.308 barrel length and throat questions....

Jason280

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I am having a rifle built on a CRF FN action, and need some advice. The rifle will be used primarily as a paper puncher/steel ringer out to 600 yards, but I will occasionally run it to 100 yards. I am sticking with a .308, and plan on shooting 168 or 178gr AMAX bullets.

Here are my questions. Will I see a considerable difference with a 26" barrel over a 20" barrel out to 600-1000 yards with a 168 or 178gr AMAX? I like the portability of a 20" barrel, but really wouldn't mind the extra velocity from a 26" barrel. I am going with a Rock 5R barrel, and need to decide on a finished length.

Also, I am trying to decide what to set the freebore to on the chamber. I would like to be able to reach the lands if necessary, but will likely be sticking to an OAL of 2.805 - 2.830". Any suggestions?
 

RollinCoal11

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Re: .308 barrel length and throat questions....

Im having a .308 built by SAC. I will be using mine for paper and steel also. I went with a 24'' barrel on mine because it will only be going from the safe to the range so maneuverability isn't a concern but I wanted max BC from the .308
 

VKC

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Re: .308 barrel length and throat questions....

If you reload and want portability, go with a 20" barrel. That is plenty to get you out to 1000 yards. I went with 22", but only because that is want the GAP Crusader comes with.

Here's a video of Lowlight shooting to 1000 yards with at 18" barrel with a suppressor.

http://www.youtube.com/watch?v=15qj032UJ1I
 

Jason280

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Re: .308 barrel length and throat questions....

Also, one other quick question. How different are the locations of the ogives on the SMKs compared with the AMAX bullets? Ideally I would like to set the lands up so that I can easilty reach them with either bullet, just in case I do switch to the Sierra.
 

Jason280

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Re: .308 barrel length and throat questions....

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">If you reload and want portability, go with a 20" barrel. That is plenty to get you out to 1000 yards. I went with 22", but only because that is want the GAP Crusader comes with.</div></div>

The original barrel was 20", and I did like the compactness of the setup. However, I do have another 20" .308 that I am running, a Remington Tactical that shoots very well. I'm just curious how much more velocity I can expect with a 24-26" barrel over a 20" tube. I guess I can always start long, and have the barrel cut down if I am unhappy with the length.

Now, I just need to figure out where to set up the lands!
 

gstaylorg

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Re: .308 barrel length and throat questions....

Jason
As a general rule, you might expect anywhere from 15-30 fps increase in muzzle velocity per added inch of barrel length in the range of barrel lengths you're describing. For example, two of my rifles with the same manufacturer barrel/twist rate but different lengths (22" and 24") have average muzzle velocities of 2646 and 2711 fps, respectively, using Applied Ballistics 175 gr ammo. The change in MV range vs barrel length listed above is only an estimate and you may see more or less of a change depending on the ammo, barrel, etc.
 

Cork Shoes

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Re: .308 barrel length and throat questions....

The Winnie has a 3" box.

Use it.

Hint.
 

Jason280

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Re: .308 barrel length and throat questions....

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">I had ask a very similar question in regards to the length of a TRG22 barrel. I ended up going with a 20" due to the compactness and that the velocity lose between the 26" and 20" was not enough for me to worry about.</div></div>

Thanks for the information. I've actually decided to go with a 25" barrel? Why you may ask? Because its not a 24 <span style="font-style: italic">or</span> 26" barrel. I know it seems odd, but it will be different from most other rifles. Plus, I already have a Remington 20" .308, so I really don't need another. Besides, I can always have the barrel cut down if I need it shorter!

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">The Winnie has a 3" box.

Use it.

Hint.</div></div>

Actually, I'm currently using the FN detachable mag system, which isn't that long. I believe I am limited to 2.9" or so to ensure reliable feeding, but all of my loads have been under 2.830" (so its really moot).
 

Cork Shoes

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Re: .308 barrel length and throat questions....

My FN SPR A1 wore the FN DBM POS too.

Throat geometry in relationship to COAL is never moot,unless you've an abundance of empty mag box that's setting idle.

You do NOT.

Hint.