View Full Version : Misfire central...Check out the dents on this brass
Factory new Rifle, cleaned, well lubed, gas key tight/staked, gas block tight/straight/pinned, barrel, barrel nut and rail all appears to be properly installed and tight. Took it to the range for a BZO, fired around 35-40rds, accuracy compared to my norm was disappointing, overall extraction was pretty weak with intermittent FTE's, stovepipes, one double feed. Ammo was 2011 Winchester RANGER M855 (all of my other 556 AR's love it), mags used were known good magazines both USGI and PMAGS. I've never experienced any problems with a AR-15 like this before. Always used high quality weapons, parts etc and good quality ammo and mags. Looking at the brass it seems that there is something in the chamber that is denting/gouging into the brass and causing the extraction problems. The flash is drowning, but there are also scratches down the length of the brass on the same side as the dents and some gouging on the case rim from the extractor having to work hard.
What do you malfunction guru's think is going on. Chamber out of spec?
http://i767.photobucket.com/albums/xx311/LONEWOLFTACTICAL/Winchester%20M855%20Brass/DSC02933_zps068612d3.jpg
http://i767.photobucket.com/albums/xx311/LONEWOLFTACTICAL/Winchester%20M855%20Brass/DSC02936_zps0580de2c.jpg
http://i767.photobucket.com/albums/xx311/LONEWOLFTACTICAL/Winchester%20M855%20Brass/DSC02941_zps077fb8d8.jpg
http://i767.photobucket.com/albums/xx311/LONEWOLFTACTICAL/Winchester%20M855%20Brass/DSC02937_zps753768f6.jpg
Those marks are not coming from something in the chamber. Something in the chamber leaving that much of a dent would have the brass sticking. They are getting there during extraction and/or ejection. If the brass were being dented prior to being fed into the chamber, the pressure from firing would push them back out
Those marks are not coming from something in the chamber. Something in the chamber leaving that much of a dent would have the brass sticking. They are getting there during extraction and/or ejection. If the brass were being dented prior to being fed into the chamber, the pressure from firing would push them back out
Not sure what it could be hitting that would make the mark. Maybe the rear of the ejection port due to a weak ejector? The marks are def NOT there prior to firing.
TacticalMark
09-17-13, 22:32
For troubleshooting what position does the brass eject? Are you sure the dents aren't from the brass deflector? Whats the run down on the rifle?
armed_zebra
09-17-13, 22:34
What happens when you chamber a round and then eject it without firing?
What happens when you chamber a round and then eject it without firing?
I manually chambered and ejected rounds from the chamber on two or three occasions prior to pulling the bcg and checking the barrel for obstructions after several FTE's/Stove pipes. The rounds ejected no different than expected with a properly functioning AR. That is what prompted me to take a look at the fired brass.
In all of my years of shooting I've never seen mil brass hit a shell deflector so hard it dented it. If that was the case it would be extremely violent overpressure type extraction, not weak extraction right?
Can you please provide more details about the AR in question.
You may also want to check this- http://www.winchester.com/library/news/Pages/product-recall-556mm-m855.aspx
polymorpheous
09-17-13, 23:53
The failures to extract, (eject? Which one is it? FTE can mean either), and stovepipe are a gas/action issue.
Check for gas leaks and check your buffer spring buffer combo.
The double feed is a magazine issue.
The swipes on the base of the brass, combined with the dents mid-length down the brass from the brass deflector, are both signs of over pressure.
How does it perform with other ammo?
Can you please provide more details about the AR in question.
You may also want to check this- http://www.winchester.com/library/news/Pages/product-recall-556mm-m855.aspx
Thank you for that link. I can certainly check more closely tomorrow, however the ammo I'm using is stamped 2011, from the RANGER LE line RAM855, in RANGER packaging 1000rds per case (not the brown box 900rd cases as listed) and I've fired hundreds of rounds from the same case through my other AR's without a hitch.
The weapon I experienced this with is a new KAC SR-15E3 Mod 1. I've owned several SR's in the past...from SR-15 Matches to the 1st Gen E3's and they all performed extremely well with above average accuracy. This shocked me, mostly because I've had next to zero malfunctions with the AR platform in 20 years of running them. This just stumped me as to what the cause could be. Top shelf weapon, good mags, good ammo etc. That's why I decided to post up here and see if it was something blatantly obvious that I was simply ignorant about.
Thanks gent's.
The swipes on the base of the brass, combined with the dents mid-length down the brass from the brass deflector, are both signs of over pressure.
How does it perform with other ammo?
Well, now that I think of it I also fired some Winchester M193 and had the same result. I don't have any standard .223, because I train with what I will deploy the rifle with. I do remember reading that some early runs of E3's had trouble cycling some .223 because they were tuned and tested with 556. It has me wondering if what they did to help rectify that situation is now showing some over pressure issues with some 556? I don't want to get ahead of the curve...I honestly have no clue what the issue really is which is why I posted.
It seems to me like your BCG is cycling too fast which is why the cases are getting dented - they're hitting the back of the ejection port or the base of the deflector. In the case of a stovepipe, they're bouncing back into the ejection port where the bolt closes on them. I wouldn't say its because of overpressure per se - I've seen a lot of factory ammo show mild ejector swipes: IMI M855, PPU M193, various LC heasdstamps, etc. Too much gas drive is a better explanation I think, although too much gas drive could be a function of overpressure. The gas port could be a little big or the action spring could be weak/short.
What they would do is open the gas port which, yes, could contribute to the issue if that's what was done.
I do remember reading that some early runs of E3's had trouble cycling some .223 because they were tuned and tested with 556. It has me wondering if what they did to help rectify that situation is now showing some over pressure issues with some 556?
Have you spoken to anyone at KAC? Maybe F2S can help you out.
It's over gassed, bolt cycles to fast not giving enough time for ejector to kick the brass. The dents left on the brass are from slamming into the brass deflector and are to strong.
constructor
09-18-13, 08:28
Factory new Rifle, cleaned, well lubed, gas key tight/staked, gas block tight/straight/pinned, barrel, barrel nut and rail all appears to be properly installed and tight. Took it to the range for a BZO, fired around 35-40rds, accuracy compared to my norm was disappointing, overall extraction was pretty weak with intermittent FTE's, stovepipes, one double feed. Ammo was 2011 Winchester RANGER M855 (all of my other 556 AR's love it), mags used were known good magazines both USGI and PMAGS. I've never experienced any problems with a AR-15 like this before. Always used high quality weapons, parts etc and good quality ammo and mags. Looking at the brass it seems that there is something in the chamber that is denting/gouging into the brass and causing the extraction problems. The flash is drowning, but there are also scratches down the length of the brass on the same side as the dents and some gouging on the case rim from the extractor having to work hard.
What do you malfunction guru's think is going on. Chamber out of spec?
http://i767.photobucket.com/albums/xx311/LONEWOLFTACTICAL/Winchester%20M855%20Brass/DSC02933_zps068612d3.jpg
http://i767.photobucket.com/albums/xx311/LONEWOLFTACTICAL/Winchester%20M855%20Brass/DSC02936_zps0580de2c.jpg
http://i767.photobucket.com/albums/xx311/LONEWOLFTACTICAL/Winchester%20M855%20Brass/DSC02941_zps077fb8d8.jpg
http://i767.photobucket.com/albums/xx311/LONEWOLFTACTICAL/Winchester%20M855%20Brass/DSC02937_zps753768f6.jpg
Normal marks but extreme dents.
The lengthways scratches comes from the round being drug over the barrel extension lugs. The dent as big as it is comes from an over-gassed rifle slamming them into the rear of the ejection port.
If those dents have a sharp line they are hitting the rear of the port. If rounded they come from the shell deflector. I think the gas port in the barrel is too large. Try an adjustable gas block to cut back on some of the gas.
Normal marks but extreme dents.
The lengthways scratches comes from the round being drug over the barrel extension lugs. The dent as big as it is comes from an over-gassed rifle slamming them into the rear of the ejection port.
If those dents have a sharp line they are hitting the rear of the port. If rounded they come from the shell deflector. I think the gas port in the barrel is too large. Try an adjustable gas block to cut back on some of the gas.
This is good information to know. As an armorer I have been able to make rifles work, but I am still learning the technical aspect of being over/under gassed.
constructor
09-18-13, 12:09
I should have expanded a little.
A weak or sticking ejector and or overly strong extractor could cause larger than normal dents in the cases too but with other symptoms like poor accuracy and sticking cases the "over-gas" alarm is ringing pretty loud.
Thanks to all that responded. Some great info and it makes total sense to me now as to what is actually occurring.
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