Issue fixed. (Can delete)

[MIGUEL RUVALCABA]

Well according to local shop my lower ACTUALLY is machined right fits and fired with him... I get all input on here but I'm just updating with what I get.. I was trying to save $ and get insight on here but I spent $ on three different gun smith and finally one here in Elk Grove stated lower wasnt to DPMS specs but upper receiver wasn't a DPMS nor any mas distributor he knew of. Hence shop that sold to me LCG is closed. So NOW BEING told to try a new low mass upper receiver. 😳🔫

[Rock6.3]

So there is nothing wrong with your lower.
Now the problem is with your upper.

Are we still meeting at the range this weekend?

[Central Coast Gunsmithing]

So you should start trying what we told you systematicly going through your upper reciever

But if that picture you posted was normally it looks like a short cycle and you need to look at your gas system also check your bolt carrier for lopsided wear patterns that can cause binding too

[kcstott]

So you should start trying what we told you systematicly going through your upper reciever

But if that picture you posted was normally it looks like a short cycle and you need to look at your gas system also check your bolt carrier for lopsided wear patterns that can cause binding too

^^^^this once again. You need to go through every thing.
In reality I'd ship it down to arbarrels and have Randal take a look at it. His time is worth the money. If you wanted someone a little closer there is Kendog on the board too but you'd have to ship as well.

[MIGUEL RUVALCABA]

I have two video clips of what it's doing now but don't know how to post them. Did load only one round at a time and noticed the brass just bounces around in side. Almost like can't make it out the upper. 26 rounds shot only 1 cycled correctly. I'd post video but don't know how sorry.

Response, BCG is starting to get some rubbing on the siding right before bolt. But think I'm going to just buy a stripped upper from Brownhells and if that doesn't fix it then buy JP adjustable gas system.

[ar15barrels]

Did load only one round at a time and noticed the brass just bounces around in side.
Almost like can't make it out the upper.

This is usually over-gassed.
In an overgassed situation, the bolt unlocks before the bullet makes it out of the barrel.
The extractor jumps the cartridge rim.
The chamber pressure in the barrel keeps the case in the chamber until the pressure in the barrel subsides.
As pressure is dropping, the case is freed from the chamber and pushed out of the chamber into the action where it bounces around.

Read this: www.ar15barrels.com/prod/operation.shtml

The correct solution for overgassed operation is to reduce the amount of gas getting to the bolt carrier group which will slow down the unlocking.
The "patch job" fix is to just increase extractor tension so the extractor does not jump the case rim.

[MIGUEL RUVALCABA]

Believe it or not.... After so many different parts replaced..... The upper receiver wasn't DPMS... Lower worked great and the no name(Sold to me from LCG) didn't line up straight across. causing the carrier to rub on the sides and slow down.... So now I have a upper that I can't use and would need to machine that one more to make it work correctly.... Thanks everyone for your feed back and help.

[bigcalidave]

I don't get it. Other companies make uppers, lowers, etc. you should be able to see and feel if the carrier is hitting or rubbing on either. Without something majorly wrong I can't see the lower causing ejection problems, I've made crazy out of spec lowers, and not had a problem lol. On one of my 308s it really needed to break in. There is a lot of lug surface there, any little burrs and sharp edges need to wear in before it is smooth. I was having the exact same problems, hell the first round just jammed in there. Sprayed it wet with lube, ran through 40-50 shots and now it is perfect.

[kcstott]

Believe it or not.... After so many different parts replaced..... The upper receiver wasn't DPMS... Lower worked great and the no name(Sold to me from LCG) didn't line up straight across. causing the carrier to rub on the sides and slow down.... So now I have a upper that I can't use and would need to machine that one more to make it work correctly.... Thanks everyone for your feed back and help.

I'd like to see the upper in question. and if you don't want it $$$$

[kcstott]

I don't get it. Other companies make uppers, lowers, etc. you should be able to see and feel if the carrier is hitting or rubbing on either. Without something majorly wrong I can't see the lower causing ejection problems, I've made crazy out of spec lowers, and not had a problem lol. On one of my 308s it really needed to break in. There is a lot of lug surface there, any little burrs and sharp edges need to wear in before it is smooth. I was having the exact same problems, hell the first round just jammed in there. Sprayed it wet with lube, ran through 40-50 shots and now it is perfect.

You assuming he's mechanically inclined. Which from his posts is definitely not, (RUVALCABA This is not an insult it's just what it is)

He's having a hell of a time trying to figure out what the hell is going on. And after going to a few gun shops where some dip behind the counter that cant change his own oil but can give sound trouble shooting advice on firearms mis directs him sure I can see him being confused as hell.

Still want to see the upper

[MIGUEL RUVALCABA]

Well upper is off and in hand and yes I'm not an idiot if 3 other gunsmiths were confused with it.... So bigcalidave No Lube, spit shine, or taking about and re shooting it doesn't fix the issue. But a damn Brand new upper fixed it!!! So this high profile upper that I can't use or don't want to try and take a dremel tool to bottom of it(so it will align flush with lower.

[kcstott]

You say three other gunsmiths were confused. The problem would have confused my six year old daughter. The gunsmiths should have been able to narrow it down if not identify it. The problem is we all assume these aluminum parts are correct and sometimes that ain't so. A good set of eyes a set of calipers and some gray matter between the ears would have nailed it.

Like I originally suggested, pull up a print dig out your calipers and check your parts and in this case you would not even need a print you would just need to make a comparison

I'm still not following what you mean by "fits flush with lower" what do you mean side to side or up and down??

[MIGUEL RUVALCABA]

Up and down. There was a gap between lower and upper small enough to see through. Slowing down BCG AND Causing it to Rub against lower. Tried first upper on two lowers same issue. After all parts changed same issue. Last to get replaced was stripped upper receiver. Once it was replaced fires like a champ with TIGHT 5 round group. So again don't want to beat a dead horse but yes the rear lower part of upper was longer than DPMS pattern causing it to rub against the back of lower before sitting flush. Would need to use dremer tool against rear bottom end of upper to get it to sit flush with any lower.

[kcstott]

Up and down. There was a gap between lower and upper small enough to see through. Slowing down BCG AND Causing it to Rub against lower. Tried first upper on two lowers same issue. After all parts changed same issue. Last to get replaced was stripped upper receiver. Once it was replaced fires like a champ with TIGHT 5 round group. So again don't want to beat a dead horse but yes the rear lower part of upper was longer than DPMS pattern causing it to rub against the back of lower before sitting flush. Would need to use dremer tool against rear bottom end of upper to get it to sit flush with any lower.

Ahh.. NO your take down pin holes determine how low your upper sits on the lower. if the take down pin holes are drilled and reamed to far from center line of the upper it will make your upper sit higher with a gap.

No amount of dremaling on the rear of the upper is going to allow your upper to sit flush. it is the Hole location that is off slightly.

Now do me a favor put these two part together with the pins holding them together. Then start off with some post it notes and start checking the gap. stack up post it notes until you can't get them to slide under anymore. Tell me how many post it notes you have stacked up and i'll tell you how big you gap is. # of post its X.003" = total gap.

or if you have a set of feeler gages use those. but in this day and age that's doubtful

In any event I don't see that gap causing an issue. I've seen worse gaps on rifles that worked fine. That gaps look to be about .015" and I doubt that would hurt anything. Have you tried assembling your rifle with out the buffer and spring to see how it feels?? If you can feel a significant and pronounced rub when you pull back the charging handle your upper is fine.

Now the other question is did you use all your original parts on the new upper that worked for you. did you change anything else but the upper?? see in ruling things out you should swap one item at a time.

[ar15barrels]

0.010" is NORMAL between upper and lower receiver.
I'm betting that his takedown pin hole in his lower is mis-located and tolerance stacking between his upper and lower is the issue.
The new upper just hapens to be at a different end of the spectrum on tolerance and the stacking is correcting the problem instead of exaggerating it.