Spring Is In The Air

No, spring is in the Glock…

The 13 pound recoil spring worked as expected. I did have two ammo issues, but they appeared to be ammo dimensional issues.

As I was rushing somewhat to have 100 rounds of this low recoil ammo recipe ready for the match, I QA’d the rounds with the gauge block only. Usually, I run all rounds through the Bulge Buster first, then case gauge block. In the interest of cranking out 100 rounds that morning, I just cleared all rounds though the case gauge only. If they drop unrestricted into the block, I called them good. I’m not sure if that allowed a couple of marginal rounds through or not. Shrug.

What I really need to do is take a few hundred rounds to the range and test them under non-competitive conditions, with the chronograph, too.

I have also been looking into a bullet trap for easier and safer ammo testing at home.

We have about 12 acres of land in a subdivision with a minimum lot size of 5 acres. We have a pond on the property which includes a dam that I have used as a firearm backstop before. However, that area is muddy much of the spring rainy season, limiting access to keep it mowed. Consequently, it is overgrown much of the rest of the year. It is a good place for daytime target practice, for part of the year, but it less than convenient for the kind of shooting needed to work up a handload recipe.

After shopping for commercially available bullet traps, I have found that there are a few available that would suit my needs fairly well, but they tend to be $1000-2000 and I just can’t justify that kind of cost. I think I’m going to have to go homebrew.

There are three *basic* designs for small bullet traps, four if you include clearing traps. Clearing traps are designed to simply be a safe direction to point the muzzle when unloading and clearing a weapon. They are not truly intended to be fired into regularly. For bench work, a sand filled bucket is adequate for most handguns.

The other bullet trap designs are variations on a theme of safely dissipating a bullet’s energy. The most common design, both commercial and home made, uses a hard steel plate, generally at somewhat of an angle to the shooter, to absorb most of the bullet’s energy and deflect it into a soft material, often sand, to absorb the rest of the energy and capture the projectile. The home made version might be adaptable to indoor shooting and in fact, many indoor and even outdoor ranges use another variation of this technology wherein the angled steel plate deflects upward, but the plate is covered in several inches of shredded tire rubber.

Another very common design that is a little more complex is some form of a design that uses highly angled plates to deflect and guide the projectile into an enclosed tube to dissipate the remaining energy in the tube. This design makes recovery of the spent projectiles easier, thus making the lead easier to recycle. The specifics vary somewhat, but they mostly look like a big funnel connected tangentially to the side of a pipe. This would be my favorite design to try, mostly because there is no need for any kind of sand, ground rubber or other media to sift spent projectiles out of.

The last common design is really basically a scaled up clearing trap, a tube filled with baffles or some other energy absorbing media, large enough to safely shoot at from a distance. One of the slickest example of these was from a company called Target Shooting Solutions. As of November 2017, their web presence is now for an indoor range in Pennsylvania, with no bullet traps to be found. Sadly, their least expensive model was $1000. However, their basic design lends itself somewhat to the DIY builder, a tube filled with absorption media.

The easiest to build your own tube trap with would be 12″ or larger steel pipe, about 3 feet long, with a heavy plate securely welded to one end, the other end made of something a bullet should be able to pass through, like a piece of a horse stall mat.

Punching Holes Gently

I loaded up some soft shooting 40S&W ammo to take to Winchester last Thursday. In the past, I have loaded a lot of 165 gr RNFP rounds and got very comfortable with them. 4.5 gr of TiteGroup send those at about 960 fps (per chrono stage at a major match) for power factor of 158. That round worked really well. Hotter than necessary, perhaps, but as I say, I had gotten pretty comfortable with them. I never did chrono the 155 gr RNFP with the same charge, but those are probably a little faster, still in the 160 or so range in power factor.

I decided that since I espouse custom ammunition as one of the two main reasons to handload (economy being the other) that I could probably do better.

The rule of thumb is that, for a given power factor, heavier bullets at lower velocities will recoil with less energy. The math works because power factor is a simple momentum calculation of mass time velocity whereas energy involves the square of the velocity. So, the next heavier common 10mm bullet is 180 gr. To make minimum power factor of 125, the 180 gr needs only run at a pretty pokey 695 fps, as opposed to 758 fps for a 165 gr bullet. I consulted various load data sources and found a few loads with fast powders that showed 180 gr bullets at 750-ish fps and I decided to try 4.4 grains of Power Pistol. The slightly longer 180 gr bullet was seated a little bit deeper in the case, but as the profile/ogive is the same as the 165 gr, I used the same OAL of 1.125″ and all rounds gauged properly in my EGW case gauge.

There is, however, a caveat.

Using the math referred to above, my 165 gr bullets at 962 fps works out to 339 foot-pounds of muzzle energy and by inescapable physical law, 339 foot-pounds of recoil, though a goodly portion of that is used to operate the pistol. My 180 gr bullets at an estimated 750 fps works out to 225 foot-pounds, 34% less energy. That, it turns out, is enough reduction to make the pistol cycle less reliably.

The round was an absolute joy to shoot. Reacquiring the front sight was fast. Power Pistol is a bit flashy and boomy (and I have in fact some pretty smokin’ hot, bright and loud loads using Power Pistol) but in this charge, it was a nice report and very light recoil. It won’t be confused with a 22, but very gentle. On the other hand, I had several jams that centered around incomplete extraction and ejection. I was initially disappointed, fearing I had a dimensional issue, but as I paid closer attention to the jams and noticed that it was empty brass gumming up the works, I realized that my pistol just has too much recoil spring for these far-lighter-than-factory loads.

This is a Glock 20 with a Lone Wolf 40S&W conversion barrel but the stock recoil spring designed for 10mm Auto. It kind of surprised me to learn that the stock recoil spring for the Glock 20 is the same 17 pound rating as the stock spring on almost all other models. Then I realized that what is different for the Glock 20 (and 21) is the larger, heavier slide. The combination of the heavier slide and the 17 pound spring is what helps the pistol cope with the 575 to 800 foot pounds of recoil energy of full power 10mm ammo. Compared to that, its no surprise that my 225 foot pounds, a paltry 60% less energy, might have trouble operating the pistol reliably.

I ordered a 13 pound spring on Friday. Tracking said it woudl be here by Friday, but it arrived today! Bonus!