KAC SR-15 owners - anybody got micrometer?

[YVK]

What’s the OD of SR-15’s barrel? I assume it is a straight contour, but if not, then OD between muzzle and gas block.

Thanks!

[Robb_Jensen]

I’m getting .643" with my crap micrometer.

[YVK]

Robb, thanks. This came up in discussion of safety while shooting 5.56 through lightweight bbls. I had thought KAC’s were thinner…

Are you comfortable letting 5.56 out of your 0.565 featherweight? Mine is 0.590, I think it is fine but there is really not much info on this.

[87GN]

@YVK

Robb, thanks. This came up in discussion of safety while shooting 5.56 through lightweight bbls. I had thought KAC’s were thinner…

Are you comfortable letting 5.56 out of your 0.565 featherweight? Mine is 0.590, I think it is fine but there is really not much info on this.

The SCAR-L has a barrel that’s thinner than the SR15 - I don’t recall the exact OD but it’s very light.

Whoever told you that 5.56 wasn’t “safe” in a lightweight barrel needs to get a new hobby.

[YVK]

SCAR 16s barrel measures .575 on my rifle and with my plastic micrometer. SCAR heats up less than di though.

Regardless, question wasn’t about lightweight profile but featherweight in di system - say, up to .600 OD.

[Robb_Jensen]

@87GN

The SCAR-L has a barrel that’s thinner than the SR15 - I don’t recall the exact OD but it’s very light.

Whoever told you that 5.56 wasn’t “safe” in a lightweight barrel needs to get a new hobby.

I just mic’d a SCAR-L at .575"

[87GN]

@YVK

SCAR 16s barrel measures .575 on my rifle and with my plastic micrometer. SCAR heats up less than di though.

Regardless, question wasn’t about lightweight profile but featherweight in di system - say, up to .600 OD.

According to my own experiments, piston/op-rod weapons have hotter gas blocks than DI weapons, which in turn leads to a hotter barrel near the gas block.

Beyond that, there is going to be little temperature difference between .223 and 5.56. Both have a lot of friction and a lot of heat/pressure.

[87GN]

@Robb_Jensen

I just mic’d a SCAR-L at .575"

Thanks, I was getting that confused with the .565" barrels I have on some other ARs.

[Robb_Jensen]

@87GN

Thanks, I was getting that confused with the .565" barrels I have on some other ARs.

I did Project Featherweight at .565" I think .555" is about as light as you’ll want to go. I shoot 5.56mm NATO through Project Featherweight all the time.

[87GN]

@Robb_Jensen

I did Project Featherweight at .565" I think .555" is about as light as you’ll want to go. I shoot 5.56mm NATO through Project Featherweight all the time.

Agreed…my CETME, by the way, was .575"…and a .308! Hot hot heat…

[YVK]

@87GN

According to my own experiments, piston/op-rod weapons have hotter gas blocks than DI weapons, which in turn leads to a hotter barrel near the gas block.

Beyond that, there is going to be little temperature difference between .223 and 5.56. Both have a lot of friction and a lot of heat/pressure.

According to second sticky in other assault weapons, scar is insignificantly cooler at gb and even more cooler in chamber. Don’t know if it makes practical difference in ability to withstand 5.56 vs 223. Thanks to both of you for answering.

[87GN]

@YVK

According to second sticky in other assault weapons, scar is insignificantly cooler at gb and even more cooler in chamber. Don’t know if it makes practical difference in ability to withstand 5.56 vs 223. Thanks to both of you for answering.

Yes, but the SCAR has many different features that may or may not contribute to different temperature profiles, so a direct comparison with an AR requires evaluating more than just one variable change, whereas it is easy to see the differences between otherwise identical gas piston/op-rod and standard ARs. And the chamber area is going to be thicker for all barrel types and operating systems.

You’re welcome.