Armory Sponsor
Posted: 1/1/2017 5:49:46 AM EDT
|
Firearm: SIg MPX, suppressed
Ammo: Precision Delta, 147 grain, 5.9 grains of AA#7, CCI small pistol primers. The AA#7 I am using is old. Probably 15-20 years, but did not smell or look bad and had been stored in a cool, dry area. I've been using this load for my suppressed shooting. It's quiet, and accurate, though I have noticed some powder residue left over. Yesterday, when using these I noticed a bright flash from the ejection port, something I've never seen before. Is this normal ? Was it some of the unburned powder residue ignighting? It happened after about 15-20 rounds than didn't happen again. |
|
Powder is still on burn as case uncorks the chamber end of barrel.. may find debris come out eject port also.
2 way to work around,, first be more buffer weight to slow the bolt opening to allow more trapped chamber-suppressor pressure to vent out the front.. 2nd be to change to a faster burn powder so powder burn up faster which is what I did, as I had originally started back in 2000 with AA-5,, then played with 3N37 (similar burn rate),, then change to Titegroup in 2007. |
|
Quoted:
Powder is still on burn as case uncorks the chamber end of barrel.. may find debris come out eject port also. 2 way to work around,, first be more buffer weight to slow the bolt opening to allow more trapped chamber-suppressor pressure to vent out the front.. 2nd be to change to a faster burn powder so powder burn up faster which is what I did, as I had originally started back in 2000 with AA-5,, then played with 3N37 (similar burn rate),, then change to Titegroup in 2007. ok..so in other words its normal.. Once the AA7 is used up Im switching to N340... just looked at the brass as well...no issues there. |
|
"Powder is still on burn as case uncorks the chamber end of barrel."
Smokeless powder is notoriously under-oxidized. That means it does not have enough oxidizer to bring all the hot gases to a stable state after it chemically breaks down. 'Flash suppressor' chemicals are added to the powder to try and release extra oxygen and reduce muzzle and port flashes. The compounds are not the most stable (some are slightly volatile) and may be less effective in older powder. |
| Part of it could be the AA #7 is a really slow burning powder. You simply arent burning everything before the bolt opens. N340 would be a much better choice and VV powders burn really clean. TiteGroup isnt a bad choice either for 147's, especially if you are loading subs. |
|
Quoted:
AA#7 is fairly slow burning some flash doesn't surprise me but that said the MPX is gas operated and shouldn't be immediately opening like a blowback rifle. That's interesting, but I don't think it's anything to worry about. Yup my thoughts exactly. The bolt on the MPX doesnt have any real lockup does it? Its just a rod operated blowback in reality isnt it? |
Armory Sponsor