- Thread starter LRI
- Start date
Wowser, that's incredible!!
So how much machine time did that “fluting” take?
That is HOT!
As I was setting up a 6- fluted barrel for chambering yesterday (and the outboard spider tips nested perfectly in two of the flutes) I was thinking about all the crazy options. I don't see any way to hold something like that other than a custom tapered bushing to slip over the barrel down to where the spider screws are.
Not my cup 'o tea, but beautiful machining. With so much material removed, does that act more like a light sporter as far as heating/stringing- or do the "fins" retain enough rigidity (plus addl cooling too) of the original bull profile to handle heavy strings...
I'm guessing a shit ton of light passes so as not to stress the barrel?
Not my cup 'o tea, but beautiful machining. With so much material removed, does that act more like a light sporter as far as heating/stringing- or do the "fins" retain enough rigidity (plus addl cooling too) of the original bull profile to handle heavy strings...
I'm guessing a shit ton of light passes so as not to stress the barrel?
It basically acts like an I beam; material further out is much more effective. Start with an M24 profile, do that fluting with a featherweight inner profile, end up with around the weight of a light sporter and the stiffness of a heavy sporter.
Since it has the mass of a light sporter it absorbs heat like a light sporter. This particular fluting profile is an increase in surface area compared to the light sporter, but lots of profiles aren’t. Still, though, I wouldn’t expect the convective heat transfer to be too much higher than a light sporter without some heavy winds creating some turbulence. There are too many traps that keep an intact boundary layer.
Wow!
Truly beautiful work.
You are supposed to fill them with chia seeds and it becomes natural camouflage that you can harvest for your lunch in the afternoon.
Powerwash?
Wow! That's a unique beauty
Okay thanks, it makes total sense now. I will switch out all my barrels to this style ASAP.
That thing is STOOOPID (in a good way)!
Any range reports from barrels you’ve fluted in this manner or is this the first?
John
Thus far it's been good. We've not heard of any stringers or weird stuff from clients and the popularity of this pattern has gone ape shit over the last couple of months.
It's roughly a full day between code work, setup, and cycle time. Small tools and short cycle times have never been good bed fellows, unfortunately.
First, I'm not an engineer. I am however a fairly well-versed machinist and thus far this pattern has been an overwhelming success for those looking to shed weight off a heavy stick.
I look at it like this: If I am a barrel maker and I'm going to turn a 20-sumpthin inch long stick of 1.250" diameter steel into a #3 sporter barrel, I'm doing that AFTER I've drilled, reamed, rifled, and finished the bore. I grab it with a chuck, load it on a center, set up a follower rest, and start chewing. My biggest concern on that operation is that the barrel doesn't start to whip, climb up the tool, and kill itself with a dissection.
The point here is that I did just as much (if not more) heavy lifting with the machine work on the turning center than I'm doing with a fluting tool. I'm not a barrel maker but I'd be willing to bet that the same "time is money" rule applies here as it does with any other industry. If a tool on a big turning center is capable of a .150" or .200" depth of cut on a single pass then I'm willing to bet that's exactly what they are doing simply because they cannot afford not to.
As far as "stress".
My fallback example is if I take a bag of rubber bands and make a ball from it the ball is "stressed" in this state because the bands are stretched in every which direction. If I randomly start snipping the bands, I am relaxing that state of "turmoil/stress". I may very well turn the ball into some other shape as part of the "stress-relieving" process, but I'm not creating more of it by doing so.
The smarter approach I think would be to normalize the material prior to machining. Simply to mean the ball gets cooked at a temperature that relaxes the material. Again, it may not stay in the parent shape but if I did this well before I started cutting on it, I can predict what it will do and size my stock material accordingly.
The steels used for barrel work are often normalized. They can be ordered that way and/or manufacturers have the ability to do it in-house as it's really not that big of a deal. Simply throw the shit in an oven and cook it for a few hours.
My final example falls back to when I used to do a lot of parts from plate 17-4 H1150 stainless for General Atomic. You face mill one side and it bananas in that direction. Did I stress the part or take some away which caused it to pull in that direction?
I flip it 180* and do the same thing to the other side and it pulls back in that direction some as well. You play this game back and forth a few times to get it close enough with a finish pass on the grinder afterward.
Now, bear in mind that I'm using sharp tooling and being careful not to work harden the part by being stupid with my feed/speed/chip load as I do this. Assuming I got that part right I never applied some magical force into the material that "stressed" it. It's literally quite the opposite. I took some of the stress away and the shit just went in the direction it wanted to as it normalized.
It's my understanding/experience that this is what's actually happening. The only time "stress" would be really applied is when you go off the reservation and get carried away with the machining fundamentals. Heating a material up like 17-4 will get you into a nightmare of trouble real fast.
A peck drilling cycle has all the prerequisites to test your patience (and wallet) like a boss. -X2 with coolant. The drill creates a thermal wave traveling ahead of the tool in the material as a byproduct of the friction taking place as it cuts. The drill retracts and a blast of cold coolant enters the hole. (Heat material, then quench with water...what do you get? -A mess! lol.) Last, the drill pokes back into the hole stopping just short of where it ended the previous cycle, then it goes back to the cutting speed/feed. Only now the shit is hard/tough as woodpecker lips and it has to rip through the candy shell in order to get to the Tootsie Roll stuff underneath it. You do this a few times and the drill starts to look like a smashed asshole. Regardless of whether it's carbide, cobalt, or whatever.
The better option here is a through coolant fed drill where the cutting surface of the material is in a constant bath of coolant which mitigates it reaching the critical temp where the chemistry change takes place. For those who don't have that luxury, the best pathway is to use cutting oil and try like hell to get it all in one continuous poke and/or avoid quenching the stuff by not blasting it with cold water or air between cutting pokes.
Make sense?
Last edited:
I am an engineer (and a mediocre machinist)… and that makes sense to me 
Worth a bump for how good it looks. I don’t have much experience in the precision rifle game, but I can tell you that’s higher quality work than I’ve ever personally laid my hands on.
Worth a bump for how good it looks. I don’t have much experience in the precision rifle game, but I can tell you that’s higher quality work than I’ve ever personally laid my hands on.
I have one and it's easily as accurate as any other quality barrel I've ever had.
