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As in a driving band just in front of the boat tail, with land engravings? Or a slight rebate before the boat tail? Both of those being common features of some of the boat tail air gun slugs.

There could be a number of reasons why a match director might have a minimum FPE limit. In the past (before the electronic sensors), there could be a minimum needed to activate a target sufficiently to call a hit. Though not FPE, but related, there are a few competitive shooting organizations...

If you are using a ballistic app, there is a good chance that it will do all the math for you. For pellets below about 950fps, the GA drag model is fine. Your phone can give you the local environmental conditions either using a weather app to download current conditions or some phones have the...

If your drag model is a good match to the projectile, and you account for the environmental conditions (mostly air density), your BC should be constant. Most of the popular ballistic apps let you input the environmental conditions before calculating the BC. If you try to calculate the BC...

Wouldn’t a properly sized, smooth boat tail maintain attachment at the rear better than any other “rough” shape?

Most all projectiles I use have a relatively smooth surface. How rough does the surface need to be in order to see benefits?

I started casting for my powder burners. Since getting into slug shooting airguns, I’ve gotten a lot more molds. I prefer to find a mold that works for any particular airgun, and then cast slugs rather than buy. I sort by weight and size them. I’ve gotten fast enough casting so that any slugs...

A rough surface can promote turbulent flow. That might be good for down stream of the carburetor in an IC engine. Keeps the fuel atomized. I can’t imagine any benefit for a direct injection IC engine. For lowest drag in an airgun projectile I’d say smoother=better

FPE = 1/2mass x velocity^2 For that basic equation, velocity is in FPS, but mass is in slugs (not grains). For grains and FPS we need to convert grains to slugs. FPE = 1/2 x grains/(225218 grains/slug) x FPS^2 or FPE = grains/450436 x FPS^2 BC is more complicated as it requires the amount...

I have the .22 version of that magazine. Works good in semi-auto mode. Does not work in full auto. The standard magazine works OK in full-auto.

I think there is some confusion between factor of safety and overpressure factors used for hydrostatic testing. The minimum factor of safety is probably 3.5 based on tensile strength. That puts 5/3 test pressure just below 1/2 of tensile strength, so below the endurance limit. (5/3)x...

I had a similar issue with a factory Delta Wolf magazine. The magazine was very tight inserting and would not seat completely. I ended up using my pocket knife blade to scrape the anodizing out of the recess perimeter on the front of the magazine. That fixed it. It’s a problem of dimensional...

AAFTA rule book: “No energy-level adjustments allowed during the match….” Usually, you’ll be hitting high or hitting low if your velocity is off significantly. If your velocity is off, you can’t adjust it during a match. If you suspect that your velocity is low or high, your best bet it to use...

And the irony is that a carbon fiber wrapped bottle that is never hydro tested is more likely to outlast one that is tested regularly. A leak down during use could be a fatal failure if it is being used as a breathing tank. So regular hydro testing is warranted in order to catch a potential...

The only 60x FFP scope I have ever seen is a March Genesis ($6000).

If the .177 has any detectable recoil, an inertial trigger might work. I get some errant readings when I bump or move my gun as that will trigger the Labradar. The .177 is more of a short range airgun round. Labradar is probably not well suited for that. Even if it triggers, it will not be able...

That’s a great deal for a Labradar. I’ve had mine for a few years. I added an SD card, an aftermarket inertial trigger, and a rechargeable external battery pack. It’s reliable. I mostly use the built in screen and SD card rather than the Bluetooth app. There are now a number of <$1000 Doppler...

It’s certainly possible that 600mm was the “sweet spot” for that particular tune. While a different tune might use an 800mm barrel for the “sweet spot”.

An “extra target every 2 or so lanes” is more money to spend and more work setting courses. It’s not really necessary when we already have two targets per lane, one easy and one hard.

The barrel length limit for my latest build was set by the length of the gun case that I already had. I left enough room for 1” of padding on each end of the rifle. Long black case for .308 with 61” barrel: