Palmetto PA-10 failure to eject

[98Z5V]

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

comparison of old tube and new tube

 

Notice the difference in the bends in the 15.5" gas tube?  AR15s and .308ARs have a different height-over-bore, when you're looking at barrel centerline-to-gas tube entrance in the upper receiver.  The .308ARs are just bigger, and have a higher height-over-bore in that area, than an AR-15.

Just another reason why AR15 gas tubes shouldn't be used on .308s...  

[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.

[W.E.G.]

Note that the front end of the gas tube sits at some depth inside the gas block once the cross-pin has been secured.

Here's our protrusion of the tail of the 15.5" gas tube into the upper receiver.

Fulton Armory did a good job of pre-bending the tube. Excellent clearance at the barrel nut.

Pic of the passage at the cloverleaf-hole.

Clearance of the gas tube without interference with the charging handle.

Bolt and carrier assembly in full battery without interference.

Rear view of bolt and carrier assembly in full battery.

[shooterrex]

Gas tube looks good. Finishing nails work sometimes.  I made a take down  pin detent out of one once. It worked till I replaced the one that flew across the room.

[washguy]

WEG   Go shoot that mofo...be sure and take more than one mag....now if it doesnt hold back this time...we move on to tbe buffer system....lol    one time i couldnt get a 6.8 to hold...tore it apart and it still wouldnt hold back...no matter what...it was tbe ffffin mags... two of them...brand new same brand...Wash

[Cliff R]

Considering the effort required to drive out some of the roll pins retaining gas blocks I've ran into here, making a custom pin isn't really a bad idea.  Roll pins can and will vary some in diameter when you measure them due to the air-gap.  The higher quality ones are more consistent, dark in color, hardened and good memory.  I shy away from the shiny chit you see for sale these days coming in from off-shore.

Anyhow, let us know how it runs, hopefully you've made big improvements........Cliff

 

 

[jtallen83]

I use stainless steel coiled roll pins. They are stronger AND drive much easier. I get mine from a Texas seller off Ebay and never had an issue;

https://www.ebay.com/itm/162085837963?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649

[Robert@FULL30]

Fantastic photos, certainly looks cured, and a 4 penny nail, nice

[W.E.G.]

70 degrees and sunny and no work 

range trip today 

I’ll take a Pmag and a metal mag and several types of ammo and the DPMS rifle in case I need to scavenge parts.

[washguy]

Weg    It oughta work fine...lube the upper nice ...gas block wfo...I wouldn't even worry bout tuning this piece if its new...give it time to get loosened up before you go nutz on the gas block.     Wash

[W.E.G.]

Bad news.

and

Good news.

 

The bad news is, the gas tube replacement did NOT solve the failure-to-eject issue. With the new gas tube, and loaded with a single round, the rifle would fire, and it would extract the spent case, just like before,  leaving the spent case languishing on top of the magazine follower.

I had the foresight to take a second AR-10 (actually a DPMS LR-308T - which is a "first generation" DPMS AR-10 type rifle) to the range also today. By happenstance, the DPMS gun was equipped with a Fulton Armory bolt https://www.fulton-armory.com/bolttitanstripped-2.aspx which I have been successfully testing in the DPMS gun. I removed the entire bolt/carrier assembly from the DPMS gun, and I installed that assembly in the Palmetto gun in place of the entire Palmetto bolt/carrier assembly. Immediately, the ejection problems were solved.

With the DPMS-carrier/Fulton-Armory-bolt, the Palmetto gun ran just fine.

One establishing that the Palmetto gun would run fine with the DPMS/Fulton assembly, I then installed JUST THE FULTON BOLT in the Palmetto Carrier assembly (including Palmetto cam pin and Palmetto Firing pin). The gun continued to run fine with the Fulton Bolt installed in the Palmetto carrier. The remainder of the day's firing was done in this configuration.

The adjustable gas block was set such that the port adjustment was three revolutions out for all firing today. I did not try to "tune" the gas block whatsoever during today's outing.

I fired about twenty shots with Santa Barbara milsurp ammo to verify function. Then I fired about thirty rounds of a handload that has served me well through the years. 41.5 grains IMR-4895 and a 168-grain Sierra MatchKing. The pic below shows a group I fired for accuracy at 200 yards. All firing was prone, and supported only by a military sling. I am encouraged by the accuracy delivered by the Palmetto barrel. The two high shots in the group were each shots that just felt a little awkward when I fired - as though I was anticipating recoil, and tensing my body. Also the gun is butt-heavy in its current configuration. The heavy butt may simply be the reason for the two high shots. A little weight forward tends to keep the muzzle down at the moment the trigger breaks.

The rifle was equipped with a Geissely National Match trigger that weighs about 5 pounds. The buttstock was a Magpul UBR at full extension (no way I'm shooting nose-to-charging-handle) with this hard-kicker. The buttstock was equipped with the Stealth Ballistics butt-weight. Overall weight of the gun currently is about 12.5 pounds. I plan to add about another pound to the handguard to get it to balance a little more forward. Right now, with the weighted buttstock, the gun is butt-heavy. 

Edited March 15, 2019 by W.E.G.

[Robert@FULL30]

Can you visually see differences in the bolts/extractors/breech face anything?

[Lane]

On 3/11/2019 at 12:24 AM, Lane said:

FTE post that sounds like the problem you think you have at least:

Sounds like the tits on this one after all (the edges of the extractor clip). I've only ever had to polish those to protect my brass. Seems like you might have to go a bit further; I've seen this referred to as "shark toothing". Not sure how much you have to take off your extractor to get it right. Just be careful not to shave the wrong area, or go too far...

[Lane]

98Z5V posted this for me a while back in reference to a similar problem. Look at the edges and contact faces (inside the cup).

"Check this:"



 

[W.E.G.]

The two significant differences I can see between the Palmetto bolt and the Fulton bolt are:

1. The claw on the Palmetto bolt is narrower than the Fulton bolt.

2. The Palmetto bolt uses a pair of counter-wound springs. Whereas, the Fulton bolt uses a single spring with a central insert of some sort of orange polymer reinforcement.

Both extractors measure 0.312" across at the location for the axis-pin.

Palmetto extractor in top of pic. Fulton extractor in bottom pic.

[W.E.G.]

At this point, the gun works just fine with the Fulton bolt. I'm not sure how much study I'm going to do "in the name of science" to figure out why the Palmetto bolt continues to fail.

I'm tempted to give the JP Enhanced extractor a try https://jprifles.com/buy.php?item=JPEB-308EX in the Palmetto bolt.

Their comment in the instructions is encouraging if you take it at face value:

Engineered to provide a much longer service life

than standard extractors, the JP .308 Enhanced
Extractor is an easily swappable component for any
DPMS pattern bolt to eliminate extraction
problems, premature extractor failure and other
malfunctions resulting from the extractor not
clearing the case rim. While designed to remedy
these extractor‐specific problems, the JP Enhanced
Extractor will not solve issues stemming from poor
chambering or over‐gassing. If your rifle continues
to experience extraction issues with this
component installed, the problem lies elsewhere.

[jtallen83]

Curious if the PA would function using the Fulton spring. Seen a spring change do the trick in a couple applications.

[W.E.G.]

Although, for another $50 over the price of the fancy-shmantzy JP extractor, I can get another complete Fulton bolt, and not be concerned about mix-matching parts in the Palmetto bolt - a bolt that might be snakebit in who-knows-what sort of way.

Plus, I need to make another order to Fulton anyway to get another 15.5" gas tube to install on the original non-adjustable gas block from the Palmetto gun. CMP rules have been interpreted to dis-allow adjustable gas blocks on service rifles. I'd rather not molest the Seekins block with my Harbor Freight welder to render it non-adjustable. And I don't feel like swapping a single gas tube back-and-forth between different gas blocks every time I futz with the configuration. I'll just put a new (longer) gas tube on the Palmetto block, and keep myself in the clear on Service Rifle competition rules. The adjustable block with the new tube can hang around in the spare-parts-box in case I feel like playing with gas adjustments.

[W.E.G.]

5 minutes ago, jtallen83 said:

Curious if the PA would function using the Fulton spring. Seen a spring change do the trick in a couple applications.

Well, remember I've got the Magpul Gen 1 UBR stock on the gun now. The UBR is staying. I'm not sure what margin there is in re-installing the spring from the A5-length Palmetto crapsalapsible $8 stock setup just to see if the A5-length spring will work in a Gen 1 UBR. 

As an aside, if you happen to install a Gen 2 UBR on your rifle, the Gen 2 UBR receiver extension is A5 length. So, you could (and you should) make sure you use an A5-length spring unless you use the spacer that comes with the Gen 2. The spacer allows you to use carbine-length components (buffer and spring) in the Gen 2 UBR. I have a Gen 2 UBR on a different AR-15. I'm going to keep the Gen 1 UBR on the Palmetto PA-10 for reasons that are unique to my circumstance.

[SimonSays]

It may be an optical illusion, but the Palmetto extractor claw seems to be a smaller radius than the Fulton. Will a 5.56 extractor fit in a .308 bolt? 

[Lane]

9 minutes ago, jtallen83 said:

Seen a spring change do the trick in a couple applications.

I have no reason to doubt jtallen83's experience. I've had to mess with more than springs in that department. That o-ring also looks significantly larger; but the cut on the Palmetto extractor is significantly different than the Fulton. The shape of the grip is very different on both front and back. There may also be thickness issues at play here.

[98Z5V]

32 minutes ago, SimonSays said:

It may be an optical illusion, but the Palmetto extractor claw seems to be a smaller radius than the Fulton. Will a 5.56 extractor fit in a .308 bolt? 

I was thinking that exact same thing - everything about that extractor is smaller.  It could be because it's further from the camera, though.  I'd like to see it measured out, at least with a tape measure - wouldn't necessarily have to be with vernier calipers.  It sure looks like it...

[W.E.G.]

Not an optical illusion.

The Palmetto claw is 0.020" narrower than the Fulton claw at the outer lip of the claw.

Hard to measure the DEPTH of the claws, but my Mark I fingernail senses that the depth of each claw is pretty similar.

[Lane]

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

Not an optical illusion.

SimonSays had a point here still. That radius isn't right in any light.

There are so many variables here that, I can't even recommend trying to fix it other than for the fun and education in the matter.

[jtallen83]

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

Well, remember I've got the Magpul Gen 1 UBR stock on the gun now. The UBR is staying. I'm not sure what margin there is in re-installing the spring from the A5-length Palmetto crapsalapsible $8 stock setup just to see if the A5-length spring will work in a Gen 1 UBR. 

I should have been clearer, referring to the extractor spring. On a couple occasions I have seen an Armalite extractor spring, same as the Fulton, fix an ejection issue. It would be a cheap and simple fix if it worked. If I remember correctly it was a double spring that was replaced.