problems with AR-15 accuracy

[BRIGUY]

Did you swap the uppers yourself or did you have someone else do it? There , really is no reason to take the FSB off a barrel unless you change the barrel nut or if you decide to go with a different sight on the existing barrel or if you go with a different handguard setup. So I am wondering why the taper pins are missing . There is essentially nothing holding your fsb on your barrel and I am surprised the pressure of the delta ring isnt pushing the hanguards and causing movement in your front sight . Is there a hidden set screw under the sling swivel? Oh yeah , this probably has nothing to do with accuracy

 

[atilla]

i swapped the uppers myself, i didn't mess with anything on the FSB aside from the gas tube roll pin.

there may be a set screw underneath where the bayonet lug was ground off. i will have to take another look at the rifle. i am leaning more towards just buying a new FSB if i buy a new barrel.

 

[BRIGUY]

I think I would definately either put the taper pins back in or tap the holes for set screws like I did here:

Not saying it will help out your accuracy but you never know, I would definately try that first before I spent $250 on a new barrel . Not sure if this would be true or not , maybe someone else can chime in , but I am guessing that if your gas block has any play at all you could be getting inconsistant pressure down the pipe with every sliight movement of the block, which could cause difference in muzzle velocity.I realize the gas system is to cycle the bolt , so in order for it to do that task, it must steal back pressure from the barrel , so if that pressure is inconsistant each time I would think it could affect the accuracy . Like I said if someone else wants to chime in , this is just a guess. Also a loose fsb could be the reason why your handguards are a little wobbly.

i swapped the uppers myself, i didn't mess with anything on the FSB aside from the gas tube roll pin.

there may be a set screw underneath where the bayonet lug was ground off. i will have to take another look at the rifle. i am leaning more towards just buying a new FSB if i buy a new barrel.

 

[atilla]

ok, there is a set screw where the bayonet lug would be on a rifle more evil than mine. of four spots (either side, under the lug spot, and under the sling swivel) there's only this one set screw.

if getting some taper pins would help me out with this that would be awesome. doubtful but awesome--if anyone who knows more than i do about the gas system on the AR could chime in that would be awesome.

 

[atilla]

thanks to pdm i've got a rockin' M4-gery going now with a brand spanking new heavy barrel. there were a few snags getting everything squared away with the upper but that was all operator error.

the upper slipped in the vise and i took a chunk out of my shell deflector so i've got a nice silver spot on there right now. the hard part is over--the barrel is installed (with the lug ground off!), the rifle is lubricated with CLP, and it's ready to go for this weekend.

i will post an update after i can get to the range!

edit: with the weather so nice today i just had to go to the range right after work. i grabbed my rifle and two mags as soon as i got home and i was very pleased. i still need to fine tune the aimpoint as it's still a little low but i shot a quarter sized group standing and a nickle sized group proned out at 25 yards. once i adjust the zero i will be golden and maybe i'll even hit up the 100 yard range.

thanks to everyone for your help in this thread and who knows... maybe i will drop the barrel off at a shop and see if they can salvage it.

 

[atilla]

the difference a trigger makes

this is the target with my lower and my upper:

this is the target with my upper and tele_mark's lower:

when i handed him the rifle to give it a try he said the trigger was so bad that he thought the safety was on. sure enough the trigger was way lighter on his lower than on mine--in fact his trigger spring had one fewer coil on each side!

after getting settled back in at the bench and getting a proper sight picture i walked the rounds down on the target with those first four shots and then the next four were exactly where i wanted them to be.

the upper is solid and now i just need to mess with the trigger a little bit. would i be able to lighten it up myself or would it be best to:

1. buy a drop-in trigger.
or 2. just get a lighter spring somewhere?

 

[jrbtzx12r]

Glad to see it's finally hitting the target.

A drop in is always sweet, but expensive.

There's a guide out on the web called 15 minute trigger job, you could try that. Google 15_Minute_AR_Trigger_Job. If it fails then go to option 2 if you want to go the inexpensive way.

 

[atilla]

thanks, i'll check that out. i can't imagine it is that difficult but that was also what i said when i first bought the rifle!

i checked my 9mm AR and the trigger wasn't as hard, too. this one is just really stiff.

 

[BRIGUY]

Glad to hear everything works , sorry about your upper , I am guessing you didnt use a action block to hold the upper in the vise.

 

[atilla]

yeah... i'm thinking that if i ever want to do work on uppers in the future that it would be a good idea to pick one up. you can only get so far with pine and an old bath towel.

is there anything out there i could use to touch up the bare metal?

had the PC off for a while thanks to these thunderstorms (we got hail!) but i'm going to check out the trigger job videos right now.

edit: i ended up getting a timney 3# trigger which i installed and just took out to the range to test. i was doing good after dialing in the aimpoint just a little bit further. at 50 yards i was able to land three rounds through an area about the size of a nickle from a prone unsupported position. that was mostly luck but now i know the rifle is shooting good. for a 16" barrel i think that it's about as good as it's going to get.