Building first AR, have questions

[Grindstone]

Red,

Good choice getting the pre-assembled front sight and barrel, drilling and reaming those holes is not for beginners. It looks like you chose correctly on the barrel as it comes with an F marked front sight base that is compatible with flat top uppers. The difference is the sights are mounted slightly higher with a flat top and the post needs to be a little taller.

I think the DPMS National Match carry handle is expensive only because they put a high price on the 1/4 MOA adjustments. It is equally expensive to buy their 1/4 MOA adjustment pieces for installation on an A2 upper. I think 1/2 MOA is fine enough. Buy something that is from a reputable manufacturer, and don't get bent out of shape about 1/4 MOA. Any cheap carry handle sight can be upgraded with better peeps if you want. You may notice the sight has some side to side wiggle; this is OK because there is a spring that always keeps it to one side. All the back-up sights I have looked at also wiggle, but shot to shot it may be on a different side.

Another common compatibility issue is the M4 feed ramps, but I think you got that right as well. The cuts for M4 ramps extend into the upper receiver and must approximately match. M4 ramps on receiver but not on barrel extension is a no-go.

Have you looked at a parts diagram and checked that you have all the little items covered? You will probably also need a delta ring assembly to attach your handguards. Also ejection port cover, charging handle, front sight post detent and spring, sight adjusting tool, gas tube, flash hider, crush washer, buffer...

Also consider the grease you will use when installing the barrel. If you are a mil-spec guy, you will probably need to order the stuff. I got a manageable quantity (enough to build 50 ARs instead of 5,000) from Umbrella Corporation. Be cautious about using standard anti-seize grease because it contains graphite which can cause corrosion in aluminum.

55 grain bullets will make it to the target at 400 meters and you can probably keep them inside of 4 MOA even in a wind. Match shooters will make up special loads with 80 or 90 grain bullets that are so long they must be single loaded. All this is get a little advantage in the wind from the higher ballistic coefficient (they are also shooting for a 2 MOA 10 ring at 600 yards). If you hand load or buy specialty ammunition, 77 grains is said to be the heaviest you can go and still feed from the magazine.

[Red Alder Ranch]

Finally got all the rest of the parts in the mail today, and put it all together this evening. Wow. Sure didn't take that much time at all!

Yes, this has the feed ramps in barrel and receiver. I used the Del-ton carry handle sight, which they said matched the front sight tower that it came with.

I do need to buy another sight adjustment tool for the front sight; the one I have for my 10/22 Tech sights does not work.

I had some lubromoly cv joint grease in the toolbox, and put a very light coat of that on the barrel nut threads.

Just under $700, including two mags, sales tax and shipping on everything.

Anything special I need to know about breaking in a new barrel?

[slim]

Nice rig!

I do need to buy another sight adjustment tool for the front sight;

Use a bullet. The AR was designed with sights that could be adjusted by using the point of a bullet. Always with you in the field!

Anything special I need to know about breaking in a new barrel?

No.

If you read the internet you'll hear mumbo jumbo about shootin a round, cleaning it, shooting another cleaning it, pushing up, up, down, down, left, right, left, right, b, a, b, a, select, start but the truth is, advances in modern metallurgy have rendered all that bull unnecessary. Just shoot it!

[Two Wolves]

Good job! Thanks for sharing. 

[Red Alder Ranch]

First three shots, kneeling at 25 yards. Still needs a little dialing in, but that was good enough to hike out to the back and plink some cans and check basic functions.

I did run into a glitch that I'm not sure I've solved. Shots 19 and 20 both ejected the case and chambered the next round, but then it acted like the safety was on, and wouldn't fire, even though the selector was still set to "fire". Next mag started doing the same thing, and in between each shot, I would flip it to safe, and then back to fire, and when I flipped it to safe, you could hear and feel the trigger reset and then it would function fine. After about five of those, then it started resetting the trigger like it was supposed to, and worked fine for the rest of that magazine.

I need to get more ammo now, before I can check and see if it is really solved. What would cause that?

[Red Alder Ranch]

OK, picked up some more ammo (man this thing is sure easier shopping for than the 10/22s!) and if it doesn't rain too hard I'll get out to try again this weekend.

Regarding that malfunction, (rifle goes on safe in between shots without the safety selector switch moving) what should I be looking for?

thanks!

[jmdavis]

check your cross pins (for the tigger). I had this happen with a build and the problem was the the pins were moving under recoil. My solution was some lime green duct tape on each side of the receiver. Many thousand rounds later, no additional problems. When the problem is bad the pin may shift so much that you cannot fire the rifle at all. I ate 4 shots on a KD AQT because of this with a new build one day.

[slim]

Sorry we missed the updates on this and glad to see you got to shoot it!

The malf sounds to me like your disconnector isn't functioning correctly. Typically the cheap LPKs (not to disparage, just saying) have something missing or tolerances that allow something to slip or walk-off.

I had one (don't even remember the brand name - I think it was so cheap it didn't have a name!) where the little spring inside the hammer was missing and it caused everything in there to hit all caddy-whompus and I'd get failures. I swapped out with an anti-walk pin and that fixed the issue by eliminating the lateral movement. (I see jmdavis posted the same issue/fix. That's my number one suspicion as well.)

Yours may be caused by something similar or maybe the little spring that's supposed to push up on the disconnector popped out. Pull your upper off and then go step by step through a YouTube video on the fire control group. You should be able to see if something is out of place.

[Red Alder Ranch]

I'll check those out when I get out shooting tomorrow.

Another newbie question:

I'm getting ready to order some ammo for a KD shoot, and I'm looking at 55 and 62 grain, for not much difference in price. Looking at PRVI and Federal American Eagle in the 55 grain, and Fiocchi in the 62 grain.

Any reason to prefer one or the other for a KD shoot? Barrel is a 1:9 twist. How many rounds do I need for a KD event?

thanks!

[slim]

In a 1:9 you probably won't notice much difference between the two. Get what's cheapest. If you're not a reloader, buy even cheaper Wolf steel cased stuff.

For most KD events 250rds or so is enough. You may want to contact your Shoot Boss or State Coordinator to get an exact count.

[AFTERMATH]

Trigger spring.   

[Red Alder Ranch]

I got out this afternoon and ran another 20 rounds through it, and it was trouble free this time.

[slim]

Sometimes ARs are just finicky. Shoot the crap out of it and you'll get all the bugs worked out.