Fitting bolt to bolt carrier.

[skyhanger00]

I purchased a PSA NiB bolt carrier recently, and it looks beautiful and perfectly machined. Now I'm trying to replace the 5.56 bolt with another NiB bolt for a 6.5 Grendel project I'm building working on. However, I've found that the 6.5 bolt diameter happens to be 0.001" larger than the diameter of the original 5.56 bolt, which fit tight in snug in the PSA carrier.

The new Grendel bolt can also fit into the bolt carrier, but it fits extremely tight, and takes some force to move around. I think i need to remove 0.001" from the bolt exterior ring of the new bolt. What's the best way to do so? Getting a some lapping compound and stroking the bolt back in forth in the bolt carrier? Or will gun oil and metal on metal be enough?

[buellster]

NiB is really hard, that's the point. Sounds like the 6.5 bolt might be out of spec. I would contact the manufacturer

[valley82]

Possible the manufacturer did not take into account the layer of NiB on top of the bolt.

[Patrick Aherne]

Just shoot it.

[Full Clip]

Or will gun oil and metal on metal be enough?

Yes. That and 500 rounds.

[kcstott]

Yes. That and 500 rounds.

and 30Kpsi of gas pressure

[skyhanger00]

Just shoot it.

Don't want my gun to blow up on me. It's need pliers for removal tight. I think I might need to lap the bolt exterior ring on the bolt just to be safe.

Is it the gas rings or the bolt exterior ring that's the source of contact between the carrier and bolt?
(This grendel bolt has a unique gas ring made of up a long coil that goes around 5 times instead of 3 seprate rings with gap)

[6mmintl]

I can Polish it out for you if you want to come to mid peninsula, redwood city area.

[kendog4570]

On NiB bolts and carriers, usually the bolt tail is tight in it's bore, due to the build up of the coating on one or the other, or both. If there was a spec. for this from Uncle Sam, there would be enough clearance. Not so with boutique market items.

A solution for where no problem exists.

[kcstott]

Don't want my gun to blow up on me. It's need pliers for removal tight. I think I might need to lap the bolt exterior ring on the bolt just to be safe.

Is it the gas rings or the bolt exterior ring that's the source of contact between the carrier and bolt?
(This grendel bolt has a unique gas ring made of up a long coil that goes around 5 times instead of 3 seprate rings with gap)

Its the gas rings that make contact. every thing else has about .012" clearance

[skyhanger00]

Its the gas rings that make contact. every thing else has about .012" clearance

Looks like the one piece gas rings the grendel bolt has (McFarland?) appears to have a reputation for a super tight fit when new. I hope that's the case here.
Both sets of 5.56 bolts have the traditional 3 gas rings.

[kcstott]

Looks like the one piece gas rings the grendel bolt has (McFarland?) appears to have a reputation for a super tight fit when new. I hope that's the case here.
Both sets of 5.56 bolts have the traditional 3 gas rings.

Yeah I replaced all the gas rings on my ARs with the single coil style ring. It is tight but it shoots just fine.

[skyhanger00]

Yeah I replaced all the gas rings on my ARs with the single coil style ring. It is tight but it shoots just fine.

Success! I oiled up the new bolt with the single coil and tried again. After a dozen times stroking the bolt back in forth in the carrier, it started sliding more easily. Still tighter than the 5.56 bolts, but perfectly usable.