AR Sponsor
Posted: 3/15/2009 1:53:08 PM EDT
|
When I got my new Colt 6920 a few months ago, I broke it open, removed the BCG and oiled (Break Free CLP) all the accessible moving parts in the upper and lower.. After that I fired about 250 rds over several weeks, after every 50 rds I would lock the bolt open and run a slightly-oily Bore Snake through the barrel twice, then put a several drops of oil on the bolt and anything else that looked like it might need lube from the outside. Last night I broke it open again and relubed the more hidden parts, but the BCG has not been removed since the original lube job.
Ammo is PMC "Bronze" 55 gr FMJ, mags are NHMTG in almost new condition. Today the bolt started hanging open when firing. It was way toward the rear, like the bolt catch was holding it open, but the bolt catch wasn't doing anything- the bolt was simply "sticking" near the rear of its travel or maybe when it tried to strip the cartridge out of the mag. Pulling the charging handle back and releasing would cause the bolt to close. This started out as once per mag, by the time i fired 100 rds more today it was sticking open about once every 5 shots. I had been doing the minimal cleaning routine because the gun is not "in service" yet, and I wanted a feel for how often it needs a complete cleaning. This is not encouraging, my 580 series Mini-14 got the same treatment two years ago when it was new and then went through a 1,000 rd rifle class with even less cleaning, never had any problem with it. The Mini shoots 3" groups while my 6920 shoots 2", but still... Diagnosis? |
|
Quoted:
Do a complete field strip and cleaning IAW the -10 Operators Manual. Re-lube IAW the -10 Operators Manual and see how she functions at the next range session. I agree with your suggestion. What I should have made clear in my original post is the real question: "Is this kind of problem common on an AR with that many (~300) rounds and only minor clean/lubeing?" |
|
Quoted:
Quoted:
Do a complete field strip and cleaning IAW the -10 Operators Manual. Re-lube IAW the -10 Operators Manual and see how she functions at the next range session. I agree with your suggestion. What I should have made clear in my original post is the real question: "Is this kind of problem common on an AR with that many (~300) rounds and only minor clean/lubeing?" Did you initially remove, clean, and inspect the buffer, buffer spring and receiver extension? Someone here not too long ago, posted a cycling problem with a new weapon. The problem? A plastic bag with parts, stuffed down into the receiver extension. I always recommend a complete teardown, cleaning and thorough inspection of a new weapon before firing. I also recommend going a little extra on the heavy side with the lube, until things break-in and loosen up on their own. |
|
Quoted:
when the bolt was "held up" did you try the forward assist button? could your replicate the problem if you cycled the bolt manually? did you try a different mag? The bolt was 'way toward the rear, almost where it locks open on an empty mag. I didn't think the BFA would be any help in that location. Am I wrong? Manual cycling the bolt seems ok, but i didn't try feeding rounds through the action by hand. Problem happened with two different mags that have worked fine until now. |
|
Quoted:
Quoted:
Quoted:
Do a complete field strip and cleaning IAW the -10 Operators Manual. Re-lube IAW the -10 Operators Manual and see how she functions at the next range session. I agree with your suggestion. What I should have made clear in my original post is the real question: "Is this kind of problem common on an AR with that many (~300) rounds and only minor clean/lubeing?" Did you initially remove, clean, and inspect the buffer, buffer spring and receiver extension? Someone here not too long ago, posted a cycling problem with a new weapon. The problem? A plastic bag with parts, stuffed down into the receiver extension. I always recommend a complete teardown, cleaning and thorough inspection of a new weapon before firing. I also recommend going a little extra on the heavy side with the lube, until things break-in and loosen up on their own. I did not remove the buffer, just pushed it in about an inch and dribbled a little Break Free along the edges. The gun was pretty wet with CLP in most areas, but as mentioned the BCG had not been removed since the initial lube. |
|
Quoted:
............as mentioned the BCG had not been removed since the initial lube. Some times weapons come from the factory with tacky corrosion preservative compounds applied. If those compounds are not removed before firing, they can cause slow cycling as the weapon accumulates firing debris. I always clean after each range session regardless of number of rounds fired, and I always clean the buffer, buffer spring and inside the receiver extension. 
|
| This may be a stretch but check the gas key on your bolt carrier and make sure it is tight. If it is not then your problem may be caused by short stroking. It may be blowing far enough back to eject the spent round but not enough to fully pass back and load the next round. Also you (in my opinion) are over oiling your AR. |
|
And come to think of it, someone chronographed the PMC Bronze 55 gr and velocity was rather low, definitely .223 and not 5.56
Maybe a little crud plus the low power ammo would cycle the bolt just enough to pick up the next round, but the bolt didn't go back far enough to get a running start before hitting the top round in the mag. Sometimes it would have enough power to strip the round into the chamber, and sometimes the bolt would hit the top round and just stop. Is that a possibility? |
|
Quoted:
And come to think of it, someone chronographed the PMC Bronze 55 gr and velocity was rather low, definitely .223 and not 5.56 Maybe a little crud plus the low power ammo would cycle the bolt just enough to pick up the next round, but the bolt didn't go back far enough to get a running start before hitting the top round in the mag. Sometimes it would have enough power to strip the round into the chamber, and sometimes the bolt would hit the top round and just stop. Is that a possibility? For shits and giggles, you could try measuring your buffer spring to see if it’s in spec. I purchased an LMT SOPMOD stock and experienced the same problem your having. Ended up being an out of spec buffer spring, it was almost an inch too short. I replaced the spring and the weapon functioned fine. |
| When you said you used a slightly oiled bore snake, that brought up concern. You clean your barrel with a proper barrel cleaner, not oil it. Excessive oil in the gas tube from the barrel could cause more debris to collect and keep the gun from cycling properly. Some break free products are cleaners, not lubricant. Get some Millitec for lubrication. Also it sounds like you may be over lubing with the wrong product. Creating a sticky mess. |
|
i have a different take on lube, regardless of what everyone else uses.
i use two lubricants in my ARs: heavy oil for the BCG and in the main areas of the upper (i use Royal Purple SAE30 motor oil), and light high temp grease in the charging handle recess and in the buffer tube. ive experimented with a few different kinds, and i use tetra gun grease in my buffer tuber. it makes the gun run and sound so much smoother, and it lasts a good while. ive been told i was retarded for doing this by a few people that are strictly by the book, but my guns seem to run longer and smoother than the doubters, so its what im sticking with. ive put 1000rds through one of my ARs without a single cleaning, and probably could have gone longer. that being said, the first thing i do when i build or buy and AR is to pretreat all the metal with tetra gun metal conditioner as was recommended to me by Clint McKee of Fulton Armory. all i can say is it must be working. |
|
Quoted:
When you said you used a slightly oiled bore snake, that brought up concern. You clean your barrel with a proper barrel cleaner, not oil it. Excessive oil in the gas tube from the barrel could cause more debris to collect and keep the gun from cycling properly. Some break free products are cleaners, not lubricant. Get some Millitec for lubrication. Also it sounds like you may be over lubing with the wrong product. Creating a sticky mess. BF CLP on his bore snake will not harm a thing, and for as low of a round count as he has, will suffice just fine for cleaning the bore. If any BF was to find it’s way into the gas tube, it would simply get blown out during firing. Break-Free CLP will not cause a sticky mess and there is no such thing as over lubing. Excessive lube if applied will simply be blown from the rifle. |
|
Listen to Quib, he knows what he's talking about. Also make sure to keep that gun properly lubed. Pat Rogers wrote that he has guns run perfect without cleaning and nothing but lube for 500-1000
rounds. I like SLIP 2000 but others have their preference as well. Pat Rogers on Gun Cleaning |
AR Sponsor