I am new to posting so please let me know if I am in the right place, missing a previous post on same subject, or breaking some other rule . I just dropped off my DPMS 308 with 24 inch stainless bull barrel at the local well respected gunsmith to have the barrel fluted and shortened, and threaded for a compensator.
I am looking for advice on barrel length, the best compensator, and thoughts on fluting. They are willing to do straight or spiral fluting, or probably anything I can come up with. I want this rifle to be light, unique, cool, and effective. I don't want to give up too much muzzle velocity, but the weight is currently unbearable for me. I don't expect to run around with it shooting from my shoulder, but it would be nice to be able to get off the ground with it. It weights a TON with Nightforce optics and Harris bipod. They also said they could Teflon coat the indentations in the flutes for a contrasting color... cool, but I don't see the return on investment there. They will match the stainless finish of the barrel to the compensator, so any advice on best stainless compensator. I'm looking at the Benny Hill. I am very happy with PWS on my AR15, but it doesn't come in stainless to match barrel that I know of. Should I care? What do you guys think? Blue comp on SS barrel OK? They generally order compensators from the Brownells catalog, otherwise I would purchase on my own and carry in.
They can thread the barrel anything I want. Would I do something other than 5/8x24 for any reason?
I want to hear people's creative ideas! I don't want another cookie cutter rifle. I have basically an unlimited budget for this build. Thanks for any help designing my dream rifle! I need to call them ASAP for how to proceed. Please help!!!!
The 24 heavy stainless was my first barrel on my lr308. I know exactly where your coming from on the weight, it is one heavy pig. I went a slightly different route. I bought a new barrel. I went with a 20 inch medium profile from rainier arms. The 20 inch is a good trade off to keep your velocities up while shortening the length and dropping some weight. Alot of people drop down to even an 18 inch and have good results. Hell even knights armory re did the m110 to an 18 for their 2.0 version.
I cant say much for fluting. I have seen arguments both ways. I can see it looking cool, and maybe decreasing the weight some but not as dramatic as you think. Honestly if your not planning on putting lots of rapid rounds down range your barrel will probably never heat up so much that re profiling your barrel to a medium profile width would be a bad idea. It will save you even more weight over fluting.
As for threading the barrel, most compensators and brakes for 308 will come 5/8x24 so I would stick with that for ease of parts acquisition. I cant speak to compensators as I only run a brake on mine. Good luck, your gonna love the rifle.
Other than weight reduction, and jaw dropping beauty, what are you trying to get out of it. That will go a long way towards what the end product should be. What is your intended use of the rifle? Do you hand load or use commercial ammo?
Most people who get long heavy barrels are looking for long range accuracy (or short range accuracy and haven't done a lot of research).
A 16" barrel is as good, and sometimes better than the long barrels at short to mid ranges. Around 600yards is where they become equal. Beyond that is where the longer barrel lengths become superior. If you don't shoot over 5-600 yards, your accuracy is as good as the longer barrel while removing 6" worth of bull barrel weight. Black Ops Precision (formerly known as Underground Skunkworks) makes almost all of his 308 bolt rifles with 16" barrels.
You might also be surprised at how little difference there is in muzzle velocity, as well. Poweder burn rate will play a bigger role in shorter barrels. I read one article about a rifle development program that did an experiment with a 26inch barrel. They cut a it by two inches at a time, and tested the barrel at each length. They didn't see any velocity drop all the way down to 20 inches, using Federal Gold Match ammo. Going from twenty to eighteen, less than 40fps was lost. A simliar experiment with 300WinMag started dropping velocity under 22". Only with slower burning powders do you see much of a velocity difference with the longer barrels.
Fluting reduces weight, without taking away "much" of the bull barrel's structure or rigidity. Barrels flex when they shoot. It's unrecognizable to us, but they do. A fluted barrel is stronger than a straight barrel of the same weight, but less than a heavier smooth barrel with the same OD.
Going back to basic, public school physics, (an object at rest, stays at rest until acted upon by an unbalanced force, and Force = Mass * Acceleration) heavier barrels also tend to stay on target, and make the rifle less susceptible to outside movements, such as side winds, etc. IOW the same increased effort it takes for you to pick it up out of the dirt, is the increased effort it would take for wind to push you off target while you're squeezing the trigger. The higher overall weapon mass helps absorb recoil, and having forward weight in the barrel reduces muzzle climb.
If you decide that the length reduction is enough of a diet for that gun, you could still get some "pretty" work done on the outside. A few things that you probably won't see around the campfire at elk camp would be cutting it to an octagon or hex profile, slab sides, etc. You could also have flutes cut narrower and shallower so as to not reduce as much of the barrel mass. You could even get them cut perpendicular to the bore, instead of along the length of the barrel. Kind of like the cooling fins on an old Thompson barrel.
In regards to the barrel thread, the only other ones of possible consideration would be metric threads. Since you don't live in Europe, though, the 5/8-24 will give you the most options.
Thanks for the ideas! Maybe I should be thinking brake instead of compensator to save my shoulder. This rifle will be used for the long range only. I have a 6.8 SPC and more 5.56 ARs than I care to admit for CQ to mid range. I bought this just to project a little more power further downrange, and just because I wanted one I do my own reloading, and have a ton of supplies sitting in my shop. I can't wait to try all the different bullet/powder combinations I have.
I found this data that I found interesting. I had always heard that each inch of barrel had a constant increase/decrease in muzzle velocity, but it actually has more effect the shorter you go, and on the other hand, as you get longer there is diminishing return on barrel length. This test used the same powder for all barrel lengths. It seems you could tune your powder burn rate to the barrel length for better MV in longer barrels.
Baseline: DPMS 308 24 inch barrel
150 grain bullet
40.5 grains IMR 4895 powder
2820 initial muzzle velocity
Result of shortening barrel:
22 inch -36 fps from baseline (approx 1.5%)
20 inch -40 fps over 22 inch barrel
Lengthening to a 26 inch barrel added 32 fps.
My very rough estimates mean we're talking 1" more drop at 500 yards by removing 4 inches of barrel. Not enough difference to justify all the extra size/weight. I have a bad back, hip replacement, and arthritis so no reason to haul around all that extra dead weight .
I've decided to cut the barrel to 20 inches, standard threading, but still need a good stainless brake or compensator - will tell them Benny Hill unless someone else has suggestion. I wish I could make my own. I bought a gunsmith lathe and mill but am nowhere near good enough with it yet to tackle a compensator.
I love the idea of hex or octagon barrel since I collect old Winchesters. I wonder if they can cut a hex barrel with rounded small fluting on each flat surface. That would be unique. The perpendicular cuts intrigues me. I need to think what that would look like. Maybe a combination of hex and perpendicular cuts... hmmm
Thanks for all the great info to all of you, I'm in the same position with the same gun (but not the same budget!). I think I will also go for the trim to 20" on the barrel. Anyone know a good smith in eastern PA? What should a trim and re-crown cost from a good smith? The LR-308 is my first entry into the AR-15 family (but not shooting... 35+ yrs), enjoying the forum as well as the design of the rifle. So many interesting options available!
I don't know if this will help, but I went down similar roads with my LR-308 and have some observations from the point of view of using the firearm as a practical firearm as well.
Mine was to be a precision rifle, but also a hunting rifle-- meaning that it needed to be of such length and weight that I could-- if not perfectly-- maneuver the rifle in a variety of conditions.
First, I started out with a 24" Fluted Stainless Steel barrel, rifle gas system. It had no brake or FH, and had a target crown.
It did not take me long to realize that I was not able to effectively fire it off-hand. On the way to one of my deer stands, the inability to hold the rifle steady enough to take a 100 yard shot costs me a trophy 10 point whitetail.
At the end of that season, I changed out the upper receiver for the LR-308B upper. It had a 18" bull barrel with no fluting and a target crown. It uses a carbine gas system.
Dropping from 24" to 18"-- even with losing the fluting allowed me to actually fire the rifle free-hand if I had to. It is still a heavy beast, but it is more practical now.
After the next deer season, I took the rifle in and had the barrel threaded for a JP Enterprises "Ben Cooley" Muzzle Brake.
Frankly, the rifle doesn't need a muzzle brake due to its weight. Recoil was manageable without one, and it is practically non-existent with the Cooley Brake.
Now, mine does have the added weight of a Magpul PRS stock, and a SWS E10 Freefloat forearm.
Pic is below. It is pictured with the 4" sunshade on the Leupold Mk IV that I use when I am in one particularly nasty deer stand that gets evening sun right in your face. Not pictured is a Harris bipod that I bring, but rarely put on the rifle. It has the limited capacity hunting magazine in it. I took the palmrest grip off and replaced it with a Magpul MIAD. The palmrest grip was comfortable, but bulky.
Overall, I am happy with the changes that I made.
Sorry for the bad picture.