I have a friend with a BCM 16" mid-length cold hammer forged barrel. He is trying to make his AR as light as possible without compromising functionality. If he is willing and able to spend whatever it takes, what would be the best way to remove as much weight as possible without compromising accuracy? I have read a few posts about fluting, dimpling, turning, etc. but am still confused.
Dimple or fluting will help as well…add a troy trx rail too 
Thanks for the reply. That is exactly what I have on my AR, but my friend wants the barrel life and marginal accuracy advantages of the CHF in the lightest practical configuration. I guess my question is whether fluting, dimpling, or turning down would take the most weight off without compromising accuracy- or conjuring up any other negative side effects. Again, he is willing to pay what it takes and he will probably end up sending it to ADCO for one of their services.
What marginal accuracy advantages? If CHF barrels did offer some kind of accuracy advantage, why are no match barrels made by this process? Shooters concerned with accuracy avoid CHF barrels because of stresses this manufacturing process creates stresses in the steel which can cause the barrel to warp enough to cause noticeable changes in the point of impact.
Fluting/dimpling also creates stresses in the steel.
If the barrel is lightened, throat erosion, with the resultant loss of accuracy, will occur at a faster rate because the barrel will reach higher temperatures with each shot. Sure, the light barrel cools faster but it has less mass to deal with the same amount (BTUs) of heat.
Before cutting the barrel, look to see where weight can be saved elsewhere. What kind of buttstock does it have? Forearm? Does he have widgets & gadgets attached that can be removed or replaced with something lighter? Does he have a foregrip he can ditch? Does he have gear stuff stashed in the stock or grip he can remove? Can the widgets & gadgets be moved closer the the CG of the carbine to reduce that muzzle heavy feeling?
Does he have an adjustable stock? If so, have him reduce it’s length by one or even two clicks. A stock that’s too long for the shooter makes it feel awkward & heavier than it really is.
The barrel is the one place on a rifle where weight actually contributes to performance and reliability and should only be removed after everything else is trimmed
cav arms lower helps if he is fine with a fixed stock.
SBR.
If you want lightness, easy handling, etc… just shorten the barrel (legally).
A lot of shooters looking for accuracy also avoid CHF barrels because match-grade barrel makers who are turning out relatively small amounts of barrels avoid dropping the insane amount of cash required to purchase and set up a hammer forging machine. Sort of apples and oranges.
SBR if don’t want to go that route cut the barrel down to 14.5" and pin/weld the muzzle device.
Instead of a rail:
http://www.cavalrymanufacturing.com/C8.html
about 15 years ago i had a close working relationship with two of the match barrel makers and can assure you that if hammer forging didn’t have the mentioned drawbacks they would use that method. hammer forging creates a very dense barrell that is stronger than a standard blank and more wear resistant. the problems as stated are trying to make them accurate and keeping them accurate. hammer forging makes hard and soft pockets that wear unevenly and expand unevenly. 99% of the people will never notice the difference in accuracy but some will. a forged barrell can be turned marginally thinner due to its increased strength but it was already denser/heavier so no real gain. as far as fluting/dimpling if the barrel is made fluted(at the beginning before heat treat, lapping and chambering) there are no stress problems. fluting/dimpling technically doesn’t cause stress it relieves stress unevenly which is why it needs to be done early in the process. the barrel blank needs to be as close to finished dimensions as possible before final heat treat.
Just for reference…
I had my 16" BCM CHF Middy dimpled in-front of the gasblock only. Prior to dimpling the stripped barrel weighed: 28.16oz.
After dimpling: 26.0oz.
While slightly over 2oz. doesn’t sound like much, that amount of weight reduction taken from the muzzle end of the barrel made a noticeable difference in the balance of the complete weapon.
I can only imagine that having it dimpled under the handguard as-well would drop another 4-6oz off of the total weight.
From what I have heard from those doing the dimpling process (KAC, ADCO, and a former KAC employee doing it on his own), it offers the best compromise in weight reduction & retaining rigidity. Now I cant comment on their science one way or another, but my barrel shoots the same in-terms of accuracy as it did prior to being dimpled.
two questions - first, is he trying to get his carbine as light a possible, or is he trying to get his barrel as light as possible?
these are different matters that can affect the balance and “feel” of the gun. it’s possible to have a relatively heavy gun that still feels lively in the hand. reducing weight at the front or even adding it toward the rear will make the rifle seem more in balance.
by your question, I’m going to guess he’s just interested in the barrel so is he interested in total weight reduction or just that it “feels” lighter?
I am in a somewhat similar boat as I have two BCM middies - one standard, and one LW. the standard is awesome but can be a bit of a bitch to keep on target or at low ready all day at a class with its FSP, 9" rail, G2 light in VT mount, and VFG. I’d like to reduce the front end weight of this gun while making it handier as a general purpose carbine mostly for HD, with only a light and RDS attached.
thinking of a lever, every ounce added or taken away from the end of the barrel has more effect than that same weight taken closer to the center of balance.
because dimpling or fluting is out of the discussion for me - as I have neither the $$ nor definitive proof that doing this doesn’t hurt accuracy - I’m looking at shortening the barrel from 16" to 14.5" and pinning a FH on.
1.5" of 3/4" barrel steel with .22 cal hole through it is probably going to weigh more than a few ounces and removing it from the very end of the barrel is going to have the most effect.
in theory, a shorter barrel of the same diameter is a more accurate barrel but not everything is an absolute. however, it will be significantly cheaper than fluting or dimpling and will improve the handling over all.
this is the direction I’m going but I’m also going at this in stages. I’ll evaluate and see if I like it, then I’ll probably replace the rail with something lighter. I may shave the FSB and install one of the Extreme rails, etc…
but in doing this, I’ll be starting at the muzzle end and working backwards as that will give me the most benefit in “feel” and handling.
What is the cost of having the barrel cut and FH pinned? Never bothered to look at rates, but I’m interested in shaving some weight.
do you have anything that proves this? i have always heard the opposite.
Also, what is the weight on a BCM lightweight middy? I’ve been selling off my rifle in pieces, and now considering wether I should keep the barrel and cut it down to 14.5 and pin or go for a BCM lightweight. I haven’t seen one, but does BCM offer a lightweight BCM 14.5"?
I don’t have a quick answer for you but it should be roughly 1/3 to 1/2 of the cost of fluting. I don’t know about dimpling…
anything that proves it??? well, how about physics?
who have you heard the opposite from? I would seriously question anyone who says a longer barrel, of the same diameter, is more accurate than a shorter one or whether I actually understood them correctly…
wow very detailed and concise answer. don’t like your beliefs questioned i guess.
in my years of shooting bench rest and other forms i have done a lot of testing, have read a lot and talked to barrel makers and other shooters and all this led me to believe that 18" is about as short a center-fire rifle barrel can be and expect the best mechanical accuracy. down to 16" will sometimes be ok with lighter or slower rounds. any shorter than that and accuracy and ballistics suffer exponentially. i guess all those competitive shooters with their 24 in barrels need to go back to school and learn physics.
accuracy due to external ballistics is not the same as pure physics in this case. shorter barrels of the same diameter are stiffer. stiffer is better. in order to make a longer barrel stiffer you need to increase the diameter, or vice versa…
longer barrels increase velocity. some cartridges/calibers shoot better at a certain velocity and need extended barrel length to attain that. that, and weight, is why benchrest rifles have fat barrels. this is limited by weight categories in that sport.
benchrest is not Palma, F-class, or varmint. I’ve never seen a pure benchrest rifle with a 24" barrel…
16" BCM middy LW upper with no handguards, rear sight, BCG, CH weighs 2 lbs 11.6oz. This was the .750" gas block too, the newer runs are .625" so it will be a tad lighter.
first off i said that mechanical accuracy and ballistics suffer with a short barrel. i brought up the ballistic loss to show an added disadvantage of short barrels. yes a long thin barrel will have flex and whip problems and i figure everyone knows that. when i shot silhouette i built up two guns on Remington actions one left and one right handed so that one could be a pistol. both were trued and chambered with the same new reamer in 7mm08. barrels were hunter profiled. over a three year period i chased accuracy in the pistol and changed the barrel 3 times. the last time with a shillen barrel. i experimented with different lengths and crowns and did exhaustive load work. while the gun was very accurate it would print what i can only describe as a radial pattern with inconsistent flyer’s going out in a circular pattern. in a conversation with a person from shillen he stated that what i had done was remarkably similar to a test he had read from Aberdeen proving grounds where they studied bullet stability from different length barrels. in their testing they had the same circular spreading. they blamed it on the shorter barrel not being able to completely stabilize the bullet due to the harmonics and they also believed that the bullets were not spinning on their center axis due to inadequate time in the barrel. as a final test i took the original hart barrel off the rifle and put it on the pistol and it shot fine.
you keep stating physics says, but you won’t explain what part of physics or any details. i know little of actual physics and am honestly interested in all forms of science and would like to hear it.