Lyman GPR AGAIN

[AZbpBurner]

I'm sorry to disagree with old ford BUT valve grinding compound is diamond dust in a binding agent and will stay in the pores of the barrel no matter how much you clean it. I have seen a teaspoon of it DESTROY a car engine in less than a half hour!!!! I saw another engine that was sabotaged with the stuff and it was replaced with a short block and head with the sheet metal( pan, valve cover and timing cover) being hot tanked and re used. Not good enough this engine was also destroyed from the residue in the pores of the sheet metal. This was confirmed by Pennzoil. JB paste is designed for this app valve grinding compound is not. That barrel is a machined product, why wipe out the good machining for a few burrs that will wear off in a short period of time? I'm not trying to start a fight just telling you my experiences.

Valve grinding compound is going to be silicon carbide or some other less expensive material, NOT diamond.

But I agree, why not just get JB bore paste, its MADE for firearms!

While JB Bore paste is labeled as a non-embedding abrasive, it is also designed to scrub lead and crud from a bore. It isn't made for lapping or polishing a bore. You're wasting your time.

Valve grinding compound IS silicon carbide. Why wreck a good barrel diddling around to try to lap what doesn't need working on?

 

[Sinner]

Brownell,s sells a water soluble lapping compound that cleans up nicely and won't stay imbedded. You can also buy water soluble valve lapping compound that will work.
I think the best thing, though, is too simply shoot 100 rounds through it first.

 

[maineguy]

I have a GPR in 50 caliber and its a great rifle