Posted: 7/16/2009 1:24:06 PM EDT
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Having built up a couple of 5.56 projects (both 16"), the last completed only two months ago, I have definitely been leaning towards a longer range precision build (not bench rest mind you and a semi not bolt action) and the OSR is quickly becoming the next gun on the wish list. WIth my leaning towards a larger caliber and longer range capability I guess I always envisioned a longer barrel. The question I am pondering with the 16" standard length OSR and the option for custom lengths mentioned on Larue's site is obviously what length. The experts have weighed in with their standard configuration the 16". What mission is this optimized for? If I am wanting a 400-1000 yard gun should I be thinking 18", 20" (I am not really considering longer)? Anyone else pondering the possibilities?
These below seem obvious to me. What considerations am I missing? Misguided assumptions? My rifle experience outside of 5.56 is limited. Thanks. Pros of the 16": lighter weight, improved maneuverability/portability, ?. Cons: reduced range?, ... Pros for longer lengths: Increased range, accuracy? Cons: longer, heavier (pretty much the analogous opposites to the 16" pros), Longer lead time on delivery, ? |
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Thanks. Did Larue give you any feedback on if ordering a custom length puts you way down at the bottom of the list delivery wise? I understand the wait time is already huge on these so maybe it is not even a factor.
I am still interested on peoples thoughts of what the 16" is optimized for with the long range benefits of 18-20". |
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The 16 inch is optimized for tactical operations. The operator will not look like a sniper with a 16 inch barrel. External ballistics and operator knowlage and environment will play a bigger roll than barrel length.
That said, a friend has a 18 inch ordered for his DPMS build and I have a Classic 20 inch upper with standard front sight on order. It's up to you as what length you need / want. All three, 16, 18, and 20 are good to go. Some want looks, handling, velocity, etc. so you will have to weigh the information you get from research and decide how your dollars will be spent. That said, for an OSR I would order the 18 inch. |
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Quoted:
I'd go with the 16"...as demonstrated below. Quoted:
16" OSR group shot by Todd Hodnett yesterday ... ... some of the folks were mumbling something about bolt gun accuracy. 
http://img.photobucket.com/albums/v145/AUSTINWFT/LT%20Post/OSR_Targetgroup.jpg That is what I was thinking after seeing that pic. |
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Quoted:
Quoted:
I'd go with the 16"...as demonstrated below. Quoted:
16" OSR group shot by Todd Hodnett yesterday ... ... some of the folks were mumbling something about bolt gun accuracy.
http://img.photobucket.com/albums/v145/AUSTINWFT/LT%20Post/OSR_Targetgroup.jpg That is what I was thinking after seeing that pic. I had the fortune of watching that exact group develop, looking through a spotting scope. All I could think was..."damn...". |
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Quoted:
http://img.photobucket.com/albums/v621/Clutch99/OSR.jpg Only concern of mine is will this fit on a 16" 
yes, it does. 
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Quoted:
Quoted:
http://img.photobucket.com/albums/v621/Clutch99/OSR.jpg Only concern of mine is will this fit on a 16"
yes, it does.
 How sweet it is 
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Quoted:
Quoted:
http://img.photobucket.com/albums/v621/Clutch99/OSR.jpg Only concern of mine is will this fit on a 16"
yes, it does.
In the Ron Hayes posting, what is the rifle configuration in the picture? Is it safe to assume the OSR upper rail is a fixed length and only the barrel length changes? Or as the barrel get longer, the upper rail will also, similar to CAR, M/L, Rifle length...... The Surefire brake adds how much to the OAL of the barrel? Right now I have eliminated the 20", tossing around the 16 or 18", Leaning to the 16", but something is telling me the 18" to take advantage of the USOPtics I have on order, but based on the 16" performance in the postings, 16" may be the way to go..... 77 |
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Not sure I understand why the performance of the 16 at 100yds would influence a decision on barrel length, unless you plan to shoot only at 100 yards. Theoretically, the 18 and 20 are going to be equally accurate; a different 16 may not shoot as well as the one pictured; and if your goal is the best shooting rifle at 600 yards or longer, velocity becomes a priority.
As I asked in the other thread, what are the actual differences in velocity as you move to the longer barrels in .308? I am familiar with .223, and the advantages of a longer barrel fall off quickly, even with heavy bullets. Is that the case with .308? For example, at 600 yards, what would be the difference in holdover between a 16 and 20 inch barrel with a 168gr bullet? One inch? One Mil? 2 feet? |
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Quoted:
Not sure I understand why the performance of the 16 at 100yds would influence a decision on barrel length, unless you plan to shoot only at 100 yards. Theoretically, the 18 and 20 are going to be equally accurate; a different 16 may not shoot as well as the one pictured; and if your goal is the best shooting rifle at 600 yards or longer, velocity becomes a priority. As I asked in the other thread, what are the actual differences in velocity as you move to the longer barrels in .308? I am familiar with .223, and the advantages of a longer barrel fall off quickly, even with heavy bullets. Is that the case with .308? For example, at 600 yards, what would be the difference in holdover between a 16 and 20 inch barrel with a 168gr bullet? One inch? One Mil? 2 feet? SWAT article Not sure if you've read that, but it's interesting. I think after everything I've seen, I've going to go with an 18" barrel on my OSR with a surefire can. |
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So these are rough numbers. It looks like we'd pick up 25fps(rough numbers) per inch. So assuming the baseline for us is 2500fps for a 168gr round according to ML's trials we're looking at the following:
16" = 2500fps 18" = 2550fps 20" = 2600fps So 16" = 14.03 mrad drop. 18" = 13.38 mrad drop. 20" = 12.76 mrad drop. Obviously if you reload you can tweak those numbers and speeds depending on how hot you make the load. But with Mark using a FGMM factory I don't know how much better you can get. Like I said...my math could be wrong, but eh I think its close enough. Right now I'm debating on the 18 or 20 at this point. |