Flash From Ejection Port

[Ledge]

Yesterday, I got to the range right at dusk. We generally wrap up shooting outside when it gets dark, but this time of year, we squeeze in every minute of outdoor trigger time we can get. One of the guys I shoot with just got an MGM double swinger, so I had to try it out. After I got done shooting, one of the other guys that was watching us said that about every fifth round, he could see flash coming from my ejection port. When you look at my brass, you can see where gases are coming around the case a bit. The pistol is an M&P 40. The rounds that I was shooting are not very hot by any stretch of the imagination. How concerned should I be about this?

[enoon]

First, if the rounds are not very hot, the gases coming around the case have the room to do that because (probably) the brass has not expanded to seal the chamber. Maybe better to say the gases come around the case because the load is not very hot. Second, the flash at the ejection port probably has several "causes" in combination. The "not very hot" load allowing the gas to go around the case (breach not sealed), perhaps the powder, perhaps the gun's timing, perhaps...

I would alter my load, but more out of personal prejudice (the I just don't like that attitude) than a concern for safety, chamber erosion, and/or...

Edited November 11, 2006 by enoon

[Flatland Shooter]

I've noticed something similar on my open gun.

For years I've used Starline brass on my 9x21 and recently switched to PMC brass. The fired PMC brass shows a burnt mark along one side of the brass. Never saw this with Starline brass.

I shoot major (PF = 169+) at an indoor club often under what would be considered "dusk" conditions but no one has ever made a comment about a flash from the ejection port.

I assumed that the new brass is a little bit tougher than the old brass resulting in less expansion into the chamber and therefore insufficient seal.

If there is a concern about safety or destroying the gun, please chime in.

Bill

[Ledge]

A little more info on what I was shooting last night when this was noticed:

40 s&w

135 gr. berrys bullet

5.8 gr. titegroup

1.125 oal

Looking back at spent brass from previous outings, I think that the symptom of the "flash mark" on the side of the brass might date back to roughly the same time as I started using a lee factory crimp die. Is this a possible correlation? My main concern is my health and safety, followed by the lifespan of my firearm.

[ParaJoe]

A little more info on what I was shooting last night when this was noticed:

40 s&w

135 gr. berrys bullet

5.8 gr. titegroup

1.125 oal

Looking back at spent brass from previous outings, I think that the symptom of the "flash mark" on the side of the brass might date back to roughly the same time as I started using a lee factory crimp die. Is this a possible correlation? My main concern is my health and safety, followed by the lifespan of my firearm.

I don't know why but that seems like a LOT of powder.

Joe

[Ledge]

I don't know why but that seems like a LOT of powder.

Joe

For a 135 gr. bullet though? I built the load based on a few sources, one of which being hodgdon's web site.

[ParaJoe]

I don't know. I load a 180gr bullet with 4.3gr of Titegroup. I guess I'm just used to hearing lower powder charges with TG. What are your loads chronoing at?

Joe

[sargenv]

After looking at the Hodgdon web site, he has a bit of room to go up with those 135's. Max charge of Tightgroup for a 135 is 6.4 gr while a 180 it's 4.7 max. Bear in mind that we are talking a difference of approx 25% less weight between the 180 and 135. In that light, 5.8 is quite a bit lower than he can go. Hodgdon also lists their COL as 1.125".

Vince

Edited to add:

I've seen the same kind of thing when shooting my Browning Gold at night under the lights at the skeet range. It's weird seeing the flash come out the side, I just chalked it up as a fluke and did not worry about it after I'd talked to some Hodgdon techs about it.

Edited November 13, 2006 by sargenv

[ipscbob]

I would agree with all said so far with one caution. Take a close look at the area around the primers and be sure that the flash is NOT caused by leakage around the primer. This is somewhat common in very light loads with fast powders and WILL cause breachface erosion over time.

[wsimpso1]

OK, I am going to add to your basic load of shooting trivia here:

Primers and gunpowder is oxygen deficient. This allows your barrel to last as long as it does. If there was excess oxygen or even just enough oxygen, the barrel features would oxidize and be blown out the barrel so fast that it is not even funny.

So, that means that there is still lots of fuel in the powder gases coming out of the gun. CO, HC's, and quite a bit of hydrogen (both H2 and H). And that stuff has expanded and cooled quite a bit and comes out the muzzle when the bullet flies free, as well as out the breech when the empty is pulled out and tossed away.

When the powder gases mix with the air, they are all set to burn some more, but have little to ignite them. Well, unless your primers produce incandescent ash. This is ash that is still orange hot from the primer firing.

The primer ash is at the back of the powder column, and comes out last, and acts as a spark plug, tripping off the hydrogen and making a fire that you usually can not see in daylight, as well as lighting the CO-HC-O2 mix in the plumes at the muzzle and breech.

We were working on making shotshell primers work better in the cold (I worked for Rem in the early 1980's) and found that shotguns can be quite spectacular at dusk if you include finely divided aluminum to primers. We had fire at the muzzle, gas port at mid barrel, and at the breech. Sometimes twice. Yeah, we had too much incandescent ash...

Anyway, I would not feel any need to cure it. It never bothered you in daylight did it?

If you just must cure it, cases that conform to the chamber wall will cut down on leakage, and might reduce it. Changing primers might fix it, but all of the makers like ash because it helps with ignition when things are cold or in rounds with a lot of free air space. Another solution might be to go with faster powder to seal the case better and further reduce gas temperature at ejection. That might also delay ash introduction to the inflammable gas and make the problem worse...

Billski

[L9X25]

When the projectile leaves the barrel the pressure drops to zero and any remaining powder burns very slowly, if at all. It is possible that there is a small amount of slowly burning powder still in the case as it is ejected and creates the flash that you are seeing. Not a big deal.

[wsimpso1]

All of the conversion (burning) of gunpowder into gases has actually happened shortly after peak pressure, which is pretty early. Usually the bullet has not travelled but an inch or less at that point. Then the gases expand as the bullet travels downbore and temps come down adiabatically (not through heat transfer, just through expansion). In a comp'ed racegun, the more pressure you have at the muzzle, the better the brake works, so those guys use slower powders, extending the peak further down bore and raising muzzle pressure, but even then the burning is done by about halfway downbore.

So L9x25 is approximately correct - there is no basic gunpowder burning going on out late in the cycle. What is left is watching the flames. Remember (High School Chemistry) that flames are visible because the hot gases have electrons excited to energy levels above the rest state, and when the electrons fall back down, they emit photons. Each element has its chaecteristics. And this means that the flames are visible not where the burning occurs but where the hot gases are cooling down... So the first flame is a little orange flame at the muzzle, and the second flame is after the ejecta gases mix with air, are lit and burn some more and have commenced cooling, and can be either orange/yellow (CO and HC to H20 and CO2) or mostly invisible but slightly purple (H and H2 to H20).

If all of this makes your head hurt, don't worry over it. Your ammo was not frying the hair off of your hands and lighting your clothes on fire before, so just because a friend saw the flashes does not suddenly mean that you have to fix it. Heck, I know a couple guys who have great big beachball sized muzzle flashes and ejection port fires off of their AR15's and they never knew they had it until someone told them. Then they started looking for ammo that would not do it. It took the fun out of watching them shoot...

Billski

Edited November 16, 2006 by wsimpso1