New Rifle Build

[NigelTurner]

Hi,

I'm new here and looking for some input an a new rifle that I'm considering putting together. This rifle would be for tac shooting out to between 600 - 1000 yards. My first such rifle.

I'd like to build it around the Accurracy Int. Chassis and a Krieger barrel chambered in .308, together with a Surgeon short action repeatable reciever.

I haven't given much thought to the optics yet, but would be interested to hear your opinion of the above set up.

Thanks...

 

[jasonk]

Re: New Rifle Build

Sounds like it will do the trick, keep the barrel 22" or under would be my advice.

Optics, anything quality in the 4-16 range or 5-25 if you're a magnification whore like me.

 

[NigelTurner]

Re: New Rifle Build

Thanks Jasonk,

Any reason to keep the barrel lenght at 22" ?

I was thinking of going to a 26" barrel personally.

 

[pj68]

Re: New Rifle Build

Nobby,
It depends on the barrel contour. If you have too heavy a barrel at 26" its going to be front heavy. With a 22" your not gonna lose much velocity and balance will be better.
I gotta McM a5 stock with a rock 20" mtu fluted barrel. It balances just in front of the floorplate. Mine is a 223.
If i may suggest. Contact the smith you would like to do the build and talk to him. He can walk you through the build. If he is any good he can tell you what will/won't work.

SOTA

 

[jasonk]

Re: New Rifle Build

Like sota mentioned, there's not much to gain besides weight when going over 22" in a 308. For a tactical match rifle the balance and compactness will be in my opinion.

Now if you were going 243 or 260/6.5/etc then I'd say 26" for some extra speed.

 

[Dagsta]

Re: New Rifle Build

Nobby, jason is right on, I have 22" Bartlien and I'm getting 2730 with 175VLD's. You'll regret a 26"bbl, especially if you start moving around and shooting tactical matches

 

[NigelTurner]

Re: New Rifle Build

Thanks for the replies chaps..

I appreciatate your input and I'll gladly take it onboard.

But a couple of things.. what twist would you recommend on a 22" barrel for .308, and what kind of contour?

I'm sure I'll have many questions, but I ought to let you know a little about me as it's my first time here.

I spent 12 years in the British Army, with the Infantry and was dragged up with the L1A1 FN 7.62 FAL before we moved over to the SA80 as you know is 5.56 NATO. I owen a couple of M4's but as I really enjoy longer ranges and all the problems (challenges) that that comes with, is my reason for wanting a really good precision rifle.

Cheers.

 

[Criver600]

Re: New Rifle Build

Nothing wrong with a 26 inch barrel. Seems most of the really short barrels have some kind of muzzle brake/suppressor and end up 26 inches or longer. I shoot 1000 yards every Monday evening at our gun club in Oak Ridge Tennessee and we get a lot of new shooters with fairly short barreled 308 rifles. Its the rare rifle/shooter with a shorter than 26 inch barrel that can get to 1000 reliably with factory ammunition. Good Luck & Good Shooting

 

[jasonk]

Re: New Rifle Build

criver is correct, it does depend on what you're shooting, are you reloading?

 

[NigelTurner]

Re: New Rifle Build

Hi Criver,

One of the reasons I went with the 26" barrel was because I didn't intend to add a muzzle brake. The other thing that drew me towards that lenght was that it seems to me that most of the rifles that AI sell in the AW range seem to come with the 26" barrel.

One other thing is that I live in Nevada, and I have ample room for long range shooting out on BLM land under all sorts of various conditions which helps with the challenge. I don't really intend at my age (47) to do much running around with this wpn.

As I've said.. I'm just looking for all opinions and I certainly don't want to cause any riffs here between anyone.. I just want honest input that I can put to good use, as this rifle is going to cost me a lot and I'd like it to be right for me, as its the only one I'll probably ever have the opportunity to own.

Thanks and please keep your suggestions coming.

 

[NigelTurner]

Re: New Rifle Build

Hi Jason,

I don't reload at the moment, but will certainly consider that at a later date. To start with I will probably just use match grade ammo.

 

[wnroscoe]

Re: New Rifle Build

Nooby,

Start off with either a 24" or 26" barrel. You can always cut it off but they're hell to stretch. With the 175SMK's I've found the velocity that shoots the best is around 2,620 fps. This velocity is very easy to produce, easy on brass and drills. I know for a fact though that 2,700 fps is a reality out of 22". I know a guy, a very prominent rifle builder, that went to the range one day with a .308, his ammo, a hack saw and a hand crowning tool. Determined to find the node he fired groups, cut off 1", re-crowned and fired again. When it was all over, 18.75" and 21.75" were the two barrel lengths that produced the best accuracy with acceptable velocity.

The accepted myth is about 40-50fps per inch of barrel loss or gain........the myth is wrong.

Criver nailed it, decide what the requirements of the rifle are and move forward. For 600+ yards, I’d opt for 24” to 26” of barrel length. Less than 600 yards, 20” to 22” will work fine. For conversation, my personal rifles sport 26” and longer barrels.

7/300 WSM 27”
.260 RP 26”
6XC 26”
6 Dasher 28”
6BR 27”

 

[Dagsta]

Re: New Rifle Build

Well I certainly won't argue with William, I haven't the knowledge or experience as he. I just know the 22" with brake serves me well and gets to 1K just fine.

 

[kombayotch]

Re: New Rifle Build

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: wnroscoe</div><div class="ubbcode-body">With the 175SMK's I've found the velocity that shoots the best is around 2,620 fps.</div></div>

This is because it's right on the OBT node with powders around the Varget burn rate.

It is true that a longer barrel will produce higher velocities if you load it to the limit (or a fixed charge). However, most people don't load to the limit... they load it to where they get the best groups. A lot of the time, they end up on the an OBT node without realizing it.

I took my data from my chrono and RSI Pressure Trace system and used it to calibrate my QL powder data for Varget. I then used it to simulate where the OBT nodes were with different barrel lengths. I found the following with the 175 SMK:

21": node #6 - 2549 fps., node #5 - 2668 fps.
22": node #6 - 2541 fps., node #5 - 2660 fps.
23": node #6 - 2531 fps., node #5 - 2650 fps.
24": node #5 - 2639 fps.
25": node #5 - 2633 fps.
26": node #5 - 2625 fps. (accurate for my barrel)

The charge weights were different for each barrel length of course, getting higher as the barrel got shorter. This is just a simulation, I can't guarantee that it is accurate since I have no way of testing it. But, it may explain why it seems that a given bullet gives the best accuracy within a certain velocity range.

 

[kombayotch]

Re: New Rifle Build

With the 190 SMK (my fav. bullet):

21": node #6 - 2506 fps.
22": node #6 - 2502 fps.
23": node #6 - 2491 fps., node #5 - 2603 fps.
24": node #6 - 2479 fps., node #5 - 2588 fps.
25": node #6 - 2477 fps., node #5 - 2585 fps.
26": node #6 - 2468 fps., node #5 - 2579 fps. (both accurate for my barrel)

I've definitely re-considered the value of a longer barrel...

 

[wnroscoe]

Re: New Rifle Build

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: kombayotch</div><div class="ubbcode-body">26": node #5 - <span style="font-weight: bold">2625 fps</span>. (accurate for my barrel)</div></div>

 

[NigelTurner]

Re: New Rifle Build

Exactly what does 26": node #5 mean?

Please excuse my ignorence.. just wanting to learn!

 

[wnroscoe]

Re: New Rifle Build

26" barrel length, Node #5 was the 5th load that produced a velocity of 2,625fps.

While developed in quick load, a computer based reloading program that helps with estimated pressure and velocities, the fps is close to what others have experienced in real world occurrences.

I'm reading it as the 26" barrel was his and the data was produced from it as well.

 

[kombayotch]

Re: New Rifle Build

Nope...

It means that it is the velocity that occurs at the 5th Optimum Barrel Time (OBT) node.

Read about it here:
http://www.the-long-family.com/optimal%20barrel%20time.htm

When the rifle is fired, the initial "explosion" of the powder create a shock wave (pressure wave, P-wave) that reverberates back and forth in your barrel. The best time for the bullet to leave the barrel (the optimum time) is when that shock wave is back at the receiver. When it is at the muzzle, it distorts it and bullet release is erratic. The idea is to tune the load so that that the bullet leave when the muzzle is nice and calm.

There is a practical way of doing this called an Optimum Charge Weight (OCW) test. More here:
http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=1087404#Post1087602

When you perform this test, the "scatter group" is what is produced when the bullet leave the barrel with the shock wave is at the muzzle.

 

[pj68]

Re: New Rifle Build

William,
I know a well known smith did the exact same thing you mentioned. He started with a long barrel kept cutting it down. He cut it down to 16" i think. He found the 50ish fps loss per inch was wrong. Interesting findings.

SOTA

 

[NigelTurner]

Re: New Rifle Build

Spoke to Scott today at Kreiger barrels, and he recommends that I go with the 26" .308 with a 12" twist in #10 which will give me great barrel for up to 175 SMK and out to 1000 yards.

Any thoughts on this... as the way I see it he must know what he's doing.

 

[kombayotch]

Re: New Rifle Build

I wouldn't go any slower than 1-11" myself. My next barrel will be 1-10". Its better for stabilizing heavier bullets (175 is a med. weight bullet IMO) and subsonics, but will still shoot the lighter stuff decently.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sota</div><div class="ubbcode-body">
I know a well known smith did the exact same thing you mentioned. He started with a long barrel kept cutting it down. He cut it down to 16" i think. He found the 50ish fps loss per inch was wrong. Interesting findings.</div></div>

I believe the test you are referring to was done using a 6mm of some sort. The loss gets bigger as the velocity gets higher.

http://www.chuckhawks.com/rifle_barrel.htm

 

[kombayotch]

Re: New Rifle Build

From that article:

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">The average loss for the .30-06/180 grain bullet was 15 fps per inch.</div></div>

This is more in line with what people on here have reported from chopping down 308's and 30-06's

 

[pj68]

Re: New Rifle Build

NOBBY,
Just rough estimating it here. With a 26" MTU barrel, aics stock. Your looking around 14ish lbs WITHOUT optics, rings, base. I don't know what a Surgeon weighs.
How much do you want to get this to weigh? I would consider balance and weight when looking at a build.
In regards to twist what bullet weights do you wanna use? A 1/12 will work with 175 grain SMK. If you wanna step up a little in weights you might wanna look at 1/11 or 1/10 twist. Probably 1/11 will work just fine. Shilen has a twist recommendation table on their website. Might help you a little with deciding on barrel twist rates.

SOTA

 

[pj68]

Re: New Rifle Build

Kombayotch,
If i remember correctly the smith was testing .308. Its interesting to find out the loss wasn't much at all. Compared to what everyone claims is a standard loss.

SOTA

 

[kombayotch]

Re: New Rifle Build

Ask MontanaMarine, he's chopped down both a 308 and a 30-06.

If you use the Miller stability formula (corrected for velocity and atmosphere), it says that you need a 1-11.25" twist in order to stabalize a 175 SMK going at 2650 fps. in -40F temperatures, at sea level... if you want to plan for worst case.

1-10" will do a 190 SMK in those conditions doing 2575 fps.

 

[lanwickum]

Re: New Rifle Build

Mine is a 308 at 21.75" with a brake or can on it. Usually a can. It shoots very well. Under .5 most all the time. Best I did was lucky timing for a smack the smiley shoot. .12 or something.
I reload, nothing serious for prep. I shoot right around 2620fps. I would hack it off more if anything. 18" would be nice.
It shoots to 1100yards well. Shoot it at 1500 something once. with the 2 impacts on steel it appeared the bullets made a good nose first impact. Around 7500ft denisity altitude that day.

 

[Criver600]

Re: New Rifle Build

Nobby
My first custom rifle was a winchester push feed, 26 inch 1/11 Hart Barreled 308 NRA match rifle. It shot 125 ballistic tips to 210 Bergers phenomenally. I have two Palma rifles with 1/13, 32/34 inch barrels and a Tactical/Hunting 308 with a 24 inch 1/11.25 Obermeyer. 1/13 will shoot 175's all day long. 1/12 is money in the bank, 1/11 gives you the option of throating for a heavier bullet. Its hard to go wrong.

 

[NigelTurner]

Re: New Rifle Build

Thanks for all your replies, much appreciatated. I think I'll have to do a little more homework.