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View Full Version : AR chrome lined barrels and accuacy


Metal god
September 3, 2012, 10:15 PM
Hey guys just got back from the range . I was checking the accuracy of my recent AR build .It's a PSA lower with a DTI upper .16" Heavy barrel 1-7 chrome lined .

Here is a pic - I changed out the red dot for a tasco world class 3-9x40 scope for this accurcy test . I had the scope on my 308 ruger American and it did very well .

http://img35.imageshack.us/img35/4607/phone2004.jpg

As you can see I've done a few things to make it a better shooter . Free float Todd Jerret hand guard , Magpul CTR stock. It has the stock trigger and barrel on it . I did do some work on the trigger and got the pull down to 4 pounds .

My question is, Does a chrome lined barrel get better with age ? I was barely shooting 1 MOA at 100 yards with Fed gold metal match . and 2 MOA with everything else ,PMC ,UMC . Lake city XM193 and some Privi match .

I'd shoot a nice-ish group with the gold metal Match then shoot a few of the others types of ammo .All the others would be around 2" groups . I then would switch back to the gold metal match and the group would shrink back up to about 1MOA . I say about cus there were some at 7/8" and one at 1 1/8" most around 1"

By putting a thousand plus round down range. Will that smooth out the lining ? Or is what I got ,what I get .

It may do better with a better trigger there is a bit of travel .

Am I asking to much out of a DTI barrel ? Should I just take the scope off and put a red dot back on it ? I sure like the look of it with the red dot

Creeper
September 3, 2012, 10:27 PM
5.56 NATO chamber? They have a long leade, so the bullet jump may be contributing to your (lack of) accuracy. At least it likes one load... but in theory, it should shoot better than 1" when you get the right load in it.

Or... it might just be the DTI barrel. :p

C

Metal god
September 3, 2012, 10:47 PM
Its a 5.56 . I was thinking well after the fact the only heavy bullet I was shooting was the Gold Metal Match they were 77 grans .All the rest were 55 grans. Can a bullet be over stablized and or is a 55 grain bullet to light for a 1-7 twist ? Could the lighter bullets be an issue ?

Creeper
September 3, 2012, 11:59 PM
You are correct. 1:7 is not the optimum twist for a 55 grain... and with a average quality bullet, yes, the over stabilization can produce inaccuracy. Try a match grade 55 or heavier bullet load and see what you get.

C

10-96
September 4, 2012, 04:30 AM
It has the stock trigger and barrel on it . I did do some work on the trigger and got the pull down to 4 pounds . I have no hard concrete evidence to back it up, but I really would like to recommend you spring for a new trigger kit/system. There's just too much info out there that says AR triggers don't lend well to much tinkering- there's bound to be something to at least some of it. I do know the depth of the hardening is really thin, and once that's gone, doubles and such begin. This all makes sense to me with my very limited knowledge of metalurgy. I don't know what you did to lighten it, but if you stoned, or removed metal in any way- please think about a new trigger before you start really putting a lot of rounds down range.

Now, if all you did was apply little dabs of grease and swap springs- then please disregard my humble little post.

plouffedaddy
September 4, 2012, 06:48 AM
Are you running that MBUS front sight on a railed gas block?

Fishbed77
September 4, 2012, 09:42 AM
I was barely shooting 1 MOA at 100 yards with Fed gold metal match . and 2 MOA with everything else ,PMC ,UMC . Lake city XM193 and some Privi match

Those groups sound pretty respectable for a 16" chrome-lined 1:7 twist barrel.

Technosavant
September 4, 2012, 10:18 AM
A few things to keep in mind:

1) Some barrel makers tend to have more accurate barrels than others. I'm assuming that by DTI you mean Del-Ton, and they're definitely toward the budget end of the spectrum. Definitely serviceable, but not anywhere near the same league as you'd get with a Noveske barrel or LaRue Stealth upper. Sorry, but this is one of those areas where more money can mean a better product. The cheaper stuff may work just fine for you, but it is not truly just as good as the higher end components when you start getting demanding.

2) I wonder if you have a clear purpose in mind for the rifle. I'd advise to not throw together an AR based on what looks cool (be it optic, handguard, attachments, etc.), but figure out what you actually want to DO with the thing, then go from there. If it's a defensive rifle for shorter ranges then there's no point to the scope or the bipod; the faster target acquisition of a red dot is worth the trade off in accuracy and the bipod is just useless weight. If you want a longer range rifle that has more precision, then a scope is worthwhile, but that stock may not be the best option (the collapsible Magpuls, while good kit, can give some users issues trying to get a consistent cheek weld).

3) Chrome lined barrels do give up a little bit in accuracy to unchromed bores. The chroming process doesn't produce as regular a bore as one without. This is why you will usually see folks with national match type ARs using stainless steel barrels. Nitriding is also gaining some favor. However, for most shooters, the corrosion protection and cleaning benefits of a chromed bore is worth the slight loss in accuracy.

Metal god
September 4, 2012, 11:30 AM
OK first things first . I did do some stoning and bent the hammer spring a little . I have not heard that the hardening on a FCG was so shallow . How do you harden just .002 of a piece of steel and not the rest of it when it is so small . I did what I consider very little stone work maybe 10 to 15 light circles . just enough to feel the burs go away . I think the real lightness comes from the hammer spring work and I took a roto zip with a small buffing wheel and buffed the hammer and triigger so they were smooth as glass .

Yes the front sight is on the gas block . I do know it's not recomeneded . Im testing it to see if it starts to melt or looses zero . I want to see what is going to happen . Im not a high rate of fire guy so I think it's going to be fine . we will see

As for purpose I started out with only one purpose in mind for this gun . I call her little EVIL and she had to look cool and EVIL that was it . .It works great in that configeration I never intended it to have a scope on it , just a red-dot . I have others that are more purpose built . I put a scope on it to see how accurate it was and see if I wanted to change its purpose . Thats the reason for the thread .

The next build is going to be a 6.8 mm . I'm planning on going with a match grade barrel and trigger , fixed stock , scope . Already have the stripped lower just begging to get in the game

Bartholomew Roberts
September 4, 2012, 12:57 PM
My question is, Does a chrome lined barrel get better with age ? I was barely shooting 1 MOA at 100 yards with Fed gold metal match . and 2 MOA with everything else ,PMC ,UMC . Lake city XM193 and some Privi match .


Actually, chrome lined barrels will settle in and shoot better after 100-300 rounds supposedly; but you won't see a dramatic jump in accuracy after that. It may tighten up 0.10-0.25" at 100yds. However, the accuracy you are getting is much better than average (assuming 5 or more round groups) already. I would be real happy to get that out of a chrome-lined barrel.

Marquezj16
September 4, 2012, 01:40 PM
I was barely shooting 1 MOA at 100 yards with Fed gold metal match . and 2 MOA with everything else ,PMC ,UMC . Lake city XM193 and some Privi match .

Nice shooting. That's not bad considering you don't have a match barrel.

Also, most of the time match ammo will give you better groups than standard ammo. I find that handloads gives the best results through trial and error.

Technosavant
September 4, 2012, 02:11 PM
As for purpose I started out with only one purpose in mind for this gun . I call her little EVIL and she had to look cool and EVIL that was it .

Very well, carry on. :D

Let us know how long it takes to melt that MBUS up front... I don't know I've seen anybody try testing that out.

Noreaster
September 4, 2012, 07:46 PM
My current S&W AR15 is not chrome lined and I didn't find the accuracy any better then my chrome lined Bushmaster. It does shoot 5.56mm a little better then .223, but just barely. I think the original factor specs for the 20 inch M16A2 was 3 inch groups @ 100 meters.

moxie
September 5, 2012, 08:41 AM
Well, good shooting I'd say with what looks like mostly 55FMJBT off the shelf.

You noted 1 MOA with the 77 gr. target stuff. Try other heavy target rounds and see. Practice with the one that works best.

Then again, start hand loading and you're in there.

madcratebuilder
September 5, 2012, 09:31 AM
OK first things first . I did do some stoning and bent the hammer spring a little . I have not heard that the hardening on a FCG was so shallow . How do you harden just .002 of a piece of steel and not the rest of it when it is so small . I did what I consider very little stone work maybe 10 to 15 light circles . just enough to feel the burs go away . I think the real lightness comes from the hammer spring work and I took a roto zip with a small buffing wheel and buffed the hammer and triigger so they were smooth as glass .

Typical surface hardness penetrates .008-.012. A experienced hand can feel when to stone goes through the hardened part of the FCG. The drag increases as it is cutting more metal.

A typical fluff&buff to the FCG well not take off more than .001. The FCG springs are heat treated after the are bent in to shape. Bending the legs may cause a weak area that can fail. Keep a spare or even better get some reduced power springs and play with different weights.

I don't see anything wrong with the groups you are getting with that barrel, good shooting in my book.

Fishbed77
September 5, 2012, 09:54 AM
Let us know how long it takes to melt that MBUS up front... I don't know I've seen anybody try testing that out.

My guess is that the melting won't be dramatic (i.e. it won't turn to liquid and pour off the gun), but that the heat will deform the front BUIS slightly and cause it to continually lose zero as the plastic expands and contracts due to the heat and expansion/contraction of dissimilar materials.