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Posted: 6/2/2020 12:59:28 AM EDT
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CMMG only makes their 45acp Banshee with an 8 inch barrel and a 5 inch barrel. When shooting suppressed, I hope the CMMG Radial Delayed Blowback (RDB) system should help reduce ejection port pop noise since the bolt is delayed. Questions : 1. Which of the two barrel lengths would be quieter suppressed, the 8 inch barrel or the 5 inch ? 2. I wonder if the 8 inch would let the expanding gas pressure drop before it enters the suppressor and then have less pressure and sound come out of the suppressor. However, would the bolt open while the bullet is still traveling down the longer 8 inch barrel, therefore letting higher pressure gas escape out causing more ejection port pop ? 3. Would the 5 inch barrel be quieter than the 8 inch because the expanding gases should be inside the suppressor sooner before the bolt is open enough to allow expanding gasses to escape causing ejection port pop ? Or would those expanding gases hitting the suppressor sooner cause more blowback pressure to escape causing more ejection port pop ? 4. Have any of you shot the 5 inch barrel next to an 8 inch barrel at the same time with the same Can to hear if one is quieter at the shooters ear ? Thanks in advance for any helpful replies |
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Regarding 5 vs 8.... but only with 9mm: There was a post on subguns.com from Tom Bowers back when he still owned the domain where several were discussing the CMMG 'Guard' (what they called it back then). This was right when they were starting to transition to the Banshee naming. He mentioned that he thought the 5" 9mm was loud using his Bowers cans as well as using the CMMG branded Defcans. I posted on that thread to clarify the lengths and he confirmed that he only got to try the 5" and not the 8" and that he thought the 8" would be quieter but he didn't get a chance to try one. Conversely, I only have experience with the 8" CMMG 9mm RDB and mine are all plenty quiet to me. I haven't heard a suppressed 5" CMMG RDB yet to compare. I think a longer barrel should be quieter as it should be less pressure for the suppressor to deal with. I like to shoot unsuppressed sometimes as well so I like the 8" length and also have more rail space and handguard length to closer match my 556 builds. |
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Most 45 factory ammo is subsonic out of a pistol (~5”) barrel. I would be slightly concerned more about some rounds going super sonic with the extra length more than increased port pop personally. A brief check showed this to be true with some ammo. http://www.ballisticsbytheinch.com/45auto.html |
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Quoted: CMMG only makes their 45acp Banshee with an 8 inch barrel and a 5 inch barrel. When shooting suppressed, I hope the CMMG Radial Delayed Blowback (RDB) system should help reduce ejection port pop noise since the bolt is delayed. Questions : 1. Which of the two barrel lengths would be quieter suppressed, the 8 inch barrel or the 5 inch ? 2. I wonder if the 8 inch would let the expanding gas pressure drop before it enters the suppressor and then have less pressure and sound come out of the suppressor. However, would the bolt open while the bullet is still traveling down the longer 8 inch barrel, therefore letting higher pressure gas escape out causing more ejection port pop ? 3. Would the 5 inch barrel be quieter than the 8 inch because the expanding gases should be inside the suppressor sooner before the bolt is open enough to allow expanding gasses to escape causing ejection port pop ? Or would those expanding gases hitting the suppressor sooner cause more blowback pressure to escape causing more ejection port pop ? 4. Have any of you shot the 5 inch barrel next to an 8 inch barrel at the same time with the same Can to hear if one is quieter at the shooters ear ? Thanks in advance for any helpful replies I just ordered the 8" barrel and bcg last week for the .45 RDB. I already have a 5" 9mm RDB, but havent gotten to shoot it outside. Inside it sounds more quiet than the Scorpion to me. Which lower are you going to use? In the PCC section, someone mentioned putting .45s in a standard PMAG, but I have my doubts. I'm using the endomag guts for my 9mm RDB. |
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Quoted: Most 45 factory ammo is subsonic out of a pistol (~5”) barrel. I would be slightly concerned more about some rounds going super sonic with the extra length more than increased port pop personally. A brief check showed this to be true with some ammo. http://www.ballisticsbytheinch.com/45auto.html Here’s some chrono data in FPS of common factory loads that I measured through my .45 ACP conversion AR awhile back: AR-15 .45ACP Carbine (16" barrel) Winchester 185-gr STHP.......................1067 Aguila 230-gr FMJ..............................924 Remington 230-gr FMJ.........................911 Remington Golden Saber 230-gr JHP.........1035 Speer 230-gr Gold Dot HP......................953 As you can see, even the 185-gr remained subsonic (barely). If you stick with 230-gr regular pressure I think you have very little worry. |
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With proper chamber size and powder selection the pressure in the bore will seal the case walls against the chamber until after the bullet leaves the barrel muzzle. The pressure at the chamber when the case walls relax and allow blowback/extraction will be similar. So I don’t know if you’ll be able to hear a difference in port noise between a 5” or 8”. Total gas flow back through the port probably has more to do with suppressor design. I suspect suppressor design will also impact whether the lower muzzle pressure of the 8” translates into something you can hear. Unless you have a stable of cans to try it’s probably more fruitful to choose the barrel length that meets your handling and ballistic needs. |
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