Accuracy change in new AR-15 barrel [for the better].

[Orion8472]

New AR-15, M4 profile barrel, chrome lined, 16". Unshot until:

Took it to the outside range Saturday, . . . got a pretty wide grouping at 50 yards. I was using some sort of bulk type ammo. Shot a magazine [30 rounds] worth. Groups looked to be around 4" [again, at 50 yards], using a 4x scope.

Wednesday, I took it to an indoor range with an excellent bench setup. Pulled out some Tulammo [62gr HP] and got the following for 10 shot group [aiming at the center, first two at the bottom to see where it was hitting, "zeroing" closer, then the grouping]:





Now, last night, I took it back to the indoor range and shot the rest of the box, and for some reason, it grouped a lot better. . . . for steel case bulk stuff.

I also took it out to 100 yards and shot some 60gr. TAP and here's the results [5 shot group]:



Maybe I had it more solidly on the bench. Now, I've only had 55 rounds through this rifle thus far. I'm planning on putting the steel case stuff away and using brass from this point out. Anyway, I'm pleased with these groups. Oh, the 100 yard group POA was the mid point of the target between the two smaller lower targets.

 

[rcmodel]

Nothing strange about that.

Quality ammo using bullets with the jacket opening in the nose will always group better then FMJ military type ammo.

Here is a couple of groups from my old Colt carbine.

Identical handloads, except bad one is Win FMJ-BT and the good one is Nosler Ballistic-Tips.



rc

 

[Orion8472]

What's odd about the situation in the OP is that one night, 10 shots from the Tula box gave the groupings in the first image, and the next night, the second half of the Tula box gave the groupings in the second picture. Same bench. I wonder if there was some sort of "barrel burr", from the factory, that was causing the wider grouping, but is now gone, thus better groupings?

As a side note, it is an excellent example on how a GOOD loading [the 60gr TAP] can be quite a bit tighter out at 100 yards than cheap bulk stuff is at 50 yards.

 

[adelbridge]

too many variables. If he was shooting a 300 win mag to warm up and switched to 5.56 and then went back a day later with one gun......

 

[Ramone]

Usually, IMX somewhere between 100 and 300 rounds, the groups will suddenly tighten up- it happening as early as you seem to be saying in much quicker than my experience, but I have seen groups go sudden half the size of previous groups (with the same ammo, same range, same rifleman, same day).

Here's some ammo comparisons:







Same rifle (m4gery with cheepo 4x scope) same shooter, same everything, Ammo being XM855, Black Hills Reman 69gr Sierra Match King, and Handloads, respectively.

 

[Orion8472]

What causes that to happen? Is it "burrs" or something that has to be "shot out"?

Anyway, I was going to sell it, based on its apparent poor accuracy, . . . but now that it seems to be doing much better now, I'm definitely keeping it. Especially with the nearly 1" group at 100 yards with the 60gr. TAP.

 

[788Ham]

I don't believe its "burrs" being shot out of it, the barrels getting broken in. By the time you get 300 to 400 rds through it, thats when you'll see the difference! Good luck!

 

[TonyAngel]

I don't know guys. I've never heard of a chrome lined barrel needing to be broken in. Breaking in a barrel serves to smooth out machine marks and rough spots left from the manufacturing process. Once a barrel is chrome lined, that's it. It should be slick as butter and the only way that any rough spots are going to get ironed out is if the chrome lining comes off. If that happens, the barrel is defective.

If there are any slivers or some such thing around the gas port, that gets blown out with the first couple of rounds.

 

[Orion8472]

Tony, what you're saying may very well be true, but how would you account for the much better grouping on day 2? It could be debated that my rifle was better secured on the bench on day 2, but I was still shooting the same spot.

 

[Ramone]

If I can offer my opinion without getting into a big debate...

I *do* think that even a chrome line barrel smooths out a bit in the first few 100 rounds- but I think most of the difference happens in the throat of the chamber. The first few hundred rounds (I believe) smooth out the lede, and make the rifle more accurate.

this is simply my opinion, and I welcome anyone who has a better explanation.

in this case, it make also reflect the trigger smoothing out with use, or possibly the shooter 'breaking in' to the rifle.

one recent day at the range, using a reliable sub MOA rifle, with Consistent MOA capable Ammo, I could not get my groups below about 1.8" at 100 yards. this over 10 10 round targets.

Couldn't figure out What the Heck I was doing wrong- I went through all my basics, switched positions, took a break, double checked my dope, tried a different lot of the same ammo...

I just sucked that day.

It happens.

 

[jim243]

The rifle is not broken in. Chrome lining is not a solve all. The plating process produces high and low spots in the barrel at different points and needs to be smoothed out. The fire control group will have machining burrs on it and will need to be fired to bump off any spurs. The bolt carrier needs to be worked to smooth out it's function and work in it's fit to the upper receiver. The gas port needs to crud up a little to seal it to the barrel and stop any leaks. The Delta ring will need to heat up with firing to seal the barrel to the upper. The feed ranps will need to be smoothed out if there are any burrs on them. ETC............

If the rifle has less than 200 rounds through it, it is not ready for prime time. These are not hand fitted 1911's but production guns.

OP, you are doing fine, you will notice an improvement as time goes on, just get your trigger control with pratice.

Jim

 

[M1key]

In my experience, brand new chrome-lined AR barrels generally show an increase in accuracy after 200 rounds or so, shooting the same ammo.

M

 

[Orion8472]

Will do, Jim. Thanks for the input.

 

[chaser_2332]

chrome barrels, tula ammo, steel case, non of those go along with accuracy. however you last groups seam to be in line. i would just chalk the first day up to having a off day with a new rifle and not put too much thought into it.

 

[TonyAngel]

Tony, what you're saying may very well be true, but how would you account for the much better grouping on day 2? It could be debated that my rifle was better secured on the bench on day 2, but I was still shooting the same spot.

Orion, I can't account for it. My guess is that it was due to either a change in the shooter or the setup. I know from shooting benchrest that the slightest change can make a night and day difference.

I also know that they don't call hard chrome "hard" for nothing. It's very hard and brittle. If there was a burr in the barrel that was chromed over and subsequently knocked loose by shooting the rifle, I wouldn't be surprised if the OP discovered flakes of chrome coming out on his cleaning patches. I really doubt that any wearing in that may occur over the course of a few hundred rounds would make that drastic a difference in the accuracy. I could see maybe going from 1.25 MOA to 1 MOA or something like that; but not 3 MOA to 1 MOA.