Is the barrel index pin killing my barrel nut?

[W.E.G.]

Palmetto PA-10.

I removed the barrel nut three times as I was doing inspections and other adjustments.

Each time, the barrel nut came off the gun with a lot of binding, and damage to the barrel nut.

This pic shows what the barrel nut looked like when I removed for the third time. On each removal, there were bits of aluminum from the barrel nut left behind in the barrel nut. This third time seems the worst.

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Next pic shows the barrel mounted in the receiver. Is this index-pin standing-proud too far, and contacting the barrel nut, and shearing the point off the threads of the nut?

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Here is a pic of the barrel mounted in the receiver after the third removal of the barrel nut. Notice that the threads on the receiver are completely undamaged.

[W.E.G.]

I should also mention that I separately mounted a replacement barrel nut, JL Billet part #JLB-308-BN16, and I experienced the same sort of binding and damage to the nut.

All the pics you see above however are the Palmetto barrel nut.

I'm pretty sure its the index-pin standing proud that is causing the problem. But, I'm fairly new to wrenching on AR-type guns. Figured I would make inquiry before breaking out the dremel, and shortening the index-pin.

[W.E.G.]

Someone asked:

Have you tried tapping the pin down to seat it?

I beat on the pin and down she went.

I have concerns that she'll just migrate back up.

Can I yank it out and then fill the hole with JB Weld and beat it back in to hope it will stay put?

[DNP]

I can’t say from any experience, but from the photos and the details it seems like reasonably logical assessment.  Take a little off the top of that index pin and see if that clears it up. 

[W.E.G.]

The theory that the pin is moving around seems to be supported by the fact that the worst damage to the barrel nut didn't occur until the THIRD time I removed the nut.

[DNP]

If you have it down, throw a nut on with good threads, the threads themselves should keep it from backing out. 

Edited November 8, 2019 by DNP

[W.E.G.]

I just tried yanking the pin out with a pair of needle-nose vise grips.

She aint coming out that way. BTW, that pin is hard metal. 
Put a divot in the tip of the cheap vise trip pliers.

So, banged it back down as deep as I could get it. 
Probably won't chew up the barrel nut during install.
Fully expect it to migrate back out and chew the nut some more on next removal.

[Ravenworks]

The pin is going to float,I would NOT epoxy (JB Weld) it in.

The pin will expand with heat hence the reason you want it to float.

 

[98Z5V]

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

I beat on the pin and down she went.

This was exactly what my recommendation was going to be, when I first started reading this thread - and saw the pin sticking up.

I don't think it's gonna come out anymore, and it certainly doesn't "float" in the barrel extension.  It's a pretty good interference fit, the way it's designed.  They're a bitch to get out, when you need them out.  I think you're safe now.  It's seated, fully.

[Ravenworks]

39 minutes ago, 98Z5V said:

and it certainly doesn't "float" in the barrel extension.  It's a pretty good interference fit, the way it's designed.

Well maybe I had a poor choice of words, you are correct in saying that pin is an interference fit.

However by design the pin should expand and contract freely at it's own rate.

You have three dissimilar metals converging together all three will move at different rates.

[98Z5V]

2 minutes ago, Ravenworks said:

Well maybe I had a poor choice of words, you are correct in saying that pin is an interference fit.

However by design the pin should expand and contract freely at it's own rate.

You have three dissimilar metals converging together all three will move at different rates.

You have to put a MAPP gas torch to your barrel extension, and heat the hell out of it, to get a barrel index pin out, and you need one evil set of pliers to do it, after it's hot enough.  You're never gonna get your chamber that hot, by firing the gun, and have that pin "expand and contract."   It won't happen. 

[Matt.Cross]

9 minutes ago, Ravenworks said:

You have three dissimilar metals converging together all three will move at different rates.

That's true but it's also a matter of proportion. There's more similarity between the metals of the barrel extension and pin than between the barrel assembly and aluminum receiver and barrel nut. The difference in expansion in terms of the pin (and it's hole) isn't enough that it should ever float. As @98Z5V pointed out, it's an interference fit.

[Cunuckgaucho]

For an interference press fit, stick the pin in the freezer overnight. I suggest throwing in the needle nose pliers in the freezer to. Place the part with the hole in a warm environment such as close to a baseboard heater.

Because the pin is small don't touch with bare hands and move quickly. If the pin and the hole are the same size( three decimal places in inches) the pin will slip into the hole with some but not much effort( light tapping). Once the temperatures equalize on both parts  it ain't going anywhere. 

[Ravenworks]

I'm not disagreeing, but I also had problems with two extensions on barrels I got from Criterion barrels of all places.( the hole was too big and the pins fell out and were lost between them and me during shipping)

Josh actually wanted me to send the barrels back and I told him no way.

He ended up mailing me half dozen of the pins because I get stuff the next day from them through the mail.

It would have been a week screwing around waiting on someone else to ship them.

Edited November 9, 2019 by Ravenworks

[Matt.Cross]

5 minutes ago, Ravenworks said:

I'm not disagreeing, but I also had problems with two extensions on barrels I got from Criterion barrels of all places.( the hole was too big and the pins fell out and were lost between them and me during shipping)

No worries, you're good brother. I don't think anybody would doubt your experiences. I know full well myself how easily drills and reamers get dull and how tool offsets change over time. An undersized pin or an oversized bore is not difficult to believe in the least.

[W.E.G.]

Got it all put back together now.

Gave the bore the bizniss with some JB while I had it off the rifle.

Torqued the original nut (the ate-up one) to 55 foot pounds.

Installed the new ToolCraft bolt/carrier group. Small-diameter firing pin, double ejectors. Less and less of this rifle is still Palmetto. Sure hope that Palmetto barrel extension doesn't eat up that new bolt. Headspace measured out at 1.634". That's about where it was at with the Palmetto bolt. I know that's a little on the long side (Forster No-Go gage is 1.634"). I could tell the 1.634 gage closed tight. Should have known better than to try to get it to swallow the 1.635" gage. Man, that thing stuck in there like a sumbitch at partial batttery. Mortar/pogo was no-go. Had lay the big rubber mallet against the ear of the charging handle and wail on the rubber mallet with a four-pound sledge to get it to open up. I gotta stop doing that. But I just HAD TO KNOW. Now I know what I knew before I pulled that stunt. It aint gonna swallow a 1.635.

So yeah, 1.630 is the "perfect" headspace for .308. I doubt 0.004" is the cause of the up-down stringing. But, who really knows. 

Still need to put the scope and sling back on. I'll do that, and shoot a pic in the morning when the light in the room is a little better.

Taking it to the range in a couple of days. Sure hope it at least cycles with the new bolt.

[jtallen83]

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

Mortar/pogo was no-go. Had lay the big rubber mallet against the ear of the charging handle and wail on the rubber mallet with a four-pound sledge to get it to open up.

I gather you did not remove the ejector or extractor to check headspace?

[W.E.G.]

4 hours ago, jtallen83 said:

I gather you did not remove the ejector or extractor to check headspace?

No. I did not.

[W.E.G.]

Below is the Dremel bit I used to de-burr the locking lugs on my barrel extension.

I used only my fingers to "drive" the bit. I did not install the bit actually in the motorized rotary tool.

I spent about 45 minutes, while watching TV, going over the radius-edge of each lug of the barrel extension. 

Prior to the de-burring job, the lugs on the barrel extension would "grab" bits of Q-Tip cotton when cleaning the lugs. Now, the lugs do not grab any cotton.

 

I went back to the old thread and I'm re-posting the pic of the lugs 
of the barrel extension as it appeared 
some months BEFORE last night's adjustment with the dremel bit.

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[jtallen83]

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

No. I did not.

IMHO it is worth checking it with at least the ejector removed, it puts a good deal of pressure on the gauge and could cause a false reading. I was taught to remove both ejector and extractor when checking headspace, so far that has worked well for me.

[W.E.G.]

7 minutes ago, jtallen83 said:

IMHO it is worth checking it with at least the ejector removed, it puts a good deal of pressure on the gauge and could cause a false reading. I was taught to remove both ejector and extractor when checking headspace, so far that has worked well for me.

I understand the principle of your concern.

[W.E.G.]

Range report.

 

TLDR version - Accuracy still sucks. Rifle is junk.

 

I fired prone all shots today.

Beautiful conditions. Light overcast, which is perfect lighting conditions for this type of shooting.

 

I fired at four targets. I'll post pics of three of the targets below. No point in posting the target I used to re-establish zero, and on which I was cranking sight knobs. I had to come down about two minutes from what I thought was my correct zero.

 

You may care to know that the targets for the 13-shot and 10-shot groups are correct reduced targets for 200 yards to simulate the 600 yard NRA highpower rifle target. The Shoot-N-C centers very closely approximate the correct location of the scoring rings for that target. The aiming-black area of each target is approximately 13-inch diameter.

 

All firing from prone, sling-supported position.

 

I normally like to test accuracy by shooting 10-shot groups.

 

First target has 13 shots because I concluded that my zero was actually off by a couple scope clicks (1/10 mil - same as 1/3 MOA per click). Group is pretty much all over the place. I called one shot low, and two shots left. I called one shot "loose" - no call really - but you know when you shoot one of those that it could land anywhere - which it did out to the right in the 7 ring. Otherwise, all shots broke solid center. I shot the extra three shots in this group because it was already such a mess, I wanted to see where two clicks left would put me.

 

Second target is a 5-shot group. I fired this on a different bank of targets,a and also after making the aforesaid two-click adjustment. This actually gave me some hope that maybe that first mess of a target was just me. I could live with this kind of accuracy.

 

Third target is 10 shots. This target was right next to the nice 5-shot target, and was fired immediatly after that 5-shot target. Again, we've got shots pretty much all over the place. First two shots were high 8's. Each called a good center shot. After that, the hits just danced around wherever. That, despite me calling the shots good. I definitely had my position and trigger control established by the time I was on this third target.

 

The gun ran fine with the new ToolCraft BCG. The bolt seems to have weathered the day without being chewed-up like the Palmetto bolt.

 

But, accuracy just suck.

 

Only three things could be happening here.

1. Maybe the ammo is terrible - I doubt that. I've always said that if you shoot a good bullet through a good barrel, you will get good results shooting at service rifle targets. Things like choice of casing, or primer, or powder tend to matter very little compared to the major factors of "good bullet and good barrel."

2. Maybe I just can't shoot this rifle, even though its a slightly large version of the same rifle which I can consistently shoot high master scores (97%+) on a 200-yard range. So I doubt its the shooter.

3. Maybe its something about the rifle - who knows what. I suspect its simply the barrel. Like I said, "A good bullet through a good barrel..."

 

At this point, I'm going with "bad barrel" as the major reason this rifle can barely hold the 8-ring on an NRA highpower rifle prone target.

 

The cost of a replacement barrel is really not the issue at this point. Unfortunately, I live in goddamfugkingVirginia, and this gun is about to be BANNED by the asswipes who just took over our government.

 

I'm not gonna spend money on a new barrel I can't legally shoot.

 

The new laws will go into effect July 1. I'll decide what to do about this gun sometime between now and then.

[W.E.G.]

TARGET 1

 

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TARGET 2

 

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TARGET 3/

[98Z5V]

Have you always had this load, and it does good from other .308 Win guns?  168 SMK and 41.0gr of RamShot TAC?

[W.E.G.]

It shoots about the same as 41.5 grains IMR 4895 out of my M1A.

I don't shoot the M1A much these days, because it has iron sights, and I just can see them well enough most days to make spending a day with it worth my while.

Give the load a try in a rifle that you shoot well. The 168SMK is for-sure a good bullet. Be sure you shoot it in a rifle with a good barrel.