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Discussion Starter · #1 ·
I been thru many engineering and design changes and reviews and doing the repairs more than i can count. I have saved the many companies i have worked for and saved many dollars and down time in the past years before i retired. I can apply my many experiences to fixing anything now to make it a better reliable repair. I just hate doing things over and over when i determine a quick fix won't last. I'm not tooting my own horn and i'm no guru i just want my m14 to last forever and when it gets handed down to my son it will last for him too.

Ok the op rod guide block is just a tad loose on the barrel. I figure the pin in it has probably flattened out in it too. I believe its a spirol pin to begin with.

I feel that knurling the raised boss on the barrel and assembling it with loctite could fail in a sustained fire situation when the heat tempeture increases. Some of the loctite products can loosen up and maybe fail from 400 to 600 degrees. Even with a new pin this still has me worried. Its just a quick fix to me until it comes loose again sometime down the road it will for sure. Remember i'm new to this and look at it from a different view.

The proper fix to me that will last forever;

1st. I figure to knurl the barrel first to the proper size so the guide block becomes a press fit. Not too tight and not too loose.

2nd. Drill and tap the dowel pin hole from both sides this way when the guide block is finally pressed in place we can install two set screws from each side to bind it. The two set screws will keep it aligned and bind it in place from both sides.

One extra step we can take is to use a flat bottom drill the size of the tap drill to spot face two flat spots so the set screw can push against a better solid surface rather than it forcing it into the dowel pin slot. Once the set screws and in place with the guide block algined we then prick punch the set screws so there locked in place near the threads in the block. This stuff is just too small to use a dutchman. Thats were we drill a hole down in the middle of the threads of the two mating parts and then drive a dowel pin between the threads to lock the screw from turing. We did that on the bigger applications so the screws can come loose in any way.

What do you guys think about my forever fix??? Bill
 

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I don't see any reason why this fix wouldn't work. It may not be necessary, but it will work.

I have found that just knurling the barrel works fine. I've never had one shoot loose once knurled properly.

I've also used Loctite on some heavy barrel installations when the oversized guide wasn't as tight as I prefer. An application of 290 works well. I also used 290 on the gas block of my AR space gun. The block was a close but not tight fit and it hasn't shot loose in over 3000 rounds of competition shooting. The block has no screws or pins. It's only held in place by the Loctite. I don't think the barrel gets hot enough for heat to be a factor.
 

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Knurled the barrel and used a little JB Weld and it hasn't been a problem since.
 

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Discussion Starter · #4 · (Edited)
Ok guys i'll trust you. I'll knurl it and get the loctite for the diameter round stock. I'll keep my fix in the bank incase it ever comes loose again but from whats said here it won't.


I have some loctite here from the past that i have used before that can take up .015" of space/gaps. I used it on tapered couplings that were in such great shape on the test stand. We never sent the loctited stuff like this into the field for people to use. For support on the test stands in the lab it was ok plus i like to test other companies products too. The loctite was used on the load machine that puts a torque on the recent redesigned new machine. Sometimes the torque can be up to the equilivent of 25 to 30 427 chevy bigblock engines like the electric motors on the elevators that were in the world trade center.

I used JB weld on my sons dirtbike engine case when he put the drive chain thru it. It held up for many years until he sold the bike and its still running and not leaking tranny oil.
 

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Discussion Starter · #5 · (Edited)
Ok investigated further into the loctite products looking for a cylinderical loctite that will fill gaps if neccessary and allow it to still hold during higher temps(sustained fire). I found the loctite 620 is for the cylinderical parts. Its still securing at 200c temps way beyond what i need but i feel safe with it. I think the 200c temp is way beyond our needs but i sleep good at night knowing i used the best product for the job. The 620 loctite is used to bond the cylinderical parts(round) and gaps up to .015'' and viscosity Cp is 8,500 and for fitting parts patically when a high resistance is required.Used for the locating pins in radiators, sleeves in pump housings and sleeve bearings in auto tranny's. I think its ok to use it in our application. Any loctite will probably work i'm just above and beyond the call of duty with a little over kill. I just like the odds on my side more if i'm in doubt remember i'm new to this and my luck isn't so good sometimes so i over kill everything when i repair it. But i will take the good advise given here and use the loctite with a new pin and stake the pin. Bill

BTW; I have some lake city brass on the way with some 175gr FMJBT bullets and i'm dying to shoot the m14 after going thru it and making it right. I have one more thing to maybe add or not its the larger paddle type mag release what do you guys think??
 

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I just took the little roll pn out, opened up the hole s bit, and made a solid pin that's a good tight fit.
The larger pin diameter gives more surface area for bearing, so it's less likely to become loose.
It's been fine so far.
 

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Discussion Starter · #7 · (Edited)
I just took the little roll pn out, opened up the hole s bit, and made a solid pin that's a good tight fit.
The larger pin diameter gives more surface area for bearing, so it's less likely to become loose.
It's been fine so far.
I was just rethinking about this. I was thinking they use the pin to hold the op rod guide block inplace so it can't have any side to side play. The op rod guide is only a snug fit on the barrel. There depending in the spirol pin to hold it in place only. If there using a standard spirol pin with a one sided wall it can compress over time and get flat spot if it sees any force. They do make a heavy duty spirol pin thats wound a few times so it has more than one side wall. The heavy duty spirol pin won't compress. I just researched into the heavier spirol pins yesterday. We use them on the tractors. If we just use the one sided wall spirol pins the drive shafts will just compress them and shear them up. Sounds familair right? I think we have this "pinned" down now were the problem really is. Bill

www.mcmaster.com (mcmaster carr industrial supply company in new jersey) who has next day shipping, i get everything within 24hrs offers the heavy duty spring pins in metric and inch sizes, i ordered both the 3mm metric and the 1/8'' inch just incase there good to have inhouse. I have the reamers too so i can make anything fit it.
 

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Discussion Starter · #8 ·
Update; I have the op rod guide block inplace with the 620 loctite and aligned. Once the loctite hardens i'll reream the pin hole to 1/8'' and install a new 1/8'' pin. The orginal 3mm pin is tight in the op rod guide block but slot of the barrel is worn and the 3mm pin won't hold the block tight anymore. I'm not sure if the block as ever tight even when it was new. I'll do the loctite and new pin fix and that should do it. Thank's for all your help and support. I can't wait to pull the trigger on it finally its fixed. But this repair gave me the chance to paint the handguard/plastic stock with the epoxy brownells aluma-hyde II in black matte. I'd like to do the barreled receiver in gray park. Bill
 
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