Troubleshooting Cycling Problems

[Wessir]

I'm sure this topic comes up a lot but I haven't found the answer yet. Hoping for some tips here.

Chambering the first round by releasing the bolt catch from a charged position it works 90% of the time. The other 10% the bolt ends up somewhere on the side of the casing like the picture.

The second round 99% of the time will jam the same way. The bolt coming down on the casing somewhere (usually at the bottom near the primer).

I ground and polished the feed ramps on the Ballistics Advantage barrel. I checked the non adjustable gas block for proper position. With a chambered round and an empty magazine it locks back every time. I have tried different spring weights in the JP Silent Captured Spring. I've used 3 different brands of ammo. I tried 3 different brand new PMAG magazines.

It appears the round gets caught up when coming forward and the casing is pushed back into the magazine as the bolt moves forward. Is it really getting caught up on something? Is the bolt moving around too much inside the upper receiver? Those are the only parts that don't have some company name on them.

 

[sagebrush]

bolt looks very dry. these guns need engine oil type lube that is almost dripping till broken in

[Radioactive]

Give us some details on the parts used as many are not interchangeable between platforms. Take some close up pics of the bolt locked back, inside the ejection port with loaded mag installed, inside the upper looking at feed ramps, upper and lower fit up etc. the more and detailed the photos the better. What’s going on with the front pin in that pic? Is is fully inserted? Looks off but maybe because of the angle. Have you ever built an ar before? Is it doing this cycling with the charging handle only or does it also do it releasing the bolt from the locked back position with the bolt release? Are you sure the mag was fully seated? What caliber?

[Wessir]

I'm using ptfe for lube on the bcg. Feels smooth and slippery even though it isn't 'dripping'. Is the thought short stroking?

Aero lower parts kit on a PSA lower, that is why the front pin sticks out. Otherwise it does fit and is secure but it does stick out. I bought the upper from Moriarti Arms. It isn't labeled who manufactured the bcg and upper receiver. It chambers rounds properly from the locked back position and releasing the bolt catch. It locks back on an empty magazine as well. Magazines seat well. .308/7.62 20" Ballistics Advantage barrel.

I built an AR-15 and used an adjustable gas block. It works perfectly, very boring. I did this one knowing it would be a bigger challenge because of lack of standards.

I'll check the gas block again, does this kind of jamming indicate short stroke?

[edgecrusher]

Don’t be offended but so far your choice of parts are not meshing well. I’m just trying to help and I’ll explain:

Your upper: moriarty is known to have out of spec parts, that’s why they are so cheap. Could be your upper, bcg... who knows.

Your lower: just look at the mountain of PSA headaches on here. Good news? Most of them are fixed with the correct recoil system, which PSA does not understand in the least. Please give us detailed measurements of that.

 

Now, your barrel is gtg. I doubt it’s a gas issue since you have other things going on, as mentioned in your op. Like dropping from catch to chamber a round. Pictures and detailed info are going to be a must. Tolerance stacking is almost certainly at play here. We can try to make it work but....

 

For what it’s worth, may want to start saving up for a matched receiver set and known bcg. Maybe even a stripped PSA upper would get you closer. Please reply with requested info for more help. Also, search our water boarding thread to see exactly what we are looking for

[Radioactive]

26 minutes ago, Wessir said:

does this kind of jamming indicate short stroke?

It certainly could. So it only does it when firing then?

 

4 hours ago, Wessir said:

 

Chambering the first round by releasing the bolt catch from a charged position it works 90% of the time. The other 10% the bolt ends up somewhere on the side of the casing like the picture.

This is what has me confused.

[Wessir]

It mostly does this when firing. When I pull back the bolt and use the bolt catch to hold it, then put in the magazine, then release the bolt catch it chambers a round and the bolt locks, ready to fire. It has only jammed that way once or twice. I may only have 50 rounds through it so far.

The second round, gas cycled, is the opposite. 9 out of 10 times it is jammed.

[Albroswift]

@Wessir

Here is the waterboarding thread mentioned above. It really helps to zero in on the issue. Lots of good has come of this procedure. 

 

[98Z5V]

9 hours ago, Wessir said:

 

Where did you buy this Aero Precision lower parts kit from?  That pivot pin is not right.  All Aero Precision - hell, ALL manufacturers - flatten the back side of the pivot pin. 

This one is round all the way around.  Not a known pivot pin, from any manufacturer, that I've ever seen, and certainly not how Aero Precision makes their pivot pins.

I once tried to mount a PSA upper on an Aero lower, and there was no way in hell it was going to lock both pins.  Something was wrong.  I tried that same PSA upper to a Matrix lower - No Go.  There's something to be said here for using PSA parts when building a .308AR.  You either go all-the-way-PSA, or don't.  When you DO go with full PSA, prepare to do some work to the gun. 

You've complicated this process simply with the choice of the lower receiver, I kid you not.  You compounded the problem using a Moriarti upper assembly.  Not joking here.

@edgecrusher's recommendation for a matched - or at leastfrom the same company - known receiver sets is the way to go, without further headaches, alot of cussin, alot of wasted ammo, and holes in the garage walls - because this combination is gonna make you throw expensive tools...  

Edited November 2, 2020 by 98Z5V

[edgecrusher]

@98Z5V, nice catch on the pivot pin, didn’t even see that. Good catch, that’s all sorts of wrong

[shooterrex]

I also suspect the captured recoil system is part of the problem. They work well on 5.56 builds but not many folks seem to have good luck with these set ups on the large frame guns.

[Wessir]

Quite by accident I realized the magazine isn't sitting in the well properly. There is a lot of forward and backward slop which changes the angle the rounds are feeding toward the barrel. When I release the bolt catch with my left hand I'm naturally pushing the magazine forward and that is why it chambers the round properly. When I'm shooting, the magazine is hanging free and at that angle the bullet is stopped at the magazine well and the back end of the cartridge is then forced into the magazine. 

It is exactly what it looks like. That's an easy thing to check for and see with your eyes. Hope that info helps somebody out someday.

Palmetto State Armory lower seems to be the real problem. Maybe the magazine catch from the Aero M5 parts kit isn't just right for it. Maybe something else about it. My PSA AR-15 lower works perfectly so I'm not wanting to throw stones at PSA but the least they could do is have the lower parts kit in stock to match with it? It really seems like the lower might be a paperweight without the exact matching parts from PSA.

I am seeing an Aero M5 lower available now so I guess I'm buying that and go from there. 

At least with that my pivot pin will fit the way it is supposed to.

[Wessir]

@98Z5V fyi from the Aero site.

And here's a pic of that mag catch that might be the problem. There isn't much to hold it in either, it is tightened as far as possible and I still push it through when releasing it.

[shooterrex]

Do you have a pic of the other side of the receiver. Doesn't look like the mag catch is screwed in enough. Take a small punch and push the button in and screw that thing in some more.

[Wessir]

@shooterrex Here's the other side, not much to see. It's all the way down as far as it can go I even removed the bolt catch to spin it down. Maybe the PSA made mag release is thicker in some parts to keep it pushing through.

[Wessir]

PSA AR-15 magazine wall is built up to keep that from happening. Good idea don't know why they didn't do that for the AR-10.