Where do I stop

[Deadshot2]

I need to shorten a 24" bbl on my .308 and the "flaw" I need to remove gives me a max finished length of 20".

Should I stop there? Or go for the increasingly popular 18" length.

I've heard some say that 20" is the shortest one should go with the .308 but others are touting the tactical rifles coming out in 18" that are supposedly obtaining fantastic results due to the stiffer barrel.

Just curious and wanted some input before the hacksaw comes out. OK, I know that I could always cut the extra 2" off should I decide to go to 18" but being basically lazy, why not just do it once?

All Ideas, thoughts, and advice, are welcome.

 

[hewlett260]

First off, what "flaw" do you have? Honestly 22" is the shortest I would go on a "precision" rifle. The whole argument over barrel stiffness is bullshit since there is no real scientific method to test it, and a big part of it is people trying to justify to themselves why they went with what they did. Find the right balance for what you are trying to do. coming from my own experience, I will never run a 308 shorter than 22", the velocity and consistency just weren't there for me. I had a 20" 308 and got nothing but frustrated with it. Still have the 24" 308 though and have never had a bad experience with it. I like 22" better for the calibers I have as its the perfect blend of performance, accuracy, velocity and handling. In case you were wondering I run a Weatherby Mark5 300 Win Mag and an Accuracy International AW260 both with 22" barrels.

 

[Cacciatore]

How do you know that this "flaw" is not affecting the entire barrel, and not just aforementioned section? And, depending on how bad the flaw is, do you feel safe with a 60,000 psi combustion next to your face?

Anyway, I do agree with the above poster. I have 28" barrels on all of my rifles. 18" barrels are popular on tactical rigs set up with a heavy stocks or chassis systems, that absorb a great deal of recoil. If you are shooting a R700 with the factory tupperware stock and an 18" barrel, the gun is not going to be friendly to your shoulder.

 

[Dirty D]

The whole argument over barrel stiffness is bullshit since there is no real scientific method to test it.

Take 2 identical barrels made from the same barstock, one 18" and the other 26". Anchor both barrels at one end (in a reciever etc.) and hang an identical weight at the other end of both barrels and you will have a measurable difference in deflection.

 

[Deadshot2]

Take 2 identical barrels made from the same barstock, one 18" and the other 26". Anchor both barrels at one end (in a reciever etc.) and hang an identical weight at the other end of both barrels and you will have a measurable difference in deflection.

Not to mention the different harmonics between the two lengths.

As for what the "flaw" is, let's just say I'm not worried about the rest of the barrel. I've done some extensive testing and if I remove 4" from the barrel I'll have a nice safe, serviceable barrel.

As for recoil, the action is mounted on a B&C "A-5" style (2094) and really doesn't shoot all that bad as is. I just want better. I may end up replacing the barrel next year or so but for now I've decided it's "18 or 20".

BTW hewlett260, with all due respect, there is a definite scientific method as well as a formula for barrel stiffness. High speed video will prove what the formula predicts.
Also, I will be going from a muzzle diameter of .825" to .860" or more, depending on the finish length. This is no "buggy whip" barrel.

For now, I'm leaning to 20". If I was planning on shooting distances over 600-800 yards I'd probably just replace the barrel. For now, ill see how I like a "shorty".

 

[scudzuki]

Relevant info;

SWAT Article BARREL LENGTH

Joe

 

[080107=2112]

I build rifles for APO in .308 that are only done in 20". Barrel stiffness is increased and velocities from M118LR are right around 2650fps. All our rifles are sent out with a test target from THAT rifle. Our standard is sub half MOA and nothing leaves the shop until that accuracy is proven.

You won't go wrong with 18"-20" on a .308 precision rifle. Save the weigh, barrel length does NOT always equal extended range or accuracy.

 

[Deadshot2]

Update:

Well, I made my decision. 20" it was.

First some of the backstory. I was at the range one morning with my 5-R milspec. Had set up my chronograph and used a laser bore-sighter to speed the process. A cheap Bushnell that gets stuck in the muzzle. To cut the story short, I overlooked the fact it was still there when I fired my first shot. Didn't notice anything other than the fact that my chronograph didn't register the thought. I thought that the muzzle blast might have moved it so I went back out to adjust the chrono. Worked great for the rest of the day.

When I got ready to pack up I picked up the case for the bore-sighter and WTF? Where did I leave it. It then dawned on me that it had gone down range. I took a look down the bore and checked the outside of the barrel for damage and noted none. Went home, kicking myself in the ass all the way.

At the next range session I noticed that I was having a heck of a time getting small groups, even with known loads. Rifle usually shoots sub .5 moa, even on a bad day.

When I got home I did some serious checking of the barrel and bore. About 3" from the crown there was an obvious ring. CRAP!

So then I started thinking, 20" bbl? 18"? Well, based on the comments here, and reading the SWAT article I decided to go 20". Two hacksaw blades later and about 20 minutes to cut a new crown (I have an 11 degree crown cutting "reamer" from Brownell's with pilot), I was ready to go back to the range. I had 'slugged' the bore and it was perfect at the end of the barrel. On the piece I had cut off a bullet would drop 3/4 of the way into the bore and only stop when it hit the "pressure ring".

At the range, what a difference. The first shots fired were with two loads I had shot the previous week with unsatisfactory results.

Here are the before and after targets. Rifle is a Rem 5-R Milspec shot from a Sinclair Tactical Bipod up front and a sandbag at the rear.


42 gr. H-4895 with Hornady 178gr A-Max 2.820" OAL (shot one missed target, shot two was high. 3,4,5 were grouped and only those used for measurement) 2" target spot

After cutting the barrel and re-crowning, here's the same load, Shot one was excluded from the measurements shown as the scope was adjusted after it was fired. 1" target spot

Here's another comparison with a load I've been working with. CFE223 with the same Hornady 178gr A-max. Needs some tuning as this load was developed using the old Latin method known as "extractamus ex wazoo". I just looked at some load data then took a guess. Had some extra rounds after firing the first batch with the damaged barrel so I thought it might make a nice comparison.

Before (2" target spot

After (1" target spot

On this "un-tuned" load, getting rid of the damaged portion reduced the group size by 75% (to .537 MOA from 2.119 MOA)

On a further note, this rifle has had many, many, rounds through it's barrel. I quit counting but best guess is that since I bought the rifle 5 years ago it's close to 8k (and bullet purchases confirm that's close). If I can still get .212 MOA groups out of it, I won't be replacing the barrel soon.



I just need to keep better track of my bore-sighter

 

[080107=2112]

Good to see it all worked out for you.

 

[Deadshot2]

Good to see it all worked out for you.

Thank you. I know that this is definitely not the preferred method to end up with a 20" BBl. Next time I'll just buy either a new barrel in 20" or a complete rifle with 20" bbl.

I feel like the guy who fell in the outhouse and came out smelling like "roses".

FWIW, I compared data from the same loads before my "brain fart" and the data from my chronograph at the session after I shortened the barrel. I lost exactly 28.3 fps from 24" bbl to 20" bbl per inch removed. Total was 113.3 fps which I think I can get back with new load workups. Most of my pet loads have been in the middle of most published data.