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Posted: 11/6/2009 1:00:29 PM EDT
About a month ago I ordered a new Noveske LoPro 14.5". Much to my surprise what showed up was a LoPro switchblock model (AAC FH and Switchblock). Suppressors and SBRs are illegal in Michigan (Michigan FTL  ) but I've been thinking about this a little bit...theoretically speaking...wouldn't turning the switchblock to the "Suppressed" mode and then to the "Off" mode (making it effectively a single shot rifle) increase the MV respective to the position of the switch? I'm not talking about a lot of gain...but wouldn't decreasing the volume of space that consumes the expanding combustion gases increase the maximum pressure inside the barrel and thusly, increase MV? That is, of course, assuming constants of loadings, ammunition, and environmental conditions.
I'm currently working on a BS in electrical engineering...the little details about how things work has always interested me. I know there are many of you like me on this board. 
What does the hive think about this? Has anyone coincidentally tried this in a Chrono? I don't know of anyone with a Chrono...but if I did I would certainly give it a try. |
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I run a switchblock on my 3 gun rifle. I have not used it on "s" yet but I do know when in "o" or OFF, it does go to single shot, not sure about the "S" option yet, can isnt here.
Edited, opps I totally mis read the question, I thought you were asking about what do the letters mean, sorry, skimming. |
| From a MV stand point by the time the gases have expanded to the point of traveling down the gas tube to the BCG and the process of rearward bolt movment occurs the bullet has left the barrel. i see your theory and it is sound in principle. That being said i would say the MV difference would be marginal probably a few FPS, if that. I did see one of the slow motion reels from one of my college buddies of a silenced HK USP 45 in very slow motion and by the time the slide had come back a fraction of an inch the bullet was 4-6 inches out of the barrel. I would be interested as you to see the actual data. Im sure some one in the hive with a similar set up as yours and a crono can set us straight. |
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While not using a switchblock, I did chrono my 14.5" SBR a month ago. I shot unsuppressed and suppressed. As a civil engineer I figured that the can would hold pressure on the bullet longer and provide a little more velocity. I was wrong. I chrono'd exactly the same velocities. I suspect that a significant portion of the gas is bled off by the time the bullet reaches the can. I suspect you may be correct that reducing the pressure bleed off or eliminating it with the switchblock might provide some additional velocity, and in turn momentum. I am waiting for a 10.5 in from Noveske so that test is on my too do list. |
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I'd be very interested to hear the results of your test on the 10.5" switchblock. It doesn't surprise me that the bullet velocity didn't change with the addition of a suppressor...the volume available for gas expansion inside the can(and also the baffles deflecting both the sound waves and expanding gases) would almost certainly negate the effects of the longer "barrel" created by attaching the can. I think the switchblock will provide different results, however. I do suspect the results will be minimal.
Does it seems logical to you that since the dwell time of the 10.5" will significantly less than that of the 14.5" (luckily they share the same gas-tube length) the *potential* gain in MV by closing the switchblock on the 10.5" will be less than that of the 14.5"? Once the bullet has left the barrel there is no effect at all in velocity due to the reduction in size of available space for the combustion gases to travel. |
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