FN 18” heavy barrel accuracy: A little disappointing

[kevin1]

I have a couple of heavy Ars.
One is with from PSA with a heavy FN 18” barrel chambered in 5.56 with a 1/7 twist, Faxon nitride BCG, Larue 2s trigger and PSA lower
The other is complete upper (with BCG) from Anderson. It has a fluted 24” heavy barrel chambered in 5.56 with a 1/8 twist, Larue 2s trigger and PSA lower as well.



I loaded a bunch of ammo using:
Once fired processed LC brass
CCI 400 primers
Varget
73 ELDM and 69 SMK bullets

Below pic is the average groups I’m getting with these two uppers at 100Y. The average is for four 5 shot groups.
I’ve borescoped both barrels and the FN looks pristine and better than the Anderson barrel.

I’m thinking the accuracy is a little disappointing with the FN barrel.

What are your thoughts and what kind of groups are you typically out of this type of barrel?

[GH41]

Let me guess... The FN barrel is chromed and the Anderson barrel is SS. Not to many people make really good chrome lined barrels. If you throw out the largest group of each load they don't look bad for what got to me.

[SmugPePe]

I expect better groups than those for FN barrel. I believe you need to find bullet and load that FN barrel might like better, even changing primer and powder can cut those groups in half. I would continue use 69gr SMK just change powder and primer and vary their charge make sure you employ all marksman fundamentals. Also from my experience single loading produce better group or next best would be keeping magazine mostly full. Like, if you are shooting from 20 rounder magazine refill that magazine every 5 shot never let it go below 15 round to minimize the difference in upward pressure against BCG between round 1 to round 5 of the group printed. The primer and powder change may produce more consistent pressure curve behind the bullet. Consider how different barrel length are between your uppers you need to find load that suit the very different harmonic of 18" barrel from 24" barrel. You may want to check out reloading recipe of others on here or other forums for 5.56 that made tiny groups with similar barrel. I can almost guarantee you the FN can print submoa, you just need to find it's load.

[Stickman]

Where does it say FN on the barrel? Check the roll marks and let us know what it says.

[ryanm]

I saw that you are chambered in 556, are you reloading for 556 or 223? FN should be more accurate with 77gr vs the 73gr and 69gr rounds. If you are reloading to 223 spec that will screw you over all day in 556 chambered rifles. 77gr SMK reloaded to 556 pressure specs in the FN should be your optimal load and get you where you want to be.

[kevin1]

I saw that you are chambered in 556, are you reloading for 556 or 223? FN should be more accurate with 77gr vs the 73gr and 69gr rounds. If you are reloading to 223 spec that will screw you over all day in 556 chambered rifles. 77gr SMK reloaded to 556 pressure specs in the FN should be your optimal load and get you where you want to be.

Some of my loads are pretty stout. I don't have any pressure so I can increase the powder a little more.

[kevin1]

Where does it say FN on the barrel? Check the roll marks and let us know what it says.

It's this upper:
https://palmettostatearmory.com/psa-...516444448.html

And here's a pic of the roll marks I just took.

[Dino11]

Gets some rounds down that barrel and get some copper fouling in it, I bet the groups will tighten up a bunch.

That barrel will shoot 1 MOA or better with the right cartridge. You just need to find it.

I have an FN barrel that I have about 5000 rounds through, I recently bore cleaned the barrel and removed the copper fouling for the first time. Groups opened up just a little. It took about 60 rounds to get some fouling back in it before the gun was shooting 1 MOA or better again.

[themonk]

How many rounds though the barrel?

[crossgun]

Honestly I dont think your going to get any better and a couple of the loads your at sub MOA. Just to many variables in the gaser and your screwed by the mag in not being able to seat the bullet where it may ideally want to be. I know I have spent a ton of money trying to get a DMR/SPR to shoot like a bolt gun and they just dont. At the end of the day the system was designed for minute of scum bag. Even if you had some true premium barrels spun up I dont believe you would see anything drastically different. I would be very happy with your third loading and drive on.

Just curious as to what your goal here is, simply accuracy or accurate as can get at longer distances? Did you chrono and if so what did the SD look like?