This is a post I have been meaning to make, but now that I have done enough testing, I feel comfortable posting. This is not an official release, as this is not my original design, nor is it anything new. This is my adaptation of a safe dryfire device, [https://makerworld.com/en/models/1338091-nerf-dry-fire-training-device-manual-priming-dry-f#profileId-1377936](https://makerworld.com/en/models/1338091-nerf-dry-fire-training-device-manual-priming-dry-f#profileId-1377936), that is modified to fit u/TofuKat 's mounting solution for the 5xR BCAR. Note that the limits of my testing are up to 290-300 fps with my SBL, so I cannot guarantee low wear with any spring loads and systems capable of higher fps.

  
For those who will make the argument that it is still unsafe, it's a device for protected dryfire, i.e., it significantly reduces the force and wear on the plunger assembly when dryfiring. It is meant as a training unit, not something to just futz around with. I have personally used this on my SBL 1 for the last 5 months when I train. It is a lot punchier than a dart being fired, but it is safe for my system. I would only recommend this for systems with reinforced plunger assemblies (metal and Delrin), as that is what I have tested it on. 

I argue that it is safe for the plunger system, because I have a setup to measure the force of springs and the spring constant, and everything over the last 5 months indicates that the spring is losing its potential on schedule with the regression of spring force over a normal k25's lifespan, which is minimal. I do not think I can disclose the actual numbers, because it is a spring from u/potatofeeder, and I'm sure he doesn't want the details of his products out there. The metal and Delrin components show no increased signs of wear outside of what is considered normal. I will state that u/potatofeeder had an SBL with over 10k darts through it with these upgrades and saw very few signs of wear. In my case, I do have a medium to high firing schedule for the SBL with these upgrades, and I have seen no concerning wear and tear. This brings it to my final point: do not use this if you don't feel comfortable with the concerns that are raised.

  
pm me if you want a version adapted for 17/32 brass. I'd be happy to design another mount.

Safe(enough) Dryfire device for 16mm