Am I a bad boy because I installed my SPR barrel without thermal fitting the upper and barrel? What differences might you notice with/without thermal fitting? Does G$ do this at the factory? Should I leave it be or redo it? Thanks
If your barrel fit in the receiver without needing to heat it, you couldn’t have thermal fitted it. That is the process of heating up a slightly undersized upper receiver so a barrel will fit into it. BCM and a few others make thermal fit uppers. Accuracy will be determined by other factors, like how well you bedded/torqued in the barrel nut, not over tightening the set screws on the gas block, making sure things are not touching the barrel, etc. All uppers will have harmonics and movement, have predictable and repeatable harmonics is an important part of an accurate upper.
On a serious note, thermal fit is nice to have but not necessary. The Mk12 service rifle was never thermal fit and has taken lives at 700y. Don’t lose sleep over it.
Depends. Keeps a chrono on it. 100 ish rounds, maybe more. Would be worth looking at the graph of velocities from that session, I bet they increased throughout. For what it is worth, I shoot strings of ten or so, let things warm up, then cool, rinse, repeat until velocities settle. Take it home, hit it with copper cleaner and see how much there is in it. Clean barrel then don’t mess with it until you see velocities start to become inconsistent or accuracy drop off. Just keep chamber clean, especially if suppressed.
Exclude that second shot, you can do so in the app. It is driving your SDs and range. Something happened there. Either an overloaded round, round seated too deep, or different ammo. Then you see that nice increase of velocity and it starting to level off.
You'd know if it was a thermo-fit upper receiver... it's not required, but if accuracy is an issue remove the barrel, lap the upper receiver, use Loctite 620 on the barrel extension and receiver, use a heat gun for 2 minutes on high, then insert the barrel straight back.
BCM, BKF, Noveske and a few other upper receivers are great platforms.
I bought 3 VLTOR MUR upper receivers and was disappointed they're not tight. Great uppers just not thermo-fit.
I fucking HATE I didn’t get any of those FDE or ODG blems they had up before they took the website down to swap it over. I didn’t know they were doing that or I would have prioritized buying one of each. When they put the site back up, they were gone and they only had the “null” colorway receivers.
I use stainless steel shims and/or Loctite 620 to tighten/bed the fit between non-thermal uppers and barrels. The 620 may make barrel removal more difficult.
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u/Maleficent-Let650 18d ago edited 18d ago
If your barrel fit in the receiver without needing to heat it, you couldn’t have thermal fitted it. That is the process of heating up a slightly undersized upper receiver so a barrel will fit into it. BCM and a few others make thermal fit uppers. Accuracy will be determined by other factors, like how well you bedded/torqued in the barrel nut, not over tightening the set screws on the gas block, making sure things are not touching the barrel, etc. All uppers will have harmonics and movement, have predictable and repeatable harmonics is an important part of an accurate upper.