Has anyone seen ammunition testing done with very short barrel 5.56?

[HeavyDuty]

The current PDW thread has me wondering...

A few years ago I built a 7.5” AR pistol as a range toy. However, somewhat to my surprise I’ve found it is actually very handy and reliable over the course of 800 or so rounds, and with current events it has been pressed into trunk service. I figure it’s better than throwing rocks, and I can easily make accurate hits under stress out to the limited distance that I could reasonably and legally be expected to defend myself as a civilian. It has a 1/7 barrel.

By way of background (and as an attempt to head off the “7.5” 5.56 is crap and will get you killed” comments) I’m using it strictly as a “oh shit” weapon - when I feel the need a more capable carbine rides on the floor behind the front seat. The 7.5” currently stays in the car all of the time stashed and tether locked under the parcel deck just like my fire extinguisher, trauma kit and jack. I realize it’s not optimal, but neither is the small fire extinguisher I carry.

My question - has anyone seen testing on what type of quality load is likely to stabilize best in such a short barrel? Heavy or light? I’m not concerned about terminal effects beyond the ability to stabilize at this point - there is a bit of talk in the PDW thread where commonly used defensive rounds tumble. I’ve shot mostly crap range ammunition through it (probably 90% WWB .223) and have never seen evidence of tumbling.

This is likely to get rebarreled as a .300 BLK at some point but it’s what I have right now.

[DocGKR]

What is the barrel twist?

With such a short barrel in 5.56mm, you are likely best off using an expanding projectile like a 50-55 gr TSX or GMX, 55 gr Gold Dot/Fusion, or 55 gr TBBC.

Under 10-12" barrels or so, .300 BLK is superior to 5.56 mm.

[HeavyDuty]

It’s a 1/7 - that was buried above.

[diananike]

There’s a series Of 7.5 gel tests in the YouTube channel poboyspecial
Also great for figuring out what 5.56 does at long range.
Spoiler it’s not like getting smacked with a .22

[rob_s]

Do we already have a thread or resource on this? Perhaps 8" is the wrong threshold, maybe it should be <10"?

I'm curious as to where we hit the "floor" with specific loads as well as perhaps recommendations for loads given that the decision to fire them from (for example) a 7.5" barrel has already been made.

[HeavyDuty]

I started this one about 5.56, but it didn’t attract a lot of attention.

https://pistol-forum.com/showthread.php?41537-Has-anyone-seen-ammunition-testing-done-with-very-short-barrel-5-56

[LittleLebowski]

Shit, the blast alone from 5.56 at that barrel length is enough for me to go .300BO, not to mention that if you want to suppress it, your choices are somewhat limited.

[rob_s]

I started this one about 5.56, but it didn’t attract a lot of attention.

https://pistol-forum.com/showthread.php?41537-Has-anyone-seen-ammunition-testing-done-with-very-short-barrel-5-56

maybe we could get LittleLebowski to merge them to talk about both calibers

[rob_s]

Shit, the blast alone from 5.56 at that barrel length is enough for me to go .300BO, not to mention that if you want to suppress it, your choices are somewhat limited.

I know there are a ton of other issues, but I was hoping to strip this down strictly to the ballistics at various lengths.

[shane45]

I was going to start a similar thread but since its already here.... Id be interested if 7.62X39 could be added to the discussion? The data im looking for is what is the barrel length threshold for effectiveness to distance X. This would be helpful for individuals to evaluate which solution fits their circumstances.

[LittleLebowski]

maybe we could get LittleLebowski to merge them to talk about both calibers

Done.

[HeavyDuty]

Done.

Thanks! Maybe we should edit the thread title to make it apply to short barrels of all calibers?

[OlongJohnson]

For extremely short barrels, I would think .300 BLK is the way to go, since it's basically a pistol cartridge. Case diameter close to bore diameter, likes the same powders as .357 and .44 Magnum loads. Charge weights are in between those two. Following the logic, one might investigate .350 Legend in short barrels. I think Ruger has a factory pistol option.

[Joe45]

VERY short barrel

https://www.thehighroad.org/index.php?threads/ballistic-gelatin-test-results-223-remington-derringer.280327/

Sent from my SM-G975U using Tapatalk

[diananike]

I wish that all the bullet manufacturers would publish expansion/fragmentation thresholds for their bullets.
Then we could all make our own determinations using velocity tests and ballistic coefficients.

[03RN]

Shit, the blast alone from 5.56 at that barrel length is enough for me to go .300BO, not to mention that if you want to suppress it, your choices are somewhat limited.

Value added my friend. Shoot, cook, or scare the threat.

[TGS]

HeavyDuty, rob_s

Please see my post here for some preliminary: https://pistol-forum.com/showthread.php?41496-Let-s-talk-PDW-s&p=1019911&viewfull=1#post1019911

Also see further testing from a law enforcement/industry shoot demo (the PDF of test results attached at bottom of post): https://pistol-forum.com/showthread.php?41496-Let-s-talk-PDW-s&p=1025781&viewfull=1#post1025781

[rob_s]

HeavyDuty, rob_s

Please see my post here for some preliminary: https://pistol-forum.com/showthread.php?41496-Let-s-talk-PDW-s&p=1019911&viewfull=1#post1019911

Also see further testing from a law enforcement/industry shoot demo (the PDF of test results attached at bottom of post): https://pistol-forum.com/showthread.php?41496-Let-s-talk-PDW-s&p=1025781&viewfull=1#post1025781

Thanks!

I was trying to get the ballistics side of that discussion broken out from the "which folding stock to use" because the ballistics seem to get buried in there.

[HeavyDuty]

HeavyDuty, rob_s

Please see my post here for some preliminary: https://pistol-forum.com/showthread.php?41496-Let-s-talk-PDW-s&p=1019911&viewfull=1#post1019911

Also see further testing from a law enforcement/industry shoot demo (the PDF of test results attached at bottom of post): https://pistol-forum.com/showthread.php?41496-Let-s-talk-PDW-s&p=1025781&viewfull=1#post1025781

Thanks! That thread is what caused me to start my now-merged thread here to split out the discussion.

[Wondering Beard]

HeavyDuty, rob_s

Please see my post here for some preliminary: https://pistol-forum.com/showthread.php?41496-Let-s-talk-PDW-s&p=1019911&viewfull=1#post1019911

Also see further testing from a law enforcement/industry shoot demo (the PDF of test results attached at bottom of post): https://pistol-forum.com/showthread.php?41496-Let-s-talk-PDW-s&p=1025781&viewfull=1#post1025781

Out of curiosity, what ammo is your agency issuing for your carbines, if you are allowed to tell us?

[TGS]

Out of curiosity, what ammo is your agency issuing for your carbines, if you are allowed to tell us?

FBI3T, though I'm sure there's M855 floating around in certain locales still.

ETA: Just to be clear we're using 10.3" and 14.5" carbines, not 7.5". We T&Ed a few 7.5" guns a couple years ago but I don't think it went anywhere.

[Wondering Beard]

FBI3T, though I'm sure there's M855 floating around in certain locales still.

ETA: Just to be clear we're using 10.3" and 14.5" carbines, not 7.5". We T&Ed a few 7.5" guns a couple years ago but I don't think it went anywhere.

I don't know what FBI3T is. Is that Federal's 5.56 62gr bonded JSP?

[TGS]

I don't know what FBI3T is. Is that Federal's 5.56 62gr bonded JSP?

Yup, the 62gr Trophy Bonded Bear Claw bullet.

[rob_s]

has 300BLK ever lived up to the idea of a subsonic round that "performs"? if so what is it, and what is the minimum barrel length for said round? Does adding a can change that minimum length (does the can act as additional barrel?)?

[OlongJohnson]

Hornady has a 190gr bullet sold as both loaded ammo and component that is specifically designed for .300 BLK sub use. Some discussion and link in the PDW thread. The only benefit I see to it over a 230 +P HST is external ballistics.

[KevinB]

I loaded some of the 185gr Powdered tungsten as a .300BK Sub Sonic -- I was looking for an interesting performer at lower velocities.
I have not gotten them into any gel at this point yet.

Years ago some of the 4-6" M2Corp AR PDW's where tested - this was before the newer 5.56mm loads - and they didn't perform well at all, and the 7.5" didn't either.

With personnel experience from Sig 552's, a very short barrel 5.56mm is absolutely not what one wants to use to defend ones self.

[rob_s]

Hornady has a 190gr bullet sold as both loaded ammo and component that is specifically designed for .300 BLK sub use. Some discussion and link in the PDW thread. The only benefit I see to it over a 230 +P HST is external ballistics.

this?
https://www.hornady.com/ammunition/rifle/300-blackout-190-gr-sub-x-subsonic#!/

[OlongJohnson]

Yes.

[Duces Tecum]

Following.

[Velo Dog]

has 300BLK ever lived up to the idea of a subsonic round that "performs"? if so what is it, and what is the minimum barrel length for said round?

I have no other information on this subsonic hunting load, but SIG recommends a 9" or longer barrel.

https://www.sigsauer.com/store/300blk-205gr-subsonic-tipped-hunting.html

[DiscipulusArmorum]

FBI3T, though I'm sure there's M855 floating around in certain locales still.

ETA: Just to be clear we're using 10.3" and 14.5" carbines, not 7.5". We T&Ed a few 7.5" guns a couple years ago but I don't think it went anywhere.

Is it the 5.56 or .223 version? Federal seems to make a variety of different T3 loads for various LE contracts. Aside from the XM556FBIT3 that's 5.56, I've also seen XM556FBIT3M (.223 pressure), XM223T3HSPB (.223), and XM556SBCT3 (5.56).

[TGS]

Is it the 5.56 or .223 version? Federal seems to make a variety of different T3 loads for various LE contracts. Aside from the XM556FBIT3 that's 5.56, I've also seen XM556FBIT3M (.223 pressure), XM223T3HSPB (.223), and XM556SBCT3 (5.56).

The stuff I have is XM556FBIT3M, with 223 listed below that.

No idea why they don't just call it XM223FBIT3. :confused:

We very well might have various forms to the FBIT3 floating around depending on what year it was bought.

What's different about the HSPB and SBCT3?

[DiscipulusArmorum]

The stuff I have is XM556FBIT3M, with 223 listed below that.

No idea why they don't just call it XM223FBIT3. :confused:

We very well might have various forms to the FBIT3 floating around depending on what year it was bought.

What's different about the HSPB and SBCT3?

Thanks!

Regarding the differences among those various SKUs, I don't know anything beyond what I've been able to piece together from publicly available gov contracts and a few tidbits from other sources.

The HSPB load was in use by ICE (https://digital.library.unt.edu/ark:/67531/metadc298837/m1/43/). I would bet it's the same as the .223 spec FBI load, just with a different SKU due to packaging (instead of 20rd boxes, it's loaded on stripper clips in 30rd cardboard sleeves, 900rds to a case if the TargetSports description (https://www.targetsportsusa.com/federal-223-remington-ammo-62-grain-tactical-bonded-police-barrier-blind-900-rounds-on-stripperclips-xm223t3hspb-p-109719.aspx) is accurate.)

I can't find reference to SBCT3 in any official sources, but I've seen speculation that it's a 5.56 spec load optimized for the 11.5" guns that the FBI has standardized on (I guess SBC could stand for "short barreled carbine"?) or just a different SKU for non-FBI sales.

[MandoWookie]

Does anyone have any resources on the effectiveness of loads like Gold Dot or Barnes TSX out of barrels as short as 4.5"? I would assume that there would be little to no effective expansion, but I'm curious if there has been any documented testing of barrels that short. Other than getting the most compact package possible but staying in a mainstream calber I'm just not seeing the benefits, yet there are several companies now offering such things.

[Velo Dog]

Does anyone have any resources on the effectiveness of loads like Gold Dot or Barnes TSX out of barrels as short as 4.5"? I would assume that there would be little to no effective expansion

The estimated 4.5" barrel velocities and expansion thresholds for most loads do not look very encouraging.

https://www.ar15.com/forums/ar-15/Updated-data-for-223-5-56-defensive-rounds-specs-from-a-10-5-inch-barrel-/16-721162/


http://ballisticsbytheinch.com/223rifle.html

[MandoWookie]

The estimated 4.5" barrel velocities and expansion thresholds for most loads do not look very encouraging.

https://www.ar15.com/forums/ar-15/Updated-data-for-223-5-56-defensive-rounds-specs-from-a-10-5-inch-barrel-/16-721162/


http://ballisticsbytheinch.com/223rifle.html

Yeah, even at the muzzle it looks like most loadings would fail, making it an exercise in sound and fury over substance.

[OlongJohnson]

I know you'll see it in the other thread where you posted the same questions, but for people coming along later...

https://pistol-forum.com/showthread.php?41496-Let-s-talk-PDW-s&p=1062735#post1062735