Project Reject

[Stickman]

Originally, I posted this on M4c, but I thought it was worth posting here as well.

This idea came about after I got to thinking about returned barrels. Companies that offer an accuracy guarantee are stuck at the hands of the installer and trigger puller. I'm certainly not above thinking bad barrels come off the machines, but I still wonder what the real issue is with many of these barrels. Buyers remorse? Poor shooter? Low quality ammunition? Improper scope or optic mount? Low quality installation? A receiver that sucks in the barrel extension and wobbles like a drunken donkey?

Here is the barrel we will be dealing with. While it is a SS match barrel, that is all the info I have on it. I won't say who the company is who has these made, or who the maker is at this point. I have already stated we know machines put out bad barrels sometimes for a variety of reasons. The more important issue is how well the seller stands behind their product.

From a first look, we can see the barrel is obviously used and has been fired. Black marks near the gas port, and a layer of grunge are in the barrel extension. HOWEVER, as we look closer, we can start to see more interesting things. Do you think the barrel extension index pin left the manufacturer that way?

[Stickman]

This block will encompass what we built up, and how we built the upper....

The first thing to figure out once the barrel decision has been made, is to determine what parts are used for the rest of the build. This becomes much more of an issue when we want to eliminate build and component issues to determine overall accuracy. Below is the parts layout.

The upper receiver we decided on is one from Cross Machine and Tool. We had a few options to chose from sitting over here in our parts bins, but chose Cross Machine and Tool because Jeff Cross likes to keep the receiver to barrel extension index tight. If you have ever put a barrel extension into a receiver and it dropped in easily, or worse, had some wobble once inserted, you got a low quality part. It is true that the barrel nut provides compression, but only in one direction (realistically speaking), and only to a certain degree.

The rail is also from Cross Machine and Tool, this was chosen because it had just showed up in the mail, and is a rail we have used before, and is of known good quality. There are a lot of other parts which could have been used which are also high quality, this is just how this selection went.

The Geissele charging handle was selected because there was a bag of them sitting next to the work bench (thanks to a buddy who finally mailed them).

A Lantac USA gas block was used because they provide a nice fit and aren't loose on barrels. The first gas block chosen is shown in the below picture, was unmarked for mfg name, and was a horrific fit. It now resides in the garbage.



We used Aeroshell 33MS Grease MIL-G-21164D around the outside of the barrel extension, the inside of the receiver, and on the receiver threads. While people can argue against the use of grease, we find there are too many reasons to use it, in addition to the military and armorer requirements.



We also used the above grease inside the threads of the barrel nut. In the below picture you can see the assembly method of the rail, barrel and upper receiver (the barrel is not shown to keep the pic cleaner). The barrel is inserted into the receiver, the barrel nut is tightened down. Tightened then taken off, and tightened again 3 times. The reason for this is new threads will compress a bit and mate to each other when this is done. It is often overlooked, but a lengthy conversation with John Noveske explained it in great detail, and not doing this was a fire-able offense when John ran the shop.

Once the barrel nut is in place, the rail slides over, and the anti-rotation tabs lock in place. Each side of the lower section of the rail has locking pieces along with two screws. One locking section on each side, and tighten the screws into place locking them to the rail. If you have read this far, it is novice level easy.



Here you can see the tool provided with the Cross Machine and Tool rail which makes installation of the barrel nut simplistic. You do not need to time the barrel nut, which allows you to torque it down as much or as little as your person preferences allow.



Once the barrel nut is in place, install your gas tube and gas block.

[Stone]

Do you have any more input from the end user? Why was it returned?

[Stickman]

Do you have any more input from the end user? Why was it returned?

I don't have any idea what the issue was other than "accuracy" written on the barrel.

[Stickman]

What we have built up and the whats and how of getting it ready to fire.

We decided to use a Wilson Combat 3 prong flash suppressor. We did throw a couple shims behind it, and tightened it down by hand. No extra pressure from a crush washer to possibly offset groups, then again, we have no idea how the barrel was treated before we received it, so it may be a moot point.




We then chose a lower, and in this case the decision was pretty easy. We already have a lower which we use for testing, and it happens to be a Cross Machine and Tool. Fit between the receivers is nice and snug. The glass up top is from Vortex, and their 3-18 Razor HD Gen II is what we try to use when we do ammunition and weapon testing. The mount is from Geissele because it fits incredibly well on 1913 rails, and doesn't mark up or crush receivers and items we are working with.

[Calico Jack]

These results should be interesting. I am leaning towards more shooter error than machining error.

[cjd3]

This is a great thread. The literal build up is fantastic. looking forward to the result.

[fledge]

Is this the build that shot the clover leaf you posted on IG?

[din]

Gross, that barrel has pubes.

[Stickman]

A minor update. We took Project Reject out today and plugged it in at 30 yards. At this distance, the idea was to see how groups were with the dirty barrel, and see if we could get the scope on paper. After finding out where we were hitting, we fired from the first magazine which was filled with unknown 55 grain hp ammo. Some of it was pretty dirty, and some was bright and shiny. No point in wasting time by checking headstamps and weighing each round, we fired it as it went into the magazine loaded out of one of our generic ammo cans.

The groups were as shown below. Again, this is from 30 YARDS, add in to this, I was not on my game. Nothing felt quite right behind the trigger, and while I am not making excuses, I want to make sure we are blunt and honest about how things go with this project. I don't think being "on my game" would have made much of a difference with these groups. The ammo was assorted, so there wasn't much expectation things would group super tight.

At this point, all we could think of was multiplying this group times 3, and that the barrel certainly wasn't pretending to be 1 MOA, or even anything close.





Next we loaded up a magazine of 55 grain Gorilla Ammunition. The results were much different. We have used this ammunition before and found it to group very well, but there was a large difference between this ammo and the previous mag. As mentioned above, this was not a great shooting day, and most of the times I pulled the trigger with these groups, it felt like I was shanking a round, but the group was still decent, even though it wasn't from 100 yards.

[Pyzik]

Looking forward to this. Great read so far. I've not used grease. That is something I'll be grabbing going forward.
Also, never put much thought into gasblock fit-ness.

Interested to see what you come out with at 100 yards.

Glad you posted this here as I likely wouldn't have ever seen it over on M4c.

[Former11B]

I grease my barrel extensions also. I have read that corrosion is possible between different metals (and 416R is susceptible even if the upper is anodized), and it also makes removal easier in the event you decide to change things up.


Stick: What other types of ammo are you going to try? Factory match ammo and/or handloads?

Thanks for posting this.

[UWone77]

I grease my barrel extensions also. I have read that corrosion is possible between different metals (and 416R is susceptible even if the upper is anodized), and it also makes removal easier in the event you decide to change things up.


Stick: What other types of ammo are you going to try? Factory match ammo and/or handloads?

Thanks for posting this.

I always grease my extensions because the grease makes it generally easier to install into the upper (as I find stainless barrels are especially tight in a lot of uppers) and it makes it generally easier to uninstall later if you have to.

I haven't read that corrosion is prevalent but I don't doubt that's possible.

[din]

I use Loctite C5-A on mine. Irazgunz recommends it, and I figure he's built at least a couple more ARs than I have so I tend to respect his advice more than most.

[Dstrbdmedic167]

I use aeroshell 33mm grease I got from umbrella corp years ago. Still have plenty.


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