Ar308 jam

[timelinex]

So I've taken out my lrp07 3 times now and 2 of the 3 times, the rifle jammed after the very first shot. I'm not 100% sure but both times might be after a cleaning.

Subsequent shots all cycled just fine and it was just the very first shot.

The way it jammed is that the empty casing didn't get ejected and was still inside the upper, while the bolt tried to put another round in. So the empty casing and new round would get double stacked into upper.

I was using southwest ammo sw118xr ammo. Basically their 175smk load in Fc brass.

Any suggestions on how to diagnose this?

 

[ipsick]

Have you tuned the gas block for this load yet?

 

[timelinex]

I have not touched anything yet.. Is it most likely a gas issue? It has only happened twice, so even if I was to tune the gas block, these jams would most likely not show while I'm testing if I need to out more or less gas through...

 

[ipsick]

Well there could be timing issues as the rounds feed from the magazine as well as inconsistencies in the ammo load. By tuning the block with that ammo you're at least eliminating as much as possible the gas issue. I usually tune my gas to the point just where it locks back on the last round and then open it up another 1/4 to 1/2 turn. Where is your brass ejecting now? 1 o'clock, 2 o'clock, 3 o'clock, 4 o'clock, etc.?

 

[sentry1]

Is the case stuck in the chamber, or is it extracting from the chamber, and just not ejecting?

I had issues similar to this with my MATEN, and the fix was just to break it in. I spent a lot of time talking to Mega about the barrel, Seekins about the adjustable gas block, and in the end, I tried a simple suggestion: Lube the bolt and upper until it's sloppy wet, run 50 rounds through it.

I did just that, gave it a good cleaning, applied the usual amount of lube, and the problem was solved.

 

[mtrmn]

I find it interesting that it's only the top round out of the mag. Are you stuffing your mag to full capacity? If so try just a few rounds in the mag and note whether the troublesome round was stripped from the left or right side of the mag. Is it always the same side?
Have you tried another mag?
Are you using the bolt release to charge the weapon or are you charging by hand? Since it's always the first round I assume it was one or the other.
Is the extractor ripping a chunk from the rim? If so probably overgassed.
I'm assuming the fired round is still fully chambered and the new round is trying to feed into the rear of the first.

 

[1Sg (ret)]

I have had the same problem on several rifles.I think its a combination of over gassing and break in as has already been stated.They always work there self out.The d fender on the bolt has helped.The over gassing is pulling the extractor over the rim and loading another round.Most of my problems was on the first round also.

 

[Ballista One]

Well there could be timing issues as the rounds feed from the magazine as well as inconsistencies in the ammo load. By tuning the block with that ammo you're at least eliminating as much as possible the gas issue. I usually tune my gas to the point just where it locks back on the last round and then open it up another 1/4 to 1/2 turn. Where is your brass ejecting now? 1 o'clock, 2 o'clock, 3 o'clock, 4 o'clock, etc.?

Really? What gas block are you using?

 

[ipsick]

Really? What gas block are you using?

JP. This is just about how they instruct you to tune their gas block. I haven't run into any issue yet tuning it this way.

 

[timelinex]

Let me clear up a few things. By first round jamming, I mean that the EMPTY casing of the very first round that gets fired, gets jammed on its way out. Here is a picture of exactly what happens.

As you can see, the empty casing gets taken out of the chamber, but for some reason the extracter doesn't do its job of flicking it out. Instead the casing gets extracted but just breaks free during the extraction process and stays in the upper. Then the bolt cycles back forward and the jam happens when the next round gets pushed into the same space that the empty casing is. This bends the end of the empty shells case nek, since its forced against the upper side of the feed ramp, and leaves a dent in the next rounds bullet.

I use the steel dpms 10 round mag that is included with the JP. As far as lube goes. I lubed the bolt with froglube (heated bolt,applied lube, let cool, then rubbed off excess), and then added just a bit more lube into the bottom raceways. So its definitely all slick , but its far from 'wet'.

 

[retiredcop]

Whenever I get a new bolt carrier group I oil the hell out the area where the bolt seals inside the carrier. Then I drink a beer and watch TV for 20 minutes or so as I work it back and forth manually. There is a big difference in how smoothly it moves after just 10 minutes. It helps to wear a leather glove too. Your fingers get pretty sore pulling on those bolt lugs.

 

[ipsick]

Does it do this if you manually cycled it with a full magazine? Have you tried any other magazines?

 

[SICARIO]

It could be your extractor. Is it a JP bolt? If so, you can contact them and get their enhanced extractor. I had the same problem.

 

[mtrmn]

It appears to be extracting, perhaps the ejector spring is weak or the ejector is sticking in the bolt? IF it is only the FIRST round out of a STUFFED-FULL mag, then upward pressure from the next round may be overcoming the weak ejector spring's ability to flip the empty case out the port. OR perhaps the extractor is weak and needs the new spring/o-ring treatment.

Just put 2 rds in the mag and try it. If the problem does not re-appear, and the last round will lock the action open, then I would replace the ejector spring and make sure the ejector itself moves freely in its bore. Run the gun wet, including the gas rings. I recommend Mobil 1.

Try other mags.

After looking at the pic again, it appears that the bolt is over-riding the top round in the mag. In other words maybe the bolt did not come back far enough to pick up the next round, but far enough for the next round to foul up the works. BUT, the empty should have been ejected regardless.

 

[timelinex]

Ok so the picture I provided is me reproducing what happens when I get the jam, not an actual image after the jam. SO the position of the bolt might not be 100% accurate.

Also, I have only shot the rifle 3 times and it happened only twice. So I don't have any concrete patterns down to describe the issue further. The point is just that it should never happen period, so that's why I came on here.

The magazines are never full, as I generally put 5 rounds max into the magazine (at this time).

I think I will put more lube on there, ,maybe try some mpro7, and try this a couple more times. Then I will report back.

 

[Brad28753]

My Armalite AR10 would do the same thing with the first round being fired if the door was closed. Once it was open, it wouldn't do it..... I just figured it was taking too long to kick the door open and getting stuck on the way out.

Just an idea

 

[ipsick]

Have you contacted JP about this? They really are experts with this stuff.

 

[timelinex]

Have you contacted JP about this? They really are experts with this stuff.

I have not... Since I've shot it so little and it's happened so rarely, I didn't want to call and not be able to describe the issue in depth.

I figured posting here will give me insight into what to look at, and it did.

I will lube the bolt up heavily and if it does it again, I will take a picture of the exact malfunction and then call them to see what they say.

 

[wildfowler]

For your 4th shot in this rifle try this:

Put only one round in the magazine and drop the bolt to make sure the weapon feeds properly and fully chambers the round.

Then fire that one round and make sure it ejects properly and confirm that the bolt will hold open on the empty magazine.

If the bolt stays open and the case is ejected take notice where it lands in relation to the ejection port in the side of the receiver.

Please report back.

 

[Metal Gear]

Sounds like it could possibly be an issue with the extractor. I would agree that it could just be something as simple as the ejector spring. Having read some good input from other people on this thread, I will just add by saying that it may also just be a case of needing a little extra lube and a short break in period to work out the bugs. Either way, this shouldn't happened, but I have seen stranger things.

 

[timelinex]

U lubed up the bolt heavily and everything ran just fine yesterday.

The brass flies out completely perpendicular to the rifle. Interestingly my southwest ammo goes maybe 4 ft, while fgmm goes in the same exact direction but literally 20ft away.

Is this a sign of very overgassed?

 

[wildfowler]

Normally if the brass ejects forward of your position is a sign of over gas not the distance.

I can only speculate why there would be such a great difference between the distance the brasses tomorrow between the two loads.

Experiment with your gas block adjustment if possible. Turn the gas down quarter to half-turn and try the Southwest ammo to see if the distance is reduced or increased.

You can experiment with an adjustable gas block and answer that question yourself. And know this, it can be problematic to "tune" and adjustable gas block to work perfectly for different loads in the same weapon.

 

[lennyo3034]

I'm having the same problem:

http://www.snipershide.com/shooting...es/247986-ar-jamming-only-when-its-clean.html

 

[30calDeath]

I had similar issues when I first started using my new to me LWRC REPR. I had changed out the stock from what was on their previously and added a Slash's Heavy Buffer for an AR10. I ended up going back to the stock buffer and buffer spring combo from LWRC and no issues since. The few times that I took my rifle out with the Slash's combo the issues got better and better but I was sick of the jamming and FTE/FTF's.

If your JP is a full build from them then more than likely they have the correct buffer combo in their and it could be a different issue like over gassed or something else someone else is mentioning. I would try and go through every part to narrow it down.

I know it sucks going to the range and having issues with your new, expensive AR only to have it let you down. It will get better, 308 AR's can be finnicky from what I have been experiencing and hearing.

 

[mercracing]

I'm having a very similar problem with a 5.56 SBR build. From what I heard try an adjustable gas block and maybe an upgraded extractor spring from bravo company.


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[mtrmn]

I have found that "the chart" showing ejection patterns is useful to a certain extent, but IF YOUR WEAPON IS RELIABLE WITH NO OTHER SYMPTOMS other than ejecting brass in the "wrong direction" it's best to leave it alone. Use the chart sparingly, IMO it has caused many AR owners to perform much unnecessary work on their weapons. JMO and YMMV

 

[mercracing]

View attachment 36273

I have found that "the chart" showing ejection patterns is useful to a certain extent, but IF YOUR WEAPON IS RELIABLE WITH NO OTHER SYMPTOMS other than ejecting brass in the "wrong direction" it's best to leave it alone. Use the chart sparingly, IMO it has caused many AR owners to perform much unnecessary work on their weapons. JMO and YMMV

Many thanks!! I was going to google and find this but you saved me the trouble!!


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[timelinex]

So I just wanted to update everyone on this. I applied lube onto the carrier/bolt much more liberally and this has not happened again since. I have taken it out 3 times since.


But to be fair I haven't cleaned it again yet.... So time will tell.

 

[lennyo3034]

Mine was a combination of being slightly undergassed, and weak ejector spring. I swapped to a Mcfarland gas ring and new spring.

 

[wxl]

For your 4th shot in this rifle try this:

Put only one round in the magazine and drop the bolt to make sure the weapon feeds properly and fully chambers the round.

Then fire that one round and make sure it ejects properly and confirm that the bolt will hold open on the empty magazine.

If the bolt stays open and the case is ejected take notice where it lands in relation to the ejection port in the side of the receiver.

Please report back.

+1. It could be short stroking. Too heavy buffer or spring. If so it is under gassed.