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Switzerland's SIG 510 in Detail - The Other Roller Lock

Combloc

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Here are a couple shots showing where the takedown pins pass through on each receiver:


Both rifles are heavily reinforced in this area. As stated earlier, the HK uses two pins because they actually hold the entire rifle together and take some shear forces because of the bolt group hammering on the stock. The SIG pin does nothing more than hold the rear of the trigger box to the receiver. The dished area machined out of the trunnion is the clearance for the takedown latch. The telltale signs of brazing are evident in the copper-colored lines where the various parts meet. You can also see the "L" shaped cut in the bottom of the receiver where the hammer passes through.

Here's a better shot of the seam between the pressed steel receiver box and the milled rear trunnion:


Let's take a look at the takedown pins.
The SIG pin is on the left and the HK is on the right:

The HK pin is made from two parts. These are the pin proper and the attached spring that is used to hold it in place. The spring is inserted into the pin and snaps in place via a hole drilled into the pin. It is not intended to be disassembled and is simply replaced if damaged. To remove it from the rifle, you simply press from the small side and pull it out from the opposite side. That's far too simple for the Swiss! Their pin is made of four parts and can be rebuilt if the spring is damaged. These are the pin body, the push button, the spring and the roll pin that holds it all together. To remove it from the rifle, you first press the button (on the left of the pin in the picture above). This causes the bobby pin shaped spring inside to squeeze together. Then, while still holding the button, you push the pin out from the opposite side of the rifle. If you release the push button before it is completely removed from the hole, it will remain captive in the trigger box after field stripping the rifle.

In these remaining pictures, the SIG pin is on the right (oops! continuity error there).

One end:


Other end:


Length comparison:


Last comparison picture of the two rifles showing their receiver bottoms. Not much to say here but it shows something of the two different approaches taken with the same goal in mind:
 

Combloc

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Now let's take a closer look at the interior of the receiver.

First is a photograph looking up through from the rear:

Out of focus at the bottom rear is a slightly dished out area. This is the clearance for the recoil spring. Part way up the bottom is the hammer slot and the magazine well further along towards the front. Along the sides (still out of focus) we can see the stamped corrugations that give strength but also provide a place for dirt to collect thus keeping the bolt group sliding back and forth reliably. The main purpose of this picture though is to get a look at the breech face and loaded chamber indicator. The barrel is threaded into the trunnion and is cut with a feed ramp bevel all the way around so there is no need to index the barrel upon assembly; it's just screwed down and torqued to whatever the designers specified. Notice the machining marks in the trunnion. I'm surprised the detail oriented Swiss ever allowed it to leave the factory looking like that!

Here's a view up through the magazine well showing one of the locking recesses:

I expect that this will be much easier to clean than the HK because there are FAR fewer contours to the trunnion (it's basically a hollowed out box) and it's easier to get your finger up in there. Something to notice about the magazine well is how the trunnion is beveled to funnel the magazine into the opening for quicker magazine changes. The sheet metal sides don't need to be funneled because the magazine is rocked into place front first.

Here's one last shot of the breech area showing again just how simple it is up in there. It's proof that a roller lock DOES NOT necessarily need to have a complicated trunnion.

We can also see some of the fluting done to the chamber and a locking recess. Unfortunately, there is some light glare but, if you look carefully, you can see that the indicator is beveled on its rear face. This is done so that it will rise easily without getting caught on things as the cartridge is rammed home by the bolt group.

That's all there is to the insides......it's a pretty simple receiver really. The really remarkable thing about it is the attention to detail with regards to its build quality.

I give you the charging handle!

Side that slides along the receiver:


Top:


Bottom:


It is non-reciprocating and is held forward by a piece of spring steel that snaps into a cut on the trunnion. Honestly, the only reason I mention this part at all is for the fact that it represents the very embodiment of what it means to experience a Swiss product. This one 2 5/8" long component, which would be a simple, simple thing if made by any other manufacturer in the entire world consists of at least 8 parts and possibly twelve! The precision with which it is built and finished is really something.....it's like a little sculpture to honor the mechanized age. If you can't tell, I love my little beer keg charging handle! Alright......enough about that.
 

Combloc

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Bolt Group Disassembly:

I was amazed that the following information does not seem to exist anywhere (in English at least) on the internet so I'm going to fix that little problem. By design, the SIG 510 bolt group can be completely detail stripped without any tools other than a Swiss Army knife and that is needed but very little. Proceed at follows:

1. Start with the bolt head pushed back toward the carrier and the rollers pushed fully out of the bolt head:


2. While placing finger pressure on the right side of the transverse pin, slowly pull bolt head forward until pin moves to the left:


3. Remove transverse pin and separate bolt head from carrier. No further disassembly is needed for general cleaning. For detailed cleaning proceed to Bolt Head and Carrier disassembly sections.




Bolt Head Disassembly:


1. Set carrier and transverse pin aside leaving only bolt head.


2. Lift front tip of ejector spring from ejector and move to side, thus relieving tension on spring:


3. Lift rear tip of ejector spring from spring support and move to side. Remove spring support:


4. Turn ejector counter-clockwise to position shown:


5. Remove ejector:


6. Lift roller retainer bar straight up and remove. Rollers and roller supports may now be freely removed:


7. Disassembled Bolt Head. Further disassembly is neither required nor recommended.




Carrier Disassembly:


1. Set bolt head and transverse pin aside leaving only carrier. Press up on impact lever pivot pin from bottom:


2. Remove pin:


3. CAREFULLY pull impact lever to left and stop at position shown still keeping sprung firing pin captive:


4. Continue to SLOWLY pull impact lever to right until it clears carrier while ensuring that firing pin DOES NOT forcefully eject from rear of carrier:


5. Remove firing pin and spring from rear of carrier. Disassembly of carrier is complete:



Fully disassembled bolt group:



Notes on Bolt Head and Carrier:

1. Assembly is reverse of above procedures.
2. Reversing of rollers and roller supports is NOT recommended. Keep left and right side rollers and supports on their respective sides upon reassembly.
3. The ball bearing pivots for the roller supports are pressed into bolt head at the factory and ARE NOT to be removed!
4. When assembling carrier, use reamer from Soldier Knife Model 1951 (or equivalent) to hold firing pin and spring compressed into carrier while seating impact lever.




That's it. I'm done until I get to the range with this thing. That will happen as soon as I get a nice warm day alone and free. I will also cover the Estes Adams scope mount once I obtain one. I would love to have an original but I'm just not willing to lay out the of dough required for one. I sincerely hope that my ramblings will be useful to someone. Judging by some of the contacts I've received, I think that it will. I am grateful for all of the words of encouragement I have received from you kind folks and, as always, do not hesitate to contact me if I can be of assistance. I will help in any way I can. Thank you again and God bless!
 
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Ron E Smith

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You're going to love shooting that weapon. I purchased a 510-4 marked Sig from Larry at Capital City Firearms many years ago. It was 1 of 4 brought in for evaluation by the ATF in 1968 or 1969 (can't recall) to gain approval for sporting importation. Unique dual recoil buffer spring works very, very well. Ugly but quite effective with typical Swiss craftsmanship.
Ron
 

21HK

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I express my gratitude for your efforts, time and passion that it takes to put something like this together.
Your attention to detail, not only in the photo's but also in your writings truly outline subtle fine points that may be often over looked.

In other words...your pretty good at this sorta thing.:biggrin:

Regards
 

Combloc

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I very much appreciate the kind words my friend! Thank you!



However, I typed much of this on the fly so it is rife with grammatical and continuity errors. It's almost painful for me to read! At some point, I'll rework it to make it flow better. I am very happy that you enjoyed it though. There are many pictures of details that simply were not available on the internet before now. I'm happy with the result.....for the most part!
 

SAFN49

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I checked the prices in the books and the last one that sold at auction $5000 NIB.
I looked at both of them on GB, I talked to the guy in CO, and he wont come down any. Oh well. I'll wait.
 

jdinabqnm

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What years was the 510 in production?

Combloc thank you for some great info and all the hard work to share it with us.
What years was the 510 in production?

I remember see several on the shelf of a gun store kind of like the mid 70's IIRC.
Thanks
Jeri
 

Combloc

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Time to update to this post. Mr. Adams was kind enough to make a scope mount for me a couple of months ago. He only produces these in small batches so there was some wait time but the end result was well worth the wait. The box was well packed with bubble wrap and the mount was inside a small box with the tools and scope mounting screws in a bag taped to the lid:



Opening the box revealed the anodized aluminum mount. I opted for the one set up for a stanag mount but regular rings could be attached if desired:



Here's the mount unboxed:



While the main body is aluminum, pretty much everything attached to it is made of steel to ensure maximum durability. On the right are the screws used to attach the scope. The rod in the center of the picture is inserted through the holes seen in the locking bar coming out the back of the mount and used to adjust the fit to your rifle. The hex wrench is an off the shelf tool the Mr. Adams has modified so that you can get in between the hex screws and the mount base to tighten your scope down. The finish looks spotty in the picture but that is just oil. The finish is excellent and even throughout.

Here's a top view of the mount:


The three punch marks seen on each scope mount point are put there in order to keep track of which parts go to which base. Every part is hand fitted to each base to ensure maximum Quality.

Here is the rear of the mount showing the locking bar that fits into the hole at the front of the rear sight on the rifle:


The lever on the left side of the mount moves an internal cam which pushes the locking bar out of the base and into the mounting hole on the rear sight on the rifle. The adjustment holes can clearly be seen. The internally threaded locking bar is adjusted in or out until the lever locks the mount on the rifle snugly. The idea is to have it adjusted so that enough pressure is required on the cam lever to keep the mount from working itself free under recoil. However, you do not want it adjusted so that undue force is required to lock the lever in place because this will quickly destroy the locking mechanism.

Here is the front of the mount:



Front right side of mount:


The rectangle seen at the lower front is made of steel and is the front attachment point. I'll explain that as we look at the bottom of the mount which is seen here:



Front is to the left. Here we see three allen screws which hold the steel front attachment to the base. The tab on the attachment point slides under the tab welded to the receiver on the rifle. This attachment also straddles the tab on the receiver and keeps the mount from moving from side to side on the receiver. It is a VERY precise fit and is required to ensure zero is retained regardless of how many times the mount is removed or reinstalled on the rifle. In the middle, we can see the cam mechanism. The steel block itself does not move, only the cam rotates within it. Sticking out the back of the block is the front of the locking bar. It has flat sides so that it can move back and forth in the slot cut into the block but it cannot rotate. The rear portion of the locking bar threads over the front portion. The spring is captured between the mount base and the rear portion of the locking bar. This is constantly trying to push the locking bar out the back of the base. Notice that almost every part has the three identifying punch marks discussed earlier. That pretty much covers the basics I think.

To install mount on rifle:

1. Ensure that the cam lever is resting on front stop pin and mount assembly is parallel with top of rifle receiver.

2. Tilt rear of mount down, insert locking bar into hole on rear sight of rifle and push to the rear.

3. Lower front of mount down over tab on receiver and release mount. The internal spring will force the mount forward and hold it in place.

4. Rotate cam lever clockwise until it contacts rear stop pin.

To remove:

1. Rotate cam lever counterclockwise until it contacts front stop pin.

2. Pull mount to rear thus disengaging front mounting tab and lift front of mount.

3. Pull mount forward and away from rear sight.

If cam lever is loose when mount is installed on rifle, insert adjustment rod into a hole in locking bar and turn counterclockwise until desired tension on cam lever is achieved.

If cam lever will not fully rotate to engage rear stop pin or undue force is required to do so when mount is installed on rifle, insert adjustment rod into hole in locking bar and turn clockwise until desired tension on cam lever is achieved.


That pretty much covers it. I cannot say enough good things about this product. It is equal in Quality to the rifle it is intended for and Mr. Adams was very responsive to any questions I had during the ordering process as well as those about the product itself. The only complaint I have is that the irons cannot be used with the mount in place. Similar to an HK, here are holes in the mount to accommodate the use of the rifle sights but the allen screws used hold the scope to the mount hang down and partially block the line of sight. Screws with shorter heads would solve this problem but I don't know if that would affect how well they would hold up while torqueing them down. I'm no machinist so I can't say. The price is right too. While an original Swiss made mount can easily cost you several thousand dollars, Mr. Adams can be had for under $400. If I remember correctly, the total bill for the mount, a front sight adjustment tool and a min/max bolt gap feeler gauge set was right around $370 shipped. I would have paid a lot more and been happy to do it. Thank you Mr. Adams!

Now for a couple of shots with a Zeiss ZF51 NV scope attached. It wasn't really made for this rifle and the eye relief is a bit awkward but it would work in a pinch.







In the next post, we'll take a look at what this thing can do at 100 yards in my incapable hands!
 

Combloc

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A while back, I took the SIG out to the range for the first time in its life. I didn't have a scope mount at the time so I just used the iron sights. I didn't bother to report then because I frankly had very little to report. It was already sighted in and required no adjustment. Recoil is extremely mild because of the rifle's geometry and design. As I had already read in the past, the sights are adequate for combat but terrible for precise target shooting because the front sight post is so wide. I'm sure that plenty of rounds down the pipe would engender you with the necessary experience to shoot it extremely well though. As expected, the safety lever exhibits dreadful ergonomics but the wonderful trigger pull is a thing to behold. Ejection is nothing like the brass rocket launches we seen with an HK (I really do think that there is brass in orbit thanks to our German friends in Oberndorf). Instead, the brass lands within about five feet out to the side. Some of it even ended up on the shooting bench. Well, as seen in the above post, I finally got myself a scope mount a little while back. My first range trip with a scope was used to zero it and I was impressed. However, I was using various different NATO surplus ammo mixed in with some South African stuff so there was some variation in groups and POI. My second range trip with the scope (but my third time at the range with the rifle) gave me the results that I suspected this rifle is capable of. I was Using some 1985 Radway Green which has always given me excellent service in both My HK and my Cetme and I did even better in the SIG. The scope I was using was a surplus 4x Hensoldt Z24 and I was shooting at 100 yards. Here is my target:



Now, I'm a pretty poor shot and I'm usually just happy to hit the target. Also, if I were to use a smaller red circle, I would probably shoot a little better. My first group of 5 was so small (I should have marked them but I forgot) that I got over excited and ended up with three fliers in my second group of 5. In the hands of someone who knows what they are doing, I'm sure that an even better group is possible. I think this rifle would be well served with a higher magnification scope. I'm really liking that Zeiss Conquest......

Anywho, for me, the above is excellent results. Here is an assortment of how the brass looks once the SIG is done with it:



Some of them get a little misshapen but nothing like the mess I am accustomed to seeing coming out of a roller lock:



Let's look at some propellant art. On the right is a casing from the SIG and on the left is a steel case that was shot in either my Cetme of my HK (I forget which):



And a comparison of case necks. Again, SIG on the right and Cetme or HK on the left. Notice that the SIG has more flutes. Probably not necessary but we ARE talking about the Swiss here:



Lastly, a comparison shot of the SIG compared to an FG42. While the '42 is of comparable build quality to the SIG, there is absolutely no comparison in target results. But that's a story for another post.

 
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