Scars thread concentricity???

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Thread: Scars thread concentricity???

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    Scars thread concentricity???

    I have a used 16 I picked up a few weeks ago and I finally got around to shooting it today. Older model, was a safe queen and barely shot, I used a bore scope before I purchased it as I do with all used guns!I installled an ASR quick detach mount on it for my Specwar 556, ran it to the shoulder and loctited like I do with every other gun I own. 1st shot and I got a baffle strike... couldn't freaking believe it. Are the older models known for threads not being concentric??? I've never had this happen before and I'm sortof stumped. I checked the mount before I left with a wrench and it was tight before and after firing it. I also made sure I locked the can up right before I fired it as I do every single time I go to the range. Is this something Scars are known for? I'm thinking I'm going to chop it down to 14.5 now and have a ASR brake pinned and welded... Kind of disgusted though that something would happen with a gun like this> Any one have any thoughts...?


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    Senior Member Smurky's Avatar
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    Quote Originally Posted by billysorge View Post
    I have a used 16 I picked up a few weeks ago and I finally got around to shooting it today. Older model, was a safe queen and barely shot, I used a bore scope before I purchased it as I do with all used guns!I installled an ASR quick detach mount on it for my Specwar 556, ran it to the shoulder and loctited like I do with every other gun I own. 1st shot and I got a baffle strike... couldn't freaking believe it. Are the older models known for threads not being concentric??? I've never had this happen before and I'm sortof stumped. I checked the mount before I left with a wrench and it was tight before and after firing it. I also made sure I locked the can up right before I fired it as I do every single time I go to the range. Is this something Scars are known for? I'm thinking I'm going to chop it down to 14.5 now and have a ASR brake pinned and welded... Kind of disgusted though that something would happen with a gun like this> Any one have any thoughts...?
    Thatís a bummer, I canít say Iíve never seen it occur but it isnít a common occurrence. Anything on the barrel shoulder or if the barrel shoulder was distorted would make a difference. I put a SilCo FH on my 16 SBR and had a brake on the 16Ē, both were good to go. After installing I confirmed with an alignment rod. If you donít have an alignment rod I would strongly suggest getting one. I have the Geissele, Griffin has them as well as others. SilCo should take care of you and has a quick turnaround.
    Last edited by Smurky; 05-17-2020 at 08:51 AM.
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    Im not convinved it is a thread issue unless this has been verified with a rod. What ammo? It could have been a tumbler, a unbalanced projectile, or other issues. I think yours is the first listing this as a possible issue with the 16. Lets start with the ammo and check concentricity using a rod. I recommend that anyone using a can get a suppressor rod to rule out why you get a baffle strike. They are inexpensive, save for the Gissele rods. My rod cost $19 and it was well worth it. You can also use a wooden dowel, not 100% accurate but it would show if there was a severe tilt of the can......

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    Senior Member Milspec's Avatar
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    Quote Originally Posted by HK SD9 Tactical View Post
    Im not convinved it is a thread issue unless this has been verified with a rod. What ammo? It could have been a tumbler, a unbalanced projectile, or other issues. I think yours is the first listing this as a possible issue with the 16. Lets start with the ammo and check concentricity using a rod. I recommend that anyone using a can get a suppressor rod to rule out why you get a baffle strike. They are inexpensive, save for the Gissele rods. My rod cost $19 and it was well worth it. You can also use a wooden dowel, not 100% accurate but it would show if there was a severe tilt of the can......
    Where did you score rods for $19 sir?
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    Senior Member vertigosol's Avatar
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    I have run a specwar 556 (and others) on a 10" and 16" scar 16 with no issue. What was the mount torqued to when you installed it? Was it a break and you used a crush washer? A alignment rod would help diagnosis this

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    Senior Member vertigosol's Avatar
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    Quote Originally Posted by Milspec View Post
    Where did you score rods for $19 sir?
    cheapest I found for a full length rod
    https://www.cncwarrior.com/223-groun...od-p/28654.htm

    he may of got a "barrel straightness gauge" which also acts as a alignment rod
    https://www.brownells.com/gunsmith-t...prod55159.aspx

    or you could get a ground rod from mcmaster in the correct diameter of your bore
    Last edited by vertigosol; 05-16-2020 at 07:27 PM.

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    ^^^^ This
    My source at the time. They were $14.99 at the time but the design has changed.

    https://www.cncwarrior.com/category-s/2086.htm
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    Go to McMaster.com. Precision ground steel rods are available in all the drill sizes.

    Bore diameter for a 223 is somewhere around 0.219, some match barrels are 0.218, though military rated are probably not that tight. Anyhow, 7/32" precision ground is 0.2188. Here is a link https://www.mcmaster.com/88915K16

    It is sized to be +0, -0.001, so it should be a nice smooth fit. In my experience, the last 1/4" of the rod can be a little out of round from the cutting operation, so you might have to trim it back a little or spin the first inch on a grinding wheel to make sure it is not oval, but 3 feet is $15. To test, I just got a 7/32 drill bit, and tried it in 3 different new barrels I have in the shop, it was a beautiful slip fit in all 3, though interestingly, the slight raised roll mark where the drill size was rolled on the shank would fit into a groove, but not in the bore. So this is the size I would get.

    Other option is 0.212 diameter, which is a #3 drill, a 3 foot piece is only $5. https://www.mcmaster.com/8890K189-88725K23 the 0.007 diameter difference means you could just about wrap a piece of paper around it and get it to fit. I also grabbed one of these drills, and it was a good fit, with just the slightest amount of rattle. So if you have a match barrel that you are suppressing, this might be your option. Fit is certainly still tight enough to check for baffle strikes.

    Of course for 5.56mm, a 5.5mm rod (0.1969) would be awesome, unfortunately McMaster only carries these in 4" lengths. Someone else might have them ...
    Last edited by ShootingSight; 05-16-2020 at 08:08 PM.
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    Art Neergaard
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    Rolled Plate Steel Triggers.

    513-702-4879

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    Quote Originally Posted by HK SD9 Tactical View Post
    ^^^^ This
    My source at the time. They were $14.99 at the time but the design has changed.

    https://www.cncwarrior.com/category-s/2086.htm
    If you (or anyone who has one) can throw a caliper on yours to see what the rod diameter is. As stated, this does not need to be fit to less than a few thou tolerence, so I'd bet all these advertised rods are simply commercial ground rods with the ends cleaned up, maybe some fancy laser engraving, and a price markup.
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    Art Neergaard
    ShootingSight LLC
    Rolled Plate Steel Triggers.

    513-702-4879

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  11. #10
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    I'd probably spend another $5 and get the carbon fiber ones available elsewhere.

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