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Discussion Starter · #1 · (Edited)
First let me say. This is a great site filled with volumes of useful information. I have enjoyed spending many evenings reading the various post. Thanks!

Now my question...My first M1A was a Springfield Loaded. I bought it and enjoyed shooting it very much. I have since picked up a second rifle. I would like to convert it to all G.I. parts if I can. It is a Springfield Inc. receiver but with the following HRA parts, barrel, op-rod, trigger group and G.I stock. I would like very much to install a G.I. bolt. Should I expect any problems with a G.I. bolt matching with a commercial receiver? And secondly.....I could certainly use some advise where to pick up a quality bolt. Unless someone would have a nice unissued one sitting around and would want to make a few bucks off a new guy. GI2

Thanks.
Gary
 

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I have a SAI receiver with a TRW bolt and it works just fine. Like all new bolts they usually need some fitting/lapping for headspace and the like. Every now and then you can just drop them in and be alright but I don't suggest you do that. But once you get them installed properly it's all uphill from there. Try 'RA parts' they have a banner on this forum. The last NIW TRW bolt I got was from them.
 

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Discussion Starter · #3 ·
So it appears I should be GTG with a G.I. bolt. Is a TRW bolt the only one I should reasonbly expect to still find in unissued condition?
 

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So it appears I should be GTG with a G.I. bolt. Is a TRW bolt the only one I should reasonbly expect to still find in unissued condition?
Pretty much. They had the last contract for spares.
 

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Bolt Replacement

What kind of bolt is in it now ? Could you post the numbers and letters on it ?

If you have calipers, and can take the left and right lug measurements, you can get pretty close to finding a bolt that will need minimal lapping to fit properly, by asking potential sellers to furnish their lug measurements.

The process is touchy at best, due to the rounded sections on the lugs, and one needs to be diligent and check several times to arrive at an average length. I have found a rocking motion with the calipers is best when measuring, until they settle in. Then record this reading, then do it again. Also move up and down on the lug height from bolt body at the base. Take several measurements.

G.I. lugs will range in size from .460-.465 ( left )...and .570-.575 ( right ) ...with the mean average of .462-.463 Left and .572-.573 Right, from my experience. I have found that Winchester Bolts are the longest lugged.

No, you can find other HR manufactured bolts by watching closely to the PX. The real challenge is finding all four of the original makers bolts. Check with Claude at raparts.com for bolts. He will measure them for you and might can pick you up a nice one. Claude is not cheap, and he is worth every penny, and ask anyone, I am a tightwad, and I still buy from Claude all the time....heh heh...

A new TRW bolt recently opened measured exactly .461 and .571 and was a drop in fit for three receivers and an SAI with approximately 30% lug contact between receiver and bolt lugs. The astounding thing about it was, they all headspaced out at 1.632 with G.I. barrels....But, here is where you must make certain that you have proper lug contact on both sides.

The only way I have found to do this is with Dykem Dye......or with lapping compound to shine both lugs up as you go, if you are certain they are contacting to begin with. This is where I have learned to use feeler guages and random pieces of varying thickness materials. Such as, a piece of printer paper is .0005, a business card is .010, and a piece of scotch tape is .002

A small strip of paper cut about 2-3 inches long and inserted in between the lugs when closing them, will determine if they have contact. You should not be able to remove it without tearing when the bolt is closed on it.

What I am learning about G.I. bolts, is that they are indestructable. I have some that look as if they were fired many thousands of times, with finish wear abounding, and yet the lugs still retain their full measurments from new. Very Marine proof item, .....these bolts.

Therefore, in answer to your question, you should be able to easily find a replacement bolt of your choosing, by looking and measuring carefully.

Lastly, you will need to inspect the bolt shroud at the breechface for contact on the receiver. You want to make sure it has clearance and is not hitting the barrel end.
 

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Bolts are not all the same

I don't recommend replacing your bolt unless you have an issue with your current bolt. Many rounds of ammo can be bought for the price of a USGI bolt. That's a lot of range time to sacrifice if no problem exist with your current bolt. The new SAI bolts seem to be doing well in the field with a simple extractor replacement.

What's more, even if you find a bolt with similar lug dimensions, that does not correlate into a drop in fit because of stacking tolerances and geometry. Lug placement relative to the bolt face is different to some degree on most bolts if only by a few thousandths.

That is, your headspace will probably change when you change bolts even if the lugs are dimensionally identical because the bolt face and the rear of the lug come into play. The length of the lug is just one variable. Changing headspace is not a problem as long as it's within specification, you just need to be aware that it may change. I've seen changes in headspace by as much as .005 from Springfield forged bolt and a USGI TRW with similar lug dimensions.

Lastly, the dimensional lengths of the bolt lugs have very little to do with how well a replacement bolt will fit relative to the bearing surface on the bolt lugs and its interface with the receiver lug recess. The bolt lug lengths would primarily come into play if the receiver had tight tolerances between the bolt lug recess front and rear and this is rarely an issue on Springfield receivers.

If you are set on a USGI bolt, you'll need to measure the headspace and lap the bolt with 800 grit compound to see if there is a proper bearing surface to ensure equal, or near equal contact on both lugs and that the contact is spread across a greater than 50% portion of the bolt lug. 80% is ideal. You'll also want to at least remove the parkerizing on the bolt lugs to get a proper headspace measurement.
 

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I don't recommend replacing your bolt unless you have an issue with your current bolt.
***************
That is, your headspace will probably change when you change bolts even if the lugs are dimensionally identical because the bolt face and the rear of the lug come into play. The length of the lug is just one variable.
+1. This gets back to that issue Gus reminds us about re the consistency of USGI M14 receivers versus commercial receivers. Shoot the barrel out with your SAI bolt and swap in a GI bolt when you rebarrel. I'm assuming you have the "F" ("forged") SAI bolt of recent/current OEM production. If your SAI bolt is older, you may be entitled to a factory recall replacement. But you'll still get a "F" bolt unless you got real lucky and SAI had a USGI bolt that fit your rifle.
 

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This is one case where the temptation to sip the USGI KoolAid is expensive and not really worth it. Swap the internal bolt parts if you're concerned.

And yes, there is a whole closet industry out there refinishing junk USGI parts and selling them to unsuspecting buyers because sometimes the lure of the part exceeds common sense. AR 15 owners have the same issues with "MilSpec"...


Sounds like you have an outstanding rifle, with nice parts.
 

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Put the thermos down and back away. Don't replace anything unless it needs it. SAI rifles have a LIFETIME warranty. If something breaks, they fix it provided you havent screwed with it. Want an all usgi rifle? Buy the parts, have one built on another receiver.
 

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I have since picked up a second rifle. I would like to convert it to all G.I. parts if I can. It is a Springfield Inc. receiver but with the following HRA parts, barrel, op-rod, trigger group and G.I stock.
I would expect with that many GI parts, that the bolt is GI as well.

What are the numbers stamped on the current bolt?
 

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Discussion Starter · #11 ·
I would expect with that many GI parts, that the bolt is GI as well.

What are the numbers stamped on the current bolt?
I'll post the numbers this evening when I get home. I'm pretty sure it is a commercial bolt.
 

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I would expect with that many GI parts, that the bolt is GI as well.

What are the numbers stamped on the current bolt?
Good point. SAI made quite a few GI or commemorative something or other models that featured surplus parts and barrels and a used GI stock. The box will be labeled Standard model and they are all GI, save the receiver. Maybe an SAI efficienado could enlighten.
 

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I don't recommend replacing your bolt unless you have an issue with your current bolt. Many rounds of ammo can be bought for the price of a USGI bolt. That's a lot of range time to sacrifice if no problem exist with your current bolt. The new SAI bolts seem to be doing well in the field with a simple extractor replacement.

What's more, even if you find a bolt with similar lug dimensions, that does not correlate into a drop in fit because of stacking tolerances and geometry. Lug placement relative to the bolt face is different to some degree on most bolts if only by a few thousandths.

That is, your headspace will probably change when you change bolts even if the lugs are dimensionally identical because the bolt face and the rear of the lug come into play. The length of the lug is just one variable. Changing headspace is not a problem as long as it's within specification, you just need to be aware that it may change. I've seen changes in headspace by as much as .005 from Springfield forged bolt and a USGI TRW with similar lug dimensions.

Lastly, the dimensional lengths of the bolt lugs have very little to do with how well a replacement bolt will fit relative to the bearing surface on the bolt lugs and its interface with the receiver lug recess. The bolt lug lengths would primarily come into play if the receiver had tight tolerances between the bolt lug recess front and rear and this is rarely an issue on Springfield receivers.

If you are set on a USGI bolt, you'll need to measure the headspace and lap the bolt with 800 grit compound to see if there is a proper bearing surface to ensure equal, or near equal contact on both lugs and that the contact is spread across a greater than 50% portion of the bolt lug. 80% is ideal. You'll also want to at least remove the parkerizing on the bolt lugs to get a proper headspace measurement.
Thank you for the clarification of these processes to the OP Mr. Wolfe. I purposely omitted the headspace discussion because of the OP's statement about all the reading he has done here. I assumed, which is not a good thing at any time, that he was aware of these aspects. I merely wanted to point out that he would come as close as possible, in achieving proper headspace, by choosing a bolt that more closely resembled his existing bolt in dimension of lug depths. This also should have been my wording. Thank you again for the corrections about the bolt face relationship and different dimensional specs to the lugs, from one bolt to another, being an issue. I should also add that anyone attempting these modifications or parts changing, should be well versed in doing so, or should seek the advice of a qualified armorer, experienced with the M14 platform and/or similar military style weaponry......

Example: J.Y. Wolfe- M14Parts and Armory Services.
 

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Discussion Starter · #14 ·
OK. So here are the markings on my bolt:

7790186-SA
A00023

I believe this is a commercial SAI bolt.
 

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For comparison purposes, my Poly Tech M-14/S has a US GI Springfield Armory bolt and the markings on it are as follows:

7790186-SA
CA2

Hope this helps...

7th
 

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OK. So here are the markings on my bolt:

7790186-SA
A00023

I believe this is a commercial SAI bolt.
Yep, that's a cast SAI commercial bolt.
 

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I did a little research and came up with the following.

http://www.calguns.net/calgunforum/showthread.php?t=24527

To those with B series SA INC Bolts:
To those with B series SA INC Bolts:

My standard M1A bolt has small stamped markings that read:

7790186, SA, B00038

Research tells me that this bolt is machined.

"The letter B prefix for the number under 7790186-SA means the bolt was machined from bar stock"

Factory head spacing is 1.632 and has about 500 rounds of Federal American Eagle through it with zero problems.

I e-mailed Ted Brown and he told me:
Your bolt is machined from solid bar stock steel. It is probably an OK bolt. SA recalled the cast bolts they made after several broke, but I have not heard of any of the B series bolts being recalled. You may want to give Springfield a call to confirm this.

I e-mailed SA INC this evening and I am waiting to hear confirmation.

My research shows that the “cast” Springfield Armory Inc bolts were recalled after several cracked. :

Springfield Armory, Inc. issued a recall of M1A bolts in 1987. The recall applies to M1A bolts marked as follows: 1) no numerical or alphabetical characteristics on either the top or back of the bolt (completely unmarked) 2) any bolt with any numerical or alphabetical markings at all on the back of the bolt 3) any bolt with the top marked 7790185 and with SA RRR centered below that number 4) any bolt with the top marked 790185 and with SA centered below that number. If the reader has such a bolt, contact the Customer Service Department at Springfield Armory, Inc. politely discuss your situation with the Customer Service Representative. Springfield Armory, Inc. still honors this recall if applicable to the part concerned.

My "loaded standard" bolt marking’s are larger and appear to be engraved:

PART #, SA, HEAT TREATMENT LOT

7790186, SA, F00127

Bolt - Springfield Armory, Inc. bolts are typically marked 7790186-SA on the first line and B00048 or F00059 or a similar number on the second line. They may have markings such as D and M3 on the rear end and A9 or B1 on the bottom surface. The letter B prefix for the number under 7790186-SA means the bolt was machined from bar stock. The letter F prefix for the number under 7790186-SA means the bolt is forged. See the section on the 1987 M1A bolt recall for additional markings. M1A bolts are not made by metal injection molding. Around receiver serial number 165XXX, Springfield Armory, Inc. factory installed bolts have letters and numerals with a taller and thinner font than the style found on USGI M14 bolts.

The “machined” bolts seem to pre-date the forged SA INC bolts and appear at the start of 2004. So there seems to be four types of bolts that SA INC used.

GI bolts
Cast bolts SA INC (probably some are still floating around out there)
Machined bolts SA INC
Forged SA INC bolts (past couple of years)

7th
 

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Discussion Starter · #18 ·
Great information guys. But get this....last night as I was stripping the rifle for cleaning, when I pulled the op rod and removed the bolt, the bolt roller fell off. For peace of mind I called Springfield to ask about the bolt. They asked me to send the bolt and barrel/receiver back for inspection. They are paying all shipping cost and any needed repair costs so I don't really mind that much. I just thought the timing of my bolt related question along with a bolt failure is unbelieveable!
 
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