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XM21 fitment issue in EBR

This is a discussion on XM21 fitment issue in EBR within the Modern M14 forums, part of the M14 M1A Forum category; I was mocking up my receiver and I noticed that the chassis won’t allow the receiver to sit down far enough to be flush on ...


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Old May 16th, 2020, 08:22 PM   #1
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XM21 fitment issue in EBR

I was mocking up my receiver and I noticed that the chassis won’t allow the receiver to sit down far enough to be flush on the chassis. Is this a known issue or just my luck?

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Old May 16th, 2020, 08:28 PM   #2
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Known issue with early receivers. A friend had to remove a lot of metal from the sides of the chassis in order to get the receiver to fit properly. I think I would have returned the receiver, instead.

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Old May 16th, 2020, 08:36 PM   #3
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Known issue with early receivers. A friend had to remove a lot of metal from the sides of the chassis in order to get the receiver to fit properly. I think I would have returned the receiver, instead.

Ya I agree. I will probably send it back to BULA if they will honor it. I’ve had this thing a long time. I would imagine they will stand behind it. I’m not gonna modify either product to get one to fit the other because then I’ve custom “fitted” and made both useless for other builds.

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Old May 16th, 2020, 08:50 PM   #4
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Ya I agree. I will probably send it back to BULA if they will honor it. I’ve had this thing a long time. I would imagine they will stand behind it. I’m not gonna modify either product to get one to fit the other because then I’ve custom “fitted” and made both useless for other builds.
My sediments as well. I was shocked when I saw how much metal he had to remove. The rifle turned out to be very accurate, but the chassis is essentially ruined if he decides to make changes.

He also had problems getting a Bula trigger assembly to fit in the chassis. He ended up using the SAI from his Socom.

As a side note, his M1A Socom dropped into the chassis perfectly right from the start.

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Old May 16th, 2020, 08:59 PM   #5
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I submitted my “support” ticket with BULA we’ll see what they say. I’m not to optimistic for a quick fix because they’re website says they are retooling for some reason or another. Hell, I’d let them just repair my receiver and be done with it. I’m not sure if they simply remake it or fix it.

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Old May 16th, 2020, 10:10 PM   #6
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I submitted my “support” ticket with BULA we’ll see what they say. I’m not to optimistic for a quick fix because they’re website says they are retooling for some reason or another. Hell, I’d let them just repair my receiver and be done with it. I’m not sure if they simply remake it or fix it.
If they just need to thin out the outside of the legs, I'd guess they could just machine it down, as that surface isn't one that gets a bunch of wear, and as such wouldn't need heat treatment, or at least that's my uneducated uninformed guess.

Don't know what they'll actually want to do, but I think that if it's too wide, it's probably a good argument that the width is beyond spec of what an M14 receiver 'should' be to fit into a standard stock cutout.

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Old May 17th, 2020, 02:35 AM   #7
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I think you will find it is a simple fitment issue where the receiver legs contact
your SAGE as the XM21 was engineered to compliment that chassis from the earliest. I have ser# 2 and 3 and they are both drop in.

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Old May 17th, 2020, 02:55 AM   #8
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I think you will find it is a simple fitment issue where the receiver legs contact
your SAGE as the XM21 was engineered to compliment that chassis from the earliest. I have ser# 2 and 3 and they are both drop in.

Mine is more than just a “little off” because I can’t even force it in place by hand to set flush. I understand it was made for the EBR but this one would have to be beat into place with a hammer. Serial number 1 or 1000 that ain’t right.

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Old May 17th, 2020, 03:35 AM   #9
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Rubber mallet is your friend..!

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Old May 17th, 2020, 03:45 AM   #10
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Originally Posted by TheMexican View Post
Mine is more than just a “little off” because I can’t even force it in place by hand to set flush. I understand it was made for the EBR but this one would have to be beat into place with a hammer. Serial number 1 or 1000 that ain’t right.
No need to beat anything into place.
What is needed is to remove a small amount of material from to forward edges of your Sage in the leg recess area. It is called fitment and once again, these are not ARs.

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Old May 17th, 2020, 04:14 AM   #11
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No need to beat anything into place.
What is needed is to remove a small amount of material from to forward edges of your Sage in the leg recess area. It is called fitment and once again, these are not ARs.
Beating things into place was never an option..just to be clear and I have had many receivers in this exact EBR in the past all fit snug as they should but FIT. Im aware that these rifles aren't like AR's that fit together for the most part like legos. M1A style rifles require a little more skill to assemble properly. So I guess I'm sorry I'm not in a real hurry to grind, beat or otherwise alter the expensive receiver in order for this to work. I'm not in a hurry, I will wait until BULA gets back to me on how they want to handle this either way. BTW this is not a bash on them either, mass produced parts no matter how good QC is sometimes slip up. Poo happens

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Old May 17th, 2020, 04:47 AM   #12
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As I recall, my friend's receiver was scraping along the side rails at the top of the receiver legs, underneath the oprod area. I'm trying to find out if he took pictures.

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Old May 19th, 2020, 06:25 AM   #13
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To say the least, I’m not impressed with the response to this. Basically grind the receiver or beat it in with a mallet. This wouldn’t be so bad of a response if I’ve had many SA receivers fit perfectly into this exact chassis in the past.
Their response:

“This is actually a known issue with Sage Chassis. The receiver leg pockets are undersized. Our early receivers measured toward the high end of the datum tolerance making it appear more dramatic. Lightly filing the angled portion of the receiver legs and covering with cold blue afterward will get it to sit flush if that's what you want. Keep in mind that making it loose to the trigger group will lower accuracy. You want some tension in that area. Ideally there will be a small space between the heel and chassis. Many have seated the receiver well with a rubber mallet to the heel.”

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Old May 19th, 2020, 06:45 AM   #14
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Originally Posted by TheMexican View Post
To say the least, I’m not impressed with the response to this. Basically grind the receiver or beat it in with a mallet. This wouldn’t be so bad of a response if I’ve had many SA receivers fit perfectly into this exact chassis in the past.
Their response:

“This is actually a known issue with Sage Chassis. The receiver leg pockets are undersized. Our early receivers measured toward the high end of the datum tolerance making it appear more dramatic. Lightly filing the angled portion of the receiver legs and covering with cold blue afterward will get it to sit flush if that's what you want. Keep in mind that making it loose to the trigger group will lower accuracy. You want some tension in that area. Ideally there will be a small space between the heel and chassis. Many have seated the receiver well with a rubber mallet to the heel.”
Don't see what you find wrong with the response. SAIs were know for loose fits in everything hence so much need for bedding. Folks have had the same fitment issue with all makers of forged receivers going into a SAGE. Rubber mallet is used nowadays to replace the wooden or leather mallet that was used for fitment on USGI M1s and M14s into the stock and also to close the trigger guard. Common procedure used to keep things tight.

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Old May 19th, 2020, 06:53 AM   #15
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Quote:
Originally Posted by TheMexican View Post
To say the least, I’m not impressed with the response to this. Basically grind the receiver or beat it in with a mallet. This wouldn’t be so bad of a response if I’ve had many SA receivers fit perfectly into this exact chassis in the past.
Their response:

“This is actually a known issue with Sage Chassis. The receiver leg pockets are undersized. Our early receivers measured toward the high end of the datum tolerance making it appear more dramatic. Lightly filing the angled portion of the receiver legs and covering with cold blue afterward will get it to sit flush if that's what you want. Keep in mind that making it loose to the trigger group will lower accuracy. You want some tension in that area. Ideally there will be a small space between the heel and chassis. Many have seated the receiver well with a rubber mallet to the heel.”
Would they not accept a return? Did you ask them about a warranty?

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