12.5 criterion core chrono results

[Hoody2shoes]

Not my chronograph. I think It was a Labrador (an orange box looking thing)
88°
38% humidity
No wind
Black hills 77smk red box (5.56 load)
12.5 criterion core
Superlative arms short stroke piston kit
Springco blue spring
H2 buffer

I apologize for not getting the individual data for all ten rounds or the rest of the data. The person was kind enough to let me use it in between strings he was doing for load development on his lmt 6.5cm. Had a nice Tangent Theta on top... super jealous.

High 2640
Low 2619
Average 2628

No signs of over-pressure on spent brass

 

[TonyTheTiger]

That's impressive from a 12.5".

 

[jumrobe]

I now want to chrono my 18” criterion. I suspect I’m closer to 2850 than 2750 with IMI 77gr

 

[Hoody2shoes]

@jumrobe I'm about 95% sure the velocity boost came from the sup arms piston kit. My 12.5 chrono'ed around 100fps than other 12.5 core's. Every rifle I've built (around 6) that have used that piston kit as been curiously fast. So either I've won the lottery of fast barrels (highly unlikely) or something else is creating higher pressures and pushing the rounds faster.

 

[supercorndogs]

Your piston kit is not giving you 100fps boost.

 

[Hoody2shoes]

I see. So maybe less gas bleed off = more speed. Would be interesting to test.

Your piston kit is not giving you 100fps boost.

We shall see. I have a new barrel with a DI and piston block coming from sup arms. Going to run an experiment and see. There's not a lot of info online but the bit you see on lwrc Pistons, pws Pistons, and all my piston kits seems to suggest otherwise. The all of chrono'ed fast and strangely consistent. So again either we've all won the lottery of fast barrels, or something else is boosting pressure and/or keeping it more stable

 

[supercorndogs]

Turning the gas off in a DI gun results in very little velocity gain. I.E the gas to run the action results in very little velocity loss. Not anywhere close to 100fps.

 

[Hoody2shoes]

I know. But until it's proved otherwise the statistical chance that ALL these barrels are stupid fast is pretty much impossible. Something else has to be driving it. If you eliminate the impossible then whatever is left over, no matter how improbable, is the truth.

 

[supercorndogs]

Something else is driving it and it's not the piston kit. My first suspect would be inaccurate data.

 

[Hoody2shoes]

For all of us? That's just ignorant. Agree to disagree until proven otherwise.

 

[TonyTheTiger]

I'm having a hard time seeing a piston adding significant fps, but I'm willing to be proven wrong. The tough part is how you would add that much pressure without having any negative side effects. I've tested DI guns, going from wide open GB's to completely blocked ports, and the difference has always been sub 30fps. So if a functional gun is say 2700fps, same barrel with the port blocked is 2725fps, to jump up to 2850fps requires a significant pressure increase, not just a lack of parasitic gas pressure loss. There's no such thing as a free lunch, or free velocity.

 

[Hoody2shoes]

@TonyTheTiger 100% agree it's weird but I don't have another theory yet. There's just no way all of us have either messed up data or uncharacteristically fast barrels.

 

[TonyTheTiger]

Well hurry up and test that new barrel! We've got questions man!

 

[Hoody2shoes]

I'm not going to spring for a Labradar or whatever it is. I can get a magneto speed sport for like 160 shipped. Will one of these suffice? I don't know much about chrono's and am open to suggestions. Also, is there an mlok attachment for the magnetospeed if you all say it's g2g?

 

[hlee]

So, buy a cheap bcg, gas block, and gas tube. Hell, you probably have all of the above in a parts bin somewhere. Remove the piston kit and test this barrel with a DI setup. “Testing” a new barrel set up with a piston kit does nothing to prove your hypothesis. The variable is piston v DI. The constant should be the barrel.

 

[Hoody2shoes]

... I'm literally doing that. Putting both systems on the same barrel, same day, same ammo...

 

[hlee]

... I'm literally doing that. Putting both systems on the same barrel, same day, same ammo...

I missed the part about piston AND di gas block from SA. Reading too fast.

 

[Constructor]

I have seen 5R and 3R barrels produce 60-90fps faster velocities than enfield rifling but I haven't seen or air gauged a Criterion barrel other than some 6.5 barrels 8 years ago..

 

[Hoody2shoes]

If somebody's in the west Michigan area with a chrono and wants to come out I'll give you some ammo and access to a very nice range for a day in return

 

[SolidCopper]

I just put an upper together with one of these barrels and it shoots pretty poorly. I’m quite frustrated. I need to start eliminating variables and find out what’s the problem. I faced and bedded the upper but used a BA (Aero Precision) hand guard and SA adjustable gas block. That’s probably not helping. Got a headspaced bolt from Criterion. It’s shooting 1.5 - 2.1” groups at 100y with everything from 62gr federal bonded to 77gr IMI. I’ll keep working at it.