SCAR SBR CQC replacement barrel

[variablebinary]

Yup.

What I have is an out of spec barrel, that is identical to factory 10.3 specs, and runs just as well, both suppressed and un-suppressed.

No, it isn't.

It may cycle, but you have zero clue if the weapon is functioning correctly.

[Todd.K]

The gas block and gas port are different on the 10" barrel, if those are modified correctly it should function correctly.

People have been cutting down AR barrels for a few years... If the gas port is done right they function properly.

[Dano5326]

BFD...

SOCOM CQBR uppers started as, shocking, shortened (14.5" to 10.3") uppers with enlarged gas ports. All that matters is getting the proper gas volume to enable function, not how pretty.

[99HMC4]

No, it isn't.

It may cycle, but you have zero clue if the weapon is functioning correctly.

How would you say is the right way to determine if the rifle is functioning correctly? How do you do it and how does FN do it? And what would you feel comfortable with? Not being a dick, just would like to know...

[Todd.K]

I'd be pretty sceptical about getting a SCAR barrel cut down myself, not many smiths with experience working on them.

Cutting a barrel and opening a gas port is nothing new, getting the gas system right is another thing...

[Robb Jensen]

The gas ports on SCARs is like a carburetor on an old car. It's just a threaded hole in the barrel (all are the same size). Then a jet/plug is installed on this threaded port, threaded in with a pre-determined hole in the middle of it.

FN uses a machine which fires 1 round to find the cyclic rate. They then can figure out what size jet/plug to use to keep the rifles cyclic rate very close to one another. I forget what the percentage rate of variance was I want to say 5-7% within each other on military guns.
On a semi auto gun it probably wouldn't matter as much as long as it was pretty close. A military FN armorer wouldn't have to pull this jet/plug on several real 10.3" SCAR Mk16s and see what what's the smallest and largest sized used on them to find out a round about port size to open this jet/plug too after cutting the barrel.

It's a pretty neat system which can be used to control cyclec rates in the SCARS. Example: if a rifle started having 'port erosion'. They could just replace this jet/plug if the gun started cycling too fast. They could also have specific barrels for specific purposes. For example they couldn't make a barrel which would work for suppressed use only to keep the cyclic rate manageable. They could make a SPR type barrel for use in high elevations with cold weather etc.

This technology could easily be used on ARs and would be neat for guns like the LMT MWS or MRP. It would be cool to have an MRP with say a 10" supressed barrel, a 14.5" non suppressed barrel. Both having the exact same cyclic rate and reliability.

[variablebinary]

O

How would you say is the right way to determine if the rifle is functioning correctly? How do you do it and how does FN do it? And what would you feel comfortable with? Not being a dick, just would like to know...

Doing it right would require parts FN does not sell.

The SCAR is not an AR15. Gas is not regulated the same.

The fact remains; cut the SCAR barrel and all you have is an out of spec weapon with a voided warranty

[scottryan]

BFD...

SOCOM CQBR uppers started as, shocking, shortened (14.5" to 10.3") uppers with enlarged gas ports. All that matters is getting the proper gas volume to enable function, not how pretty.

The difference is very few people have a real FN 10.5" SCAR barrel to reverse engineer or to compare to a 3rd party gunsmith job.

[buddyhoohaw]

The difference is very few people have a real FN 10.5" SCAR barrel to reverse engineer or to compare to a 3rd party gunsmith job.

SCAR CQC barrel = 10.0".

Cheers

[scottryan]

We are not being unreasonable by wanting factory short barrels.

What is unreasonable is people telling us this is no big deal and we should settle for a 3rd party reverse engineered gunsmith job on the main componet of a $2500 gun.

These people should be demading FN fix this lack of barrel problem instead.