Barrel cutting

[TANGO2072]

Considering having my 20" cut down to 16" from ADCO. ( 65$ )

But Im concerned about Ballistics ( performace ).

With the Gas block / tube being that length ( 13" i believe )

[TANGO2072]

I was informed that going to 16" is NOT a good idea. 18" is.

The gas system becomes unreliable.

[imschur]

Interesting. I wonder how DPMS over comes this in the AP4?

[TANGO2072]

So I'll be sending in my barrel to the ADCO guys and have'her cut down to 18".

I also just placed an order for the Surefire 308 brake

[imschur]

any chance we can get a before and after barrel weight?

[TANGO2072]

DOUBTFUL

dont have a scale of any sorts in the house.

[imschur]

DOUBTFUL

dont have a scale of any sorts in the house.

ha ha. I recently had trouble locating a scale to weigh my AR-15 and the LR-308

[SWshooter]

I wish I had weighed my LR-308 before recontouring it. I think it had to go about 14 lbs. If anyone would weigh theirs I would appreciate it. I had mine turned down to .750 full length and a low profile VLTOR gas block installed. With a P.E.P.R. mount, leupold vx-3 2.5-8 scope, and a Burris FastFire back-up, it weighs 10.5 lbs. Still a little heavy for hunting. I may cut 4" off the barrel and replace the butt stock with an ACE skeleton stock.

[Madhouse]

I went to weigh mine for you last night, since it's still NIB, but the scale battery was dead.    :P

Hopefuly the wife replaces it today and I'll weight it tonight for you.

[SWshooter]

Thanks. Just for general info, I took my recontoured barrel out to the range tuesday for the first time. I was disappointed that the best load I had tested was now the worst. I had been shooting a 190 gr Horn. BTSP over 44 grs of Varget in WW cases. It was doing 1 1/2" groups and now it is shooting 6" groups. The 165's were doing 2" and now 2 1/2". I'm loading 150 gr Rem SP in '83 Lake City brass and these are shooting 2 1/2" just about the same as before. I'm going to try H4895 instead of Varget with the same bullets and hope for better results. This is very disappointing as I was expecting around 1 moa with this rifle based on others results.

[imschur]

Wow that's pretty disappointing.  Any chance something else is out of whack? Loose scope? 

Do you have any Federal 168gr GMM laying about just to try?

[Madhouse]

11 lbs.

[SWshooter]

I noticed that the gas block set screws had come loose. I tightened them up but I haven't had a chance to shoot it yet. I may pick up some blue lock tight and use it on the block and the screws. I don't know if that would cause inaccuracy or not. Doesn't seem like much but the new weight of 10.5 includes the scope , mount, Burris FastFire back-up sight and cleaning kit in the buttstock. It feels a lot lighter on the forend and is much easier to mount and track targets. If I can find one good accurate heavy bullet long range load and one cheap practice load I 'll be happy.

[TANGO2072]

Got my Barrel back today from Steve @ ADCO.

AWSOME JOB.

Now....

I just cant decide if i like it with a barrel knurled cap or the Sufire 308 brake.

BOTH are DAM SEXY.

Ill post pics tomorrow as Im at work tonight.

[imschur]

Excellent!

[SWshooter]

Shot my LR-308 with the recontoured barrel today. After tightening the gas block I fired a 5 round group with the Hornady 165 gr that went into 2 1/8" and a seven round group with the Rem 150 gr Corlokt that went into 1 3/4". The Corlokts look promising for general purpose use in military brass. I'm going to work up some loads using H-4895 instead of the Varget I'm using now. I just wanted to make sure the rifle was still functioning after the trouble with the gas block.

[cevgunner]

Thanks. Just for general info, I took my recontoured barrel out to the range tuesday for the first time. I was disappointed that the best load I had tested was now the worst. I had been shooting a 190 gr Horn. BTSP over 44 grs of Varget in WW cases. It was doing 1 1/2" groups and now it is shooting 6" groups. The 165's were doing 2" and now 2 1/2". I'm loading 150 gr Rem SP in '83 Lake City brass and these are shooting 2 1/2" just about the same as before. I'm going to try H4895 instead of Varget with the same bullets and hope for better results. This is very disappointing as I was expecting around 1 moa with this rifle based on others results.

Have you tried a slower powder?  Cutting the barrel changes the time/pressure curve that the gas system was designed for.  Someone had a gas tube called a Pigtail, for the Shorty Ar15 types, to offset the time/pressure issue in the shorty AR.

The operating characteristics are determined by the distance between the muzzle and the gas port . Back in the day, the Army changed the powder in the ammo for the AR15, screwed up the time/pressure curve, ruined the reliability and accuracy of the design in the process.

You might have lost some accuracy with the velocity drop - any chance you chronographed your loads before having the barrel clipped?  How much velocity have you lost?  What twist is your barrel?

Might be that you are stuck using 165gr, at a heavier powder charge to bump up your velocity. Or a slower powder, anyway.

[SWshooter]

Barrel is the same length, had it turned down to .750 from the full .960 bull barrel. I took it out again and fired four groups with it. Two with my 150 gr Corlokt handloads and two with some russian Wolf FMJ. The two handloads measured 3 5/8 and 2 5/8. The Wolf was 3 1/4 and 3 1/4. That's c-c the widest shots and they were 10 shot groups. I fired as fast as I could reacquire the target and squeeze off the shots. I had problems with the Wolf feeding in one mag and had to stop and change mags. The barrel had a chance to cool between strings. It was about 20 degrees out so it didn't take long. I definitely need a better trigger and I need more trigger time to get used to this rifle. It is a different beast off the sand bags than the bolt guns I'm used to shooting. I ordered a skeleton stock for it today and I'm looking at a Chip McCormick drop in trigger. If anyone knows of a good deal on a single stage trigger please post.

[cevgunner]

Ok, I thought you meant the barrel was shorter.  Reprofiling the barrel wouldn't have too much of an effect , in that case.

Unless your sling is too tight, in which case you'd see some kind of stringing, in the direction the sling pulls the barrel.

Just for giggles , try this:

Do several strings, single load the rounds.  Bolt hold open should work,

just drop the round into the port, trip the bolt release , let the bolt drive the round into the chamber.  Stay in position - don't tip the rifle- break each shot carefully.

What this should determine , is if your group size will vary due to magazine pressure against the bolt, similar to what you get with an FAL.  Single loading takes out one variable.

Granted, the bolt lockup is different in the FAL, but the idea is to break this down to where you can examine one area at a time.    As well, it can show you if it's the rifle, or something you are doing , that you may not realize.

As well, shoot from the same position , if possible.  Ensure you don't rest the barrel itself against anything , as disturbing the harmonic of the barrel any more than you already have (reprofiling) will disperse your shots more.

Take your time, break your shots clean, focus on your front sight post, and follow through.

Blazing thru a magazine is fine for a function check of the mag, but gains little beyond knowing the extreme spread of your group in rapid fire.

To determine the inherrent accuracy of your particular rifle, start with one load, and go thru all the above steps, beginning with the single loading.

It's more challenging with iron sights, but the test of the marksman is his skill with whatever equipment is laid before him.  The basics of sight alignment , position, trigger control , and breathing - apply to whatever weapon you pick up.

Look for Jim Owens book, "Sight Alignment, Trigger Control , and the "Big Lie" ", JAFEICA Publishing, Milwaukee, WI - for whatever details I glossed over , here. 

Some other reading you can look into is Precision Shooting Magazine , or write a note to Peter Kokalis, at Shotgun News, or at SOF Magazine, where he was the technical editor for evaluating firearms.  Small Arms Review also does articles on things we enjoy, maybe take a look at their website.

Shooting at 20 degrees isn't so bad, it's just harder to focus on what you are doing.  Try to slow down a bit, break the shot with more care.

Have you done an Appleseed Shoot with your rifle yet?  They typically work at 100 yards, so it's just challenging enough , yet not so bad it's discouraging.  They also have experienced shooters to coach you, and spot what may be an unnoticed habit in what you are doing.  If it's not a loose pin in the sights , it might just be a loose nut behind the buttplate.

Briefly, a recap:

*One type of ammo ( load or bullet weight)

*Single load thru the ejection port

*Stay in position, consistently

*Breathing

*Natural point of aim

*Sight alignment

*Focus on front sight ( yes the target IS blurry- it's OK)

*Pressss the trigger smoothly

*Follow through, reacquire sights

*Repeat

Measure group size, see how it works out for you. 

Curious: you shot bolt actions before this?  What distance are you shooting at , presently?  Does the rifle group better warm , or hot? ( barrel may be "walking" )  What rate of twist is your barrel?

[SWshooter]

I'm used to shooting bolt guns off a benchrest. The longest range I have available is 300 yds. I shot the gun yesterday and noticed it is very position sensitive off the bags. Any change in pressure also. I need a better rest for the butt stock, it sits higher than my bolt guns and I think I'm going to have to buy an adjustable rest for the rear bag. I was trying to stack several bags on top of each other but that is not stable enough. I'm going to the range tomorrow. I loaded 150 gr Corlokt, 165 gr SST, and 190 gr BTSP with starting loads of H-4895. I'll see how they do. I just received an ARFX buttstock and put that on today, I ordered a Millett 4-16x52 scope and a new grip. The only thing I need now is a good trigger. When I say fire and acquire I mean with precision. I take the time to check position on the bags and reset everything where it should be. I just don't wait for the barrel to cool between shots. I fired a couple groups without the rear bag, holding the rifle tight to my shoulder with left hand on the forearm and back of my hand on a bag and got some better groups with it. I've been reviewing Warren Pages book " The Accurate Rifle" and brushing up on my bench technique. I've been playing with the group size calculator and I'm waiting for Ralph Wilson to send me a registration number, but he's on a mission trip somewhere and I'm going to have to wait for him to get home before I get it. Weather is getting much nicer and the snow is off the range now so things should progress much faster now. I have a 700 Rem in 222 that I can consistently shoot sub 1/2" groups with so I think I'm up to it, I'm just not used to these hard kicking 308 type AR's yet.

[cevgunner]

Hmmm... OK, mea culpa.  Didn't know you were a benchrest shooter.  You obviously have the basics down pat. 

My daughter's lawyer shoots an AR10 off the bench with an adjustable front rest with a bunny ear bag to support the foreend.  I think it's a Caldwell rest. 

He goes to So. Dakota for groundhogs , at 200 yards he uses 3/4" orange pasters for his aiming point.

He has a small bag he puts under the toe of the butt, and uses his left hand to pinch the buttstock and push it into his shoulder.  His rifle is generally set up as you describe yours, except he had Mike Bykowski build his trigger, as no one had a trigger he liked. Mike is a local High Power match rifle builder deity, very high end stuff.

As far as your trigger, you might look into a Timney drop in unit. 

As to technique off bags, I'd offer that you rest the foreend on bags, use your left hand to control placing the stock into the pocket of your shoulder, keep it tight.  Your hand under the foreend may be adding a variable to your groups. 

If you are going from a .222 to .308, I can see where you'd notice the recoil.  Stay on top the rest, butt tight to your shoulder, rest close to the receiver, bag under the foreend should be smooth.

Avoid bipods.  Look into a freefloat fore end kit, let the barrel vibrate on it's own.  Leave that for later, just work the rifle as you have it now.

Start with your 150gr load, shoot for groups, adjust your gear and position, keep shooting the one 150gr load until you have debugged the rest of your technique.  Figure out which variable gives you the change in group size before changing the load.

I shoot off a bench when I chronograph ammo, and shoot from position , so my concept of groups may differ from yours.

My rifles tend to be either .22LR, or military calibers - recoil isn't something I notice, beyond what it does to my position and alignment.  It's just sort of there, roll with it.  Different from bench shooting.

HTH,

cevgunner

[SWshooter]

The recoil itself doesn't bother me, it's the gun moving off target more than I'm used to. I shoot a 350 Rem Mag and get better groups. It's just frustrating. You get 2,3,4 shots cutting one hole and then the next one is two inches out. I'm beginning to suspect the scope isn't holding zero. I'm not going to shoot again until the new Millett scope is mounted. I can't see wasting ammo. Scope should be here Monday and if the weather cooperates should hit the range on Tuesday.