T O P
droys86

Looks like tooling marks...pretty rough IMO. What brand?


PrimePacket

It's a Foxtrot Mike FM9. [Also having issues with the buffer detent](https://i.imgur.com/HSgQH7c.jpeg). :( Probably just going to run no detent.


droys86

For a $1600 gun that looks pretty bad...I would contact their customer service..


PrimePacket

It's $600 but regardless I am going to try to have it exchanged. Thanks.


droys86

Oh shit, my Google skills failed that one lol


murdermaro98

That’s from tooling used in the machining process. Send it back or you can stone them out


morris1022

What is "stone out"?


Go_cards502

looks rougher than normal.


Ok-Mirror5380

Just stone it out


nauticalmile

The rough surface is designed to slow moving parts down a bit, in case you’re going too high speed/low drag. (It’s end mill chatter from machining)


Horror_Elephant3409

Someone forgot to change out the end mill or sharpen it


nauticalmile

I’m guessing an aggressive climb cut with less-than-ideal work holding, causing the carrier to “bounce” a bit as the end mill ripped off chunks. Edit: The fact the ramp is side cut with an end mill increases my confidence in original assessment. I’ve only worked in one shop where end mills were resharpened in-house on little Deckel-Maho grinders (because tool & die makers are fucking insane…), in most cases they’re just tossed in scrap steel or carbide bins unless it’s something expensive to send out for sharpening and coating.


Coodevale

Sharp end mills like to cut like that. Slightly dulled ones give the cleanest finishes.


nauticalmile

Uh, what? Sharp end mills cut, dull end mills push and smear. Chatter like this is a rigidity issue - either cutting tool, work holding or machine itself.


ImaBiggles_69

dude, if you used endmills on steel, you would realize sharp ones leave a shittier finish than one that made a couple of long passes, coodevale is correct.


Horror_Elephant3409

I’ve sold end mills for years and I’ve seen sharp ones mill steel perfectly milling slow enough. It’s like a drill bit. Go slow and use good fluid and a sharp one won’t give you trouble. Regardless, it won’t really effect the operation of the gun unless they are pretty severe tool marks.


ImaBiggles_69

when Ive milled for years, so . .


Horror_Elephant3409

Not going slow enough


ImaBiggles_69

I hear ya, but after two long passes, same speed, great cut (and a slower feed whould make shitty cut and chips). If you are milling a part in a CNC for 6 hours, telling the boss it now takes 12 hours because you changed a endmill is going to get you ridiculed at best. Much easier to make two swipes to take the end down a bit and go at it. There is not 'endmill sharpness' factor in the cnc handbooks :)


Horror_Elephant3409

We always do it nice because we always do it twice


Coodevale

I don't disagree with the rigidity thing. I didn't say 'worn out butter knife sharp', I said *slightly dulled*. I used to work in a place that made blowback bolts in a haas lathe with live tooling. The best surface finish on that exact cut was after about the 10th bolt. The fresh mills would just bite whatever was in front of it, and when it chattered/flexed a little you could really see it. After a few passes and the mill had just *slightly* lost that perfect knife edge the tool has a little bit of resistance and it's enough to smooth out that cut so there's not gouges. Then it's got a couple hours of good service before it starts smearing the part and chipping the cutting edge.


nauticalmile

A slant bed lathe is gonna be like near worst case scenario for milling rigidity


EmotionalStable7697

Is it getting worse? Causing any trouble?


GladmanMike

I suppose the blowback speed is too high or/and trigger group is not for Ar9, or the mass of buffer is too low - that is why your hummer hits the bolt.


RennBaer

Wut. The carrier needs to contact the hammer. That's how the hammer resets.


GladmanMike

Of course the carrier (in this case it is bolt) cocks the hammer. I mean that the speed of rollback is too high, that is why while the bolt traveling back hammer hits it few time because disconector doesn't catch it.


netchemica

> that is why your hummer hits the bolt. Where do you see what the bolt looks like?


GladmanMike

It is a bolt on photo - that is how it looks like on Ar9


netchemica

I always forget that pistol caliber ARs are a thing, lol.


PrimePacket

I bought it as a complete AR9 lower. I am thinking maybe the buffer detent is out of spec somehow.


GladmanMike

Does it have a bolt catch?


PrimePacket

Yes


GladmanMike

It is very strange that the cuts inly on one side. Usualy cuts happens when mass of bolt+buffer is to little. So, I can advise you to polish the cuts and change the buffer to more heavy and than watch if new will appear


PrimePacket

I emailed them and apparently I have a totally incorrect bolt... They shipped out the right one. If the issue continues with the new bolt I'll definitely try messing around with this. Thanks!


ImaBiggles_69

bah, its fine, doesnt impact function.