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+--- Thread: Help!!!! I sheared my index pin (/showthread.php?tid=21864)
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Help!!!! I sheared my index pin - Kaveman×39 - 08-19-2020
I was removing my 20" odin works barrel from a colt upper i had installed it in and I found the index pin had sheared
is this something I can fix my self do I need it/can I install the barrel with out if I use my magpul bev block? I have access to my welding metal shop if need be. Or should I send it to a gunsmith? Note I am a welder metal worker by trade so I feel confident in fixing not sure if its woth tackling my self or I should send it off to a gun smith
Help!!!! I sheared my index pin - A5BLASTER - 08-19-2020
Yes you need it.
You could send it in to be fixed or you could drill it out and make a new pin and hammer it in yourself.
Help!!!! I sheared my index pin - Kaveman×39 - 08-19-2020
Does the pin not just align the barrel? If I got it lined up then insert the bed block which secures it using the lug then torque on the barrel nut what wouldn't that work? Just not understanding the function of the pin beyond initial alignment
Help!!!! I sheared my index pin - tdbru - 08-19-2020
K39,
the pin also keeps the barrel extension, and barrel, from rotating during use. when the big fire lights off, the bullet hits the rifling and starts to rotate to the right, assuming right hand twist. due to Newton's second law, the barrel is trying to rotate to the left at the same time. i don't know if the barrel nut will keep the barrel extension pressed into the upper with enough friction to counter the rotational torque placed on the barrel when the rifle is fired. i wouldn't count on it myself. if you try any welding, you'll need to get the extension, and perhaps the barrel re-heat treated. i would suggest, as A5B noted, that you do need the pin. since i don't have the tooling myself to install a new one, i would take it to a gunsmith if it were me. ymmv.
-tdbru
Help!!!! I sheared my index pin - Klem - 08-19-2020
Kaveman,
I'd also be mindful that as the barrel nut is done up that the extension doesn't shift with the nut as the torque gets applied. Once you've got 40 ft lbs applied it should resist rotation with every round fired. Each bullet is not a lot of axial torque but it will be relentless, for the life of the barrel.
You could just carefully put it together and see what happens. It's not a safety issue.
Help!!!! I sheared my index pin - Lemonaid - 08-19-2020
Might want to read a similar thread posted on the forum: http://www.65grendel.com/forum/showthread.php?21581-Barrel-Extension-Separation!&highlight=extension+pin
Help!!!! I sheared my index pin - muvef1 - 08-20-2020
Rock River has new ones for $2 plus shipping. I replaced one several years ago and it dropped right out. It didn't seem pressed in. Maybe give Odin a call and get their opinion. It should be a easy fix.
Help!!!! I sheared my index pin - montana - 08-20-2020
Removing or installing a barrel can be very hard on the index pin, especially if it is or was over tightened. The Mid West receiver rod removes the torque from the index pin. The MI Upper Receiver Rod also can be used to test the barrel nut alignment . https://www.midwestindustriesinc.com/MI-Upper-Receiver-Rod-p/mi-urr.htm The Geissle Super Reaction Rod https://geissele.com/super-reaction-rod-for-556-223-caliber.html addressed this problem, compared to their standard reaction rod. https://www.midwayusa.com/product/1007066047 Clam shell clamps have the same problem.. With my Magpul bev block, the tab does not seem to be tight enough from preventing stress on the index pin..https://magpul.com/bevblock-ar15-m4.html?mp_global_color=118
Here is a good video about this subject https://www.arbuildjunkie.com/ar-15-reaction-rods-pros-and-cons-with-sotar/
Help!!!! I sheared my index pin - biodsl - 08-20-2020
Thanks, Montana. Informative video. I've owned the Geissele for a number of years. I've always thought the design could put a lot of stress on pin. But what do I know? I'm just a shade tree hack working in a home workshop. The Midwest rod seems superior.
I will say that the Midwest forces you to work 90 degree increments. Without the 'sail', the Geissele alllows you to rotate the upper just slightly off top dead, which can make things somewhat easier for us short guys.
Help!!!! I sheared my index pin - montana - 08-20-2020
biodsl Wrote:I've owned the Geissele for a number of years. I've always thought the design could put a lot of stress on pin. But what do I know? I'm just a shade tree hack working in a home workshop.
I have been working on AR rifles since the late 70's and I still learn something new every year. Your instinct was correct and sometimes we can tend to over think things without giving ourselves the credit due.....
Help!!!! I sheared my index pin - TruLbrt - 09-14-2020
A safe max torque on a geiselle reaction rod should be around #60, as deformation to index pin slot starts to occur reliably past #80.
The issue tends to be with timing barrel nuts and exceeding the torque to nudge it that last mm.
Also, slop in the index channel to begin with makes it more likely.
FWIW, I still use the reaction rod but only using midwest industries rails and the like with mild torque values and non timed barrel nuts.
MichiGuns LTd makes a cool tool for muzzle devices which is ideal vs any reaction rod type product.
Help!!!! I sheared my index pin - Klem - 09-14-2020
You don't have to go all the way up to 80 for Milspec barrel nuts. We know the range from 40 to 80ft lbs is so that the nut can turn at least one tooth to clear a path for the gas tube. But if you can't go all the way to 80 without something breaking then stop, mark the offending tooth, unscrew and file it off. You don't need all 20 teeth to do it up. Just make your own gap for the gas tube. As long as it is as least 40lbs that's all you need.
Help!!!! I sheared my index pin - montana - 09-14-2020
Klem Wrote:You don't have to go all the way up to 80 for Milspec barrel nuts. We know the range from 40 to 80ft lbs is so that the nut can turn at least one tooth to clear a path for the gas tube. But if you can't go all the way to 80 without something breaking then stop, mark the offending tooth, unscrew and file it off. You don't need all 20 teeth to do it up. Just make your own gap for the gas tube. As long as it is as least 40lbs that's all you need.
I have done that in the past with zero problems, "but I now use a barrel shim" so it looks more professional..https://www.brownells.com/rifle-parts/barrel-parts/rifle-barrel-hardware/washers/barrel-nut-shim-kit-prod96013.aspx
Help!!!! I sheared my index pin - TruLbrt - 09-15-2020
Like Shimming, lap the upper or possibly try a different upper or barrel nut will help correct for lower torque ranges.
Help!!!! I sheared my index pin - montana - 09-15-2020
TruLbrt Wrote:Like Shimming, lap the upper or possibly try a different upper or barrel nut will help correct for lower torque ranges.
Lapping, changing the barrel nut or both, can work, but I have found it doesn't always work.. It helps to know all the options available...I prefer barrel nuts that don't have to be timed to the gas tube.. I'm getting lazy in my old age
Help!!!! I sheared my index pin - The Profit Joseph Sith - 12-18-2020
Klem Wrote:then stop, mark the offending tooth, unscrew and file it off. You don't need all 20 teeth to do it up. Just make your own gap for the gas tube. As long as it is as least 40lbs that's all you need.things i wish i knew when building my first AR.
Klem Wrote:You don't have to go all the way up to 80 for Milspec barrel nuts.things i wish i knew when building me LAST AR lol!
Help!!!! I sheared my index pin - Lastrites - 12-18-2020
Klem Wrote:You don't have to go all the way up to 80 for Milspec barrel nuts. We know the range from 40 to 80ft lbs is so that the nut can turn at least one tooth to clear a path for the gas tube. But if you can't go all the way to 80 without something breaking then stop, mark the offending tooth, unscrew and file it off. You don't need all 20 teeth to do it up. Just make your own gap for the gas tube. As long as it is as least 40lbs that's all you need.
With some hand guards you can get away with a tooth removal, but not all as some use the gap bwtn teeth at 11:00 & 2:00 for anti-rotation tabs and if the teeth are not aligned properly the rail will end up canted.
Help!!!! I sheared my index pin - Klem - 12-18-2020
Lastrites Wrote:With some hand guards you can get away with a tooth removal, but not all as some use the gap bwtn teeth at 11:00 & 2:00 for anti-rotation tabs and if the teeth are not aligned properly the rail will end up canted.
What handguards are you referring to?
Help!!!! I sheared my index pin - The Profit Joseph Sith - 12-19-2020
not hand guard related, so slightly off topic but one of my pesky piston builds kinda uses that as bearing surface for the return spring..
my guess is something like the mil spec non free floating hand gaurds with the bumps that key in?
Help!!!! I sheared my index pin - Lastrites - 12-20-2020
Klem Wrote:What handguards are you referring to?
MI gen-II for one.