Building Confidence

[RKP]

Originally Posted by FfNJGTFO

OK, so find a metal rod (diameter of a paper clip over which the roll pin can fit). Put the roll pin over the rod, insert the rod and align, and then gently advance the roll pin.

The tube is definitely aligned to the upper. I will make sure I use the gun grease sparingly. And I'll use my roll pin holders to advance it to the point where I can start to tap it in.

Thanks much!

How did the above work out for you?

[FfNJGTFO]

Originally Posted by RKP

How did the above work out for you?

Oddly enough, quite well. The tube and block are now aligned, with the roll pin flush and in place. And I was able to blow on the tube and feel the air jet with my finger inside the block. so I know those holes are aligned. The way I did it was to align the tube into block by the "paper clip" method as described. Then, I taped the tube with Scotch tape directly onto the block, which did anchor it enough for me to keep the tube aligned and get the roll pin started. A little "Liquid Wrench" in the right place after I had the pin 2/3rds in place and, after a few minutes, the roll pin went right in.



The bad news is, when I was doing this, I forgot that the BCG is not fixed inside the upper and both it and the charging handle came right out! I figured out that I have to have the bolt in the locked position (bolt extended) in order ro re-insert it, and I was able to do that. It clicked right into place. But getting the charging handle to fit in again, has been an issue. I had bought the upper "assembled" so I never did go through putting the BCG and charging handle together into the upper. I guess I'll have to review my videos on how to do that, unless you good folks have some suggestions.


That said, I want to go over something I mentioned in my last update but got no bites on it. Has anyone found a good method of testing the action without having to fire a round? Once fully assembled, I was thinking of attempting to "pressure test" the action by blowing a pressurized shot of compressed air down the barrel to simulate a firing (since I can't test fire with actual firing, where I live). I would use some empty brass, so it could be extracted without difficulty. Then let a dummy snap cap be the next round to go into battery.



I want to get at least 2-3 "action tests" in before I go test fire it with live rounds on a range. The issue is going to find a module I can use to fit into the barrel to give it the "test shot of air." I also need to know what PSI would be optimal. Does anyone know what the standard PSI rating is for an xm855 green tip fired from the barrel?



Thanks all! I'll keep you posted.

[DrHenley]

On really stubborn pin alignment problems, you can use a tapered drift punch from the side you will be inserting the pin from to get the holes close, then use a pin punch or a solid pin close to the hole diameter (with the end chamfered) from the other side to get the holes lined up, then use it as a slave pin and push it out with the pin.

If you can't find a solid pin or pin punch with the right diameter you can probably find a drill bit that is very close and use that as the slave pin. I have a complete set of drill bits incremented in 1/64" that I have used as slave pins on some VERY difficult pin alignment problems.

[Caleb]

I just manually cycle the action an feel for any hang ups or sluggish movements. If that feels good, I load up one round and fire it. If the action locks back, I’ll load five in the mag and fire. If that goes well, load up the mag or two and go at it. I don’t do barre break-in on non match grade barrels/rifles.


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[Caleb]

Oh... inserting the CH and BCG is easier done upside down. You should notice two little ears on the charging handle that fit in a slot in the upper receiver towards the back. Insert the charging handle and push it in about a quarter of an inch then extend the bolt carrier group and insert together, push all the way until it clicks.


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[FfNJGTFO]

Originally Posted by Caleb

Oh... inserting the CH and BCG is easier done upside down. You should notice two little ears on the charging handle that fit in a slot in the upper receiver towards the back. Insert the charging handle and push it in about a quarter of an inch then extend the bolt carrier group and insert together, push all the way until it clicks.


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So the Youtube video showed me. All done in a jiffy.


Now, to mount the gas tube/block assembly on to the barrel and align it. Time for that "spaghetti" to work its magic....

[RKP]

On the road again ....

[Caleb]

Cool beans.


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[FfNJGTFO]

Originally Posted by Caleb

Cool beans.


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Sorry it's taking so long, but there is light at the end of the tunnel... and it's not a train coming in the other direction!


I expect the next build will go a lot smoother/quicker from what I've learned on this one.

[Caleb]

The first one is always the harder one.


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