bad barrel or other gremlins?...

[Tyson C.]

problem: shots are sporadic. not holding a "zero" @ 100yrds

story: buddy gave me his newly acquired AR15 to sight in that he got from a gun show. Plum crazy lower, ??? upper and Bushmaster 16" fluted barrel, 1-9 twist. everything is used but he was told that everything was in great shape; not shot a lot etc... he mounted a new scope "Center Point" on the rifle and it was handed to me.

1st trial run. shooting @100yrd, off my bench, with led sled. zeroing for 100yrd. factory ammo 55grain:

1st shot 6" high of bulls-eye
adjusted
2nd shot 0 but 1/2" left of bulls-eye
adjusted
3rd shot touched 2nd shot
4th shot 3" right? of bulls-eye
5th shot 2" high and 3" right of bulls-eye
cleaned barrel
6th shot 3" LEFT 1/2" high of bulls-eye
check tightness of ALL scope mounts, rings etc... everything was solid
7th shot 1 1/2" high from bulls-eye
8th shot 1" low to the left of bulls-eye
9th shot 1 1/2" low to the right of bulls-eye
10th shot 1/2" lower than shot #9
cleaned barrel
adjusted
10th shot 1" high and 1" right of bulls-eye
11th shot 1/2" lower than #10 of bulls-eye
12th shot 2" right 1/2" high of bulls-eye

thinking it was the scope. I cleaned the gun and checked the rings etc..and put on my Bushnell which I know is good. once I got it to hit paper:

1st shot 3" high 1/2" right of bulls-eye
2nd shot 2" high 1/2" right of bulls-eye
adjusted
3rd shot 1/4" left of bulls-eye
4th shot 1/2" left of bulls-eye
5th shot 1" left of bulls-eye
thinking all is good I clean barrel
6th shot 1" low and 3" RIGHT of bulls-eye!?
7th shot 1.5" low 2" right of bulls-eye
adjusted
8th shot 1" below bulls-eye
9th shot 2" right of bulls-eye?
10th shot 1" low and 1/2" right.
cleaned gun
11th and 12th shot, I aimed at bulls-eye target in upper right hand corner and was 1/2" left, then 1/2" right...figured I was good but was still skeptical

told him what was going on and we both assumed the cheaper scope could be the problem but I was still a little skeptical. he said fine no problem and was going to use a Nikon in the future anyways, so he shows up today with a new in box Nikon pro staff BDC 4-12x44

same shooting setup as before.

1st shot 3" high of bulls-eye
adjusted
2nd shot 1.5" left of bulls-eye
3rd shot touched 2nd shot
adjusted
4th shot 3" low and 4" RIGHT of bulls-eye?
5th shot 3" high and 2" left of bulls-eye?
checked mounts, screws, etc... and all was tight.
6th shot 3" low of bulls-eye?

basically from here on out we fired 5 more rounds and no adjustments were made and the shots were all over the place. basically a 4"-6" group.

I will admit that with my Bushnell the group was a little tighter but still I think it was about to become sporadic, I think I just quit while I was in the lead with it.

so he and I are assuming the barrel and if it was wore out from previous owner...bump stock shooter and or a lot of shots fired, bent??. I have helped sight in few rifles in my time, I'm no great sniper or great gun smith but I know enough on what I do. so am I correct in leaning towards the barrel and or maybe shooting a hotter load other than a 55grain.. maybe a 62 or 65grain?

thanks for your time and sorry for the long read...

 

[Glocktogo]

He's not exactly working with quality equipment for starters. My first guess would be to check the barrel nut torque. Then check the bore and crown. Check the chamber with a chamber gauge? If that doesn't find the problem, sell that hot mess and get a decent AR.

 

[Tyson C.]

He's not exactly working with quality equipment for starters. My first guess would be to check the barrel nut torque. Then check the bore and crown. Check the chamber with a chamber gauge? If that doesn't find the problem, sell that hot mess and get a decent AR.

sounds like a good starting point. I'm a little new to the AR line. i got a guy that's does gun work so he could help me out these specs and measurements. just don't want to over look something small i might not be familiar with.

what is the weakest part you see in his build up, in making the statement; "he's not exactly working with fine quality equipment for starters"....is the lower a bad lower?, or barrel, etc... he's not sure what the upper is but trying to find out. I'm just asking to learn and to inform him in future dealings. (hopefully it won't start to much of pissing contest in here..."X" brand is better than "XX" brand..)

thanks, for the help.

 

[Hog Shooter]

I would try a couple of different loads, factory or reloads, different bullet weights and what have you. I have shot a few different ARs and most will shoot inside a inch at one hundred yards no matter the brand. my 16" skinny barreled DPMS will shoot five shots you could cover with a dime with my reloads, but with 62gr wolf steel case it might shoot inside three inches at a hundred yards. I would measure a fired case and check the crown on the gun/ look at the rifling. your friend may have inherited a gun that was someones problem child.

 

[Glocktogo]

sounds like a good starting point. I'm a little new to the AR line. i got a guy that's does gun work so he could help me out these specs and measurements. just don't want to over look something small i might not be familiar with.

what is the weakest part you see in his build up, in making the statement; "he's not exactly working with fine quality equipment for starters"....is the lower a bad lower?, or barrel, etc... he's not sure what the upper is but trying to find out. I'm just asking to learn and to inform him in future dealings. (hopefully it won't start to much of pissing contest in here..."X" brand is better than "XX" brand..)

thanks, for the help.

And I don't want to trash everyone's gear either. But, Bushy isn't known for the best barrels. That means steel quality AND specs. They're usually overgassed and may or may not have 5.56 chambers, along with several other issues. QC just isn't Bushy's strong suit. On the low end of AR's, I'd rather have a DPMS or Stag than a Bushy. The Plum Crazy lower is a very inexpensive lower. Something like that can be OK for a .22lr build, but it has some critical weak spots for a ready to go AR. I recommend staying away from polymer lowers altogether. If the upper is in spec, well, an upper is an upper, so long as it's forged 7075-T6 or billet, it's probably OK. Check just above the forward assist and tell us what symbol it has on it. There are several different types. Center Point scopes are low end as well. In optics, you get what you pay for.

Hopefully he got a REALLY good deal on this mutt AR.

 

[NikatKimber]

I would think the lower quality would be another matter. It *shouldn't* affect accuracy.

 

[Spata]

Scope mount and rings properly tightened?

 

[Glocktogo]

I would think the lower quality would be another matter. It *shouldn't* affect accuracy.

It *shouldn't*, but QC is important. What if the crown is bad? Build quality would be my first guess after optic and mounting though. It's far more likely that someone using bottom tier components might not put it together properly.

Scope mount and rings properly tightened?

I assumed that when he tried his Bushnell on it, he checked that box.

 

[MoBoost]

Loose barrel nut or bad ammo - kinda hard to make 223 shoot 6" at 100 yards.

 

[dennishoddy]

I've got a Cheap M4 that will hold a sub 1" group.

I've got a high end Varmint AR barrel in .243 WSSM, and it wouldn't hold a 10" group at 100 yds when delivered.

Talked to the builder, etc, and nothing was resolved.

I had an idea, so I tested the twist, and sure as hell, the .55 grain I was targeted for wouldn't work. I loaded some 100 grain and it became a tack driver.

I suspect you don't have the 1-9 you suspect? Is it engraved on the barrel?