DA Socom 18 bolt/receiver lug issue

Smeagol, with your mag withdrawn, your action cocked, how much forward/reward movement do you have in your bolt? Not only can your left bolt and/or receiver lug be undercut, your right lug may not be cut enough to allow the bolt to bear evenly and true to the bore. If there is very little or no forward play with nothing in the chamber, I'd guess the right lug would need lapping in, but just a thought, do not do any lapping or bolt replacement till the vendor replies in regards to fix or replacement. If you are near me in N.S., we can try both the bolts each rifle to try and determine what is out of spec in yours. Most don't have the machineshop capabilitiy to measure a bolt against a design drawing establishing a datum to determine in spec, or at least I don't. PM me if you don't get satisfactory action from vendor.
 
Those last hillbilly measurements and photos with the light were done with the bolt as far to the rear as it'll go. There is a little wiggle in the bolt with the action cocked, but this is normal right? It's not a lot of movement.
 
smeagol, i think you are doing right to send it back to canam..

the rt lug is sitting square (as you can see no light on that side ) .. the gap on the left lug is big ! ... i thought that maybe the bolt wasn't sitting square when you racked it, but you mentioned that you put pressure on it ....so that is, what it is !

even if you changed the bolt, or lapped a massive amount off the rt lug... you'd still have the right receiver/ lug surface that was milled on an angle to contend with ..

if it were me, i'd wait to see what canam will do for you
 
dimeN said:
smeagol, i think you are doing right to send it back to canam..

the rt lug is sitting square (as you can see no light on that side ) .. the gap on the left lug is big ! ... i thought that maybe the bolt wasn't sitting square when you racked it, but you mentioned that you put pressure on it ....so that is, what it is !

even if you changed the bolt, or lapped a massive amount off the rt lug... you'd still have the right receiver/ lug surface that was milled on an angle to contend with ..

if it were me, i'd wait to see what canam will do for you
Click to expand...

No worries, I am in hurry up an wait mode. Not gonna touch it till I hear from them.
 
04insU7.jpg


the above picture is my opinion
so......the space being marked red is not a problem....

and, when a bullet is being fired, the gas will push the op rod back, which, will first raise up the right lug of the bolt;
and down the left lug.....

if the left side are too tight, maybe it is not good for the left lug to go under ?

correct me if wrong, with explainations :)
 
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dukecrab said:
04insU7.jpg


the above picture is my opinion
so......the space being marked red is not a problem....

and, when a bullet is being fired, the gas will push the op rod back, which, will first raise up the right lug of the bolt;
and down the left lug.....

if the left side are too tight, maybe it is not good for the left lug to go under ?

correct me if wrong, with explainations :)
Click to expand...

Duke,

The rearward part of the bolt lugs are supposed to bear as evenly as possible with the front side of the receiver lugs (the spots you have marked in yellow). My problem is that the left side is not bearing at all, and this cuts the strength in half when firing and thus exerting a $h@t ton of force on only one lug, making an unsafe condition for the bolt.

My understanding (and someone please correct my noobness if I am wrong here) is that the front of the bolt lugs (where you have marked in red) need not contact, and in fact likely will not. It is even common, as yomomma said (hahaha that screen name is awesome when used in this context!) for the bolt to be loosey goosey and have a little back and forth play, so long as the surfaces bear evenly.

Chad
 
Hi, smeagol, I might be on the same boat as you...
I will go home and check it tonight.

by the way, the right side of the receiver, where the right lug is sliding on, why the surface is not even ?
mine is the same as your in this part; there is a line in the middle ; there is about 1 mm difference in the height...

MiFOsqh.jpg
 
smeagol said:
Here's a shot of the left lug fit, with a light underneath to highlight. Note that the lug on the receiver side appears to be not parallel to the bolt lug (gets further apart as it nears the outside of the receiver). Also note the ridge in the corner there. It looks like (and this photo doesn't show it very well, the light drowns it out and exagerates the gap) the receiver lug was milled on an angle because it was too close otherwise, but it was milled way too much and now its too far.

7.jpg


No luck getting a set of feeler guages, but 2 strips of printer paper together are tight at the inside and snug-ish at the outside of that gap. Calipers show the 2 strips at .008". I know that's prob not very accurate but screw it, it's hillbilly accurate. So the math looks like this i suppose:

Lap the bolt in and minimum headspace (prob much longer in reality) sits around 1.650" and that is just to get the left lug to start contact. I don't know how much more it'll add to then lap the left lug in completely, given the slight angle the receiver lug appears to be at.

Again, I am new here to this platform, and while I have read everything I could find, my head is still up my arse. I take it I am risking lapping straight through the hardening on the right bolt lug by doing all that, not to mention getting a loooooong headspace?

I will be contacting CanAm and hopefully they can replace it, otherwise it'll be a shopping I will go for a fix (or sending it to someone with more know how than me!)
Click to expand...

You've done an excellent job outlining the issue there, good pics. The rifle is absolutely not safe to shoot in my opinion, empty chamber or not you should see even lug engagement. I think this is a vey common problem, as only the right lug engaging could very well be responsible for the lug shearing failures we've seen, like this one on my bench downstairs. You're on the right path, send it back to Canam. At least one of these drew blood as the pieces have a nasty habit of flying at the shooter's head.


8451B125-A7D6-4891-82D1-4AE124DA4AB1-16347-00001315D4A529AD_zps44cf1264.jpg


And this one, not my photo this time but from this forum:

2CE4A5F8-50B8-4CAA-B482-C58C21E1BD56-16347-0000131A2987A580_zpsa92d3637.jpg
 
Ardent said:
You've done an excellent job outlining the issue there, good pics. The rifle is absolutely not safe to shoot in my opinion, empty chamber or not you should see even lug engagement. I think this is a vey common problem, as only the right lug engaging could very well be responsible for the lug shearing failures we've seen, like this one on my bench downstairs. You're on the right path, send it back to Canam. At least one of these drew blood as the pieces have a nasty habit of flying at the shooter's head.
Click to expand...

Nasty stuff! Want to avoid this for sure, it'd be a bad introduction to this platform...
 
dukecrab said:
Hi, smeagol, I might be on the same boat as you...
I will go home and check it tonight.

by the way, the right side of the receiver, where the right lug is sliding on, why the surface is not even ?
mine is the same as your in this part; there is a line in the middle ; there is about 1 mm difference in the height...
Click to expand...

Duke, the height difference appears to be there to account for the fact that the right lug is on an angle after it rotates when the action is cycling. The line in the middle on the receiver that you highlighted seems to create a channel for the rail on the underside of the right lug (right beside the roller) to travel on.
 
dimeN said:
and that would be a big mistake ... giving this fellow some bigtime headspace.. Dude, becareful here... your piss poor advice is gonna give someone a kaboom !!!!
Click to expand...
You should just keep your thoughts to your self. As posted above he is using nork ammo that I have mic'd out to be 7.62 not as advertised 308. Plus a thou is about all he is going to nee to get 70% given the photos.
Don't worry there is a seat here reserved in the back of the bus for ya.
 
That ridge is supposed to be there.
dukecrab said:
Hi, smeagol, I might be on the same boat as you...
I will go home and check it tonight.

by the way, the right side of the receiver, where the right lug is sliding on, why the surface is not even ?
mine is the same as your in this part; there is a line in the middle ; there is about 1 mm difference in the height...

MiFOsqh.jpg
Click to expand...
 
Crazyest Canuck said:
You should just keep your thoughts to your self. As posted above he is using nork ammo that I have mic'd out to be 7.62 not as advertised 308. Plus a thou is about all he is going to nee to get 70% given the photos.
Don't worry there is a seat here reserved in the back of the bus for ya.
Click to expand...

Sorry bud, but he's 100% right. There is WAY more than "a thou" to be taken up on that left lug, to my eye, likely 20 thou (I've built quite a few of these ground up / including machining work for background). You took it to schoolyard, and only one needing to go to the back of the proverbial bus is you I'm afraid. Your advice is the most dangerous sort here, completely uninformed and confident. Not only would that no longer be considered lapping but getting into lug grinding at those tolerances. I suspect he would completely remove the surface case (hardening) on the right side going into the malleable core due to the sheer amount of metal taken off the right lug, to bring the left to bear.
 
I don't even know how you would attempt to correct that mess. I guess first you would need to confirm the bolt is in spec, then weld up the left receiver lug, re-cut it to spec, then harden it....?
 
^ hahahahaha

but seriously, I hope I get an exchange on this thing, and soon... Only 16 left in stock and closing, and CanAm is apparently busy as feeeeeeeek.
 
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