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Hamstrosity had some difficulty after he built a Winchester kit off a 762mm receiver. He was hitting very far to the right and had poor groups at 50 yards.

I inspected the rifle and found various loose parts. I decided to use the rifle as an example to do my inspection videos. Here's what I found wrong when I got the rifle:

-Loose operating rod guide
-Loose gas cylinder spline fit (GC was shimmed fine)
-Loose flash suppressor splines
-Negative draw pressure

Here's what the groups looked like at 50 yds. The 5 shots are the ones in the 6 and 7 ring at 50 yds. The rest were by my daughter shooting my AR.


I knurled the barrel and epoxied the operating rod guide. I peened the splines of the gas cylinder and the flash suppressor and I shimmed the front of the receiver to get light draw pressure.

Groups at 50 looked promising...


Then I moved out to 100. Here's my final group with Federal LC M80



5 shots, 1.792"...


It's been a pleasure to work on this rifle. Now I just need to bed it into a GI fiberglass stock. Unfortunately, the receiver is machined in such a way that it will always need receiver shimming or bedding to achieve draw pressure. I also had to move his front sight nearly all the way to the right to get within 2" of center at 100 without moving the rear aperture. I still have a little room left before resorting to correcting with the rear sight.

Tony.
 

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Other than the flyer up by the 7, the four shots in the 6 ring (first pic) aren't that bad of a group. No worse than your last pic. Not to be a negative Nellie, but I'm not seeing the group improvement other than moving it to the left slightly. Is there something I'm missing...looking to learn here...
 
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Other than the flyer up by the 7, the four shots in the 6 ring (first pic) aren't that bad of a group. No worse than your last pic. Not to be a negative Nellie, but I'm not seeing the group improvement other than moving it to the left slightly. Is there something I'm missing...looking to learn here...
The other groups he shot the first time we took it out were much worse, IIRC. I just remember that it was all over the place and the front sight was moved all the way to the left. Groups at 50yds were around 3" to 4". Hamstrosity shot it first and I was too busy testing my own rifle that day. Maybe he can chime in and recount his initial experience. This was just a small peek at what we saw before I started tweaking it.

The first group after modifications were almost in the same place, but I had already re-centered the front sight before I started shooting. Then I had to move the front sight farther to the right to bring POI closer to center. Only after I was close to center did I move out to 100.

Once I was close to center at 100, I switched over to the SR-1 target for accuracy.

Tom, do you remember how big the group size was on your first trip at 50 yards?

Tony.
 

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Nice work, Tony. What to you attribute the windage error to? Left bolt lug okay? My first two 762MM rx's were the problems with my accuracy inconsistencies. The two that I ended up with are working out great and are my most shot M14 style rifles now. One a Scout configuration and one a standard. I haven't done any tweaking with either a this point.
 

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Thanks for asking, merc. I'll take a peek at that. I do notice that there's a hang up when rotating the bolt out of battery and I haven't been able to identify it yet. I'll check out the left bolt lug. The rifle cycled but ejection was erratic and the rifle doesn't pass the tilt test. It needs a little nudge to rotate out of battery.

When it comes to bolt lugs and clearance, I'm out of my scope of experience. I was wondering if the rifle jest needs time to "break in."

Tony.
 

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No amount of break in would have helped my first two 7.62's. Both had left bolt lug contact issues. 7.62 had coated them heavily with grease but I completely degrease and inspect any gun that comes my way. 7.62 can apparently do good work as my last two are very nicely made, but they can also make a mess and then not stand up on their work.

You might talk to Ted Brown. He built one of my 7.62's and see what his opinion of this rifle's problems might be.
 
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By the way, merc, Tom installed the barrel and lapped the bolt himself and he wants to re-check his timing with the parallel bars, so at this point, I don't know if it's barrel timing or bolt lug fit that's causing the windage error. We'll find out more later.

Tony.
 

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Thanks for putting this up Tony, I really appreciate it! I also really appreciate you taking the time to work on this rifle for me!

At 50 yards, the rifle was all over the place and way right. With the sights set to mechanical zero, they were barely on target at 50. At 100, they were completely off. I attributed a lot of the accuracy inconsistency to the surplus ammo that I had that day, but I don't think that accounts for why it shoots so far to the right. Even in your targets, the rifle is still right. That's why I'd like to double check the timing. I also have a new level since I build that rifle, so I'd like to give it a test spin anyhow.

When I first assembled the rifle, I did notice that there were some bolt unlocking issues, there was a considerable amount of force needed to unlock the bolt. A friend of mine was looking at the rifle for me and noticed that when the rifle was dry fired, or pointing downwards, the weapon would require considerable force to unlock, but if the weapon hadn't been dry fired, and the muzzle was pointed up, it would unlock with only a little bit of extra force. He discovered that the firing pin cam (best way I can describe it) was not machined into the safety bridge. We filed the CENSOREDGI out of the safety bridge slot, in order to make a camming angle, until we could unlock it without tilting the rifle upwards. The bolt was still a little sticky once in battery, so I did a little bit of lapping to improve it, but I figured the rest of it would wear in as the rifle was fired.

I attached the first pattern that I shot with the rifle at 80 yards. That was 20 rounds of 168gr FGMM GI8

Yeah - It's shooting better now. I really appreciate you taking the time to go over the rifle. It's awesome you were able to use it to make some instructional videos to help the community at the same time!
 
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