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Receiver rail and bolt impact defect

This is a discussion on Receiver rail and bolt impact defect within the Art Luppino forums, part of the Gun Professionals category; In response to the interest for bolt lapping procedures it is necessary to check you M1A for another defect prior to lapping bolt. I'm sorry ...


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Old December 11th, 2006, 09:01 PM   #1
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Angry Receiver rail and bolt impact defect

In response to the interest for bolt lapping procedures it is necessary to check you M1A for another defect prior to lapping bolt. I'm sorry I didn't mention this first. All the M1A recievers I've worked on have a condition that is called, Bolt roller rail impact. When the bolt come to full lock up it is suppose to bottom out on the receiver lug cut out, not on the receiver rail. You can check this defect easy. Disassemble the rifle and place a piece of paper directly under the bolt roller as it nears the full lockup position, continue the rotation of the bolt to full lock up and see if the roller captured the paper between the roller and the receiver rail. If it does, the roller is impacting on the rail when fired, this will fatigue and stress the roller and may cause it to break. Also, this prevents the bolt from ever rotating to full lock position. You rifle was headspaced under this less than full lock up position, This is not the best for accuracy. It is easy to correct. With a small hand held Hobbie type Drimmel {spl** and a grinding wheel the same approx dia. as the roller and 1/8 "thick, grind out a radius under the bolt roller until you have approx .010" clearance between the roller and the rec. rail in full lock up position. This will give full rotation lockup and reduce the HS very little, and that litlle bit will be regained when the bolt is lapped in. This condition probably is in the cast receiver M1"s also. Art luppino

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Old December 12th, 2006, 12:37 AM   #2
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Aloha Art,

This is an interesting post, and a condition that I have not heard of before. I will certainly give my M1A's a quick test to see if any of mine have this condition.

I will also see if Hawk or SixTGunr might want to make this a "stickie" to give a heads up to the other members who might not frequent this section.

Thanks for the heads up!

Aloha,

Tom O.

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Old December 12th, 2006, 07:54 AM   #3
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Angry Impact

Quote:
Originally Posted by dighawaii
Aloha Art,

This is an interesting post, and a condition that I have not heard of before. I will certainly give my M1A's a quick test to see if any of mine have this condition.

I will also see if Hawk or SixTGunr might want to make this a "stickie" to give a heads up to the other members who might not frequent this section.

Thanks for the heads up!

Aloha,

Tom O.
Tom, If your rifles do not have this condition it would be a supprise, while you are checking this out it will be appearent if the impact problem has been addressed by a former owner. If so, run the clearance test any how just to make certain there is no impact. I've seen rifles that have been worked on in this situation and the job was incomplete. I Plan to post a number of DO IT YOURSELF messages for the guys that like to tinker. Hope you enjoy them and if there are specific things you would like to see addressed let me know. Art

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Old December 12th, 2006, 06:30 PM   #4
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Angry stickie

Quote:
Originally Posted by dighawaii
Aloha Art,

This is an interesting post, and a condition that I have not heard of before. I will certainly give my M1A's a quick test to see if any of mine have this condition.

I will also see if Hawk or SixTGunr might want to make this a "stickie" to give a heads up to the other members who might not frequent this section.

Thanks for the heads up!

Aloha,

Tom O.

Tom, Whats a Stickie??????????? Art

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Old December 13th, 2006, 08:50 PM   #5
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I hope Tom does not mind my answer to your what's a sticky. Important notes about the topic of a forum are tacked up top and considered a must read for those who wish to learn. I have been following this post myself and was happy to see Tom request this be a sticky. Otherwise you would have got a PM from me as well as a bunch of others for the details.
Thank you sir for the need to know info. I have your bedding DVD and plan on putting the others on my list to Santa. With respect, Jack

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Old January 6th, 2007, 05:01 PM   #6
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Diy

Thanks Art,
Really appreciate your sharing your knowledge...I'll be looking forward to more information.

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Old January 22nd, 2007, 05:46 PM   #7
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Excuse the ignorance...

I have a Poly that has a Winny bolt installed by a gunsmith. I did the paper test and it passed. I reinstalled the original Poly bolt and it also passed... the difference being that with the bolt locked, the Poly has a bit of fore and aft slop... the Winny bolt is rock solid. In either case, with the bolt closed and locked, the roller turns freely and is not in contact with the rail.

Did I miss something or am I just lucky?


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Old January 26th, 2007, 09:52 PM   #8
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Quote:
Did I miss something or am I just lucky?
This seems to be a problem that is associated to the M1A receiver as I read it. Again, thank you Art and we do look forward to more of your years of knowledge with the M14 type rifle.

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Old March 12th, 2007, 09:47 PM   #9
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Just checked my brand-new M1A Scout/Squad... the paper slides out easily; seems okay.

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Old March 12th, 2007, 10:26 PM   #10
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Cool



.008 clearance between the roller and the rcvr on my Norinco with the Norinco bolt, but good information here and elsewhere, as I'll be installing a USGI bolt soon. Out of curiosity, what are the front to back dimensions of the right and left bolt lugs on a USGI bolt??? On this Norinco bolt the right lug measures: .565 and the left one is: .450. Wondering how much lapping if any will have to be done.

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Old July 28th, 2007, 04:06 PM   #11
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I checked my SAI reciever for this defect and discovered it had already been relieved in the area mentioned and since this was a rifle i bought new from the factory it wasnt done Post purchase SN # 1877xx

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Old September 15th, 2009, 07:10 PM   #12
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Forgive me for being a little slow here but, any chance of there being a diagram, or pics of what this is??

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Old June 7th, 2011, 05:47 PM   #13
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all mine check out good to go.
Thanks

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Old February 5th, 2016, 05:23 PM   #14
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Also, be aware that some of SAI's own, early bolts, have a bolt roller that is bigger around. These are especially found to contact the receiver where Art is pointing out.

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Old April 30th, 2016, 03:23 PM   #15
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Roland Beaver build

Art,

My receiver is an Arms Corp. Plus it's just back from a rebuild by Roland Beaver. He was so thorough it would seem unlikely he missed something like that. I'm not a gunsmith.

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