Mossberg 715T Spontaneous Bolt Lock

Another very common problem with the Mossberg 715T is spontaneous bolt lock.  The Mossberg 715T, like it's 702 Plinkster brother, has a feature to lock the bolt in the open position for cleaning, reloading, etc.  It works by pushing the charging handle into the receiver, where a hook catches a tab.  It's handy for cleaning, and for rifle ranges that have "Bolt open when not in use" rules.  What happens on the 715 is that seemingly at random while you're shooting, the bolt lock will engage and the gun won't cycle.

I determined that the charging handle is the problem.  The bolt lock tab is part of the charging handle.  The stock charging handle is a fairly sloppy fit in the bolt, so it's got a lot of wiggle room.  What happens is that when the bolt recoils, the charging handle actually hits the plastic shell.  When it hits, the charging handle tilts ever so slightly, but just enough that the bolt lock can catch.  You can see the problem here:

And here's where it makes contact:

To correct this, I could have trimmed back the shell, or ground back the charging handle.  I didn't really want to do either, so I just made a new one.  Here you can see the change I made.  The original piece is on top, my new one on bottom.  The original handle is offset to the rear.  My new one is offset to the front.  While I was at it, I machined it with much tighter tolerances so it doesn't wobble as much.

Here's how it fits in the bolt:
Original

New:

 Now with the bolt all the way back the charging handle is no where near the shell.  Though I haven't put a whole lot of rounds through it, I haven't had a single spontaneous bolt lock since I made the change.

Way off the mark

A very common problem with the Mossberg 715s is that they can't be sighted in.  Very often, the sights don't have enough adjustment room.  Most commonly, they shoot low and left, though mine shot low and right.  The problem is that the receiver isn't located properly in the plastic shell.  The sights are located on the plastic shell, and not attached to the gun it's self.  To fix this, the action must be relocated inside the shell.  I started with milling the receiver where the mounting screws go through.  I milled off .050" from the back of the receiver.  Then I shimmed up the front of the receiver about the same amount with some washers.  For reference, .050" is about 16 sheets of notebook paper thick.  The left/right alignment is adjusted by biasing the receiver in the shell as the bolts are tightened.  The red arrow shows where I removed material, the blue arrow shows where I added shims to get the barrel to point up further.

The second problem is that there is some play in the receiver mounts.  Any time you took the action out of the case, you couldn't be sure it would go back into the exact same spot.  That means you'd have to resight it every time you took it apart to clean.  There is also enough play that it could move around under recoil.  The solution here is the same as on the Mosin, we're going to bed the action with JB Weld.  In order to not have the JB Weld run everywhere, I made a dam with modeling clay.  I also scuffed up the plastic to give the JB Weld something to grab on to.

Then I mixed up the JB Weld, smeared it in, and bolted the receiver back into the shell.  The receiver had a heavy coat of silicone and car wax on it to keep it from sticking to the JB Weld too.

With the clay cleaned out and the receiver removed, you can see how the JB Weld perfectly conforms to the receiver.  It's much more obvious how well it works on this than the Mosin.  Now the receiver will mount in exactly the same place each time it's removed, and it won't move around as the gun is being fired.

With the receiver adjusted and bedded in the shell, the sights could now be aligned, and the gun can be taken apart without messing up the aim.

The Ebil Black Rifle

This is the gun that (re)started it all, the Ebil Black Rifle.  Show it to anyone who's remotely anti-gun, and they'll scream "Assault Rifle!  Ban it!  Nobody needs a gun like that!"  Overlooking the fact that to be classified as an assault rifle, a gun must have full auto capabilities which NO commercially available guns have(even the evil black ones the media loves to hate), it's about ans far from an "assault rifle" as you can get.  In reality, though it looks like an AR-15, it's a Mossberg 715T, which is just their 702 Plinkster .22 in an evil black plastic shell.  Being just a .22, it's about as far from evil as you can get with a real gun(hence the cutesy "Ebil" moniker).

I'd been looking for something like this for awhile.  I saw this one on a Black Friday sale, and decided it was time to take the plunge.  Current .22 shortage not withstanding, .22s are fun to plink with, and this particular one is neat looking.  They make a couple different styles, this is the A2 carry handle style(for obvious reasons).  The one thing that really bugged me about it is the forearm.  It's just way too long and makes the gun look front heavy.  The front rails were kind of sharp too, and didn't feel nice in the hand.  First things first, I bought some standard length rail covers.  Using the covers as a guide, I whacked some of of the middle of the hand guard, it ended up being around 4".

After epoxying everything back together, I trimmed, redrilled, and reinstalled the removable side rails, then put everything back together.  Just that change really helped the proportions of the rifle, and makes it look a bit less ungainly.

Usually, I like meeting fans...

I filled up my camera, so I had to dump all my pics onto the PC.  Looking through them, I realized I missed a Viper update.  One day it started making a horrible rattly grindy sound when I pulled into the driveway.  My immediately thought was a broken power steering pulley, since they're known to break.  It wasn't.  After some quick investigating, I discovered that the cooling fan wasn't spinning like it should.  After taking the fan out, here's what I found:

If you've never had a fan apart, there's supposed to be a pin in there connecting the shaft to the fan blades.  Here's what's left of said pin:

Apparently it had been loose or partially broken for awhile because it had worn the groove in the back of the fan hub pretty badly:

This looks like a job for...JB Weld!

Conveniently, I had some drill rod the right size on hand too so I made a solid pin instead of using a roll pin like the original unit.

Once the JB Weld set, I filed it out so the new pin was a snug fit.  Because of the length of the pin and the shape of the ribs, the pin is completely captured when the fan is installed.

That's all for now.