Very nice looking piece, a build to be proud of!

Alright guys!

I got the rifle out to the range today and sighted it in using the method listed in the field manual: using the "L" marked aperture at 25m.
Overall things went pretty smoothly. However, several times I had a failure to feed where the bolt would ride up over the round and jam it against the feed ramp. Two of the times the actually peeled some brass off of the casing and put two lug-shaped marks into the casing. I haven't had this happen before with my other AR so I don't know what that signifies or what can be done about it.
Also, I got some marks on the rear of the ejection port and the side of the receiver from the brass. Kinda bummed because I don't know if those will go away or if they are now marks into the finish, but is that expected behavior for pre-deflector uppers? Ejection was about the 4-o'clock to 5 o'clock position and casings were typically about 10' out in a pretty regular pile.

With those things out of the way, the rifle was nearly spot on at mechanical zero. I moved over one click left and probably need to go over one more based on the 100yd target. Compared to my other AR, and even the A2's I've used at CMP courses, it is incredibly light!
The only thing I am disappointed in is that this 45 year old set of parts can get better groups than my fancy barreled semi-target AR (could be a lack of use on the new barrel, a crappy bipod, and plenty of user error though).


Anyways, ENOUGH TALK. PICTURES!
















The last question I have is what is the best way to zero this? I currently have the 25m zero, but that puts me pretty high at 100 yards, which is where I probably do most of my shooting. Should I leave it and just learn to hold over or is a 100 yard zero a good idea? Where would that put me at other ranges?


Thanks again guys.

I found also that the 25m zero put me too high for my liking at 100m. I am moving to a 50/200 zero on my ARs now.

Would a 100m zero mess me up a lot? Obviously if I have an A2 rear sight it would be a bit easier, but that would be cheating in this forum!

Also looking into the failure to feeds that I had, it seems to be a pretty characteristic bolt-over-round jam. It only happened 4-6 times out of 150 rounds but I am not sure if this is expected behavior for a newly assembled rifle or not. I know my last build did short stroke on occasion for the first hundred rounds or so, but then it stopped. The ejection pattern also changed from slamming off the deflector to going right out at about 3:30. I figured the mating parts had wore-in to each other. However, that build was much fancier, and presumably tighter fitting, components, so I was a bit more accepting of it. Could the same be true of my parts in this build?

ZMan941,  Beautiful build !!!  I'm glad it shoots strait.

As for the Brass hitting the Upper Receiver behind the Ejection Port, I always put a piece of electrical tape or Velcro back there to protect the finish.

Now, as for the Bolt Override of the cartridge, you stated that it only happened like 4 times out of what 150 rds ?  Was it the same mag?  If so maybe the mag spring is weak

and needs replacement.  Just a thought.

Nice looking range you got there!  (Nice rifle, too!)

So a few things you can try for the bolt over the round thing; which indicates the bolt is returning before the next round advances in the mag.  That can be caused by a buffer spring that's too heavy, a magazine spring that's weakened, or the wrong buffer.  I'm not an expert on buffers, so let's have someone who knows that better make a suggestion, but I'll bet it's either your choice in buffer, or your magazine spring is weak.  

So a couple of diagnostic tests

Download the magazine to 10 rounds and see if it happens.  Then add more rounds each time until you get the problem again.  If you get it at over 15 rounds in a 20 round magazine (or 25 in a 30 rounder), then you need to swap out your magazine spring.  

If that doesn't work...
This one will require to you to trim your recoil spring.  This is for diagnostics assuming you don't have a stack of buffers sitting around, you trim coils until the problem goes away.  If you clip a couple of coils and the problem disappears, you know you need to change to a different buffer, and replace the spring you just cut.  Someone make sure I'm right, but I want to say for a bolt over the round you want a LIGHTER buffer; is that right guys?.

I'm betting one of those two tests will clean up the problem; then you know what to do (change mag springs or get a lighter buffer).  

By the way, SA-WEET build dood!!!

Thanks guys!

I really couldn't have done this without your combined assistance/tolerating my numerous questions.
Parts too! The upper and BCG that started it were at a local gun show, the lower and CH are from NoDak, and the FCG is from eBay, but everything else is from EE, private contacts of "Hey I saw you needed this", and some parts from an Indiana Army Surplus order that only happened because of the thread.


I'm glad I went from a "good enough" to an all-Colt build. It brings me a bit of pride to say that only 3 parts are not Colt parts. NavyChief's barrel assembly saved me a lot of potential headache and was probably one of the biggest influences on the build becoming all-Colt. The only change I did was the flash hider as it came with an A1 (which I of course kept). I do have some spare parts because of order overlap, but the biggest thing is just handguard which I may keep for a spare (they are really nice and clean).




I'm not worried about the finish (ok, I kind of am but not enough o put Velcro on it) so much as an indication of function.




I used two Brownell's 20-round mags. They are about two or three years old but didn't get used often until this year where they maybe see use once a month. I haven't had issues with them in my other AR or in my Tavor, even with rapid fire. I do have other mags that I can try if I really have to, but they will look silly in a 604.

As for the buffer, the only other one I have is the standard rifle buffer in my other build. No idea if it is heavier or lighter. I'd guess it is the standard A2/A4 buffer. I'd rather not modify the spring but if the problem doesn't go away from trying other mags, parts wearing in, or changing buffers, I'll look into trying it (possibly with a new spring)

Looks like a beautiful rifle and a beautiful day.

Nice shooting and good looking great rifle. when I was a DS we always taught our Soldiers to keep their nose on the charging handle to maintain the same sight picture at all times. Makes a huge difference. M16s and AR15 rifle are extremely accurate rifles.

It was! The two days before were pretty rainy up north by me (I am about 45 min north of the range) so I was a little worried, but the range wasn't even muddy. Granted, I wasn't going to let that stop me!



Honestly that is the best I have ever shot. This was my first time using my new shooting bag and I think I am slowly getting better with the techniques. The range runs some CMP clinics and I went to one not too far back. I know I still have plenty of room for improvement though!

I went thru Basic at Fort Jackson, back in the later 70's, and I still shoot my AR's that way.  In fact I taught my sons to shoot the AR's that way also.