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Posted: 1/18/2022 9:49:36 AM EDT
I built a 308 using a PSA receiver set. It has a Ballistic Advantage barrel and is suppressed

If I lock the bolt back to rear and send it home, it will only load the round about halfway and then it will get stuck. If I load a full mag and cycle action from closed position, same issue. If I manually load a round in, then shoot with a full mag, it is good most of them. I tried several different kinds of ammo with same result. Also, not locking bolt back after last round is shot. I think that is a separate issue, and a realign of gas block could fix that. I tried several different mags as well. It is just a regular carbine buffer tube and the PSA 308 action spring and PSA 308 H buffer

Also, I have a forward controls design buffer retaining pin. Not sure if that makes a difference

I have other 308 setup almost identical and they don’t have any issues
Link Posted: 1/18/2022 9:50:24 AM EDT
[#1]
Quoted:
I built a 308 using a PSA receiver set. It has a Ballistic Advantage barrel and is suppressed

If I lock the bolt back to rear and send it home, it will only load the round about halfway and then it will get stuck. If I load a full mag and cycle action from closed position, same issue. If I manually load a round in, then shoot with a full mag, it is good most of them. I tried several different kinds of ammo with same result. Also, not locking bolt back after last round is shot. I think that is a separate issue, and a realign of gas block could fix that. I tried several different mags as well. It is just a regular carbine buffer tube and the PSA 308 action spring and PSA 308 H buffer

Also, I have a forward controls design buffer retaining pin. Not sure if that makes a difference

I have other 308 setup almost identical and they don’t have any issues
View Quote


When I was able to get it to fire, it was grouping very well. Sub MOA
Link Posted: 1/18/2022 10:37:34 AM EDT
[#2]
I assume you already verified the mags you are using are functioning properly and the that the ramps on the barrel extension look okay.  Also that the gas block is properly aligned and the gas tube interface with the gas key is okay.

If so, it almost sounds like it's undergassed.  Have you tried using a lighter weight buffer?
Link Posted: 1/18/2022 10:43:23 AM EDT
[#3]
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Quoted:

I assume you already verified the mags you are using are functioning properly and the that the ramps on the barrel extension look okay.  Also that the gas block is properly aligned and the gas tube interface with the gas key is okay.

If so, it almost sounds like it's undergassed.  Have you tried using a lighter weight buffer?
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I doubt it is under gassed. That being said, gas pressure would not effect the mechanical issue of the bolt not loading rounds into the chamber by use of charging handle or bolt catch. The feed ramps look good. The barrel has a pinned gas block, but now that I think about it, if it is off center the gas tube could be causing some bonding. However, bolt cycles fine with no ammo

I have a new BCG coming. Maybe that’s it?
Link Posted: 1/18/2022 11:08:58 AM EDT
[#4]
Did you try pulling the bolt out of the carrier and sliding the carrier in upper to check for any binding with the gas tube?
Link Posted: 1/18/2022 11:13:29 AM EDT
[#5]
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Quoted:
Did you try pulling the bolt out of the carrier and sliding the carrier in upper to check for any binding with the gas tube?
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Not yet. I just got done shooting yesterday evening and haven’t had time to mess with it. I will try and report back in next day or two. I am thinking BA might have pinned this gas block off center. It was cycling fine with no ammo, so I didn’t think much about the gas tube and or block. Now that you guys have raised these points, I am sure that is what it is, or at least the most probable culprit as of now. Thanks Fonty
Link Posted: 1/18/2022 11:26:24 AM EDT
[#6]
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Quoted:


Not yet. I just got done shooting yesterday evening and haven’t had time to mess with it. I will try and report back in next day or two. I am thinking BA might have pinned this gas block off center. It was cycling fine with no ammo, so I didn’t think much about the gas tube and or block. Now that you guys have raised these points, I am sure that is what it is, or at least the most probable culprit as of now. Thanks Fonty
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I had that happen with an out of spec BCM gas tube, didn’t cause any malfunctions but bcg was sluggish. Now when building an upper i always check gas tube to gas key alignment.
Link Posted: 1/18/2022 4:00:08 PM EDT
[#7]
Link Posted: 1/18/2022 6:51:56 PM EDT
[#8]
Try swapping the extractor and see if it feeds more freely.  I had a couple bad extractors and they would keep the casing at a slight angle when entering the chamber causing jambs.  On mine the shell casing could be jammed into the bolt and they'd get stuck since the dimension between the bolt face and extractor was too small.
Link Posted: 1/18/2022 8:26:12 PM EDT
[#9]
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Quoted:
If I may.... a few questions

What different brand magazines are you using ? ... or were they all the same brand ?

What specific brand ammo ?  ( Norma 308 FMJ has some very short ogives )

Are the feed ramps scratching the cases, causing drag ?

Any "odd" scuff marks or such on the BCG, Charging handle , CH valley, or the interior of the upper ?  ( without a round being fed.. does cycling the BCG bind at all ? )

Gas tube does look ok , and freely interacts ?

Bolt lugs look ok where they interface with the barrels receiver extensions lugs ?

As for the FCD retaining pin... it would be a first for me if that part was dragging some how.
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I used Federal 168 SMK, surplus M80 ball, and some federal soft tip hunting ammo.

Feed ramps look fine, that was first thing I checked

Nothing really stands out as far as marks.

Using 10 and 20 round Pmags

I think it is gas tube/gas block alignment. Even though the bolt rides home and I don’t feel binding, the signs point to that direction. I am really busy next few days, but I will really look it over soon. I will report back with my findings.
Link Posted: 1/18/2022 10:08:44 PM EDT
[#10]
Link Posted: 1/18/2022 10:47:29 PM EDT
[#11]
I had the same issues while zeroing.. FTF, FTE, name it.. but after 20 or so rounds it started to just cycle fine.. Was shooting Nosler 168gr 308 and using C Product 10/20rd Mag.. So after the 1st range trip I went home and polished the feedramps, went back for a 2nd trip on Sunday morning, everything was cycling as it should.. If anyone ask.. barrel is a Wilson Combat Ranger 16” w/ Intermediate Gas, VLTOR A5 Buffer Tube, JP 308 spring, and an Aero Precision H3 AR15 buffer..
Link Posted: 1/18/2022 11:06:52 PM EDT
[#12]
I realigned the gas block and tube. It is perfectly aligned and same issue. I load a full mag, send bolt home, and failure to feed. Loads about halfway. Everything looks fine. Headspace checks out. I will try a different BCG. All I have are Pmags, but I tried 5 different ones. I have other PSA 308s that work fine with Pmags. When I cycle it without a mag inserted, it is butter smooth, no binding

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Link Posted: 1/19/2022 1:06:26 AM EDT
[#13]
OP, if the bolt doesn't ride home when you rack it and the clearances are good, it sounds like an underpowered spring.
Link Posted: 1/19/2022 8:38:11 AM EDT
[#14]
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Quoted:
OP, if the bolt doesn't ride home when you rack it and the clearances are good, it sounds like an underpowered spring.
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This thought has crossed my mind as well. I will take a spring from a different rifle and see if that works
Link Posted: 1/19/2022 2:03:20 PM EDT
[#15]
Link Posted: 1/19/2022 2:56:51 PM EDT
[#16]
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Quoted:


I would consider polishing a few spots.

I have used a 12 / 20 gauge bore mop to polish the very end of the chamber on all my Large Frames. ( the sharp point where the feeding cone and the end of the chamber meet.  ) I bought a cheap Hoppes universal rifle shotgun kit.
You'll need the adapter for the shotgun mop to attach to the section of cleaning rod.  Add a little polishing compound at the front of the mop.

You don't want the shotgun mop to insert into the chamber, the larger size mop will just do the sharp edge, and the feed cone. Then I chuck it into a cordless drill
, and spin away.

For everyone reading.. BE SURE TO CLEAN UP ANY LINT OR RESIDUE from any chamber'ish / feed ramp polishing... That same lint can thoroughly lock up your bolt to the RE lugs if you let it slam home... ( ask me how I know. Lol )

I also would consider polishing / making sure the cartridges casehead has a smooth boltface to slide over.

And consider polishing the extractor front face so the case can freely slip past that face.

On that note... what springs / rubber insert does the bolt extractor have installed ?

oops... and just checking.. the chamber is cleaned of any packing oil or such ?

For anyone that hasn't read Hellbender's Guide.... that thread has all sorts of great info.
https://www.ar15.com/forums/Precision-Rifles/Hellbender-s-a-k-a-Lostinthewoods-Guide-to-the-Ultimate-AR-fixed-/4-6919/

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Do you use polishing compound? Never mind, I can’t read today for some reason. I will give that a shot. Do you think spring could play a role?
Link Posted: 1/19/2022 8:53:47 PM EDT
[#17]
I tried a different spring and buffer. No luck

It has to be either barrel extension or BCG. Maybe these have to use only PSA barrels?
Link Posted: 1/19/2022 9:15:34 PM EDT
[#18]
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Quoted:
I tried a different spring and buffer. No luck

It has to be either barrel extension or BCG. Maybe these have to use only PSA barrels?
View Quote


I’ve noticed on my build I lack a tad on lubing the Bolt and Gas Rings.. I slid the BCG back and forth like it was in cycle, was a tad sluggish and had to use a little force to push/pull the BCG in/out the RE but after lubing the bolt it solved the problem..
Link Posted: 1/19/2022 9:57:23 PM EDT
[#19]
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Quoted:


I’ve noticed on my build I lack a tad on lubing the Bolt and Gas Rings.. I slid the BCG back and forth like it was in cycle, was a tad sluggish and had to use a little force to push/pull the BCG in/out the RE but after lubing the bolt it solved the problem..
View Quote


It is not a lube issues. I can feel where the round is snagging. Just past the feed cone. I will try polishing it
Link Posted: 1/19/2022 10:19:44 PM EDT
[#20]
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Quoted:


It is not a lube issues. I can feel where the round is snagging. Just past the feed cone. I will try polishing it
View Quote View All Quotes
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Quoted:
Quoted:


I’ve noticed on my build I lack a tad on lubing the Bolt and Gas Rings.. I slid the BCG back and forth like it was in cycle, was a tad sluggish and had to use a little force to push/pull the BCG in/out the RE but after lubing the bolt it solved the problem..


It is not a lube issues. I can feel where the round is snagging. Just past the feed cone. I will try polishing it


Did Polish mine as well, I seen a ton of brass shavings when I was hand cycling lol.. Hope you get it running brother..
Link Posted: 1/19/2022 10:35:38 PM EDT
[#21]
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Quoted:


Did Polish mine as well, I seen a ton of brass shavings when I was hand cycling lol.. Hope you get it running brother..
View Quote


Thanks. I am sure I will. If different BCG, polishing feed ramps/cone, and or different barrel doesn’t work, I will just burn it in a fit of rage.
Link Posted: 1/19/2022 10:56:52 PM EDT
[#22]
what buffer tube, buffer and spring, charging handle are you using?  
Link Posted: 1/20/2022 4:01:22 PM EDT
[#23]
Do you have a caliper handy? If you load an identical magazine with identical ammo in this 308 and another one you have that functions, check for an angle on first round in the mag.

With charging handle pulled back on both, is the angle of the cartridge the same? I'm suspecting the problem could be the magazine angle may be tilted a few degrees, causing the cartidge to feed at a slightly lower angle. Even if the feed ramp is perfect, the angle of feed from the magazine could cause a problem if the magazine doesn't sit level.
Link Posted: 1/20/2022 4:10:07 PM EDT
[#24]
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Quoted:
Do you have a caliper handy? If you load an identical magazine with identical ammo in this 308 and another one you have that functions, check for an angle on first round in the mag.

With charging handle pulled back on both, is the angle of the cartridge the same? I'm suspecting the problem could be the magazine angle may be tilted a few degrees, causing the cartidge to feed at a slightly lower angle. Even if the feed ramp is perfect, the angle of feed from the magazine could cause a problem if the magazine doesn't sit level.
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Assuming it is the mag angle, what would be the fix?
Link Posted: 1/20/2022 4:36:35 PM EDT
[#25]
Not sure what the best fix would be, but a temporary fix to see if it runs smooth could be adding tape in the groove on the forward side of the magwell. I saw this thread and remembered that if the opposite problem happens where the mags are too tight, some people polish down a few spots inside the magwell until it's to loose, and feed angle is messed up. You have to add something to fill the gap in that case. Likewise, if the magwell is off slightly larger from a spec that fits magazines, same thing. If you confirm the dimensions are larger on this lower than others from the same manufacturer, maybe the manufacturer can help.
Link Posted: 1/20/2022 4:44:01 PM EDT
[#26]
Quoted:
I built a 308 using a PSA receiver set. It has a Ballistic Advantage barrel and is suppressed

If I lock the bolt back to rear and send it home, it will only load the round about halfway and then it will get stuck. If I load a full mag and cycle action from closed position, same issue. If I manually load a round in, then shoot with a full mag, it is good most of them. I tried several different kinds of ammo with same result. Also, not locking bolt back after last round is shot. I think that is a separate issue, and a realign of gas block could fix that. I tried several different mags as well. It is just a regular carbine buffer tube and the PSA 308 action spring and PSA 308 H buffer

Also, I have a forward controls design buffer retaining pin. Not sure if that makes a difference

I have other 308 setup almost identical and they don’t have any issues
View Quote

can you try swapping with one of your other AR-308 lowers?  hopefully you have something other than PSA just to try out.
Link Posted: 1/20/2022 4:56:10 PM EDT
[#27]
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Quoted:

can you try swapping with one of your other AR-308 lowers?  hopefully you have something other than PSA just to try out.
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I am weird and all my AR 308s are PSA.
Link Posted: 1/20/2022 5:09:58 PM EDT
[#28]
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Quoted:


I am weird and all my AR 308s are PSA.
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Quoted:
Quoted:

can you try swapping with one of your other AR-308 lowers?  hopefully you have something other than PSA just to try out.


I am weird and all my AR 308s are PSA.

still yet, if your other 308 lowers work fine, try swapping.  just trying to rule out a lower, magazine problem.
Link Posted: 1/20/2022 6:22:04 PM EDT
[#29]
Link Posted: 1/20/2022 6:25:39 PM EDT
[#30]
Link Posted: 1/20/2022 6:26:25 PM EDT
[#31]
Link Posted: 1/20/2022 8:28:07 PM EDT
[#32]
I will do a process of elimination using parts from a different rifle. If nothing works, I can deduce that it is barrel extension. A BA barrel should work just fine on this rifle, so we shall see

I appreciate all guys for your input. It has helped tremendously
Link Posted: 1/22/2022 12:29:11 PM EDT
[#33]
The PSA builder kit I received came with a standard AR15 buffer and not short 2.5” 308 buffer. I ordered a 308 buffer. That should do it
Link Posted: 1/23/2022 6:59:13 PM EDT
[#34]
Link Posted: 1/23/2022 8:44:27 PM EDT
[#35]
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Quoted:


Oof... if you have a standard AR15 carbine buffer tube ( noted in your first post ) ... then yes, you must use a 2.5" 308 carbine buffer.

I'm a little surprise your kit came with a 3.25" buffer. I thought those days were long gone.
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At least it should be an easy fix.
Link Posted: 1/27/2022 1:43:23 AM EDT
[#36]
Problem solved?
Link Posted: 1/27/2022 9:11:18 AM EDT
[#37]
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Quoted:
Problem solved?
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Waiting for new buffer. USPS decided it needed to see all lower 48 before making its way to me.
Link Posted: 1/27/2022 7:59:46 PM EDT
[#38]
It worked
Link Posted: 1/28/2022 5:25:17 PM EDT
[#39]
Link Posted: 1/28/2022 7:03:13 PM EDT
[#40]
That's good news.
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