Issue fixed. (Can delete)

[kcstott]

Now i admit i don't have a ton of experience with AR platforms but most extraction problems are going to be in your upper unless you have that upper pinned so god damn crooked that it just can't function anymore.

I would check out the upper before you scrap that lower just to give yourself more experience at the leaast

He said it runs fine on a different lower so it probably is the lower

The problem he describes leads me to believe the FCG pocket was machine off center and shifted the BCG over at the rear causing it to bind up.

Now I find that hard to believe as the front take down lug would have to shift as well. The only other issue is the receiver extension thread could be off center but that would be easy to identify.

Once again Brake out the calipers and get your print and check the damn thing.

[Central Coast Gunsmithing]

Now i admit i don't have a ton of experience with AR platforms but most extraction problems are going to be in your upper unless you have that upper pinned so god damn crooked that it just can't function anymore.

I would check out the upper before you scrap that lower just to give yourself more experience at the leaast

[kcstott]

I used a CNC machine which was to spec! And it's not the machining I had 3 guns that had no clew other than to keep trying different parts or at end of day lower since they could tell it mite be having issuers since not linking up correctly. At this moment already have a good amount of $$ into it so might just go Bolt action way or all JP enterprise. I would sell it if the offer at least made me brake even. Only 70 rounds on it now since I fired 10 rounds without any failures on buddy's lower.

Just because it was done in a CNC does not mean it was done to spec.

The offset could have shifted. chips in the vise etc, the set up is only as good as the guy putting that parts in.

Ok so if you are having failure to extract this is what i do when i check ANY GAS OPERATED RIFLE
Put in a Dummy round and see if the bolt will cycle and extract without being fired.

Does it? Good.
Check your chamber and see if it is rough. If it is polish it

Now AR Specific check your gas hole in barrel alignment with the gas block hole if they are correctly lined up then there should be a even circle of powder burn around the gas block hole if it is not lined up then the circle will be ofset to one side or the other of the gas block. Next check your gas tube alignment inside the gas block i.e. look in the hole and see if its a strait shot to the gas tube.

Next if all of that is ok check the gas key on the bolt carrier

If it is loose then that can also cause problems

Another problem can also be caused by the bolt carrier binding in the upper receiver you can check that by using a rod and pushing the bolt carrier group strait back in the hole that the gas tube goes into.

There are tons of other issues but those cause the most of your failure to extract on a very consistent bases even a poorly shaped extractor will extract as long as it snaps over the rim of the case If i could see pictures of your brass or you can at least explain what clean brass looks like after being fired in your gun once it would help

(btw I,m a gunsmith not a English major as you can tell)

Also af far as 67CUDA's problem that is normally caused by a ill fit primary and secondary sear surfaces with their respective surfaces on the hammer and can be fixed by a competent gunsmith for less than a (drop in trigger) also said fixing can give you a really nice 2 stage trigger like feel

Nope he has his mind made up. It's the crappy lower
Machined correctly on a CNC machine that could not possibly make a bad part

Listen up!! check your lower to the print then tell me whats fouled up

[Central Coast Gunsmithing]

Ok so if you are having failure to extract this is what i do when i check ANY GAS OPERATED RIFLE
Put in a Dummy round and see if the bolt will cycle and extract without being fired.

Does it? Good.
Check your chamber and see if it is rough. If it is polish it

Now AR Specific check your gas hole in barrel alignment with the gas block hole if they are correctly lined up then there should be a even circle of powder burn around the gas block hole if it is not lined up then the circle will be ofset to one side or the other of the gas block. Next check your gas tube alignment inside the gas block i.e. look in the hole and see if its a strait shot to the gas tube.

Next if all of that is ok check the gas key on the bolt carrier

If it is loose then that can also cause problems

Another problem can also be caused by the bolt carrier binding in the upper receiver you can check that by using a rod and pushing the bolt carrier group strait back in the hole that the gas tube goes into.

There are tons of other issues but those cause the most of your failure to extract on a very consistent bases even a poorly shaped extractor will extract as long as it snaps over the rim of the case If i could see pictures of your brass or you can at least explain what clean brass looks like after being fired in your gun once it would help

(btw I,m a gunsmith not a English major as you can tell)

Also af far as 67CUDA's problem that is normally caused by a ill fit primary and secondary sear surfaces with their respective surfaces on the hammer and can be fixed by a competent gunsmith for less than a (drop in trigger) also said fixing can give you a really nice 2 stage trigger like feel

[ar15barrels]

I used a CNC machine which was to spec!

Then the lower should work fine...

[67Cuda]

I have a Colfax LR-308 lower. When using a DPMS lower kit, the trigger would give multiple fires with one trigger pull. Luckily I was only loading two rounds at a time.
This was my first time out with it.

Put in a CMC drop it trigger to rectify that and now works great.

More to the point of fitment between the DPMS upper and Colfax lower. If I had to use the standard take down pins, the two would not have gone together.

The holes did not line up, I'm guessing it was the lowers fault. Being a machinist, I found the best pin size combination for them to fit together, machined the take down pins and everything is fine.

So it was certainly not smooth sailing with the Colfax lower.

Edit: I also had to fiddle fart with the bolt release as well to operate smoothly.

[MIGUEL RUVALCABA]

I used a CNC machine which was to spec! And it's not the machining I had 3 guns that had no clew other than to keep trying different parts or at end of day lower since they could tell it mite be having issuers since not linking up correctly. At this moment already have a good amount of $$ into it so might just go Bolt action way or all JP enterprise. I would sell it if the offer at least made me brake even. Only 70 rounds on it now since I fired 10 rounds without any failures on buddy's lower.

[gemini1]

Well looks like it's my LOWER!!! Colfax tactical lower(is a joke) doesn't line up to DPMS upper so failure to allow BCG to fully cycle. Causing the BCG to rub and slow down. Yup upper worked fine one friends lower... Now back to drawing bored. Might just sell it and go for custom bolt action!

So you're no longer interested on buying a new lower? I'd be interested in your upper if you're planning to sell.

[kcstott]

Well looks like it's my LOWER!!! Colfax tactical lower(is a joke) doesn't line up to DPMS upper so failure to allow BCG to fully cycle. Causing the BCG to rub and slow down. Yup upper worked fine one friends lower... Now back to drawing bored. Might just sell it and go for custom bolt action!

I'm willing to bet you machined it out of spec.

[xfer42]

So whats going on?
Ive cut out a few of these DPMS 308 lowers and have yet to fire them. Im curious as to what is off. The ones Ive cut seem to rack smoothly. Im going away for a few weeks and looking forward to testing them when I get back. I bought a few of those $95 DPMS .308 Ares lowers ($99 now).

[MIGUEL RUVALCABA]

Well looks like it's my LOWER!!! Colfax tactical lower(is a joke) doesn't line up to DPMS upper so failure to allow BCG to fully cycle. Causing the BCG to rub and slow down. Yup upper worked fine one friends lower... Now back to drawing bored. Might just sell it and go for custom bolt action!

Was contacted by colfax and to correct information, so yes I am updating it. Lower wasn't all of the issue in this failure to eject the brass... YETTT still wasn't made correctly since some of the rear had to be removed to make it sit completely flush with ANY upper. I did reach out through telephone and I quote "I would be the first person in over four thousand lowers to have issue, but since I wasn't local id need to ship in lower and after looking at it and verifying it was the issue Then another 80% could be sent."

Not trying to rile things up colfax but honoring what your PM Asked for.

[wpage]

Hang in bro... Keep working it till it runs.

[MIGUEL RUVALCABA]

I'm there!!! Hate having a weapon that I have no idea what's wrong with it!

[Rock6.3]

I'll be at SacValley May 18 and I could have an LR308 with me.....

[MIGUEL RUVALCABA]

Ok three guns store later........ I need to try a different lower on upper...YUP apparently some DPMS parts and other off brand! So if someone is willing to allow for me to connect my upper to your lower on a weekend it would save me from buying a new lower, or upper.