Why does the military no longer use the SP1 type pencil barrels?  Was there a problem with the barrels that made the switch necessary?

Didn't they have 1-12 twist barrels? They changed to stabalize hevier bullets.  And a pencil barrel in a combat situation can break?  And heavy barrels can support the M203. That is what I think

Quoted: Didn't they have 1-12 twist barrels? They changed to stabalize hevier bullets.  And a pencil barrel in a combat situation can break?  And heavy barrels can support the M203. That is what I think

The outside diameter of the barrel should not limit the ablity to change the twist rate, should it?  Stated another way, you could make a pencil barrel with a 1/9 or 1/7 twist.  BM makes its 16" pencil barrel with a 1/9 twist I believe.  

My father told me once he saw a pencil barrel folded after a trainig mission with 173rd

Quoted: Quoted: Didn't they have 1-12 twist barrels? They changed to stabalize hevier bullets.  And a pencil barrel in a combat situation can break?  And heavy barrels can support the M203. That is what I think The outside diameter of the barrel should not limit the ablity to change the twist rate, should it?  Stated another way, you could make a pencil barrel with a 1/9 or 1/7 twist.  BM makes its 16" pencil barrel with a 1/9 twist I believe.

Yea they could make them in 1/9 or 1/7 twist.  But to sustain heavy fire and support all they gizmos a heavy barrel would be better. I guess.  I heard people talk about how there barrels drooping after firing a few mags through on full auto.  Maybe that is why?  

The .mil rifle barrels in use are "govt" profile, and are still pretty much pencil under the handguards.  They are heavier out front, supposedly because of bent barrels when utilizing the bayonet.  I'm no expert..... but this is the rumor.

Pencil barrels are more likely to bend in combat, or due to misuse. Bayonet fighting and parachute jumps are both likely risks. Many barrels have been bent due to misuse as well.

Quoted: Pencil barrels are more likely to bend in combat, or due to misuse. Bayonet fighting and parachute jumps are both likely risks. Many barrels have been bent due to misuse as well.

Really?? can you site a source?  Can you tell us what the diameter of the M14 barrel is and what the diameter of the M16A1 barrel is and why one would be stronger than the other?

The fact is the M16A2's barrel under the handguards is withing a couple hundreths of an inch as the M16A1 barrels.  The M16A2  it takes M203s, Bayonets, and Airborne operations and did so for 20 years.

However when the USMC wanted a new rifle they designed it with their KD qualification range in mind they wanted a heavier barrel (to keep accuracy as it heats up) the fancy sights, and the longer stock.   Remember Marines qualify out to 500M (that's about 550 yards).  Also, you can't attached the M203 to a heavier barrel w/o spending big bucks they opted, so after testing they found by just making the portion from the front sight foward a heavier weight they got a substantial improvement.

The Army ended up buying this same improved M16 (the A2) so that is why they have the barrel.

BTW There were M16A1 barrels made in 1:7 for export to the IDF - they are rare and highly prized.

Because they adopted the M16A2, M16A4, M4 and M4A1.  No need for a lighter barrel to have another part in the logistics chain.

I can guarauntee you pencil barrels will bend if misused....

The prongs of the early 'branch catcher' flash hiders were used by dumb shits to twist the wires of C-Rat cases then break them in order to get at the C-Rats

I have seen these barrels bend and seen where they put tracers afterwards...and could not get on paper at 25 yrds...

Quoted: Quoted: Pencil barrels are more likely to bend in combat, or due to misuse. Bayonet fighting and parachute jumps are both likely risks. Many barrels have been bent due to misuse as well. Really?? can you site a source?  Can you tell us what the diameter of the M14 barrel is and what the diameter of the M16A1 barrel is and why one would be stronger than the other? The fact is the M16A2's barrel under the handguards is withing a couple hundreths of an inch as the M16A1 barrels.  The M16A2  it takes M203s, Bayonets, and Airborne operations and did so for 20 years. However when the USMC wanted a new rifle they designed it with their KD qualification range in mind they wanted a heavier barrel (to keep accuracy as it heats up) the fancy sights, and the longer stock.   Remember Marines qualify out to 500M (that's about 550 yards).  Also, you can't attached the M203 to a heavier barrel w/o spending big bucks they opted, so after testing they found by just making the portion from the front sight foward a heavier weight they got a substantial improvement. The Army ended up buying this same improved M16 (the A2) so that is why they have the barrel. BTW There were M16A1 barrels made in 1:7 for export to the IDF - they are rare and highly prized.

The parachute jump example is speculation, but has been documented as an issue with the M-14s. Hackworth wrote a good bit about it in his autobiography. Barrels on M-16A2s are bent from time to time during bayonet training. When I was in the Marine Corps, we would have rifles go down occasionally due to this. I have also seen rifle barrels used to pry things, and as levers when assembling GI cots. Were you really curious about my source, or did you just assume that I made that up?

BTW... I do believe that the M-14s barrel diameter is the same as the M-16A1s.

I don't see how an A1 barrel can bend any easier than a A2 or M4, I mean they're still the same diameter under the handguards.

And like Blackjack said, the M14 barrel diameter is about the same as A1 and I've never heard of someone bending that...

Thanks for all the replies.  Since I don't do any bayonet work, jump out of planes or use my AR as a crowbar , I really like the idea of a 20" ultra lightweight barrel.

My 20" Government profile upper is about the same weight as my 16" HBAR, but is heavier than my mid-length 16" Armalite upper that's turned down under the handguards (like 16" Government profile).  

I like the longer handguards and gas system of a 20" or 16" mid-length better than a 14.5-16" carbine as well.  

I think my next build will be a 20" SP1 barreled upper with a M4 style collapsible stock on the lower.  I mostly shoot 55 grain rounds anyway, so a 1/12 would be fine.

It was more the "crowbar" use than "bayonette work" that led to the change.  It was "quick and easy" to bust the steel bands on shipping boxes with a bayonette mounted on the rifle's barrel.  Unfortunately, this put a lot of stress on the whole barrel, mostly on the length from the A frame to the flash suppressor.  You'll note that the thicker section of the A2 barrel is that specific area...

This is the formal explanation I've seen in several sources, though I can't find any of them right now.  I'd take it for at least a good candidate for why they made the change they did.

I'm with you chp5, no parachuting, prying, etc. I really like the handling characteristics of the lightweight barrel. I had a Vietnam Veteran in the store today that asked for an AR-15 that was like his service rifle. I handed him a used A2 Colt Sporter Target with the Gov't profile barrel. He said "This isn't what I carried in the war!" His service rifle was much lighter, we know it was.  The only complaint I ever had with my SP1, was inaccuracy with heavy sling tension.

I've always heard the reason that the A2 barrel is heavier toward the end was that the extra weight reduced muzzle climb in full auto.

Prybars don't bend in the middle... they bend near the end where it is being pried on.  A pry bar will invariably bend around the fulcrum.  It is not necessary to make the barrel heavier under the handguard to stop the bending, if the barrel being used as a prybar is the cause of the bending.

Quoted: The parachute jump example is speculation, but has been documented as an issue with the M-14s. Hackworth wrote a good bit about it in his autobiography. Barrels on M-16A2s are bent from time to time during bayonet training. When I was in the Marine Corps, we would have rifles go down occasionally due to this. I have also seen rifle barrels used to pry things, and as levers when assembling GI cots. Were you really curious about my source, or did you just assume that I made that up?

I remember back in the early 80's reading an article in Army Times that cited the example of barrels being used to pry things as one of the reasons the A2 profile was developed. As an Infantryman, I was shocked that someone would abuse his weapon like that. Now.....years later, I realize that support types did not have a particularly strong bond with their rifle, thus their willingness to abuse it.

I also heard/read, long ago, that the major reason for the heavy barrel, from the FSB to the muzzle on the A2, was due to Skippy using his rifle as a prybar. Apparently with some frequency or it wouldn't have been addressed as a problem.

However, I am not now, nor have I ever been a member of the Armed Forces, so I have nothing to offer other than what I heard/read long ago, around the time the A-2 was being introduced.



Lonny

They told us at CATM school that the reason for the change was that the Marine Corps requested it because they where bending barrels when shooting with a sling. Basically when they raped the sling tight around thier arm and got the barrel hot it was bending them thus the change.

Quoted: They told us at CATM school that the reason for the change was that the Marine Corps requested it because they where bending barrels when shooting with a sling. Basically when they raped the sling tight around thier arm and got the barrel hot it was bending them thus the change.

I wonder how making the barrel heavier in front of the sling attachment point, rather than behind it, would solve that problem?

Think about it. The barrels are still light under the guards, the area where stress would be induced by a sling.



Lonny

Well my thought would be that if you beef up the area where the pressure is being aplied it wuld minamize the amount of torque transfered to the rear of the barrel. But as I'm not an engineer nor was I n the process of making the changes all I can do is guess and relay what I've heard over the years, like the rest of us. Being that the millitary dosen't always make the most logical choices in changes to weapons systems who can say for sure? All we can really do is speculate apparently. Another thought would be that it would decrease muzzel whip and improve accuracy.

Oh and IIRC the barel doesn't start to thin untill after the sling attatchment point on a standard A2.

I heard that they switched to the A2 profile because forgein whores loved GIs an even longer amount of time.  

With SP1s all you got was that puny unsatisifying "I love you long time."

3 years (1984-1987) in Infantry/Bradleys and I have never seen a bent A1 barrel.
not saying that it never happened. but my units (1st Cav and 3rd ID) kicked your ass if you were caught doing something stupid with your rifle.
it only take one moron to do something stupid and the whole class is blamed

eta: the M203 worked just fine on A1 barrels. 1/7 twist for heaver bullets is a factor.
I did just fine on the quals with a 1/12 barrel.

Boomstick.  I personally believed Kwe when she told me I love you long time.  You mean she didn't?  But I think there were several reasons the heavier barrel was adopted.  Yes the old flash hider did lend itself to abuse.  I remember being really exhausted and hungry after 4 days without rations that I did use it to jerk open C-rats cases, I knew better but was too tired to give a shit.  I also fired Combat competition (7 times at All Army level at Ft. Benning)  I remember being on the 600 meter line on at Benning and I had my sling tight, scrunched up in a really tight position.  I had fired about 10 rounds (I still have my range book so I could look it up) when suddenly my rounds started landing all over the palce.  One of the Tennssee N G folks who I had befriended told me to loosen my sling an inch and take the pressure off the barrel.  He was correct and my groups tightened up a bit, but not as tight as when the barrel was a little colder and I had a tight sling.  The A-1 did have a problem with a tight sling hold because of the barrel and the way the sling was attatched.  Wjen we went to A-2s the forst thing I noticed is that it was MUCH more stable with a tight sling and it was at that time that EBR shooters began to challange the M-14 folks at 600 and then 1,000 meters.  I remember the first time I saw a competetor taking an HBAR to the 1,000 meter line.  I actually laughed.  He was a friend, (a local doctor) and he said he loaded it with the new Sierra 69 grain bullets with 4064.  He won and I couldn't believe it.  I guarantee the old A-1 couldn't have done what the new EBRs are capable of.

Also remember that if one went over barbed/consatina wire you were supposed to use your rifle to bend it down and walk over it. I can see where you could bend a BBL, but at the same time one could break the stock just as easy as bending the BBL. I still think the A1 profile is the fastest and handiest of ALL the BBLs out there, and the 1/12 is still the best for wounding characteristics because of the instability factor. Just not as accurate at long range. [1/ 14 hasent been around  for quite a while.] [[this is with 55grain ammo, not the heavier stuff. I do not consider 62 gr to be any better then 55 for lethality, the 55 gr and 1/12 or 1/14 twist had some really nasty wound characteristics.]] As far as full auto, and the a1 a2 m4 profiles, the hottest area is all pretty much the same diameter so that point is moot. The HBAR would take more heat but also take more time to cool.

Quoted: Also remember that if one went over barbed/consatina wire you were supposed to use your rifle to bend it down and walk over it. I can see where you could bend a BBL, but at the same time one could break the stock just as easy as bending the BBL. I still think the A1 profile is the fastest and handiest of ALL the BBLs out there, and the 1/12 is still the best for wounding characteristics because of the instability factor. Just not as accurate at long range. [1/ 14 hasent been around  for quite a while.] [[this is with 55grain ammo, not the heavier stuff. I do not consider 62 gr to be any better then 55 for lethality, the 55 gr and 1/12 or 1/14 twist had some really nasty wound characteristics.]] As far as full auto, and the a1 a2 m4 profiles, the hottest area is all pretty much the same diameter so that point is moot. The HBAR would take more heat but also take more time to cool.

Please read the ammo oracle before disseminating any more myths about terminal performance and twist rate.

Airborne jumps are rough on rifles and I have seen many rifles with bent barrels. Every rifle in the army is required to be gauged annually as a small arms repairer this is part of my job. M16s/M4s are all checked for head space, barrel erosion, firing pin protrusion and barrel straightness. Most bent barrels are not bent much you can not see by looking at the exterior of the barrel, but the straightness gauge will pick it up. If the barrel is dirty you can get faulty readings so the barrel must be clean. In my experience the majority of bent barrels come from airborne units. Another method to check for a bent barrel (note this is not a procedure the army uses) is to shine a light through the barrel in a dark room. The light that hit the wall should be round if it is perfectly round the barrel is probably bent. Some gun smiths can / or will attempt to straighten out bent barrels. the army’s policy is to replace it. I really do not think the profile of the A2 barrels has helped prevent the bending of barrels as most bent barrels are bend midway.

Quoted: Boomstick.  I personally believed Kwe when she told me I love you long time.  You mean she didn't?  But I think there were several reasons the heavier barrel was adopted.  Yes the old flash hider did lend itself to abuse.  I remember being really exhausted and hungry after 4 days without rations that I did use it to jerk open C-rats cases, I knew better but was too tired to give a shit.  I also fired Combat competition (7 times at All Army level at Ft. Benning)  I remember being on the 600 meter line on at Benning and I had my sling tight, scrunched up in a really tight position.  I had fired about 10 rounds (I still have my range book so I could look it up) when suddenly my rounds started landing all over the palce.  One of the Tennssee N G folks who I had befriended told me to loosen my sling an inch and take the pressure off the barrel.  He was correct and my groups tightened up a bit, but not as tight as when the barrel was a little colder and I had a tight sling.  The A-1 did have a problem with a tight sling hold because of the barrel and the way the sling was attatched.  Wjen we went to A-2s the forst thing I noticed is that it was MUCH more stable with a tight sling and it was at that time that EBR shooters began to challange the M-14 folks at 600 and then 1,000 meters.  I remember the first time I saw a competetor taking an HBAR to the 1,000 meter line.  I actually laughed.  He was a friend, (a local doctor) and he said he loaded it with the new Sierra 69 grain bullets with 4064.  He won and I couldn't believe it.  I guarantee the old A-1 couldn't have done what the new EBRs are capable of.

For High Power or similar competitions, the sling and the problems you described with its use on the pencil barrel are real.  However, it's fairly rare to use a target sling in self defense or a fire fight.  

I love my SP1. Only problem I've ever encountered (no FA, Jumps, Prybar tactics) is the sling induced windage flyers. That's a small price to pay for such a handy, fast barrel.

Quoted: 3 years (1984-1987) in Infantry/Bradleys and I have never seen a bent A1 barrel. not saying that it never happened. but my units (1st Cav and 3rd ID) kicked your ass if you were caught doing something stupid with your rifle. it only take one moron to do something stupid and the whole class is blamed eta: the M203 worked just fine on A1 barrels. 1/7 twist for heaver bullets is a factor. I did just fine on the quals with a 1/12 barrel.

Ever drop the rear with the fire port weapon still in?

I believe many A1 barrels were replaced with the mistaken notion that they were bent.  This was found out later that a barrel straightness gauge would get stuck in the barrel.  It was found that it wasn't because the barrels were bent but because copper fouling at the gas port would cause the gauge to not drop through.  You can confirm this with Coldblue of KAC, he was my dads Major at Quantico Firepower Div.

The new SCAR-L has a pencil barrel.  What does that tell us?

The consensus appears to be issues with:
1.) Durability?
2.)Overheating under sustained fire?
3.)Acurracy?

Quoted: The new SCAR-L has a pencil barrel.  What does that tell us?

SF requested pencil barrels?
I'm curious as to the bbl. construction and specs of the SCAR-L.
Anyone?