One of the many aspects worthy of an organized study is the effect of pellet to LDC bore clearance on muffling effectiveness. There is a common belief that baffle bore size matters a great deal, and that making the bores 1 mm larger than necessary is unacceptably wasteful of suppression capability. The idea with the attached set of LDCs is to enable anyone with a printer to test this premise for themselves.
The three LDCs shown below have a very generic baffle design, using 60 degree included angle cones. The OD is 1", and the overall length is just over 4". The STLs attached in the ZIP file are identical, except for the bore diameters. They should print with bores having 0.5 mm; 1 mm and 1.5 mm radial clearance with a 5.5 mm diameter pellet, respectively.
The actual bore diameters are expected to print at 6.5; 7.5 and 8.5 mm, respectively. All baffle bores are the same in any given LDC - there is no taper or step in diameter. The front end has the bore diameter embossed. Hopefully that will show well enough in the prints to distinguish them from each other.
These LDCs are intended for .22 caliber up to 30 FPE. The threads are 1/2-20, and should be usable off the printer.
I predict a spread of less than 4 dB, smallest to largest bore; for this set of LDCs. But I could be wrong, because by "predict" I mean guess or estimate; not calculate, guarantee or certify.
Some are adamant that a 2 dB difference is significant. I would agree, if their best muffler reduced their airgun report by only 6 dB; and the second best by only 4 dB.
My goal for my muffler designs is a 10 dB peak sound reduction, over bare muzzle. If I can achieve a 12 dB reduction, I am willing to give up 2 dB for a more pleasing sound: More thud and less crack. a 10 dB reduction is not always possible, if the customer insists on a very compact muffler. Obviously it also depends on the platform and tune, to a very large degree.
On, to the subject of this thread: Similar mufflers, that vary only with regard to the bore to projectile clearance. If every tenth of a mm extra clearance matters a great deal, then a full 2 mm of extra bore clearance should show a definite signal. But, how much? Lets find out:
These mufflers need to be printed standing vertical on the printer platen, with the threads uppermost.
View attachment LDC bore clearance study STL files.zip
The three LDCs shown below have a very generic baffle design, using 60 degree included angle cones. The OD is 1", and the overall length is just over 4". The STLs attached in the ZIP file are identical, except for the bore diameters. They should print with bores having 0.5 mm; 1 mm and 1.5 mm radial clearance with a 5.5 mm diameter pellet, respectively.
The actual bore diameters are expected to print at 6.5; 7.5 and 8.5 mm, respectively. All baffle bores are the same in any given LDC - there is no taper or step in diameter. The front end has the bore diameter embossed. Hopefully that will show well enough in the prints to distinguish them from each other.
These LDCs are intended for .22 caliber up to 30 FPE. The threads are 1/2-20, and should be usable off the printer.
I predict a spread of less than 4 dB, smallest to largest bore; for this set of LDCs. But I could be wrong, because by "predict" I mean guess or estimate; not calculate, guarantee or certify.
Some are adamant that a 2 dB difference is significant. I would agree, if their best muffler reduced their airgun report by only 6 dB; and the second best by only 4 dB.
My goal for my muffler designs is a 10 dB peak sound reduction, over bare muzzle. If I can achieve a 12 dB reduction, I am willing to give up 2 dB for a more pleasing sound: More thud and less crack. a 10 dB reduction is not always possible, if the customer insists on a very compact muffler. Obviously it also depends on the platform and tune, to a very large degree.
On, to the subject of this thread: Similar mufflers, that vary only with regard to the bore to projectile clearance. If every tenth of a mm extra clearance matters a great deal, then a full 2 mm of extra bore clearance should show a definite signal. But, how much? Lets find out:
These mufflers need to be printed standing vertical on the printer platen, with the threads uppermost.
View attachment LDC bore clearance study STL files.zip
Last edited:
