Custom Ruger 10/22 Part IV - Troubleshooting

This was supposed to be a 5 shot group!

I finally made it out to the range to test out the custom Ruger 10/22 I built.  I just couldn't wait to see how accurate the rifle was.  Unfortunately, I never got to test the accuracy.  As soon as I started shooting, I experienced an unusually high rate of failure to fire (FTF) malfunctions.  A failure to fire is when a round is loaded into the chamber properly, the hammer drops, but the round doesn't go off.  Now it isn't unusual to get a few bad .22 rounds in a batch that won't fire, especially with bulk ammo.  But my FTF rate was about 44%, regardless of the brand of ammo!  Obviously something else was wrong.

I inspected some of the FTF rounds and noticed that the primer strike looked light.  In fact on some of the cases, it looked like the firing pin just barely nicked the outer rim of the case.  Since each round was feeding perfectly, and the bolt always closed completely, I thought the firing pin might be the problem.

I used the depth gauge on my digital calipers to measure the firing pin protrusion.  It measured 0.018".  It should be about 0.035".  The bottom of the pin also seemed to be rounded over, almost like it had been dropped or dry fired a lot.  Maybe I found the problem?  So I ordered a custom firing pin from KIDD Innovative Design.  It was specifically designed to address inconsistent ignition.

Stock Ruger firing pin in front of KIDD firing pin.  Notice the KIDD pin is longer.

The new pin was beautiful.  Well as beautiful as a piece of metal can be.  The extra quality of the KIDD pin  is plainly evident.  Installation was very easy, took just a few minutes.  With the new pin in, I measured the firing pin protrusion to be 0.036".  Much better.

After I reassembled the rifle, I loaded up a few plastic snap caps and pulled the trigger.  Rather than the rounded little dimples the original firing pin left, the new pin left a long, deep, well defined dent.  As long as it doesn't pierce the case rim, I think we're in business.  Only one thing left to do; get out to the range and shoot!

3 strikes from the old firing pin and one from the new pin.
I'll give you one guess which dent is from the new pin!

At the range I tested out some CCI Standard Velocity, CCI AR Tactical bulk, and Remington Thunderbolt bulk.  Without any regard for accuracy I just squeezed off 10 rounds in rapid succession, swapped mags, and continued until I had fired 100 rounds.

Here are the results.
CCI Standard Velocity: 10 shots, zero FTF
CCI AR Tactical: 30 shots, 2 FTF
Remington Thunderbolt: 60 shots, 3 FTF

Note that all FTFs were with bulk ammo.  Each FTF round fired when I loaded it back in the magazine and tried to reshoot it.  So, I went from a 44% FTF rate to a 5% FTF rate.  Much better and par for the course I suspect with bulk ammo.  I am guessing higher quality ammo will function 100%.  Problem solved.  Now to test for accuracy.

At the range.

High Standard Speed Loader

High Standard speed loader

Recently I spent a day at the shooting range with my wife.  She had a fun time shooting a couple hundred rounds through a .22 High Standard Supermatic Trophy pistol.  But we probably spent more time reloading the magazines than shooting.  And holding that little follower button down on the magazine became uncomfortable pretty quickly.

Volquartsen MagLatch for Ruger MK pistols

A day or two later I came across this MagLatch for the Ruger MK pistols from Volquartsen.  Since the Ruger magazine is similar to the High Standard, I figured I could make one to fit the High Standard magazines.  Of course I could have machined one out of nylon but I have been looking for projects for a supply of ShapeLock that I have.  This seemed like a good one.

ShapeLock

ShapeLock is an ultra-high molecular weight low temperature thermoplastic.  What that means is when it gets hot it becomes very pliable, almost like clay.  But when it cools and sets it is a very hard plastic, almost like high density polyethylene (i.e. plastic cutting boards).  It is great for quickly making prototypes, molds, tooling, custom parts, joints, mounts, etc.

Disassembled the magazine

I started by disassembling and cleaning the magazine.  Then I reassembled the magazine without the spring.  I didn't want the spring tension to work against the ShapeLock as it set.  I wedged a little piece of plastic in between the magazine and follower to hold the follower in place.

Magazine without spring.

Everything ready

Next, I nuked a mug of water taking it up to about 170 degrees F.  You are supposed to have the water at 150 degrees, but the water cools pretty quickly when you add the ShapeLock.  A small hot plate kept the temperature up while I worked.  The ShapeLock was placed in a small strainer and submerged in the mug.  In hindsight, the mug was too small for the amount of ShapeLock I was using.  I had to keep kneading and re-submerging the ShapeLock to get it thoroughly heated.  If I were doing it over, I would have used a much larger bowl of water.

Warm ShapeLock wrapped around magazine

Once it was heated, I kneaded it into a disc about 1 cm thick.  Then I wrapped the disc around the magazine and squished it in place.  I held it for about a minute until it started to set.  Then I let it cool for about 10 minutes.  By then it was holding it's shape, but it was still easy to cut.  So I started removing excess material with a utility knife.  Once it got harder to cut I used a scalpel that I heated with a torch to melt through the ShapeLock as I cut.  Be sure to save all of the trimmings.  They can be reused later.  After a bit of cutting and shaping, I installed it on the magazine.  It fit!  Looks like this thing might work after all.

Rough cutting

Test fit.  It works!

The final step was making this unsightly hunk of plastic look presentable.  I cut it down to size on my scroll saw.  I used a relatively course wood blade at the slowest speed.  Then I smoothed it up on the belt sander.  It sands OK if you keep the pressure low and let it cool every so often.  I removed any last bits with a high speed cutter in my Dremel tool.

It looks much better in person than it does in these pictures.  More important, it works perfectly!  Slide it on, lock it in place, and just drop your ammo in.  No more sore thumbs!

Update:  I have made a commercial version of this.  It is available here.  Full details in this blog post.

Another American Girl Dog House

I built this dog house for my oldest daughter's American Girl dog as a birthday present a few months ago.  Of course, little sister had to have one too.  So here is her Christmas present from Daddy.  Construction was exactly the same as the last one, just a little bigger to fit her dog.