The hand of luck giveth, the hand of luck taketh away.

As I was whiling away the hours googling "Trapdoor Springfield" and "BPCR" along with other related nonsense, I came across a product that actually looked useful.  On the Lee Shaver site he has front sight aperture inserts that are shaped like little animals.  Take a look:

The shapes are a bit blobby, but they match the general outlines of the silhouette shapes.  When testing at the range, the image just looked "icky" as each lumpy bumpy portion came in and out of alignment, then all of a sudden, everything came into alignment and it just fit "right".  I am convinced it is a much better system for me, but there is a risk that if things are going poorly, such as low light, mirage, rain, etc. I might not ever form that aligned picture, in which case I'll be lost.  I was ready for match day with my secret weapon!

I show up at the counter, pay my money, and look down at the targets.  A BUFFALO!?  A GROUNDHOG?!  A CROW?!  For a year and a half I've been shooting the same pig, goose, chicken and ram.  Today you decide to change to a buffalo, crow, groundhog, and ram.  Dejected, I put my round aperture back in.  If it wasn't for bad luck, I wouldn't have no luck at all.

But, luck is a fickle mistress.  After a frustrating sight in period where my rifle seems to throw the occasional flier, I lock in and am ready for competition.  First up is freehand (standing) at the crow, which otta be a chicken I tell ya.   Freehand is tough, with 1-2 hits out of 10 not being sneered at, 5 being well respected and 6 being the best score recalled at our club.  My first shot is just inside the back of the crow, a hit.  Immediately I relax.  Even if I miss all the rest, no-one will give me any grief.  Second shot, right inside the back.  That's a two, with eight shots to go.  I'm on air.  Sure enough, I get a flier way to the left.  I choose to ignore it and keep aiming centered.  By the time I'm done I have 4 solid hits in the body and one cheesy toe hit, but they all count.  This is my best offhand by 2 shots and a tie for best offhand target of the day.  OOOh, and I got a pin with a chicken and a 5 on it!  Worth every penny.

The sad thing, of course, is that I didn't change a thing in my equipment, training, or shooting style.  It was all just chance that a good group would eventually happen.  The hand of luck taketh away.  But that's OK if the hand of luck then giveth.

The Tortured Chamber

As I've fiddled on this old rifle, I've found that most of the forward steps I've made have revolved around the transition between the case and the barrel.  Having the bullet all the way out touching the rifling, having a heavy enough bullet to deform under load, having a soft enough bullet, all focus on the short distance where the bullet is leaving the brass and entering steel.  This got me to thinking, and measuring, and I quickly determined that my chamber is a fair amount longer than my cases.  This isn't a huge concern for a military type gun, since the case is held by the rim, but it seems a good avenue to play around with.

I picked up a product called Cerrosafe, which is basically a low melting point solder.  It is used to make castings of gun chambers so you can take a look at the shape.  This is especially useful for the trapdoor where the breech is all shouded and you can't get measuring tools in there.  You just plug the barrel with a wad, heat the Cerrosafe with a small torch or hair dryer and pour it in the chamber.  Be sure the ejector cutout doesn't fill in, or it will stick in there.  Also, be sure the wad isn't too deep or the plug will be too long to get out the breech opening.  Once it cools, it taps out with a cleaning rod.

Here's a photo of the plug:

In the center is the chamber casting.  As you can see, it was a bit cold and has folds, but it gives me the info I need, so I never remade it.  The brass on the right is one of my 45/70 cases.  The brass on the left is a 45/90 I got for this project.  What's a little hard to see in the photo is that the chamber runs straight past the end of the shell, then starts to radius in, then hits a firm chamfered taper to the rifling.  The goal is to trim back the 45-90 case until it fills the straight part of the chamber, reducing the distance the soft lead bullet travels unsupported.

WARNING - If done incorrectly, and especially with jacketed bullets, this can blow your gun up.  The mechanism is this:  If the case is too long, it rides into the radiused part of the chamber and acts like a crimping die, crushing the case onto the bullet.  Normally, this is no big deal, there are overcrimped shells shot all the time.  The trouble is that the chamber is still holding the crimp down when you fire, giving the case nowhere to expand to.  Pressures go to the moon, as do gun parts.  The solution is that the cases have to fit right, not too tight.

After measuring and trimming, I had 20 rounds where the cases were long enough to cover all the lube grooves.  At the same overall length, my regular cases leave a lube groove hanging out.  So, how did it work?  Measurably worse.  My horizontal variation went from a standard deviation of 2.2 to 2.9.  Vertical was better at 2.0 going to 2.1.  Oh well.  Even knowing what NOT to do is still knowledge.  A perverse part of me wants to try shorter cases.  It seems to be the logical direction based on the data, even if it looks odd.

One good thing I got out of my day at the range was a well managed comparison of my prone shooting to my standing.  While obviously my standing (offhand) groups are much larger, they also center in a different location.  I've just never measured it before now, because it takes a fair effort tabulating hole locations, and I'm lazy.  The data is in, and I shoot about 1/4" to the right and 2" low when I shoot offhand.  Now I can think back to all those shots just under the chicken's feet and pretend to myself that they would be hits.  That makes today a happy day, free from my tortured chamber.