JCN tests short 300 blackout barrels 5-9” in supersonic loading.

[JCN]

88026

On the docket for tomorrow.

Items for testing:
Sig Canebrake Rattler (5.5”)
AR pistol (8.5”)
Composite IIIA
Larson Davis LXT sound meter
Chrono (for close shoot through)
LabRadar (for distance)
20% gel block
Stinger rifle rest

And the most important part: two 1.5” barrel extensions….







Some background, I previously tested:

8.5 versus 16” blackout barrels.

88027

And the controlled chaos

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And suppressed sound levels subsonic

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And barriers with subsonic (3” gel then slanted steel then additional gel)

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But when I got my Canebrake Rattler I was disappointed. I tested the 110 TTSX and it didn’t penetrate IIIA.

I know the 8.5” does penetrate…

So somewhere in between the 5.5” and 8.5” is the sweet spot for me.

When testing my MPX, I was getting 30 fps with just a threaded extension and Mike C says he has seen 30 fps from a suppressor, I thought I would see if a couple inexpensive threaded barrel extensions could make the Rattler into the coveted 6.75” or 8.5” that aren’t easily available for purchase right now.

That’s the point of my testing tomorrow. How much velocity can I pick up with extensions and will that be enough to get the penetration I’m looking for.




As always, comments welcome and testing requests welcome.



DISCLAIMER: this is for entertainment purposes only.

[JCN]

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[JCN]

Mock up

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[DMCutter]

300 blackout is theoretically optimized for a 9" barrel, isn't it?

[JCN]

300 blackout is theoretically optimized for a 9" barrel, isn't it?

Maybe, maybe not.

Depends on what context and ammo.

Because when I tested the Hornady poly tip in an 8.5”….

Wasn’t fast enough to expand reliably.

And too fat to tumble so just yawed out the side of the block.

So it’s like some of the odd Sig combos. 4-5” 5.56?!! Dafuq?

I found the 5.5” 300 BO to not really be what I was looking for with commercially available ammunition.

It’s so close… so I want to see if I can gain a little more to get reliable expansion and penetration.

[JCN]

88066

Did a bunch of other additional testing that’s likely only interesting to me haha.

[jh9]

88066

Did a bunch of other additional testing that’s likely only interesting to me haha.

So the 5" .300s are just a bit too short, like the 7" 5.56s? It does seem like... almost.

Every time I think about getting a .300, I realize the upper and the 110gr barnes magic bullet (or vmax) + subs are a lot of time and effort for a combo that dips below 2000fps impact velocity before you get out to 100 yards which makes it and the subs both a big pistol caliber. And that they make 7" 5.56s that still have enough velocity to do Rifle Stuff and expand even out of that barrel. Of course "they" doesn't include anyone reputable I know of, and I'm not sure "discount palmetto upper" and "bag gun" go well together. Which leaves me thinking I should just get a 10" 5.56 upper and a slightly larger bag than the ones I have. Which eventually turns into something the size of airline luggage. So then I think "I could get a 7" .300 upper and just use the 110gr supers for a bag gun" at which point I realize I'm back where I started. Again.

[GyroF-16]

88066

Did a bunch of other additional testing that’s likely only interesting to me haha.

What is the 8.5” ATI entry at the top?
Because it’s 300 fps higher than the Rattler w/ the extenders to get it to 8.5” total length.

For the Rattler, it looks like 30-40 fps per inch in the 5-8” range.
And if the 110 gr TAC-TX expansion threshold is 1350 fps, it looks like you still have some room to work… maybe out to at least 75-100 yds?

I appreciate the data, just wanting to know what it all means…

[JCN]

What is the 8.5” ATI entry at the top?
Because it’s 300 fps higher than the Rattler w/ the extenders to get it to 8.5” total length.

I appreciate the data, just wanting to know what it all means…

That’s the black AR 8.5” 300 blackout in the pictures next to it as the control of what that length should produce.

So the 300 fps gap is what you lose with non rifled extenders as opposed to a true 8.5” barrel.

Basically it means that the Rattler is sad, lol.

[GyroF-16]

That’s the black AR 8.5” 300 blackout in the pictures next to it as the control of what that length should produce.

So the 300 fps gap is what you lose with non rifled extenders as opposed to a true 8.5” barrel.

Basically it means that the Rattler is sad, lol.

Gotcha. I wouldn’t have expected the extenders to be so leaky.

So I guess you lose 400 fps for the 3” shorter Rattler barrel.
Nice to quantify the trade-off of size vs effective range.

Have you chrono’d Barnes 110 TAC-TX out of either length?

[LittleLebowski]

Expanding subs would be really interesting.

[JCN]

Expanding subs would be really interesting.

These grappling hooks are subs.

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The Hornady Black 208 gr subs didn’t expand.

[JCN]

Gotcha. I wouldn’t have expected the extenders to be so leaky.

So I guess you lose 400 fps for the 3” shorter Rattler barrel.
Nice to quantify the trade-off of size vs effective range.

Have you chrono’d Barnes 110 TAC-TX out of either length?

My main test was to see if the Barnes 110 would get through IIIA with extensions.

It did not.

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So that makes the Rattler less functional than my ATI.

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[LittleLebowski]

These grappling hooks are subs.


The Hornady Black 208 gr subs didn’t expand.

I want load and testing data for .300Blk expanding subs, damnit!

Seriously, good thread. Thanks for sharing.

[JCN]

I want load and testing data for .300Blk expanding subs, damnit!

Seriously, good thread. Thanks for sharing.

When I tested subs before, I was disappointed that the Hornady 208 didn’t expand even out of a 16” barrel!

The grappling hook expanded fully in the 3” first gel and still had enough oomph to punch through slanted 2 sheets of 22 gauge steel… then continue through another 9.5” of gel.

Kind of an arm - car door - torso scenario.

It’s the only reliable sub ammo I own.

[Rex G]

Some truly useful information. Thanks!

Among other things, this is another “minus” in the columns of figures, as I try to sort-out whether or not to buy a Rattler, or buy/assemble a shorter-barreled upper unit for my LAW-folder-ed 10-point-something .300 DDM4 V7P. Maybe I should not bother with .300 BLK at all, any longer, as I am not yet heavily “invested.” I have a nice 16” Colt mid-length upper, with Centurion hand-guard, that balances nicely on the LAW-foldered lower.

[LittleLebowski]

I just read the thread twice, looking for more data on the “grappling hooks”. Didn’t find where to buy them, maybe I’m missing something.

[Clusterfrack]

I just read the thread twice, looking for more data on the “grappling hooks”. Didn’t find where to buy them, maybe I’m missing something.

I think this is the load?

https://www.underwoodammo.com/300-aac-blackout-whisper-194gr-subsonic-maximum-expansion.html

[LittleLebowski]

I think this is the load?

https://www.underwoodammo.com/300-aac-blackout-whisper-194gr-subsonic-maximum-expansion.html

Ah, Lehighs. I need to order some and load them up.

[DiscipulusArmorum]

Can we get more info about that IIIA plate you used for testing? I'm a little flummoxed that a .30 caliber projectile at 1900+ fps wouldn't penetrate, but then again these standalone plates might be a different animal than say an old Second Chance soft vest.

[JCN]

Can we get more info about that IIIA plate you used for testing? I'm a little flummoxed that a .30 caliber projectile at 1900+ fps wouldn't penetrate, but then again these standalone plates might be a different animal than say an old Second Chance soft vest.

Generally speaking, when I’ve tested different calibers you need 2000-2100 fps+ to get through the tougher IIIA preparations. Speed and cross section matter.

I found that regular old soft IIIA gives up earlier so I wanted a tougher standard IIIA.

These are just 6x6 composite side plates. I don’t like the YouTube videos where they shoot up a bunch of vests multiple times. If you see how the fibers interact, you can get remote weakening after more than one shot so I always test my important things on a clean, fresh plate.