Ever see a Rimfire KB before? I hadn’t. Until today. Customer brought in a Walther with a “Problem”.
This isn’t just from one bad round. The customer had a second piece of brass that looked exactly like the first.
When we have a KB, there are are two Culprits we look at… The Gun or The Ammo. Most of the time, the Ammo is the cause. Remington Golden Bullet Bulk Pack. I don’t have a lot number or anything. The Customer Cleaned and Lubed the gun, fired several magazines full with no problem and then suddenly had a jam… then another jam and the slide wouldn’t go forward with the magazine in. Then he noticed the frame and the brass. Looking at the brass, the way the casing was blown out like that… I think we have some cases that were double primed. If it was fired out of battery, the brass would be blown out differently and distinctively, indicating it… in this case, the primer material in the rim blew out the rim. A normal amount of primer wouldn’t do this, and there isn’t enough case volume for a double charge… but the pressure spike from too much primer – would do exactly this.
Luckily no one was hurt, nothing else was damaged. We’ll see what Walther and Remington does.
We just read on WTA that there has been another KB with a Semi-Auto .17HMR rifle. Most of the time the result of a KB is only stings and scares… but this time the shooter was hurt badly.
A blow back semi auto .17HMR (and even the .17 Mach 2 but to a lesser extent) is a bad idea. No matter who makes the gun or how custom the gun is…. it’s going to, at some point, have a KB. This is the same problem with EVERY semi auto .17. Which is why all of them have been recalled and dropped from production by everyone that has ever made them. Except for Alexander Arms, who is making a 1200 dollar AR type – that will still do the same thing everyone else’s did. Even in one of the Gun Rags, during the review process the writer mentioned this happening but kept shooting it.
There are a couple causes of the .17 Rimfire KB’s.
1. The bolt, rebounding off of firing the last round, slams forward into the cartridge rim hard enough to set it off while the round is in the magazine.
2. A few rounds fires slightly out of battery puts enough carbon fouling in the chamber to builds up until a case is completely unsupported and firing pressure blows it. Continue reading →