirty the gun is after my first carbine match with it running suppressed. That will decided whether I am too dirty or not.

The two factory loads above are definite super sonic in my 16-inch gun. I had a gotten a good deal on the Remington ammo and was going to use that for plinking and the Hornady Sub-X for hunting. But both proved to be super sonic in my 16-inch gun. When I started this thread I did not have the 9-inch gun yet. So I starting working up a load for a plinking and hunting sub-sonic round and this thread resulted. I will use what's left of that factory ammo in the 9-inch gun since both are sub-sonic in it.

Both barrels use a pistol length gas system and are 1: 7 twist. I am not sure the gas port size I did not measure it before assembly of either. At this point I don't think I need to play with gas. Though I do have a JP adjustable sitting on the shelf if I need it. The 16-inch gun is running well and the 9-inch gun is running a touch slow but a gas block won't help that only drilling out the port in the barrel will increase gas. But before I drill out the gas port I think changing the H1 buffer for a standard buffer and just a bit more break in will solve the occasion failure to lock open on the last round issue with some subsonic loads. This was the first outing with the 9-inch gun so its just getting broke in.

So far my 16-inch gun has run nearly everything (except a few of my early sub-sonic load) with or without the suppressor, super or sub-sonic. It has just run great. The 9-inch gun was built as a dedicated sub-sonic suppressed gun and so far I have only shot suppressed sub-sonics in it. Next range session I will try some un-suppressed shooting and some super sonic ammo in it.

I am also realizing that my eyes are just starting to get bad enough that I am probably going to replace the iron sights on the 9-inch gun with some type of low power optics. Maybe a Vortex Prism 3X.

 

[CMV]

IF you're just plinking & don't need anything special from the bullet, check out the MBC coated 240gr bullet. They work really well for me with A1680. I'm a 16" barrel that's crazy long with another 8" of can hanging off the end too......but midlength gas. Pistol gas + longer barrel = lots of tinkering most cases...midlength "just works" with 300BLK.

At work so don't have my load notebook in front of me but I think it's 10.6gr A1680, CCI #41, converted LC brass, mag length with those MBC bullets for great performance from a 16". I got slightly better groups with an extremely light FCD application, but never really got excellent precision. Around 1.7" @ 100 I think is what it does....but i was going more for working down the FPS than chasing excellent accuracy. Too cheap for SMKs or AMax, but did get better groups with the 208gr Amax.

I need to get that rifle out soon....I haven't shot 300BLK in quite a while.....

 

[mcb]

IF you're just plinking & don't need anything special from the bullet, check out the MBC coated 240gr bullet. They work really well for me with A1680. I'm a 16" barrel that's crazy long with another 8" of can hanging off the end too......but midlength gas. Pistol gas + longer barrel = lots of tinkering most cases...midlength "just works" with 300BLK.

At work so don't have my load notebook in front of me but I think it's 10.6gr A1680, CCI #41, converted LC brass, mag length with those MBC bullets for great performance from a 16". I got slightly better groups with an extremely light FCD application, but never really got excellent precision. Around 1.7" @ 100 I think is what it does....but i was going more for working down the FPS than chasing excellent accuracy. Too cheap for SMKs or AMax, but did get better groups with the 208gr Amax.

I need to get that rifle out soon....I haven't shot 300BLK in quite a while.....

For plinking I just want something heavy and quiet. For that price on the MBC might make it worth a try. I am currently using the Barry's 220gr plated for my plinking load but that is costing me about $0.24 a bullet after shipping for 500pcs. The MBC should be less than $0.20 a bullet after shipping for the same quantity. Thanks for the recommendation.

The thing that got me with the Barry's was with the IMR 4227 powder it was noticeable quieter than the 1680. This is why I started with the 4227 under the Maker bullet but could never get it to cycle and had to switch back to the 1680.

 

[CMV]

The few rifles I've seen in person with 14.5-16" barrel & pistol gas all needed adj gas blocks to handle the gamut of standard loads, suppressed, subsonic loads, subs suppressed. At least one of those 4 wouldn't run w/o it.

 

[mcb]

The few rifles I've seen in person with 14.5-16" barrel & pistol gas all needed adj gas blocks to handle the gamut of standard loads, suppressed, subsonic loads, subs suppressed. At least one of those 4 wouldn't run w/o it.

So far my 16-inch carbine with a, pistol length gas system gun has run just about everything I have feed it. No factory load has failed to cycle it yet, with or without the suppressor mounted.

 

[GarrettJ]

The thing that got me with the Barry's was with the IMR 4227 powder it was noticeable quieter than the 1680.

That’s just the nature of 1680. It is by far the loudest powder I’ve ever used. Suppressed or otherwise.

 

[Ohen Cepel]

If anyone tests any in a 16in bolt gun please let me know. Having issues with most being super sonic in it.

 

[mcb]

Another rambling update on my adventures in 300 BO sub-sonic but focused on my 9-inch 300 BO pistol this time. No new loads but I spent a fair bit of time at the range with my 300 BO pistol recently and my existing two favorite loads. I am getting happier and happier with my setup the more I use it.


Top: 16-inch Carbine
Bottom: 9-inch Pistol

Had the Lab Radar out and re-chronoed my two loads again using that instead of the old and trusty Shooting Chrony.

Plinking Load:
Bullet: Barry 220 gr
OAL: 2.190"
Powder: 10.1 gr IMR 4227
Primer: Win Small Rifle
Brass: Rem once fired
5-shot Average: 975.77 fps (SD 28.41 ) (Previously with the Shooting Chorny: 983.8 fps)

Group size is 1.74 MOA @ 100 yards

Hunting Load
Bullet: Maker 220 gr
Powder: 10.4 gr A-1680
Primer: Win Small Rifle
Brass: Rem once fired
5-shot Average: 978.07 fps (SD 2.61 <-not a typo!) (Previously with the Shooting Chorny: 977.2 fps)

Group size is 2.3 MOA @ 100 yards. If you look closely there is some evidence the the bullet is not 100% stable from my pistol by the time it gets to 100 yards, that instability evidence was not there at 50 yards in previous testing. But that is one really long bullet to spin.

The groups were shot with a Vortex Spitfire 3X prism scope. I probably could have shot better groups with higher magnification and a stock (if I had an SBR register lower) but I was happy with the groups given the optics and lack of any real rear support due to the SBA3 pistol brace.

After a bit of experimenting with the EBR reticle I could hit an 8-inch gong at 140 yards and 10-inch gong at 200 yards, at will. The weather was just right and in the bright sun you could looking over the shooter's shoulder see the bullets arcing through the air to the target. At 200 yards you could often call a hit or miss before it even hit the target the trajectory was so clearly evident. I could often get the scope back on target and watch the bullet finish its flight, hit the target and then hear the ping of the hit ~ 1/2 second later. That was pretty cool.

Using the data from the Lab Radar I calculated a BC for both of my loads. I had decent radar data out to about 100-120 yards before the signal to noise ratio got to bad to trust. Using JBM Ballistics online calculator I got the following, based on the average of several bullets of each type.

Berry's 220gr G1 BC: .35
Maker REX 220gr G1 BC: .36
I suspect these numbers are only accurate for my velocity range. I have seen other calculate the BC of the Berry's bullet a fair bit higher but they had velocities closer to 1050 fps. At these sub-sonic velocities small changes in velocity-deltas can have big effects on the resulting BC calculated.

Finally I tried my SDN-6 wet, added about a teaspoon of water into the suppressor and shook it around a bit to get some into the more forward baffles. It made a small but noticeable improvement to the sound of the loads that already sounded pretty good.

Now if I can just get a coyote, armadillo or raccoon in my sights. Well see what those Makers do on a real target.