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lapriester

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So, I bought a "Gunsmithing Special" blem 20" 6.5 Grendel barrel from AR15.com. It's a blem because during manufacture the index pin ended up almost flush or flush with the barrel extension. They probably pressed in a pin that was too short. It was very cheap at $69 so I figured, even if I screw it up somehow I'm not out much. The question is, how do I get that flush pin out and replace it with the correct length one? I've read drilling it will loosen the pressed fit. I have a good drill press so I wouldn't be trying to hand drill it. Any other suggestions that could get this done?

Thanks in advance for any ideas.
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Rifter

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Quote:
Originally Posted by lapriester
So, I bought a "Gunsmithing Special" blem 20" 6.5 Grendel barrel from AR15.com. It's a blem because during manufacture the index pin ended up almost flush or flush with the barrel extension. They probably pressed in a pin that was too short. It was very cheap at $69 so I figured, even if I screw it up somehow I'm not out much. The question is, how do I get that flush pin out and replace it with the correct length one? I've read drilling it will loosen the pressed fit. I have a good drill press so I wouldn't be trying to hand drill it. Any other suggestions that could get this done?

Thanks in advance for any ideas.

Does the hole go all the way through?  If it does, wouldn't it be easier to just push it all the way through as opposed to trying to drill a hardened pin?

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RIGGS68

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Reply with quote  #3 
Place a small nut (or something similar) on the pin and weld the pin to tge nut through the opening, place it in the freezer and pull the pin with the nut.
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Moleman

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There's a chance it might pop up if you loosen the barrel extension, but if it has been driven into the threads, there's a greater chance that it will try to strip out the threads as it is removed.  I've removed extensions where pin caused no issues, popped up a little when the extension was initially loosened and ones that tried to strip the threads out.  On the ones that tried to strip the threads out I just drilled them out.  A good drill index helps sneak up in diameter a few thousands at a time until it releases.  I'd normally do it in a mill, but set up correctly it shouldn't be an issue. You likely won't get the hole dead center so at some point as the drill bit diameter increases you'll get close to drilling into the extension.  Likely before then you could put a small screw into the hole and pull the pin out.  You'll want to watch how deep you drill.  The top of the barrel threads is roughly .100" down from the surface of the 1" diameter section of the barrel extension. The bottom of the barrel threads on the extension is roughly .145" from the surface of the 1" diameter area of the extension and I would not drill any deeper than that.   The replacement pin size is 1/8" diameter and 3/16" long.  If I just had one to do I'd tap the top end of a 1/8" drill bit or section of 1/8" drill rod into the hole then cut it off flush with the collar on the extension with a dremel. I've used both of those methods when I've run out of index pins. 
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kshunter

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Reply with quote  #5 
Quote:
Originally Posted by RIGGS68
Place a small nut (or something similar) on the pin and weld the pin to tge nut through the opening, place it in the freezer and pull the pin with the nut.

I’ve used this method to remove broken bolts before, only I put an ice cube on the welded but for a few minutes before removal. That did a decent job of shrinking the bolt enough to back it out.
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BIGGDAWG

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Reply with quote  #6 
you can drill them some but i use the center drills to get things started start small and work slow with plenty of lube, they can be a pain in the butt 
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lapriester

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Reply with quote  #7 
Quote:
Originally Posted by Rifter
Does the hole go all the way through?  If it does, wouldn't it be easier to just push it all the way through as opposed to trying to drill a hardened pin?

I'm trying to do this without removing the extension. I'm pretty certain it won't go all the way through but thanks. When I actually have it in hand I can make a better choice. But, so far there's some great ideas here. Keep em' coming.

Thanks guys. I let ya' know what I intend to do. Drilling seems simple enough but again, have to wait until it's in hand.
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BIGGDAWG

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Reply with quote  #8 
no it don't go all the way through. it is over the chamber
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madcat737

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Reply with quote  #9 
I sheared one off one time. I step drilled it until it just crumbled loose. Just dont go past the pin depth or you will drill into your chamber. It was a pretty simple job. I cut off a drill bit and made a new pin.
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lapriester

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Quote:
Originally Posted by madcat737
I sheared one off one time. I step drilled it until it just crumbled loose. Just dont go past the pin depth or you will drill into your chamber. It was a pretty simple job. I cut off a drill bit and made a new pin.


Thanks. I think that's the way I'll try it. Hell, the $200+ barrel only cost me $69 so what do I really have to lose. It will make an interesting tomato stake if I screw it up. I already have a Grendel Type1 that shoots little fingernail size groups at 100 yards and 1/2" at 200 so, no loss and much to gain if It works. Being I have the parts laying around to complete an upper this is a win win if I get it out.
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lapriester

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Reply with quote  #11 
Any reason you couldn't use a roll pin to replace it if you happened to drill a tad to large? All it does is index the barrel to 12 o'clock, and I bed all my extensions anyway, so it isn't going to move once the barrel nut is tight.
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lapriester

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Reply with quote  #12 
Got that barrel today.  Looks like Very high quality HBAR 20" barrel....well, except for the fact the index pin is indeed flush with the extension.  How they ever did that beats me.  It really doesn't look all that complicated.  Being exactly flush might make drilling it easier.  This is an after deer season Winter project.  IF Winter ever arrives in California before the whole state goes up in flames.   
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lapriester

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Step drilling was a good idea but, my Cobalt high quality bits wouldn't make a dent in the pin. Soooo, I just happened to have a 1/8" Carbide bit I've used in some gunsmithing projects and got the sucker drilled. Being new pins are 1/8 and the bit seemed to drill very slightly under that I should be good to go. If the hole is too large I verified a 1/8" roll pin will fit tight. Perfectly lining it up with the drill press was an interesting task. I ordered a couple new pins and received them today. We'll see if they're tight tomorrow. I suspecting they will be. Before resorting to the roll pin (which I certain would work just fine for that purpose), if the pins are not tight, I may try peening the end of a pin to try and tighten the fit. That and some red thread sealant should do fine. Once the barrel nut is on it isn't going anywhere anyway.
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RangerJoe

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Reply with quote  #14 
Thanks for the follow-up report... I've been wondering how this project went.  Looks like you got a great bargain for a bit of work...
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Moleman

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Reply with quote  #15 
One of my factory barrels has a several peen marks around the index pin hole.   I'd be tempted to just go the peen the pin and red loctite route.  Otherwise you could get a #30 drill bit (.1285") and tap the shank end in and gut it off level with the extension collar. Ace/true value usually have number/letter/fractional bits for a couple dollars each on the smaller ones. 
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BIGGDAWG

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Reply with quote  #16 
i also have some .002 over pins for the extensions that have a loose fit. they are a little long i just drive in and file off.
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lapriester

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Reply with quote  #17 
Quote:
Originally Posted by BIGGDAWG
i also have some .002 over pins for the extensions that have a loose fit. they are a little long i just drive in and file off.


Good news, looks like the new pins are tight enough I'll have to tap one in. I'll still put a dab of gel red LocTite on it. It also looks like I drilled the hole in the right location and right depth. This is going to work out. Thanks everyone for all the help and suggestions. I'll report back on how it shoots when I get it built up.

Larry
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lapriester

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Reply with quote  #18 
Success! I went ahead and slightly peened around the edges of the hole, added some red gel LocTite, and tapped the new pin in with a nice snug fit. Height almost perfect. I had to lightly file it with a diamond lap after finding very slight interference with the barrel nut threads. I'm resisting bedding the extension to the receiver like I usually do since this Nitrided barrel extension is nice and snug. Besides, if for some reason it doesn't shoot as well as expected that will make it much easier to remove. I'm thinking bedding isn't going to result in much, if any noticeable accuracy improvement.

Thoughts on this?
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Rifter

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Reply with quote  #19 
Quote:
Originally Posted by lapriester
Success! I went ahead and slightly peened around the edges of the hole, added some red gel LocTite, and tapped the new pin in with a nice snug fit. Height almost perfect. I had to lightly file it with a diamond lap after finding very slight interference with the barrel nut threads. I'm resisting bedding the extension to the receiver like I usually do since this Nitrided barrel extension is nice and snug. Besides, if for some reason it doesn't shoot as well as expected that will make it much easier to remove. I'm thinking bedding isn't going to result in much, if any noticeable accuracy improvement.

Thoughts on this?



Glad you got it fixed.  I think the best thing you can do when installing a barrel is to true the receiver.  That's all I've ever done with mine, and they all shoot nice tight groups.  If everything lashes up tight when you put it together, don't see the need for bedding.

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lapriester

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Reply with quote  #20 
Well, lesson learned. I ran a patch through the barrel in prep for installation and felt an odd resistance near the muzzle. Looked down the bore from the muzzle end and I saw two concentric grooves inside in line with the two machining cuts on the exterior of the barrel behind the threaded portion. I can actually catch the worse one under the deepest cut with a dental pick. Obviously the barrel is totally defective and a far cry from the simple index pin problem that was described and there's no way to determine if this defect is a safety issue. I wrote arpart.com and complained so who knows. They currently have some blem SST versions of the same barrel for sale for $10 more with "slight' external shipping scratches. I suggested I'd pay the extra $10 if they'd replace this unservicable tomato stake. We'll see but I'm not holding my breath on this one.

Never in my life have I seen such a gross defect in a barrel bore. Could it have been overheated when the external machining was done? It's too much of a coincidence that the grooves or lines are in line with the external machining don't you think.
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battle rattle

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Reply with quote  #21 
freebore in from the muzzle and fab a compensator right into the end of the barrel
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lapriester

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Reply with quote  #22 
I thought about just having it machined shorter and crowned but I'm certain that would cost more than the barrel is worth. Free boring and compensating isn't in my very limited range of expertise and having it done...well, there's that worth problem again. I'm thinking tomato stake more by the minute.
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BIGGDAWG

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Reply with quote  #23 
Quote:
Originally Posted by lapriester
I thought about just having it machined shorter and crowned but I'm certain that would cost more than the barrel is worth. Free boring and compensating isn't in my very limited range of expertise and having it done...well, there's that worth problem again. I'm thinking tomato stake more by the minute.



I can cut and crown for 25 if you want it threaded it would be 45

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lapriester

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Reply with quote  #24 
This is what I have. Never seen this before on a new barrel. Any idea how this could happen? Thanks BIGGDAWG but, based on what I see I'm not sure I trust the integrity of the barrel at all any more. It almost looks like it was counter bored but at the crown the bore is tight. Screwed up for certain.

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wikster1983

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Reply with quote  #25 
Quote:
Originally Posted by lapriester
This is what I have. Never seen this before on a new barrel. Any idea how this could happen? Thanks BIGGDAWG but, based on what I see I'm not sure I trust the integrity of the barrel at all any more. It almost looks like it was counter bored but at the crown the bore is tight. Screwed up for certain.

Would've they counter bored to reduce pressure at the threads for some reason?

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