Palmetto PA-10 failure to eject

[W.E.G.]

First post here.
I'm Admin over at the FAL Files if anybody cares.
Having trouble with a Palmetto PA-10.

Wont' eject worth a darn. Rifle fires normally, but will not reliably expel the spent case.

Configuration:

Gen 2 PA-10 20" upper

Gen 2 PA-10 lower with aftermarket buttstock and trigger
Magpul UBR Gen 1 buttstock
KAK 5.3 ounce carbine buffer 
DPMS LR-308 carbine buffer spring
Geissele National Match trigger
Seekins adjustable gas block

Same malfunction in current configuration as was present before substituting a the KAK buffer for a 3.8 ounce DPMS carbine buffer and Palmetto's factory-furnished non-adjustable gas block.

Today's range report:

Fired about 50 rounds. 
Had about 30 malfunctions.

Tried various settings on the adjustable gas block.

With the adjustment screw turned about three turns out, the bolt would cycle far enough back to pick up the next round from the magazine.

The PROBLEM is that no matter what gas-setting, the bolt would frequently fail to expel the spent case from the upper receiver. This of course caused the bolt to try to cram the spent case, and the round from the magazine, both into the chamber. Which does not work.

I tried firing the rifle single-shot a number of times. About half the time, the rifle would fire normally, except the spent case would not eject from the upper. The spent case was just left lying on top of the magazine follower.

The ejector appears to have ample spring tension, and it moves freely in the bolt. The extractor shows no obvious defects. The extractor spring is actually a two-spring jobby (one smaller spring counterwound inside a larger spring - just like the recoil springs in a FAL). A black rubber O-ring is also present to reinforce the extractor spring.

All that said, the extractor is failing to extract the spent cases sufficiently that they can be ejected from the rifle.

Inspection of the spent cases shows an extractor-mark on the rim of the cases, but no signs of bending, tearing, or any sort of worrisome deformation of the case rim. The walls of the case do not show any signs of impression into any deformations in the barrel-chamber. I probed the walls of the chamber gently with a dental pick, and I detected no roughness or irregularities such that the brass might be caused to "stick" in the chamber.

Two types of ammo were used in the test. 40 rounds of Santa Barbara milsurp, and about 15 rounds of a handload (168 SMK and 41.1 grains TAC in a Lake City Match twice-fired-previously case). My reason for firing so many rounds, notwithstanding the persistent malfunction was to hope to "break in" whatever was causing the malfunction, and have it disappear. No such luck.

My best guess is that the extractor is letting go of the spent case too soon, and thereby allowing the case to languish and interfere in the upper receiver during cycling.

If I had known the extractor was going to develop as the likely culprit, I would have brought my entire DPMS LR-308 bolt/carrier assembly, and I would have substituted the DPMS assembly for the Palmetto assembly to see if the substitution would cause the rifle to cycle. I do know the DPMS assembly has NEVER failed in the DPMS rifle.

As circumstances permit this week, I will try to make that experiment happen promptly

Looking for advice.

Edited March 11, 2019 by W.E.G.

[Lane]

19 minutes ago, W.E.G. said:

I would have brought my entire DPMS LR-308 bolt/carrier assembly, and I would have substituted the DPMS assembly for the Palmetto assembly to see if the substitution would cause the rifle to cycle.

Generally speaking; your bolt should stay with the barrel. I wouldn't consider trying this without checking the headspace.

I'm not a PA-10 expert, but I've read some other threads around here about it in the past. If you take out your BCG and post a picture of the gas tube protrusion into the upper; it may be helpful in diagnosing your issue. 

[W.E.G.]

I have headspace gages, and lots of experience measuring headspace.

 

 

The PSA gun will swallow the 1.631 gage with the PSA bolt and carrier.
That same combo will not swallow the 1.632 gage.

If I put the DPMS carrier and  bolt in the PSA gun, the PSA gun will swallow a 1.633 gage.
That same combo will not swallow a 1.634 (.308 Win. NO-GO) gage.

.
.

Now for further comparison, let's see how that swap works out on a Gen 1 DPMS LR-308T.

The DPMS gun will swallow a 1.633 gage with the DPMS carrier and "porris" bolt.
That same combo will not swallow a 1.634 (.308 Win. NO-GO) gage.

When I put the PSA bolt and carrier in the DPMS gun, the DPMS gun will swallow the 1.632 gage just barely. Bolt seems to lock up on the 1.632, but requires the "pogo" maneuver to get the gage out of the chamber. 
That same combo will not swallow a 1.633 gage.

Point of all this?

I think we can say that the DPMS and PSA bolt/carrier assemblies interchange.
My particular sets are only 0.001" to 0.002" different headspace if I swap them.

On a minor note, I will also point out that the PSA carrier is cut with serrations to accomodate the forward-assist mechanism. The DPMS gun is a slick-sided gun, and has no forward-assist mechanism. Neither does the DPMS carrier have any serrations.

[W.E.G.]

I am familiar with some threads on this site regarding substitution of a mid-length gas tube in 16" PA-10 guns and that substitution having a positive result.

Take note that my gun is not a carbine (16") or a mid-length (18").

Mine is a TWENTY-INCH barrel. This product: https://palmettostatearmory.com/psa-gen2-pa10-20-rifle-length-308-win-1-10-stainless-steel-15-m-lok-upper-with-bcg-and-ch-5165447981.html

Here's a pic of my gas tube protrusion. 

[Lane]

Looks like you have the headspace issue cleared up; just didn't want to make any assumptions there...

That looks like a short gas tube to me; but I didn't see any other mentions of that in the PSA specific threads. I'll see if I can find some gas tube comparisons for you. In the mean time, here is an FTE post that sounds like the problem you think you have at least:

 

[washguy]

Weg    Welcome to the forum ... You gave us a great photo ! your gas tube is too short for the first problem....you see the half moon...of course you do...the end of the gas tube has to protrude into the upper half way into that half moon...you are a bit short...and yes that makes a difference.

always on the ar 308 you must function check with one round in a mag...charge it ...shoot it...and the bolt catch must hold back the bcg on one round...if not you have problems of course you know that...but one round and then the bcg has to be caught by the bolt catch...99 % of the time if not held back you are undergassed...and with the short gas tube it proves out....make sure your gb is positioned properly and get a longer gas tube ...also you might wanna check the gas port opening and see what diameter it is...  Wash

I just wanna  make sure that you check to see if the bolt catch holds the bcg back on one round...this is a Must!

also you said aftermarket buttstock....check the inside of the buffer tube with a ruler...7 inches from back of tube to exit

yes you have a rifle length gas tube...but its too short

yes I see the thread bout extractor's.... but you must see if its an under gas problem first

Lane....haha...sometimes I can be faaaast

On a Seekins adj gas block 3 turns out is nothing! A wise man on here once told me to always start the adj, gas block turned all the way out...then  you can begin turning the gas down....you are under gassed ...and you must lube your new piece really well cause these 308's when new are very picky...lube and gas it...you are too short on the tube ...open the gas block all the way

did I mention that the bcg must be held back on one round by the bolt catch?....lol

 

Edited March 11, 2019 by washguy

[Lane]

You beat me to it washguy! Here are two other threads that cover the gas tube issue for reference:

 

Edited March 11, 2019 by Lane
word

[98Z5V]

WEG, you have a gas system issue.  The others stated it.  Armalite AR-10 RIfle Gas Tube, first.  Get that in there.  Not some generic POS that's advertised as "AR-10 rifle gas tube" either - the real deal, from Armalite. You can buy one from a reputable vendor, but make sure the part isn't bullshiit.  Armalite AR-10 Rifle gas tubes measure 15.5" long. They are not AR15 parts.

Next, wide-open that gas block for testing, until you get this thing running right - that will be the only way in the world to determine if your gas port is the proper size - or too small.  If it doesn't run wide-open - then you need to drill up that gas port diameter.  Replace the gas tube first, with something that will work. 

You're ending available gas pressure to the carrier key, before it's supposed to end.  That short gas tube cuts the gas pressure as soon as that BCG carrier key clears it - and the rest vents.  Having a gas tube that's too short lets that carrier key and BCG rearward movement STOP receiving it's gas pressure too early.  Doesn't look like much, but it's huge when you combine it with all the other issues - they just compound on each other, and make a gun that doesn't run. 

We measure hammer lock-time in milliseconds, and people think it's important.  With gas system timing, it's equally important- but there are so many people out there that just say, "Nah, it's okay, it really doesn't matter..."   It matters.

Welcome here, from the FAL Files - partner up with Full30.  Firearms communities need to stick together, and not be specific-snobs.  Somehow, the Dems can all stick together to shut us down, but as a community, we're more interested in in-fighting and bickering, and bullshiit like that.  Contact Robert over there, or here at...  @Robert@FULL30

[98Z5V]

2 hours ago, W.E.G. said:

Magpul UBR Gen 1 buttstock

KAK 5.3 ounce carbine buffer 

DPMS LR-308 carbine buffer spring

That first UBR was an integrated 7.000" internal-depth receiver extension.  You have the right buffer weight for a .308AR, and the KAK short buffer is good.  That spring was designed for DPMS's 3.8oz, 2.500" buffer.

Put a Sprinco Orange spring in there. 

That will eliminate any issues that might be coming from the recoil system.

[Cliff R]

"Same malfunction in current configuration as was present before substituting a the KAK buffer for a 3.8 ounce DPMS carbine buffer and Palmetto's factory-furnished non-adjustable gas block."

This is a key to the solution.  Problem was present before and after the parts changes.  High probability its a "fundamental" issue like the gas tube too short or something with the bolt/carrier assembly/extractor.

How does it function if you operate it manually with a full magazine.  If it grabs every single one and slings them out with great authority then the BCG has adequate room to move and the extractor is holding the cases well enough.

Something to mention here with reloaded ammunition is to make absolutely sure that the crimping operation doesn't occur every so slightly before bullet depth is reached.  Something very easy to overlook and when this happens the case can get "bulged" ever so slightly causing a tight fit in the chamber.  This problem is really obvious when it woln't allow the bolt to fully close but much less obvious if they are just tighter than they should be.  I know that sounds pretty "basic" and you seem to have extensive enough experience to know this, but it may help others dealing with similar issues.

Next I'd do the single fire test mentioned above and it absolutely should hold the bolt open after each round, or it's short/cycling even if it ejects the spent round successfully.

My bet is the gas tube being too short.  The buffer tubes, springs, buffer length/weight and gas block adjustments are above my job description, but certainly part of the equation once you check/correct any fundamental issue(s)..........Cliff

[W.E.G.]

Thank you all for your thoughtful replies.

I am going to pursue the too-short-gas-tube possibility. I ordered a 15.5" tube from Fulton Armory today: https://www.fulton-armory.com/gastuberifle-1.aspx

Gas Tube, Rifle, FAR-308 AR

Price: $14.95
Part #: FA-TU-062
In Stock
Approximately .325" longer then AR-15 tube, for use for FA 308 & 6.5 Barrels. Will also work on Armalite AR-10. 
- 15.5" In length

My gas tube indeed appears to be shorter than it ought to be by "rifle" standards.

The silver mark on outside of the upper receiver corresponds to the end-point of the tube inside the receiver.

[Matt.Cross]

Welcome to the forums and looking forward to seeing you get your rifle running. Post up some FAL pics when you get the chance, most of us are gun whores and rarely meet a gun we don't like.

[shooterrex]

Welcome from Ky

[Sisco]

Welcome, nice to see some cross connectivity between forums. The right people are giving you advice. Look forward to a range report when you get it straightened out.

[Robert@FULL30]

Welcome,

 

This is the place for 308AR advice no doubt, as well as firearms fellowship, comradery, patriotism and brotherhood.

 

(pause for anthem)

 

sorry, back to the rifle, since you've ordered a gas tube we shouldn't have to wait to long to know if thats the culprit, 

I'm looking forward to your report ☺️

 

 

 

 

[W.E.G.]

10 minutes ago, Robert@FULL30 said:

 you've ordered a gas tube we shouldn't have to wait to long to know if thats the culprit, 

I'm looking forward to your report ☺️

 

 

Ordered early Monday morning. Got an immediate order confirmation in email. No shipping confirmation yet. But, not sure Fulton does shipping confirmations for parts-orders.

[ar-mountaineer]

3 hours ago, W.E.G. said:

Ordered early Monday morning. Got an immediate order confirmation in email. No shipping confirmation yet. But, not sure Fulton does shipping confirmations for parts-orders.

You will probably get a shipping confirmation tonight. Last week I ordered a couple things from them and both were the next day. I was actually notified by the post office with the informed delivery app before I got an email from Fulton. 

[W.E.G.]

Shipping notice says Fulton gas tube to be delivered by end of day Wednesday.

Weather for Thursday looks favorable for range trip.

[washguy]

Weg  allright lets do the deed. While you have it diassembled use a numbered drill bit and lets see what diam the gp is.make sure the GB is centered on the gp when you reassemble everything ...what you do is...go hide in a room where no one can see you...plug up chamber with something..put lips around muzzle and blow into it...air should be coming out of gas tube..or run some air into muzzle...after you check for air...point muzzle down and insert bcg just a bit and then let go...bcg should  go into battery telling you the gas tube isn't bent or bcg isn't daragging on sumthin...lube everything up and then with GB wide open use one round in the mag making sure that the bolt is held back by bolt catch and round is ejected with authority..this must happen everytime you do this function test....Wash

Edited March 13, 2019 by washguy

[W.E.G.]

A 3/32" (0.09375") drill bit fits very snug. At most, the hole can't be more than a thousandth larger than the drill bit.

Edited March 13, 2019 by W.E.G.

[washguy]

Weg   that should be just fine for rifle length gt

Wash

[Matt.Cross]

36 minutes ago, W.E.G. said:

A 3/32" (0.09375") drill bit fits very snug. At most, the hole can't be more than a thousandth larger than the drill bit.

Yeah, .093 is a pretty standard size it seems. That's the same as my Fulton Armory barrel.

[98Z5V]

With a gas port that's where it should be, and a gas system issue, with a short tube that cuts off gas flow to the BCG before it should - you really need to wide-open that gas block.  For real.  Get the right gas tube in there, but don't rely on that - wide-open that block, at the same time as firing the new gas tube.  If that thing doesn't run...  

[W.E.G.]

Fulton Armory 15.5" gas tube rececived.

This looks promising

[W.E.G.]

comparison of old tube and new tube

 

When I tried to install the new tube, I had hopes that I might have on-hand a new roll-pin of suitable diameter.

I have a supply of various-sized roll pins from Brownells.

The 1/16" pins actually measured to 0.070", although the math says a 1/16" pin should be 0.62". Not that it mattered because the "1/16" pin was too small even at an actual size of 0.070". 

Next size up in my supply is 5/64. Which according to the math should be 0.0781" - or virtually the exact same size as the pin that came with the original Palmetto gas block. Similar to the 1/16" pins, the 5/64" pins were larger than the nominal size on the package. The actual diameter of the 5/64" pins is 0.081". I'll venture that is the size used with the original Palmetto gas block.

Remembering the ordeal of beating the tarnation out of that 0.080" Palmetto pin to get it to zig-zag its way through the Seekins adjustable gas block, I considered other options. the problem is that the Seekins adjustable block is off-center just enough that the roll pin has to do a zig-zag turn to travel from one side where it is inserted to the other side where it will emerge. For motivation, I gave the old roll pin a try, and it fought me hard. I tried a new 1/16" pin, but fit was sloppy. Enter the FINISHING NAIL - which just happens to be 0.075". Perfect. The nail went through the gas block and the tube with only the slightest friction. Once in place, the gas tube was secure, and did not rotate at all. Cosmetically not ideal. But unless you remove the handguard, it will never be seen. If I ever have to remove the nail, I doubt it would be re-usable. No problem. I have a lifetime supply of finishing nails in the cabinet.

 

 

Even got to bust out the WECSOG Dremel to clean up the rough cut from the nippers.