Bolt Carrier Rough Surface

**AndyLate** · 07-09-20, 08:20

I tend to buy parkerized BCGs and it's amazing to me how much the carrier surface finishes vary. My BCM, Sionics, and Sabre Defence carriers pretty much all look the same and typical. I have a parked Toolcraft "CAGE code" carrier that is amazingly smooth and two carriers - one LMT and one PSA (freedom) that are just rough.

Assuming the rails and bore are smooth, does the carrier finish really matter functionally?

I know the park "holds" lube and only the rails make contact with the inside of the upper. I also know that smooth surface clean up a lot easier.

Andy

**Sry0fcr** · 07-09-20, 08:34

I don't know that there's a surface finish specification for the carriers but I'd imagine that it wouldn't matter so much given where the contact points are unless by "just rough" you mean that you can catch a fingernail on the surface or something that extreme.

**AndyLate** · 07-09-20, 08:53

Certainly the US military has a specification for the bolt carrier surfaces, but I don't know what that is or honestly how I would measure it.

I would describe the bolt carriers as having a finish that looks like raw cast iron on all the non bearing surfaces.

I could of course contact LMT, but the carbine its in runs 100%.

Andy

**phixion** · 07-09-20, 09:47

Originally Posted by AndyLate

Certainly the US military has a specification for the bolt carrier surfaces, but I don't know what that is or honestly how I would measure it.

I would describe the bolt carriers as having a finish that looks like raw cast iron on all the non bearing surfaces.

I could of course contact LMT, but the carbine its in runs 100%.

Andy

0000 steel wool will knock down any rough park jobs without affecting finish.

**Ned Christiansen** · 07-09-20, 10:21

I have had the chance to see a great many different brands and configurations of bolt carrier in recent years. Sometimes it's as the armorer in Patrol Rifle classes and sometimes the manufacturer has sent me samples for one reason or another (not "free" samples mind you, samples as-in, I'm examining them or doing something to them).

As with a lot of guns parts I see some where it's clear that the mfg. process includes a step that says "remove from machine, toss into huge gondola with the 5,000 other carriers". This leads to dents and dings and burrs on the bearing surfaces and the corners thereof. Some others, even though they might not be damaged are simply rough as hell there and yes there is a surface finish requirement on those longitudinal bearing surfaces (32 microfinish). When they are rough or have burrs sticking out from dents, they tend to put wear on the upper receiver bore, although, that anodized finish is very hard and I have not seen an upper that was what you could call "destroyed" by this.

On my own over the years I have very often taken a stone to the bearing strips to get the burrs off. I don't care what consequences there may be to the finish there-- it anything but a magazine cover gun it does not matter, what matters is that it ruins smoothly and doesn't make aluminum shavings when you shoot it.

**Sry0fcr** · 07-09-20, 11:39

Originally Posted by Ned Christiansen

I have had the chance to see a great many different brands and configurations of bolt carrier in recent years. Sometimes it's as the armorer in Patrol Rifle classes and sometimes the manufacturer has sent me samples for one reason or another (not "free" samples mind you, samples as-in, I'm examining them or doing something to them).

As with a lot of guns parts I see some where it's clear that the mfg. process includes a step that says "remove from machine, toss into huge gondola with the 5,000 other carriers". This leads to dents and dings and burrs on the bearing surfaces and the corners thereof. Some others, even though they might not be damaged are simply rough as hell there and yes there is a surface finish requirement on those longitudinal bearing surfaces (32 microfinish). When they are rough or have burrs sticking out from dents, they tend to put wear on the upper receiver bore, although, that anodized finish is very hard and I have not seen an upper that was what you could call "destroyed" by this.

On my own over the years I have very often taken a stone to the bearing strips to get the burrs off. I don't care what consequences there may be to the finish there-- it anything but a magazine cover gun it does not matter, what matters is that it ruins smoothly and doesn't make aluminum shavings when you shoot it.

I understood that the bearing surfaces would have a surface finish requirement, but I think OP is referring to the rest of the carrier? Which I'm not so certain of. I don't think he's describing dents, dings, burrs ect either.

I think some pics of this carrier would go a long way towards clearing things up.

**markm** · 07-09-20, 12:34

Good God, LMT used to have THE most brutally rough/abrasive finish on their carriers. That said, if the bearing surfaces where a little broken in/smoothed out, I'd still run it.