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Posted: 1/15/2008 7:53:05 AM EDT
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I'm having an XM177E2 clone built. How far behind the FH slots should the barrel end? I know the real barrels were 11.5" but they also used the real flash/sound suppressor. What will produce the least amount of flash: The muzzle being closer or farther away from the FH slots? thanks Edited to emphasize my actual question. |
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This doesn't really answer your questions, but I suppose as long as the barrel couldn't be seen in the slots it would look okay. I think there are several members on here that have had barrels cut so that the barrel extends up the inside of the flash hider to just behind the slots. I'll try searching for a link or pics. ETA: Take a look at this thread. |
Mine is about 14" for reliability and velocity, just behind the slots. I'm just guessing here, but I suspect if you're building it for flash suppression, the short barrel may be better, since everything would have more room to expand and dissipate before the end of the FH. |
| Consider the powder used in loading the rounds. The powder has at least as much effect in the muzzle flash as the flash hider itself. If you load, use a faster burning powder, that will make as much of the burn occur in the barrel instead of out in front of the muzzle. Also longer barrels allow more room for the powder to burn inside the barrel, thus less flash. 20" barrels produce less flash than 7" barrels do. |
Anybody else with ideas about this?
Sweet!!!
I'm not trolling  , but why are you so concerned with flash? I would be more concerned about velocity which you will loose with a shorter barrel. There are a lot of good options out there including the one used by 45bravo which maximizes barrel length while keeping the look of a short barrel. Bugs762 |
| I have one of the traditionally done ones, but I have been considered doing one with the flash hider sleeved over the barrel. The only thing that concerns me is the harmonics of the barrel and what the buildup of heat will do to the sleeved portion. Anybody got any ideas about this? |
I would say a Proper-XM and a Sleeved-XM would act as a heat sink either way, drawing heat from the barrel and aiding in cooling. Sounds like a nice Myth Busters test in fact. Anyone got an infrared thermomoter and an SBR with removable XM FH to test barrel cooling effectiveness? |
The STG-58 FHs are like this, but they do have cooling fins the whole length of the FH also. |
I have the infrared thermometer, but I never shoot so much and so fast that it makes a difference... ETA: Anyways, I'm still about a month or so away from my stamp... |
Dont' have to have a fancy test, maybe something like this: XM FH attached - fire 20 rounds in 20 seconds, measure barrel temp at 1, 3, 5 minutes later. XM FH not attached - fire 20 rounds in 20 seconds, measure barrel temp at 1, 3, 5 minutes later. |
Please start a new thread if you want to talk about barrel temps.|
In general, the longer the barrel the less flash. The powder is burning in a closed atmosphere, once it hits the air, all the unburned particles will ignite, and poof into a fireball. The longer the closed atmosphere, the less powder will escape to burn in free air. You can also mitigate this with faster burning powders. |
Imagine a moveable light bult bulb (the muzzle flash) inside a four-foot long section of pipe that has holes at only one end... The room will become more "lit" with light as you slide the light bulb toward the holes. |
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