Higher Flow Than Stock Bolt
I purchased the Terminus Bolt for my MR1 as an upgrade for the stock bolt. The Terminus bolt basically has two halves. The front is a hollow tube with a detente slot and a gas port hole. The back is a solid cylinder with a groove cut in it and a hole for the cocking pin. A spring is placed between the two halves and they are pinned together. The pin goes through the front tube, and into the slot on the back cylinder. The bolt can compress when it meets resistance because the slot allows it slide past the pin. The front stops when it hits a chop ball, and the striker pushes the back forward and the energy is absorbed by the bolt spring.
When I received the bolt, I immediately discovered an issue with it. The bolt had been out in the mailbox on a 40 F day and it was cold. When I compressed the bolt, it did not spring all the way back. It stopped short and blocked half the gas port hole. I warmed the bolt inside and it worked normally, but with noticeable drag. I cooled it again in the fridge, and it would hang again.
The next day was warmer (about 70 F) and the bolt worked okay in a practice. The stock bolt weights 1.5 oz and the Terminus weighs .8 oz, so it is only about half the weight. Also, since it doesn't have a venturi like the stock bolt, it flows a bit better. I was able to reduce my pressure slightly and the gun had slightly less kick, probably due to the lower pressure and lighter weight.
I decided to try something. I put an e-trigger on from another gun and fired a full hopper on full auto using CO2. The gun cooled quite a bit and was spitting frost. I immediately pulled the bolt and it was also very cold. Again, I had the same problem with the cold bolt. It would seize up and not spring back all the way when compressed, and this would block part of the gas port. It worked normally again once it warmed up.
So if the bolt was used in the cold, and it chopped, your gun may not fire correctly after that because the gas port would be partially blocked. When cold, it also took more force to compress the bolt, which means you would be more likely to chop.
So I got my hands on a second Terminus bolt for a VS1. It worked more smoothly at warm temps. When cold, it did drag more, and took slightly more force to compress fully, but it still snapped back to the correct position when compressed, and didn't block the gas port.
So I set out to find out why the MR1 bolt didn't work as well. I had some theories, but I wanted to examine the bolts physically too. I disassembled the two bolts and started making comparisons. The front portion of the bolt on both models had a slight taper from front to back of the tube, and it had more of a taper on the MR1. This could contribute to higher drag. The MR1 bolt also had another problem. The hole for the pin that holds the two halves together was not drilled precisely through the center line of the front tube. When assembled, the end result was that the inside of the slot on the back half rubbed the pin, adding a little drag. The next problem with the MR1 bolt was coincidence, but the pin is a compression pin, with a rough seam. Well the pin was pressed in with the seam turned so that it was the part of the pin that rubbed the inside of the slot on the back half. This really added drag.
So I took 1000 grit sandpaper and cleaned up the cylinder and slot on the back half (the slot had burred slightly due to rubbing the seam of the pin). On the front half, I used 1000 grit rolled on a tube so that it had a tight fight at the back of the bore. I then sanded in a rotary motion until the taper on the MR1 bolt matched the taper on the VS1 bolt (removed a thousandth on the last 1/8" of the front half of the bolt. I couldn't do anything about the off axis pin holes. They were just off slightly, so I had to leave it be. Then when I pressed the pin back in, I made sure to orient it so that the seam was away from the side that rubbed. I made sure it lines up with the slot, so it would never rub anything on the rough seam.
After putting the MR1 bolt back together, it actually worked more smoothly than the VS bolt. I haven't had a chop scenario since fixing it, but it should work better since it operates smoothly now.
So both bolts are somewhat sensitive to the cold still, requiring more force to compress cold than when warm. So the anti-chop features becomes less effective in the cold.
So while my MR1 bolt had several build problems, the VS1 bolt seemed to be fine. I suspect this has to do with manufacturing tolerances and some bolts will just be better than others.
The bolt has some positives, with the lighter weight and anti-chop feature. However, my MR1 bolt had some build problems that required some effort and know how to smooth out. YMMV on build quality.
Even when properly machined, the bolt is sensitive to cold and the anti chop feature becomes less effective the colder it gets (I tested down to 28 F). It also has a tiny green o-ring inside the bolt, so it will be an odd size to find if you need a replacement.
So winter players may want to stay away from this bolt, or at least have a backup in case it gives you problems.
My opinion is that if it stops even one chop, then it is worth the extra money over a regular Delrin bolt. One chop that gets paint in the barrel will effect the next 50 shots. For the MR1, I think this is the only drop in anti-chop bolt and it isn't a bad one at that.