View Full Version : 14.5 Middy: LW or Gov't profile
What are you'lls thoughts on a LW barrel vs. Gov't barrel. I don't plan on anything very elaborate...probably just a G2 light. Is there a very noticeable difference? BCM has a LW in stock, but I had originally planned a Gov't profile. Not going the free float route so I did not know if the LW would be to thin. What would you do?
I hate light weight barrels. But that's the current fad. :blink:
I was a lightweight barrel nut back before it was cool, and your choices were the Bushmaster Superlight and the Colt 6520. I bought both.
I haven't lost this particular trait (being crazy about lightweight barrels).
It kinda boils down to your need. Do you plan on any kind of mag dump/high volume shooting? If so, a heavier barrel can tollerate more heat.
Are you sensitive to weight? If so a Light barrel would be better for you.
"sensitive to weight"...haha...
I really like lightweight barrels for when I need to sling a carbine and walk 12-15 miles with it.
Even if I limit what I attach to the rifle, necessary items such as an optic, NVGs, light etc cause weight to balloon above 8lbs loaded.
So I cut weight where I can.
"sensitive to weight"...haha...
Yeah... I wasn't calling you a weight sensitive guy....
Just that some newer shooters are into small or light guns.
Yeah... I wasn't calling you a weight sensitive guy....
Just that some newer shooters are into small or light guns.
Oh, I know you weren't. Just saying why I like them. I guess our respective opinions boil down to:
Carried a lot, shot a little: lightweight
Shot a lot, carried a little: gov't profile
Si?
Magic_Salad0892
05-05-11, 13:49
I'd go LW.
jonconsiglio
05-05-11, 14:08
My SCAR has a lightweight barrel and it's been great. My SR15's are kind of in the middle, I guess, and they've been great. Working on a 14.5" BCM and was thinking about a lightweight barrel for it, bu have decided the govt profile will work on that gun for my particular needs, and I carry my guns a lot.
There's no major reason on this, I've just decided it's what I want as the difference on the 14.5" Middy is about 4 or 5 ounces, I think. I'm not concerned much about the accuracy difference between them, but once they heat up there is more spread in most cases.
If I was in need of a gun now, I'd take what they had in stock. Since mine is an addition to others, I don't mind waiting for exactly what I want. They'll both work fine for most applications.
I have no need for the gov't: http://www.m4carbine.net/showthread.php?t=67198
question-
isn't the only diff between gov profile and lightweight the contour forward of the Gas block? Same dimensions from the receiver to the gas block?
That is what I understood, but maybe i under-understood. They went from lightweight to gov profile cos soldiers were trying to pry off ammo crate lids with their rifle barrels, or some form of general jack-assery...
If that is so, I don't see the need, ever for heavier profile forward of the GB. Any increase in barrel thickness would seem to do the most good closer to the receiver....unless someone gets the idea to use the rifle as a pull up bar or something...then its obvious they should go heavy barrel. LOL.
Mr. Goodtimes
05-05-11, 18:30
I don't see the disadvantage of a LW barrel over a government profile, the only difference is in front of the handguards. Given the choice I'd go with light weight. I could understand if the government profile maintained the same thickness all the way back but they don't.
I'd probably go with LW regardless as my guns aren't full auto and they aren't being used as an IAR. I think it says a lot that the original M16 and the SCAR both have lightweight barrels.
EDIT: I agree with the poster above me in that it would make more sense for the barrel to be thicker closer to the chamber (as that is where the most heat is at) than towards the end. My understanding as well was that the profile was thickened in front of the hand guards to keep dumb asses from bending the barrel doing stupid shit that barrels weren't meant to do.
jonconsiglio
05-05-11, 19:14
I don't see the disadvantage of a LW barrel over a government profile, the only difference is in front of the handguards. Given the choice I'd go with light weight. I could understand if the government profile maintained the same thickness all the way back but they don't.
You're right and I often forget about this. I wonder how much difference it would make if it had a thicker contour through the whole length.
My 14.5 LW BCM Middy is my favorite all around, hands down. Next favorite would be my 16" LW BCM Middy.
I've been having rifle barrels shortened and re-contoured for more than 30 years.
Both are fine. I like LW barrels as there is less weight up front and are easier to drive.
C4
Thanks for the help guys. I guess this build could be a carry a lot and shoot a little (since it would replace my current current patrol rifle); however, we do shoot quite a bit and fast in training and re-quals. Just trying to make sure I would not regret going with a LW BCM upper.
What are the actual diameters and weights of these profiles?
RiflemanBobcat
05-09-11, 22:41
IIRC, Gov profile will be right around .750" at the gas block (and close to it, if not exactly that, from there to the muzzle.
Lightweight/pencil/A1 profile will be .625" at the gas block, and a shade smaller for the rest of the bore, though I've forgotten what the actual measurement is.
FWIW, I have a gov't profile 14.5" midlength, and I wish I'd held out for the lightweight profile. Just based on the way the weapon feels and handles as-is, I think I'd prefer to have the CG a little more to the rear, and I'd rather not have to add weight to the butt to get that feeling. But that's just based on my preference for how it balances, not that I have any real complaints about it.
Maybe the next one I'll be able to be a little more patient for BCM...:sarcastic:
Though the m4/govt. profile barrels are bass-ackwards (thinner profile towards chamber area), Molon has demonstrated marginal accuracy increase over the LW profile (There are many variables to consider, but he was using colt barrels). Whether this matters to you in a rifle with an objective of combat accuracy (3-4moa?) is for you to decide. Most informed shooters do not think the marginal increase in accuracy is worth the added weight, and for good reasons too. I personally own a 16" govt. profile with omega rail and TA33 ACOG, and a 14.5" LW with standard handguards which will probably end up with an aimpoint R-1 or just irons. My thinking is that the ACOG and Omega rail may be able to make better use of the marginal accuracy increase of the slightly longer and heavier govt. profile. I admittedly base this merely on technical info gained on M4C and not real world experience, I haven't even shot the 14.5 yet.
wileecoyote
05-10-11, 00:33
I was trying to find out what kind of weight the SR15 barrel is considered and came across this from KevinB of Knights on another site:
http://www.silencertalk.com/forum/viewtopic.php?p=485705
When asked about what profile the SR15 was he had this to say (in late 2009)
"Lightweight.
An HBAR does you no real good unless you want a huge heat sink (no real use for civilians) or are worried about barrel deflection from mounting a suppressor.
We could make a heavier barrel, but for the vast majority of user they want the lighter gun."
Seems to follow a lot of what people are saying\experience here.
Good resource for profile dimensions for those that are looking.
http://www.ar15barrels.com/profiles.shtml
I'm a lightweight nut too, and also date back to the 6520 being one of the only options available, so I bought two and changed one into a flattop (have since sold the other one), and then bought one of the first batch of 6933s and one of the second because it was the same barrel profile just shorter. Never have I thought "I wish this gun was heavier" nor "man if I just had an extra 0.125" of barrel diameter I would have made that shot!"
As barrels get shorter and gas tubes get longer, the weight savings by going lightweight decreases but the benefits of the extra meat of the A2-profile should decrease as well. Would be interesting, albeit single-samples, to test 16" lightweight and GI, mid and carbine, and the same for 14.5" barrels. That's a lot of barrels though, and unless all other variables are equal it would mostly be for entertainment.
...As barrels get shorter and gas tubes get longer, the weight savings by going lightweight decreases...
Gas tubes don't weigh much, do they? Or am I missing something?
Gas tubes don't weigh much, do they? Or am I missing something?
Gas tube length is only a tiny part. As gas portages further forwad the ratio of .625" dia length to .750" dia length tips more and more on the .625" side.
If this still doesn't make sense I'll make up a graphic to explain it.
ETA:
Typically "GI profile" means
A: ~0.625" between the chamber and the FSB
B: ~0.750" from there forward.
Just using some basic numbers here based on the assumption that a carbine-length gas system on a 16" barrel has an A length of 7" and a B length of 9" while a mid-length gas system has the inverse. A 14.5" barrel then has an A of 7" and a B of 7.5" for the carbine, and an A of 9 and a B of 5.5" for the mid.
Taking this example, the weight savings is only to be had in the B dimension because A is already 0.625". When comparing a 14.5" mid-length gas barrel GI profile to lightweight you're talking about reducing the diameter (and therefore weight) over a length of only 5.5", whereas if you had a 16" GI-profile barrel with a carbine-length gas system you would be reducing the diameter (and therefore weight) over a length of 9".
I get it now. Thanks for explaining
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