Quoted: Quoted: I would Never put a 16inch+ Bird cage barrel on a carbine I would worry about Shot Placement over all this frag range info 14.5 inch would be MAX 12.5 would be nice How about a midlength

If I went 16 then might as well go 18inch SPR

for a carbine the barrel should be short NOT LONG
10.5 0r 12.5
I have to settle for a 14.5 for now

With that logic if you were going to get an 18" you might as well go 20" then its only 2" more. In fact why not have only a 1 or 2 barrel lengths then anyway? The 16" length is good compromise between ballistics and compactness.

Quoted: With that logic if you were going to get an 18" you might as well go 20" then its only 2" more. In fact why not have only a 1 or 2 barrel lengths then anyway? The 16" length is good compromise between ballistics and compactness.

Depends what you call a carbine
I will take the shorter over longer anyday

INSIDE WORK/CLEAR A HOUSE ETC!!   with a 16 inch plus weapon FORGET THAT!
Even a M4 14.5 is a little to long

Quoted: With that logic if you were going to get an 18" you might as well go 20" then its only 2" more. In fact why not have only a 1 or 2 barrel lengths then anyway? The 16" length is good compromise between ballistics and compactness.

How about a 10.5" with 2" threaded extensions out to 30"?  

Quoted: How about a 10.5" with 2" threaded extensions out to 30"?

Quoted: Quoted: How about a 10.5" with 2" threaded extensions out to 30"?

I'll see your and raise you !

Quoted: Quoted: Quoted: How about a 10.5" with 2" threaded extensions out to 30"?   I'll see your and raise you !

I think the TOPIC has said all that is needed

Quoted: CUT IT OUT, PEOPLE! Time to get back on topic...

Right!

In short someone needs to design a round optimized for short barrels. Using faster burn rates for the propellants and flash retardants to make it less obnoxious indoors, but for now Mk262 is best you can go with a short barrel these days.

Quoted: Quoted: CUT IT OUT, PEOPLE! Time to get back on topic... Right! In short someone needs to design a round optimized for short barrels. Using faster burn rates for the propellants and flash retardants to make it less obnoxious indoors, but for now Mk262 is best you can go with a short barrel these days.

Hornady's 5.56 75 grain TAP will give you slightly better terminal ballistics than MK262.

5.56 TAP

I can't vouch for stopping power, but I know accuracy.

M LMT 10,5 can keep its shots on a 20 inch man silhouette at 565 yards.

Using a TA31F and Black Hills blue box 75gn Match Hollow Points, the POI is about 10 inches below POI on the 600 yard hash mark, almost exactly dead on if I use the 600yard hash mark on 565 yards.

Quoted: www.box.net/shared/static/ucfxxgi7ai.jpg home.comcast.net/~gocartmozart/NATO_pressure_Sierra_77_OTM_gel_shot_16_inch_barrel.jpg www.box.net/shared/static/1ke3lxo08s.jpg

Excellent pics!

Here's the gel-shot of M855 with a gel-shot of 5.56 TAP for comparison.









5.56 TAP

Quoted: Quoted: With that logic if you were going to get an 18" you might as well go 20" then its only 2" more. In fact why not have only a 1 or 2 barrel lengths then anyway? The 16" length is good compromise between ballistics and compactness. Depends what you call a carbine I will take the shorter over longer anyday INSIDE WORK/CLEAR A HOUSE ETC!!   with a 16 inch plus weapon FORGET THAT! Even a M4 14.5 is a little to long

A 10.5/11.5 + suppressor (silencer) for indoor work would be best IMO, even though its a little long, it won't deafen you quite as much in any CQC.  

Quoted: I can't vouch for stopping power, but I know accuracy. M LMT 10,5 can keep its shots on a 20 inch man silhouette at 565 yards. Using a TA31F and Black Hills blue box 75gn Match Hollow Points, the POI is about 10 inches below POI on the 600 yard hash mark, almost exactly dead on if I use the 600yard hash mark on 565 yards.

The BDC on an ACOG is in meters.

Getting HIT at 300 will still suck all day long by a 10.5 brl. And it will HIT at 300.

My Question is this. Why sweat it? If you have an Ar Pistol or SBR, then expect to have to hit  twice.


After all....... It does have a 30rd mag.

Here is my new to me 10.5 pistola...

Carbon fiber free float tube. 65$ EE
10.5 pencil barrel chrome lined.  75$ EE
Gas block is a cut down A2 front sight.
Phantom  $20 EE
It is a bushmaster stripped upper. $60 off the EE.
Double Star lower sold as a pistol 114$ local
Aimpoint ML2  225$ Used at a pawn shop. It is a real one. And it came with the Arms Qr mount.
Chrome plated BCG $110EE
Rifle length Recoil tube and buffer 35$ Local store
Samco first Ergo grip 20$ EE
3$ worth of para chord and a crutch cap.
I threaded the safety detent spring hole and do not need a trunnion plate.
I have chosen to go without a dust cover.
I also put a sling swivel in the place of the forward assist.

As Shown $707.00

With out the aimpoint I am in it 482.00 ish.



I have been thru a 3 gun with it, and it functioned perfectly. I built it to function with wolf HP.

It is well balanced and the tube rests on top of the shoulder when shooting.

I will post pics of the three hundred meter target Thursday.

Here's a quote from Dr G.K. Roberts on the subject:


"Dr. Fackler’s seminal research at the Letterman Army Institute of Research Wound Ballistic Laboratory during the 1980’s illuminated the yaw and fragmentation mechanism by which 5.56 mm FMJ bullets create wounds in tissue. If 5.56 mm bullets fail to upset (yaw, fragment, or deform) within tissue, the results are relatively insignificant wounds, similar to those produced by .22 long rifle bullets--this is true for ALL 5.56 mm bullets, including both military FMJ and OTM (open tip match) and civilian JHP/JSP designs used in law enforcement.

As expected, with decreased wounding effects, rapid incapacitation is unlikely: enemy soldiers may continue to pose a threat to friendly forces and violent suspects can remain a danger to law enforcement personnel and the public. This failure of 5.56 mm bullets to yaw and fragment can be caused by reduced impact velocities as when fired from short barrel weapons or when the range to the target increases."

According to the works of Dr. Martin Fackler, the wound profiles for M855 and M193 are basically the same.  The first wound profile pictured below is that of M193 with a striking velocity above the 2700 fps fragmentation threshold.  The second wound profile illustrates the decreased wounding effects of M193 when it strikes below the 2700 fps fragmentation threshold.








As noted by Dr. Fackler, when M193 strikes below the 2700 fps fragmentation threshold, its wound profile bears a striking resemblance (pun intended) to that of a 22 Long Rifle.

Quoted: With that logic if you were going to get an 18" you might as well go 20" then its only 2" more. In fact why not have only a 1 or 2 barrel lengths then anyway? The 16" length is good compromise between ballistics and compactness.

And, not to mention that you avoid the TAX STAMP.

Or, the Gobernmet KNOWING what you got.

Aloha, Mark

Quoted: ... The 16" length is good compromise between ballistics and compactness.

+ 1.

Quoted: Quoted: ... The 16" length is good compromise between ballistics and compactness. + 1.

+1......
If it is a 7.62x51... not for a 5.56x45.   A silencer + 16" 5.56 does not make a handy weapon.  For a longer ranged rifle 16" .308 is still handy when suppressed.

Quoted: Quoted: Quoted: ... The 16" length is good compromise between ballistics and compactness. + 1. +1...... If it is a 7.62x51... not for a 5.56x45.   A silencer + 16" 5.56 does not make a handy weapon.  For a longer ranged rifle 16" .308 is still handy when suppressed.

Quoted: <snip> I had my barrel made to give the absoloute shortest upper possible when combining a 9" midlength rail and an AAC SPR/M4 suppressor... thus the odd 11.75" length. <snip>

Just curious ... (have wondered about this for some time now) ...

How does the OAL of an 11.5" upper - or in this/your case, an 11.75" upper - with a suppressor installed ...

... compare to the OAL of a plain ole' 16" middy upper with no suppressor installed, i.e. using just a regular birdcage F/H ?

P.S. Anyone's posting of pics of said comparison would be much appreciated.

Quoted: At any range where maneuverability of the 10.5 wasn't MANDATORY. I would pick an SBR'ed PS90 for close up before I would a 10.5" AR anyways.

Dr Martin Fackler doesn't have any kind words to say about the terminal ballistics of the P90/5.7 x 28mm platform.

". . .the amount of tissue disruption produced by the P90 bullet is less than one-third of that produced by a well-designed expanding 9x19mm handgun bullet. . . . the expanded 9mm bullet strikes about three times as much tissue as the P90 bullet at 90 degrees of yaw, and does it throughout most of its path.  Thus, the permanent cavity volume produced by the expanded 9mm bullet is many times longer than that produced by the nondeforming P90 bullet. . . the P90 doesn't even come close to matching the wounding capacity of a well-designed expanding 9x19mm handgun bullet. . .the P90 bullet's wounding potential is about equal to that of the 22 Winchester rimfire magnum bullet."

Quoted: Quoted: <snip> Just curious ... (have wondered about this for some time now) ... How does the OAL of an 11.5" upper - or in this/your case, an 11.75" upper - with a suppressor installed ... ... compare to the OAL of a plain ole' 16" middy upper with no suppressor installed, i.e. using just a regular birdcage F/H ? P.S. Anyone's posting of pics of said comparison would be much appreciated. I can't speak for Devl, but I know what suppressor he uses. I would imagine that the OAL with the suppressor mounted is right around 16"

Thanks for the input ...

Also, at the suggestion of another member, I went to the AAC website and found that they typically list figures for "length added to weapon" when using 'X' model of their suppressor.  

And based on that, I'd say you're probably pretty close with a guesstimate of ~ 16".

This thread has answered a lot of questions I've had. Very specific data chrono'd by people here. Specific info not found in the ammo oracle. This thread should be tacked.

Quoted: The 16" (barrel) length is a good compromise between ballistics and compactness.

. . . and "compromise" is not a bad word.

What am I missing here ...

On the one hand

Quoted: Quoted: The 77gr. 5.56 round will still fragment at velocities less than 2100 fps A much more realistic threshold for reliable fragmentation with the 75-77 grain OTM loads is 2,250 FPS.  From your 10.5” barrel, this will give you a fragmentation range of approximately 48 yards. Quoted: My SBR is good out to 120+ yards with my ammo of choice. If by “good” you mean effective and reliable fragmentation with adequate penetration, please tell me where I can purchase some of this magical ammunition.  The 75 grain 5.56 TAP load has the best terminal ballistics of any commercially available load for the 5.56mm platform and as shown above it only has a 48 yard fragmentation range when fired from a 10.5” barrel.

On the other hand

Quoted: I know its not a 10.5" but it gives some insight... Chronoed my LWRC 5.56 cold hammer forged, chrome lined, 11.75" barrel with 75 grain 5.56 TAP for two ten shot strings suppressed and unsuppressed. Average muzzle velocity unsuppressed was 2450, suppressed was 2485 fps. Slowest unsuppressed round was 2419 Fastest suppressed round was 2499 With a fragmentation velocity threshold of 2200 FPS that would be reached at 105 yards unsuppressed and 120 suppressed Fragmentation threshhold is between 2250 and 2150 for the 5.56 T2 TAP. Worst case scenario would be unsuppressed 2419 and 2250 threshhold and just over 70 yards till fragmentation would not occur. Best case would be suppressed 2499 velocity and a threshhold of 2150 for 150 yards till fragmentation would not occur. <snip>

Certainly not calling BS in any direction whatsoever - just wonder about this:  

Am I correct in understanding that when using comparable ammo, simply going from a 10.5" bbl. to (in this case) an 11.75" bbl. - i.e. gaining only 1.25 inches in bbl. length - will effectively extend the fragmentation range of the ammo by a MINIMUM of  45 - 50% with the possibility of even doubling (or even considerably MORE than doubling when suppressed) the expected fragmentation range ??

All because of nothing more than adding a mere inch and a quarter of barrel length ???

Again, is this interpretation accurate ... or ... am I missing something here

Precise answers require a lot of data. What we have is limited data and extrapolations of that limited data....even so, it is good and helpful information that gives us insight into what the shorter barrels can do with the best ammo available to us. I appreciate those who took the time to provide the data and contribute to the thread. This issue comes up quite a bit, perhaps at some point it can become part of the ammo oracle.

Quoted: Precise answers require a lot of data. What we have is limited data and extrapolations of that limited data....even so, it is good and helpful information that gives us insight into what the shorter barrels can do with the best ammo available to us. I appreciate those who took the time to provide the data and contribute to the thread. This issue comes up quite a bit, perhaps at some point it can become part of the ammo oracle.

ABSOLUTELY.

I am simply interested in gaining a better understanding of the "possible" or "seeming" variances.

Quoted: Quoted: Taggage I wonder if the ballistics for a 10.5" would be about the same for a 10.3" like the SEALs Mk18 Mod0 rifles? Thats what I was assuming. If the ballistics data I'm getting from this thread are accurate, why do the Navy Seals use the Mk18?

Probably because they can actually hit what they're aiming at...

Quoted: Quoted: Am I correct in understanding that when using comparable ammo, simply going from a 10.5" bbl. to (in this case) an 11.75" bbl. - i.e. gaining only 1.25 inches in bbl. length - will effectively extend the fragmentation range of the ammo by a MINIMUM of  45 - 50% with the possibility of even doubling (or even considerably MORE than doubling when suppressed) the expected fragmentation range ?? All because of nothing more than adding a mere inch and a quarter of barrel length ??? Again, is this interpretation accurate ... or ... am I missing something here You're not missing anything. Longer bbls mean a better frag range, no matter what length change we're talking about.

Indeed ... No question.

What to me seems rather unusual though is/are the proportions involved.  

With the "ratios" described above - a relatively miniscule increase in bbl length yielding a SUBSTANTIAL extension of effective fragmentation range.

Quoted: Quoted: Quoted: Taggage I wonder if the ballistics for a 10.5" would be about the same for a 10.3" like the SEALs Mk18 Mod0 rifles? Thats what I was assuming. If the ballistics data I'm getting from this thread are accurate, why do the Navy Seals use the Mk18? Probably because they can actually hit what they're aiming at...

I'm sure they have no problems with head shots at 100-200 yards. They would also want the smallest thing they could carry for very tight quarters.

Quoted: QUESTION I never heard about the 75gr AMAX BULLET? If loaded to 5.56mm pressure will this bullet frag

Here's what happens if you load the 75 grain A-MAX to magazine length.

Quoted: If you really want a reach-out-and-touch-them SBR, just do yourself a favor and get a 12.5" 1:11 twist, SAAMI-II chambered 6.8SPC barrel from Tim at Cardinal Armory (formerly Ko-tonics). He'll be offering these ready to go starting in March/April. SSA combat loads with the enhanced frag 115gr SMKs will fragment out to 150 yards out of a 12.5" barrel. In general, the pressure curve generated by 6.8SPC is much better matched to short barrels than that of 5.56, so you don't see as much velocity drop going from, say, 16" to 12.5" in 6.8SPC. As for ammo cost, if you're shooting 75gr TAP or 77gr Mk 262, you're into the $1 per round category anyway for 5.56, which is actually a bit more than you'd pay for the SSA 6.8 ammo. If you handload, ammo costs are more than reasonable and you can tailor loads for your Cardinal Armory 12.5" barrel that will fragment out to 170 yards. I've got 115gr bullets coming out of my 12.5" Cardinal Armory barrel at 2500fps, BC of .340. Fragmentation threshold of 6.8SPC (according to Doc Roberts) is 2100fps. Any ballistics program will allow you to do the math... 6.8SPC and SBRs: a match made in heaven. ETA: SSA is on the verge of releasing inexpensive (relatively speaking) plinking ammo in 6.8SPC, which should allow for range use and practice shooting at a cost at or near 5.56. Again, if you handload, ammo cost is more than reasonable.

Have you chronographed the new 6.8 SPC 85 grain TSX load from SSA?

Here's some more data on the subject from Dr. Gary Roberts.

FN 5.7 x 28 mm
________________________________________
Several papers have described the incredibly poor terminal performance of the 5.7 x 28 mm projectiles fired by the FN P90:

––Dahlstrom D, Powley K, and Gordon C: “Wound Profile of the FN Cartridge (SS 190) Fired from the FN P90 Submachine Gun". Wound Ballistic Review. 4(3):21-26; Spring 2000.
––Fackler M: "Errors & Omissions", Wound Ballistic Review. 1(1):46; Winter 1991.
––Fackler M: "More on the Bizarre Fabrique National P-90", Wound Ballistic Review. 3(1):44-45; 1997.
––FBI Academy Firearms Training Unit. FBI Handgun Ammunition Tests 1989-1995. Quantico, U.S. Department of Justice––Federal Bureau of Investigation.
––Hayes C: “Personal Defense Weapons—Answer in Search of a Question”, Wound Ballistic Review. 5(1):30-36; Spring 2001.
––Roberts G: “Preliminary Evaluation of the Terminal Performance of the 5.7 x 28 mm 23 Grain FMJ Bullet Fired by the New FN P-90 , Using 10% Ordnance Gelatin as a Tissue Simulant”, AFTE Journal. 30(2):326-329, Spring 1998.

The current 31 gr SS-190 FMJ bullet has nearly adequate penetration, but the wound resulting from this projectile has a relatively small permanent crush cavity, as well as an insignificant temporary stretch cavity. Although the 5.7 x 28 mm penetrates soft body armor, wounding potential is at best like a .22 LR or .22 Magnum. Even 9mm NATO FMJ makes a larger wound––and we are all aware of the awe inspiring incapacitation potential of M882 ball from the M9......

A few large U.S. LE agencies adopted 5.7 mm weapons––after being involved in several OIS incidents with P90's, 5.7 mm usage in these agencies plummeted as a result of the poor terminal performance.

It is all basic physics and physiology. Look at the surface areas in contact with tissue for 9 mm FMJ and JHP compared to 5.7 mm. When both are point forward, the 9 mm FMJ crushes more tissue than the 5.7 mm; for the short time that the 5.7 mm is at FULL yaw, it crushes a bit more tissue than the 9 mm FMJ. At no time does the 5.7 mm crush more tissue than the expanded 9 mm JHP––even when the 5.7 mm FMJ is at full yaw, an expanded 9 mm JHP crushes more tissue. The relatively small temporary cavities produced by both the 9 mm and 5.7 mm projectiles are not likely to cause significant injury to the majority of elastic structures of the body. As with any penetrating projectile, if either a 9 mm or 5.7 mm bullet is ideally placed to cause significant damage to the CNS or major cardiovascular organs, a fatal result is likely.






The P90 can definitely penetrate soft body armor, but then so can 9 mm AP rounds. The greater momentum of 9 mm bullets allow them to defeat vehicles and other intermediate barriers better than the 5.7 mm bullets. Standard 9 mm, .40 S&W, and .45 ACP JHP loads crush more tissue, offer ideal penetration, and are equally likely to not exit the opponent as the 5.7 mm. 5.56 mm and 6.8 mm weapons offer significantly superior terminal effects compared to 5.7 mm. Bottom line—what does the P90 offer that is not already available?

Good job on all the great information everyone.
Would anyone happen to have a picture of the fragmentation from a 75 - 77gr. out of a 10.5 - 11.5"?

i believe the 6.8SPC will fill all those requirements.  from what i've read, most of their powder burns up in 10"-12".  a guy i talked to on 68forums said he would trust his 12.5" extreme upper any day to 200 yd easily.  so yeah,i will be getting a 16" mid for my first AR build as everyone has told me to.  the ability to practice with it cheap(relatively, compared to 6.8) will be cool and it will be a good all purpose upper, but i WILL be getting a 6.8 for SBR.