I got a baffle strike! That’s just about the worst thing that can happen to a silencer. It’s something that I have always gone out of my way to avoid by shooting ammo without the silencer first, to make sure it is stable. With every new bullet, I would check the gyroscopic stability factor as well. I wanted to make sure that this would never happen to me. Well, it happened because of my lack of knowledge when it comes to shooting cast lead. I have cast bullets for many years for pistols, and in my 300 Blackout, with no problems. My understanding is/was that you can’t push cast lead as fast as jacketed bullets. Come to find out (the hard way), that’s not entirely true. It’s not about how fast per se, but the RPMs. With a typical jacketed bullet, the RPMs are around 235,000. Yes, you read that correctly; 235,000 Revolutions Per Minute. (Caliber and twist rate dependent). The faster a bullet is launched, the higher or faster the RPMs. From my research, cast lead bullets should only have a maximum RPM rate of 140,000, or else you risk the bullet being spun apart. So, it’s not necessarily speed, but RPM. There are two ways to combat such high RPM rates. Slow the bullet down, or use a slower twist rate. Aside from getting a new barrel with a slower twist rate optimized to shoot cast lead, that most likely wouldn't stabilize a jacketed bullet. I’m only left with slowing the bullet down. Again, I did not realize this; at the time I was concerned with speed.
What happened
I wanted to start shooting cast lead in my 6.5 Creedmoor 1 in 8 twist, because it was significantly less expensive. I was saving my powder and bullets for long range shooting, but still wanted to shoot my setup. I decided to load subsonic ammunition to take full advantage of using a silencer. I did a ladder test starting high and working my way down to find a good recipe. The first 4 recipes were slow supersonic in the high 1300 FPS range. But, I did find a good subsonic load. I loaded up a second batch to confirm FPS and to continue testing, but was very happy with the accuracy of the supersonic rounds. I thought I would go ahead and make some supersonic loads as well to test. I went with a different powder, and went with a minimum charge weight with an estimated 2300 FPS. I knew this was within a safe speed, as I had checked published for cast lead bullets. I tested my subsonic loads first without the silencer, and everything was good. I found my new subsonic load. On with the testing of the supersonic bullets. I knew because they were faster, they would be stable and DID NOT check bullet stability as I always do. BIG MISTAKE! The first few shots were about 2,312 FPS. Perfect; that’s right where I want them to be. Distracted by looking at my chronograph I was not paying attention to accuracy or impact. After a few shots to now check accuracy, I was seeing dirt move, but no impacts. I checked the front of my silencer and all was good. I assumed it was a large impact shift due to being a different bullet than the normal 147 Hornady ELD-M that I shoot. I shot a few more rounds with the same outcome. I decided to take off the silencer to do a quick inspection of everything to figure out what was going on. I twisted the silencer off, and it came off about half an inch, then I had resistance. I fumbled around with it and got it all the way off to realize large chunks of lead in the muzzle break. What?! How is that possible?! I looked on the inside of my silencer, only to see a ton of lead buildup. (I did forget to mention I powder coat my cast lead bullets to act as a jacket. This stops leading in non serviceable silencers, making it safe to shoot) I was confused until I realized my bullets are being blown apart. I looked at the end of my silencer and saw the end cap strike. My heart sank. I packed up and went home.
How It Happened
To make a long story short, I went home and did lots of research, and found a diagram for RPM with cast lead. With a 1 in 8 twist rate at 2,300 FPS, my bullets RPM was 211,000. Well over the now known 140,000 max. My bullets were not tumbling, they were spinning apart inside the barrel. That explains the chunks of lead in the muzzle break. I did research on cast lead shooting competitions, and found out they are pushing bullets into the 3,000+ FPS range but they are using 1/18, 1/20 and even 1/32 twist rates.
It really sucks that this happened to me as well as other people. I wanted to share this incident to save someone some grief, and to learn from my lack of knowledge. But, now I know.
The Overwatch
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