[ToddB223]

When did Kel-Tec start making their SU-16's with the 1:7 twist rate? I've read that they were originally 1:9 twist.

 

[SAN 14]

When did Kel-Tec start making their SU-16's with the 1:7 twist rate? I've read that they were originally 1:9 twist.

And if someone here can tell us the serial number range for the change too, that would be helpful.

 

[ToddB223]

And if someone here can tell us the serial number range for the change too, that would be helpful.

I'll try to call Kel-Tec today and ask them. I'll post their answer here if I get an answer.

 

[ToddB223]

I called Kel-Tec and asked when they changed the SU-16 from a 1:9 twist to a 1:7 twist and they told me 7 or 8 years ago, so 2012 or 2013, give or take. They said they could tell more accurately if they were given a serial number, but they couldn't give me a SN range.

 

[IamScotticus]

KT has this pattern. The first rollout of RDB was 1/9.
SIG Sauer USA did that with the 556.
This whole .223/556 thing is over blown. Of everything Ive read over the years, all it comes down to is the only reason for a 5.56 chamber is to have a throat to fit the ojive of a military specialized round like a tracer.
Instead of the .223 stamp, barrels could just have "no specialty military ammo" so we can shoot all that XM855 and 192 without worry.

 

[ToddB223]

The major difference seems to have more to do with chamber pressures than anything else. The military ammo/brass (LC head stamp, rated at 63,250 psi max) has thicker case walls than the non-military brass (rated at 55,000 psi max). Those max chamber pressures are from the latest Western Powders load manual.

The 5.56 chamber also has a slightly longer throat, or more "freebore".

 

[IamScotticus]

Thoese chamber pressures are not apples to apples, they are measured by different standards. the realistic end results are comparatively similar. Any .223 chamber can easily be made to handle the range of pressures. Another thing on chamberings, there is little consistency between manufacturers, and often from manufacturers. Bottom line is as long as the bullets not unusual, it should fine.
But Im not advocating running 5.56 in .223 chambers, follow the guidance. Im just TOMA the stuff I think is the reality of it.
Just for the conversation. FWIW.

 

[ToddB223]

Thoese chamber pressures are not apples to apples, they are measured by different standards. the realistic end results are comparatively similar. Any .223 chamber can easily be made to handle the range of pressures. Another thing on chamberings, there is little consistency between manufacturers, and often from manufacturers. Bottom line is as long as the bullets not unusual, it should fine.
But Im not advocating running 5.56 in .223 chambers, follow the guidance. Im just TOMA the stuff I think is the reality of it.
Just for the conversation. FWIW.

I agree! I was only adding to your previous post with some "observations" that I've learned in researching the subject.

 

[stephen urban]

Learned something I hadn't known.. So my original barrel was 1:9 but since Keltec replaced the entire barreled receiver when mine cracked I now have a 1:7.

 

[ToddB223]

Learned something I hadn't known.. So my original barrel was 1:9 but since Keltec replaced the entire barreled receiver when mine cracked I now have a 1:7.

When was that repair made to your rifle? I'll take a 1:7 over a 1:9 any day.

 

[stephen urban]

When was that repair made to your rifle? I'll take a 1:7 over a 1:9 any day.

2020