Combloc
Stop Negassing me!!!!!
Picking up where we left off, pull the bolt group out of the receiver. As you remove it, be aware that the spring in the bolt is compressed and trying to push the bolt to the rear. If you are not actively squeezing the bolt and carrier, the bolt may snap rearward with some force, banging the front of the cam slot into the front of the firing pin yoke. I'm sure that this cannot be good for the components. Here is what the right side of the assembly looks like when as it comes out of the rifle:
The two locking lugs on the bolt are facing up and down. This is the unlocked position, allowing the bolt group to reciprocate inside the receiver. Between the locking lugs is the extractor. The firing pin can be seen in the cam slot too. Part way up the operating rod is the cutout where the charging handle fits with the stainless steel gas piston in front of it farther up the rod. We'll take a closer look at all of the individual parts in a little while.
Here's the left side:
The little round nub at the rear of the bolt is the pin that holds the firing spring and all of it's hardware in place. At the front of the bolt is the ejector slot.
Now carefully release tension on the internal spring by rotating the bolt and easing it to the rear until it stops. It will now look like this:
The bolt has rotated 90 degrees and the locking lugs are now sticking out to the sides. If the assembly were in the rifle, they would be engaging the cutouts in the trunnion and the action would be locked. Up in the charging handle slot, you can see the plunger that holds the charging handle in place. This has nothing to do with the bolt position. It just slides back and forth with out the recoil spring in place and happened to be slid forward when the picture was taken so ignore that for now. The gray rectangle on the rear of the bolt is covering the serial number.
And a shot of the left side after the bolt has been eased to the rear.:
The extractor is on the bottom and the ejector slot is facing up.
Next is removal of the firing spring. I hesitate to call it the firing pin spring because it really has nothing to do with the firing pin. This spring is necessary to keep tension between the bolt and the bolt carrier; the rifle wouldn't work without it. It is also necessary when the trigger is pulled to force the carrier home with enough force to reliably set off the primer. So, instead of calling it a "firing pin spring", I tend to call it a "firing spring" as I feel that's a more appropriate name for it. Whatever name you decide to assign this spring, to remove it for further bolt group disassembly, we must first remove the pin that holds it in place. To do so, refer to the picture below:
The above picture is a close-up of the rear of the bolt. Notice that there are a couple grooves in the retaining pin. These are indexed by the edge of a hole bored into the conical spring plunger. This plunger is under pressure from the firing spring at all times, even when the bolt is fully to the rear, so the retaining pin is held in place securely. To remove the pin, the plunger must be pressed forward into the bolt and the pin can then be pressed out. This sounds simple enough but it's actually quite fidgety and, honestly, it's a big pain in the behind to mess with. The problem is that the plunger wants to rock in the bolt when you try to depress it and is ends up getting stuck in place. If the plunger were made thicker length wise, I think the problem would be eliminated. Trying to get this thing depressed straight down into the bolt is like trying to mess around with a commercial rifle that you need special tools and knowledge to disassemble. It's insanely frustrating to say the least. Is my opinion pretty clear on that? I think the original design used some sort of cup that fit into the hole and rotated to lock and it was held by spring tension too. Whatever the design, is was prone to failure so SMG came up with the pin and plunger idea as a replacement. Again, I think it would be fine if they simply made the plunger deeper so that it couldn't rock in the hole. Anyway, fidget the plunger down and pull the pin out. Now play around with the plunger for a few minutes (I'm not exaggerating here) until you get it unstuck in the bolt and pull it out. The firing spring will come out with it. There is also a spring guide that should come out. If it does not, just tip the bolt back and it will slide out.
Here's what it looks like disassembled:
Let's take a look at the individual parts.
Here's the retaining spring and plunger:
Now we clearly see the grooves in the retaining pin, the conical plunger and we can see how they fit together to lock the retaining pin in place. You can also see the wound firing spring. The spring has a slightly smaller inside diameter than the outside diameter of the stem sticking out the front of the plunger so the two parts stay together as a unit.
Here's the rear of the firing spring guide showing the hole that the spring fits into:
And here's the front of the firing spring guide showing the hole that fits over the stem on the back of the firing pin:
To separate the bolt from the bolt carrier, simply push the bolt forward while pulling up and away form the carrier:
Now tip the bolt up and the firing pin will just fall out the back. Here's the firing pin:
For those that have never seen a firing pin before, the front is to the left. The stem sticking out the back fits into the hole on the firing spring guide and the skinny part in between the two collars is where it fits into the yoke on the carrier.
Here's a picture showing it fitted to the carrier:
And here's a top view of that as well:
I want to again note that the firing pin DOES NOT move independently as it does on most rifles. It is held fast by the bolt carrier. When the trigger is pulled, the entire carrier moves forward under spring pressure carrying the firing pin along with it to fire the round. So, this rifle is striker fired, not hammer fired. I assume that's clear by now but I just want to make sure that you fully understand.
Now let's take a closer look at the bolt. Here's the bolt face:
It's resting on the bolt carrier so ignore that. At the top of the picture is the ejector slot and the locking lugs are sticking out to the left and right. Look carefully at the top of the left lug and the bottom of the right lug and you will see wear marks where the lugs strike and ride in the trunnion locking grooves. This is normal wear. When this picture was taken, I had put 80 rounds through the rifle and SMG had put an unknown number through it during test fire and sighting in. If your bolt does not look like this, it means that you are not shooting your rifle......do so immediately.
Another shot of the bolt face in slightly different light for wear mark comparison:
Here's a detail shot of the ejector slot:
Here are a couple photos of the cam slot showing what is again NORMAL wear:
SMG says in the video included with each rifle that you may even start to see chips of metal missing in this area over time. Apparently, it is normal so don't wig out when this starts to happen. Just keep shooting. SMG has over 15,000 rounds through their test rifle so I'll just take their word for it. I know I'll probably never put 15K through mine unless one of you want's to donate some ammo. I don't know what the black marks are in the wear area. It doesn't rub off so I just ignore it.
Let's take the extractor apart. Here it is assembled:
To disassemble, simply press down on the rear of the extractor and use a punch or bullet tip to push the retaining pin out. Here it is shown disassembled:
When reassembling the extractor, be careful that the spring engages the cutouts for it in both the bolt and extractor. It's small and can easily be tipped on its side during reassembly. This design is different than an original rifle but I don't know why. I do know that it works just fine. It also comes apart and goes back together very easily which is a big plus after messing with that cursed firing spring plunger earlier. Did mention that part needed to be redesigned?
That's it for the bolt. In the next post, we'll start with the bolt carrier and go from there. See you then!
The two locking lugs on the bolt are facing up and down. This is the unlocked position, allowing the bolt group to reciprocate inside the receiver. Between the locking lugs is the extractor. The firing pin can be seen in the cam slot too. Part way up the operating rod is the cutout where the charging handle fits with the stainless steel gas piston in front of it farther up the rod. We'll take a closer look at all of the individual parts in a little while.
Here's the left side:
The little round nub at the rear of the bolt is the pin that holds the firing spring and all of it's hardware in place. At the front of the bolt is the ejector slot.
Now carefully release tension on the internal spring by rotating the bolt and easing it to the rear until it stops. It will now look like this:
The bolt has rotated 90 degrees and the locking lugs are now sticking out to the sides. If the assembly were in the rifle, they would be engaging the cutouts in the trunnion and the action would be locked. Up in the charging handle slot, you can see the plunger that holds the charging handle in place. This has nothing to do with the bolt position. It just slides back and forth with out the recoil spring in place and happened to be slid forward when the picture was taken so ignore that for now. The gray rectangle on the rear of the bolt is covering the serial number.
And a shot of the left side after the bolt has been eased to the rear.:
The extractor is on the bottom and the ejector slot is facing up.
Next is removal of the firing spring. I hesitate to call it the firing pin spring because it really has nothing to do with the firing pin. This spring is necessary to keep tension between the bolt and the bolt carrier; the rifle wouldn't work without it. It is also necessary when the trigger is pulled to force the carrier home with enough force to reliably set off the primer. So, instead of calling it a "firing pin spring", I tend to call it a "firing spring" as I feel that's a more appropriate name for it. Whatever name you decide to assign this spring, to remove it for further bolt group disassembly, we must first remove the pin that holds it in place. To do so, refer to the picture below:
The above picture is a close-up of the rear of the bolt. Notice that there are a couple grooves in the retaining pin. These are indexed by the edge of a hole bored into the conical spring plunger. This plunger is under pressure from the firing spring at all times, even when the bolt is fully to the rear, so the retaining pin is held in place securely. To remove the pin, the plunger must be pressed forward into the bolt and the pin can then be pressed out. This sounds simple enough but it's actually quite fidgety and, honestly, it's a big pain in the behind to mess with. The problem is that the plunger wants to rock in the bolt when you try to depress it and is ends up getting stuck in place. If the plunger were made thicker length wise, I think the problem would be eliminated. Trying to get this thing depressed straight down into the bolt is like trying to mess around with a commercial rifle that you need special tools and knowledge to disassemble. It's insanely frustrating to say the least. Is my opinion pretty clear on that? I think the original design used some sort of cup that fit into the hole and rotated to lock and it was held by spring tension too. Whatever the design, is was prone to failure so SMG came up with the pin and plunger idea as a replacement. Again, I think it would be fine if they simply made the plunger deeper so that it couldn't rock in the hole. Anyway, fidget the plunger down and pull the pin out. Now play around with the plunger for a few minutes (I'm not exaggerating here) until you get it unstuck in the bolt and pull it out. The firing spring will come out with it. There is also a spring guide that should come out. If it does not, just tip the bolt back and it will slide out.
Here's what it looks like disassembled:
Let's take a look at the individual parts.
Here's the retaining spring and plunger:
Now we clearly see the grooves in the retaining pin, the conical plunger and we can see how they fit together to lock the retaining pin in place. You can also see the wound firing spring. The spring has a slightly smaller inside diameter than the outside diameter of the stem sticking out the front of the plunger so the two parts stay together as a unit.
Here's the rear of the firing spring guide showing the hole that the spring fits into:
And here's the front of the firing spring guide showing the hole that fits over the stem on the back of the firing pin:
To separate the bolt from the bolt carrier, simply push the bolt forward while pulling up and away form the carrier:
Now tip the bolt up and the firing pin will just fall out the back. Here's the firing pin:
For those that have never seen a firing pin before, the front is to the left. The stem sticking out the back fits into the hole on the firing spring guide and the skinny part in between the two collars is where it fits into the yoke on the carrier.
Here's a picture showing it fitted to the carrier:
And here's a top view of that as well:
I want to again note that the firing pin DOES NOT move independently as it does on most rifles. It is held fast by the bolt carrier. When the trigger is pulled, the entire carrier moves forward under spring pressure carrying the firing pin along with it to fire the round. So, this rifle is striker fired, not hammer fired. I assume that's clear by now but I just want to make sure that you fully understand.
Now let's take a closer look at the bolt. Here's the bolt face:
It's resting on the bolt carrier so ignore that. At the top of the picture is the ejector slot and the locking lugs are sticking out to the left and right. Look carefully at the top of the left lug and the bottom of the right lug and you will see wear marks where the lugs strike and ride in the trunnion locking grooves. This is normal wear. When this picture was taken, I had put 80 rounds through the rifle and SMG had put an unknown number through it during test fire and sighting in. If your bolt does not look like this, it means that you are not shooting your rifle......do so immediately.
Another shot of the bolt face in slightly different light for wear mark comparison:
Here's a detail shot of the ejector slot:
Here are a couple photos of the cam slot showing what is again NORMAL wear:
SMG says in the video included with each rifle that you may even start to see chips of metal missing in this area over time. Apparently, it is normal so don't wig out when this starts to happen. Just keep shooting. SMG has over 15,000 rounds through their test rifle so I'll just take their word for it. I know I'll probably never put 15K through mine unless one of you want's to donate some ammo. I don't know what the black marks are in the wear area. It doesn't rub off so I just ignore it.
Let's take the extractor apart. Here it is assembled:
To disassemble, simply press down on the rear of the extractor and use a punch or bullet tip to push the retaining pin out. Here it is shown disassembled:
When reassembling the extractor, be careful that the spring engages the cutouts for it in both the bolt and extractor. It's small and can easily be tipped on its side during reassembly. This design is different than an original rifle but I don't know why. I do know that it works just fine. It also comes apart and goes back together very easily which is a big plus after messing with that cursed firing spring plunger earlier. Did mention that part needed to be redesigned?
That's it for the bolt. In the next post, we'll start with the bolt carrier and go from there. See you then!
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