W.E.G.

Shooting the PA-10 a little more today. Still shooting the beat-up Palmetto bolt. TLDR version: PA-10 shoots consistently low/high. Testing today indicates that the problem is not the scope. If you’ve been following this thread, you’ve read my comments about how the rifle seems to disperse shots high/low more than I care for. I became concerned that perhaps the cause of the vertical dispersion was the Leupold Mark AR scope. Today I tested the Leupold scope on the PA-10, and also tested the same scope-and-mount on a well-worn (~5000 round-count) White Oak 5.56 (Wilson barrel) service rifle upper. The Larue quick-detach mount allowed me to easily move the scope from the PA-10 to the White Oak. I scanned the targets below from the backside of each target so as to show the group-size, and to avoid the visual distraction of the scoring rings of the targets. But, speaking of the scoring rings, my observation is that the PA-10, equipped with the Larue scope, kicks shots low and high about one full scoring ring more than what I typically get when I shoot the same scope on a White Oak 5.56 gun. Target used for testing was the MR31 target (600 yard National Match target reduced for 100 yards). There is one especially high shot on the PA-10 target. I called that shot high when I fired it. I didn’t think it would land THAT high, but full-disclosure, I called that shot high. Further in keeping with “full disclosure” I fired two shots before I touched adjustment knobs. The first two shots were a little higher within the scoring rings than I wanted to see. So, after the first two shots, I dialed it down 2 clicks (each click worth 0.1 mil – which is one-third of an inch per click on the 100-yard target). I didn’t touch the elevation after that initial adjustment. The first two shots are fairly centered in the 18-shot group you see in the pic. After that single elevation-adjustment, the remaining 16 shots danced high/low with no particular rhyme or reason other than that one called-high shot I mentioned. Hard to say what causes the PA-10 to print low/high all the time. I previously examined the barrel/receiver fit – even removed the barrel from the receiver – and the fit seems really tight. Maybe its something to do with the bolt. Although, the high/low issue was evident before the bolt got so chewed up. Current round-count on the PA-10 is about 700 rounds. I suppose the next outing I will try the new Toolcraft bolt/carrier assembly and see if it has any effect on the high/low issue. I can’t think of a good reason WHY changing bolt/carrier would make any difference. But, not much to lose by trying I suppose. If changing the bolt/carrier doesn’t make a difference, I’ll try lapping the upper receiver. I have the kit. If that doesn’t solve the high/low problem with this rifle, I’m not sure I’m motivated to invest in a high-end barrel just to see what happens. My future with this rifle has limits. So, at least two more range trips to try to “get it to shoot.” The beat goes on…

The other bolt I used for one outing was the bolt from my DPMS LR-308-T. I probably fired no more than 20 rounds with that bolt. It looks normal to me. I think I may have also fired about 20 rounds with a bolt I got from Fulton Armory. I tested with those bolts when I was in the "Why the hell does this thing just not work at all" mode. I may send the Palmetto bolt back to PSA if I can get some assurance that they will exchange it for one of the Toolcraft BCG assemblies they are purportedly furnishing with the Generation 3 PA-10 guns. My concern is that they would just send me an un-used Gen 1 or Gen 2 BCG assembly. Its not worth my time to deal with PSA just to exchange a weathered turd for a fresh turd.

I think I’m at about 700 rounds on the Palmetto bolt. It is apparent that the corners of the bolt-lugs are wearing more with each outing. So, there is less “face” on the bolt lug engaging with the lugs on the barrel extension. I had hoped that this wear-behavior would settle down such that the bolt would have reached its happy medium. Its clear to me now, that isn’t going to happen. This bolt is just going to keep giving up more-and-more of the corners of the bolt lugs until something gives out. I’d be curious to know how this bolt might ultimately fail. I’ve never actually broken a bolt on an AR-type rifle (if you don’t include the incident with the pierced-primer damage from the thin CCI 400 primers in 5.56 some twenty years ago.). I’m at the point where running this bolt further is just going to be about as interesting as the time in 1977 when I loaded-up a gas can, and drove my car on the highway to see how low the gas gauge would go before the car literally ran out of gas. As it turned out, that adventure was a whole lot of inconvenience, and not very interesting. Hoping that I’ve learned my lesson at this point in my life, I’m not going to keep pushing this bolt until it causes me a wasted range trip. As of this morning, I have a Toolcraft BCG inbound. I ordered the one with the dual ejectors and the small firing pin. $159 for the whole shebang seemed reasonable. If for some reason it doesn’t work out, at least I’ll be able to tell it from the other AR-10 parts that seem to be multiplying around here. Here’s some pics of the Palmetto bolt after about 700 rounds.

Meant to say rapid fire SITTING time limit is 60 seconds. Always with the details.

About 100 rounds downrange again today. Had to shoot on the 100-yard range because the benchrest crowd was shooting the Virginia State Benchrest Championship on our 200-yard range. Weird thing with the slow-fire prone. I was calling shots center, and it was randomly kicking shots out at 7 o’clock. Several of those shots I called a strong center-shot. Wondering if the scope is doing something wonky. Going to install the scope and mount on one of my reliable 5.56 competition guns and see if same thing happens with shots inexplicably kicking out of the group to 7 o’clock. Ammo for the prone targets was 168 Sierra Matchking and 41.5 IMR 4895. Ammo for the sitting and offhand targets was surplus Santa Barbara (Spanish military). Penny in the pics to help with viewing the scale. A couple rapid-fire targets that score pretty well, even if the groups are nothing to get excited about. Rapid fire prone time limit is 70 seconds, although I shot it in about 57 seconds. Rapid fire prone time limit is 60 seconds – needed almost all of that time. Magazine-change in each rapid-fire string. Magazines loaded five-and-five. 40 shots offhand. Fewer “bad shots” than usual in this lot. Zero could have been better. But, I’ve been chasing an offhand zero since 1991. The quest continues.

Yesterday’s range trip started with a better-than-average 20-shot offhand string. I decided to next shoot slow-fire prone. Got in position to dry fire. Squeeeeze the trigger for first dry-fire shot. Mmmmph! That looked shaky. Breeaathhhe.... another dry-fire. Wait a cotton-pickin’ minute! That crosshair ain’t supposed to shake like that! Reached up and grabbed the scope tube. Shake-shake. Rattle-rattle. Consarn-it. Scope loose in the mount! Busted out the wrenches, and tightened all the screws. Spent rest of outing re-establishing zeroes for all firing positions. Seems that re-tightening caused one MOA elevation change in what I “thought” was my “good zero.” Back to the range today to see if zeros are good, and see how my bones manage two days in a row shooting 100 rounds in “the big gun.”

I cleaned-up the rifle real good after yesterday’s highpower rifle match. With the rifle all squeaky-clean, this was a good time to re-check the headspace. I have a set of Forster headspace gages in 0.001” increments from 1.630” to 1.638” The rifle swallowed the 1.633” gage without resistance. It swallowed the 1.634” gage with some slight resistance. Had to lightly mortar the rifle to get it to spit-out the 1.634” gage. Then I got the braniac idea to “see what would happen” if I tried to feed it the 1.635” gage. Maaaannnnn…… Wish I hadn’t done that. That thing seized-up in partial battery like no tomorrow. I mortared it zealously a number of times. Not budging. It was fortuitous that the partial-battery condition it was stuck in was such that the charging-handle latch was not engaged in the “catch” on the upper receiver. If the latch had been engaged into the "catch" on the receiver I suppose I could have taped the latch in the release-position or some such or come up with a third hand somehow. Anyway, time to BRING OUT THE HAMMERS. While sort-of resting the rifle muzzle-upward, and bracing with my knee and my shoulder, I placed the face of big rubber handle against one ear of the charging handle, and I wailed on the opposite face with the 4# hammer. After several blows of the 4# hammer, the rifle spat the 1.635” across the room, and crisis was averted. Lesson learned: Once you get to the point with headspace gages that you have to mortar the rifle at all to get the rifle to spit the gage out. JUST STOP RIGHT THERE. Don’t try the next-size-up gage. With the rifle now clear, I swapped-in my spare DPMS bolt to see what difference there might be in headspace. The DPMS bolt came out of a 2008-vintage DPMS LR-308-T rifle. That bolt probably has about 200-300 rounds fired on it in the LR-308-T, and a few rounds to confirm function also in the Palmetto gun. The headspace dimension of the DPMS bolt was exactly the same as the headspace dimension of the now well-worn Palmetto bolt: 1.634” (with light mortar action required to get the rifle to spit-out the 1.634” gage. For context, I’ll mention that the headspace dimension of most match-grade .308 Winchester ammunition is 1.628”. Some milsurp 7.62 NATO ammo measures slightly longer in headspace dimension – although most NATO-spec ammo I’ve measured is the same dimension as the .308 Winchester match-grade ammo. I use an RCBS Precision Mic tool in conjunction with the Forster headspace gages to arrive at “headspace dimension” measurements of ammunition. Nothing like a little excitement on a Friday afternoon.

I count 28 coils on my spring. But the end isn't painted orange. I don't think usage has caused paint I may have failed to notice to wear-off. I'm sure I would have remembered if it had been painted originally. I honestly can't remember what packaging the spring came in. I ordered it at the same time I ordered the DPMS carbine buffer. I do remember the DPMS buffer from Midway was marked "DPMS" in packaging that had the familiar DPMS font. Wish I could remember how the spring was packaged. I want to think the spring was packaged with a generic-looking label that may have simply had non-descript-font that identified it as DPMS LR-308 carbine buffer spring. I was programmed to get both the DPMS spring and carbine buffer, because I had previously installed a UBR on a DPMS LR-308-T that started life from the factory (panic-buy right before Obama's first term) with an A2 butt and rifle-length gas system. About a year ago I converted that rifle to UBR, and read that the DPMS spring and buffer were the way to go when setting-up an LR-308 with a collapsible buttstock. Indeed, the two work great in that carbine-length gun. Probably would never have messed with the Palmetto 20" gun except for the NRA/CMP service rifle rule which allows you to compete in the service rifle class, with an "M-110" type rifle, provided that the rifle meets certain specifications - most conspicuosly the 20" barrel. If I continue to shoot scores like I shot today, I doubt anybody is going to be breaking out the tape-measures and calipers to be sure all my stuff is just so. The only way I can say getting into the Palmetto gun was a good idea is that it has served as a focal point to keep my interest in the game and to distract me from some other bothersome stuff that's been going on around me for the last several months. Thanks for looking at my specs/numbers. I'm thinking about re-installing the adjustable gas block to tame the ejection a bit. Right now, it really will smoke the shooter on my right with spent brass. Will lessening the AMOUNT of gas slow the TIMING of the unlocking enough to influence wear on the bolt?

This looks encouraging. I wonder whether they’ve corrected the stubby gas tube on the 20” version? Also wonder what size the gas-block journal on the Gen 3 is. Gen 2 journal is 0.750.

Gonna get some lunch, then head out to the Centreville IWLA to shoot their second-Thursday-of-the-month afternoon 100-yard highpower rifle match. 50 shots for record. If I get there early, might get a few sighters before the match starts. Pretty sure I've got good enough 100-yard sight-dope that I should at least be inside the 9-ring if I do my part.

Rifle was never fired in exact original factory configuration. Never was fired with Palmetto buffer spring or Palmetto buffer or Palmetto buffer tube. To best of my recollection, this is the history of modifications: FIRST MODIFIED CONFIGURATION (Day 1 configuration): 1.Magpul UBR buttstock and UBR buffer tube. 2. Geissele National Match trigger 3. DPMS LR-308 buffer spring. 4. DPMS LR-308 carbine buffer. Rifle would not extract/eject with first modified configuration. Maybe 30 rounds fired in first modified configuration. SECOND MODIFIED CONFIGURATION: 5. Replaced Palmetto bolt with Fulton Armory bolt (complete Fulton bolt assembly in Palmetto carrier, with Palmetto firing pin and Palmetto cam-pin 6. Replaced Palmetto gas tube with Fulton Armory gas tube. 7. Replaced DPMS LR-308 carbine buffer with KAK 5.3 ounce buffer Second modified configuration extracted/ejected 100%. THIRD MODIFIED CONFIGURATION: 8. Installed Seekins adjustable gas block to see if any noticeable reduction in recoil achieved. Fired about 20 rounds. Inconclusive results. Tried various settings on the gas block to see how rifle behaved. When adjustment was set to sufficient setting to reliably eject brass, I could not tell any appreciable difference in recoil on that setting as opposed to the when the setting was adjusted to wide-open. Because competition rules disallow adjustable gas blocks, I re-installed the Palmetto OEM (non-adjustable) gas block with the Fulton gas tube. The Palmetto-block/Fulton-tube configuration has been on the rifle for at least 90% of the usage of the rifle. FOURTH MODIFIED CONFIGURATION: 9. Removed Fulton Armory bolt 10. Installed Fulton Armory extractor assembly (extractor, polymer insert, spring, O-ring) in Palmetto bolt. Testing showed that the Palmetto bolt operates fine (except for the accelerated-wear issue) with the Fulton extractor assembly. ---------- 90% of firing of rifle has been done with these modifications: A. Magpul UBR buttstock and buffer tube B. Geissele National Match trigger C. KAK 5.3 ounce buffer D. DPMS carbine-length buffer spring E. Palmetto bolt with Fulton Armory extractor assembly -------- Measurements/Specifications follow: GAS TUBE PROTRUSION Current depth of gas tube protrusion (Fulton Armory tube) Original depth of gas tube protrusion (Palmetto OEM tube) BUFFER SPRING DPMS Buffer Spring LR-308 Carbine From Midway USA Product #: 813595 Present relaxed spring length 11 15/32” Spring-wire diameter 0.075’” https://www.midwayusa.com/product/1003344651?pid=813595 RECEIVER EXTENSION (A.K.A. “BUFFER TUBE”) DEPTH Magpul UBR Generation 1 Depth: 7.00” KAK BUFFER Weight: 5.3 Overall length: 2.520” https://www.kakindustry.com/lr308-carbine-buffer-heavy GAS TUBE Fulton Armory Gas Tube, Rifle, FAR-308 AR https://www.fulton-armory.com/gastuberifle-1.aspx GAS BLOCK JOURNAL DIAMETER Journal on barrel is 0.750” GAS PORT DIAMETER Gas port will accept a 3/32" (0.09375") drill bit with a very snug fit. BARREL LENGTH Barrel length is 20”

Prior to solving the extraction issue, I did not scrutize the wear on the bolt, as I was never able to fire enough rounds to consider wear-patterns or such. I fired maybe 40 rounds (relentless malfunctions) before I started dissecting the rifle and replacing parts.

Thank you for these replies. If I understand correctly, the consensus is that it is unlocking too soon. I am currently running a 5.3 ounce buffer, DPMS LR-308 buffer spring, and OEM Palmetto non-adjustable gas block. Any particular preference as to which to approach first? — gas block vs. buffer vs. spring? Why pursue one versus the other first? I get it that there is also a possibility that the carrier could contribute. Not sure how to evaluate that feature. FWIW, I already own an adjustable gas block with gas-tube already installed. I previously experimented with that device when I was still chasing the extraction issue, but removed it for the sake of limiting variables while the extraction issue was still in play.

As promised, I painted the bolt lugs in order to test to see how much engagment of each lug-face was engaging with each barrel-extension face. I am using a 1.631" headspace gage to provide ample backthrust to see how much paint wipes off when the bolt is sent into battery. Typically, .308 Winchester match-grade ammunition, and most milsurp 7.62 NATO measures 1.628". Freshly painted: Headspace gage used for test: Pics of two sides of the bolt after re-assembling the bolt-carrier assembly with the bolt, and working the bolt a couple dozen cycles with the headspace gage in the chamber. Looks like all the (remaining) surface area of the backside of each bolt lug is getting good engagement with the lugs on the barrel extension. Clear evidence of a "chamfer" worn on the edge of each bolt lug from friction with the respective lugs on the barrel extension.

Fired another 100 rounds today. No malfunctions of any sort. Here's what the bolt looks like after I wiped it off with a paper towel. ____ 200 yards. Prone. Sling-supported. Single-feed each shot (rifle removed from the shoulder for each shot per NRA/CMP rules) 168 Sierra Match King with 41.5 grains IMR 4895 I'm mostly satisfied with this target. That 7 that leaked out at 5 o'clock hurt. But that's 100% the shooter and failure to follow-through on the shot. The 10 o'clock shot is what happens when you don't get your head down on the gun properly. The shooter again. Frankly all the low shots are simply poor execution (mostly follow-through). If you look at 10 o'clock in the 10-ring, you can see one abnormally small hole doubled into a .30 caliber hole. My buddy shooting 5.56 on the adjacent target could only find 19 of his shots. We just found it. On my target. So, I'm going with accuracy is still good. Not great. Not "X-ring." Although 6 of the 20 shots fired were in fact X's.

As I look at the backside face of the bolt lugs (the area of the bolt-lug) that engages the corresponding lug on the barrel-extension, I wonder just how MUCH of that backside face of the bolt lug has physical contact with the correspondeing lug on the barrel extension. I've got the gun all cleaned up and oiled for this weekend's outing. So, I don't want to do any experiments until after Sunday. But, when I clean it up after Sunday, I think I'll degrease the lugs on the bolt, and hit the back side of the bolt lugs with a dusting of spray paint. Then I'll assemble and drop it into battery and see how much spray paint gets wiped off the back side of the bolt lugs. Its clear that one corner respectively of the backside of each of the bolt-lugs is getting "chiseled" off by the process of moving into and/or out of battery. It occurs to me that the more one side of each of the lugs gets chiseled, the more-narrow the engagement face (the engagment that has to contain the pressure of firing) diminishes. If this chiseling progresses, at some point there will be so little face on the bolt that something will have to yield. It would be good to know how much engagement I actually have right now. I am of the belief that there is a "clocking" issue as to the engagment of the bolt already. I wil be concerned if I discover that those dwindling corners of the bolt are the only actual engagement. Judging from the smear-patterns of lubricant on the back of each bolt lug, I'm pretty sure I've got a whole lot more engagment than just those damaged corners of the lugs. Although, I am perplexed by the relative absence of wear of the black-oxide-or-whatever finish on the engagment surface of each lug. If it holds together for about another 100 rounds, I will do the spray-paint thing and find out what I've got.

Or conversely, what are the locking lugs of the barrel extension doing to the bolt? We can be sure the bolt and the barrel are nothing special. I don't think anyone would dispute that the wear-rate on this bolt is highly accelerated. That said, the chamber will just accept a 1.633" headspace gage. It refuses a 1.634" gage. So, headspace has grown 0.002" since everything was brand new. That's highly accelerated growth of headspace for sure. I will be keeping an eye on that. If headspace continues to grow, I will take measurements using two other bolts, and determine whether the growth is accountable to just the Palmetto bolt, or a combination of the bolt and other factors (biggest factor being probably the barrel extension). If superficial damage from small bits of metal floating around is the primary concern, I acknowledge that circumstance, but don't assign a lot of weight to that concern. Theoretically, some small bit of metal could get between the bullet and the bore, causing some sort of scratch within the bore. I tend to doubt that such scratch would show up in accuracy perfomance. I guess there's a chance that some foreign object could cause a "just-wrong" out-of-battery condition, and which would still allow primer-ignition. Those events do happen. Probably just as likely to have an ammunition case-head rupture. Either variety is always "exciting" on the firing line. I do wear eye protection. Albeit probably a minority viewpoint, I regard this sort of rifle as a consumable item. The bolt and barrel especially. If the bolt breaks to the point of being unserviceable, I have a spare bolt (Fulton Armory sourced) I can use. If the whole gun "breaks" (I'm not sure how that happens - but for the sake of discussion) I won't be distraught about it or even significantly inconvenienced. I like this gun, but I'm more enamored with several other more-accurate guns I shoot often. I can just move on from the Palmetto experiment if need be. If I get really motivated, I suppose I can install a much better barrel and a much better bolt. Which would make this a much better (and much more expensive) investment. For now, its as accurate as I need it to be, although less accurate than I want it to be. I'm still having fun with it. Which is my point of having it in the first place.

Let's think about this for a minute. If one lug breaks, what happens? Plenty of accounts of that happening with AR15 guns. Thousands of accounts actually. Bolts break in two at the cam pin too. Its a testament to the design that we never hear (or at least I'VE never heard) about bolt failures that cause injury to the shooter. I'm not indifferent to the concern. And I appreciate your concern. I'll monitor it closely for now.

Thanks. Should be interesting to see if this bolt continues to take the beating. I keep waiting for an entire lug to snap-off.

Here are a few pics of the condition of the bolt after yesterday's 100-round outing. I decided to shoot the pics before cleaning. May better-highlight the wear-points.

Fired another 100 rounds today. Good results as far as accuracy and function. Might post more pics of the bolt when I get around to cleaning it. Here we have 10 rounds fired prone, sling-supported, 100 yards. I called the low shot. Looks like I lucked out and still clipped the 9-ring. Not sure if it scores a 96 or a 97. That one shot 8:45(ish) may or may-not have clipped the 10-ring. Even when I peeled-off the mini Shootn-N-C, still can't tell. I called that wide 9 left too. Didn't think it was that far when I let it go. But, it is what it is. I have a harder time calling the high/low shots as high or low. I'll keep working on that. Not all the targets were this good, but the problem was all me when I flung an 8 or a 7.

The index pin is furnished with every AR-type barrel I’ve ever seen.

I wish I'd played-around with the bolt/carrier assembly right before making the adjustment, to get a feel for what amount of friction or contact I could feel before makeing the adjustment. After I made the adjustment, I could not feel any dramatic impact or friction. I do wonder whether I made any actual change in the timing, as the direction I moved the timing today is the same direction that the barrel would normally move when tightening the barrel nut. Speaking of the barrel nut, I can say the barrel nut (Michigan Industries I believe) on this upper does not like to be removed, re-installed, re-torqued repeatedly. I could tell that the threads were starting to shed some anodizing on re-tightening this nut now for the third time in the life of this upper. There was some grittiness that could be felt while tightening the nut today. At first-engagement of the threads, the grittiness was giving me a real scare. Really was acting like it was trying to cross-thread. Maybe I stretched the threads a bit on the previous removal/replace. I was able to get the situation under control without actually cross-threading. But, I caution it was touch-and-go for a couple minutes. Replacement Palmetto uppers can be acquired if you ruin one. I haven't seen a source for replacement barrel nuts for this exact handguard if you bugger a barrel nut. My advice is don't get the notion that you can take that barrel nut off-and-on repeatedly without encountering problems with the threads.