AR guys

[Lil Foot]

you can probably guess what i was doing..

That's pretty close to what I had guessed.

dead stopped that lathe & i was running at 2200.

The ONLY advantage to a belt driven machine. A gear head machine would not have stopped.
A 5.56 AK? Sounds interesting.

 

[CaveCreekRay]

SDK,

Attitude is everything.

One day many years ago, I was out by myself flying a model plane. I had put up my shade tent. The weather was gorgeous. For some reason, no one else was at the field.

I was dropping plastic bombs off the plane. With a tank of gas, I could make like 5 short drop runs before refueling. On the second drop, I decided to stick the bomb back on with the engine running (hot re-load). Somehow, my left index finger found the prop and it exploded my finger. I was bleeding like a pig and the engine was still idling!

I wrapped my finger in paper towel and started packing up with one hand. In the course of packing I managed to get fuel on my finger and that only made the pain worse. Getting the shade tent disassembled and repacked single-handed was a huge challenge. I managed to make it home with a little blood left in me and realized that I had to go to work the next day. I fashioned an aluminum splint to protect the tip and drove in to work.

On the first flight I realized what a dumb idea that was as the low cabin pressure caused the wound to start weeping again. I managed to make it through that day and each day it got a little easier. The guy I was flying with was amazed I showed up for work. By the fourth day, the pain was virtually gone.

Amazingly, it healed up and I still have feeling in a very important guitar-playing finger.

 

[sdk1968]

CCR,

great story! thanks for sharing!

2 things here: on the AR part of this..... if you need components or uppers?

can seriously save you guys some coin.

we have a Vendor on our site that is super solid. deal with him every week. for our Members he is running a $68 complete nitrided bolt carrier & he was running nickel borons for $89!!

on the tractor front for you KingKutter guys.... the man who started that outfit lives right here in my little town. He's a tiny guy who walks a couple miles every day waving at all the regular Joe's... Just dont ask him about KK & he's the nicest old guy you'll meet. dont know if he is salty from selling it off or what..

 

[shootem604]

The pricing is nice for you 'muricans. Cheapest ARs in the great white north are Norinco M4 clones at $600-700 CDN. S&W M&P15 is $700-800. My current stable is Colt Canada: a SA20 (C7A2 clone) at $1700 plus extra goodies, a 15.7IUR (Danish military contract overrun) at $1500 plus extras, and a surplus CAF Diemaco Gen 1 C8 with new semi-auto lower from Colt Canada ($1300). Loving the cold hammer forged barrels.

I've had some good American made toys too like the Colt HBAR 20", a dedicated .22lr build with a Tactical Solutions upper, an Armalite M15 14.5" and more that I forget now.

 

[twomany]

Yeah, me neither. Although I have heard of a Jacobs type chuck that is mounted on a bearing- useless for drilling, but works as a support like it appears you're doing.
I'm guessing what you need is a live center, either standard or reverse cone.

A little further "off topic", but....
Jacobs used to supply their big chuck with bronze jaws. The market was the DC motor armature turning repair shop. Those chucks made for quick setup and support for both truing and cutting back the mica. You can imagine that the chuck jaws would only be lightly closed on the bearing section of the motor shaft during the turning, and tight down when cutting mica..
Oh Well, machine tool trivia... ;-)

On topic. An 80% LR-308 lower came in the mail yesterday. (Sunday delivery! What's with that? Service!) I'll be building a "No gas, straight pull" this time. I want something that will shoot soft loads behind cast boolits.

I might go "minimalist" as well. Simple peeps, and abbreviated fore grip. (Not just sure how that hand guard is gonna come to be yet ;-)
18 inch barrel for weight considerations, and the truth that I seldom see ranges over 100yds. If long range presents, I'll bring the heavy barrelled gun.

 

[sdk1968]

hee hee...

ive done 4 more of these 556 AK's since this happened & for sure didnt repeat that move... LOL


YES a live center is something i really need to get, actually have the type that has the cone on the end & free rolls..

but really need the pass thru type for these things where im working "on" the end of it.

sold a couple more of the AR's off, 450bushmaster, 50 beowolf, 9mm, TOK & a 5.45x39 are all gone now..

trying to resist the urge to do more of them & still get rid of a few more....

gun building is an addiction of its own. its soooo hard to stop once its in your blood.

kinda like tractors, im constantly looking for the next deal on a Kubo.

 

[Lil Foot]

gun building is an addiction of its own. its soooo hard to stop once its in your blood.

Been there, done that.

 

[Yooper]

hee hee...

ive done 4 more of these 556 AK's since this happened & for sure didnt repeat that move... LOL


YES a live center is something i really need to get, actually have the type that has the cone on the end & free rolls..

but really need the pass thru type for these things where im working "on" the end of it.

sold a couple more of the AR's off, 450bushmaster, 50 beowolf, 9mm, TOK & a 5.45x39 are all gone now..

trying to resist the urge to do more of them & still get rid of a few more....

gun building is an addiction of its own. its soooo hard to stop once its in your blood.

kinda like tractors, im constantly looking for the next deal on a Kubo.

Uh oh! This is on my bucket list and I am probably going to build one within the year.

 

[David Page]

Sdk, to change to a .50 Beowolf do you need aything besides the barrel?

 

[sdk1968]

Sdk, to change to a .50 Beowolf do you need aything besides the barrel?

bolt head/extractor
magazine follower
buffer(depending on your spring set up)

the 450Bushmaster was better to shoot. ammo was cheaper/available everywhere, so are complete mags. its actually one of the more impressive AR alternative calibers ive ever done.

give it a serious thought before you go to the Beowolf.

 

[David Page]

Thanks sdk, We had a reloading die from doing some for a person years ago but dies are inexpensive.

 

[lugbolt]

Someone mentioned spinning the bullet apart and it got me to thinking.

Couple years ago a guy I worked with at the time was selling out of his AR/M4 stuff and I bought into it not knowing a single thing about them. And I mean nothing. I'm not a gun nut. I buy what I think will do the job for what I'm hunting and that's all I need. Sell it after the seasons' over and do it again next year. So anyway, I bought all this crap mostly so I could throw something together for my dad who's a vietnam vet. Dad never talked much about wartime other than firing different weapons and how he was impressed with certain ones; and he always mentioned the XM16A2 platform, how versatile it is/was, how natural it is to fire it, and it's accuracy (they were 20" as I recall). So I threw together a 20" 1:7 jobbie and I had already bought a Marlin 25MN for squirrel hunting, and we headed to the range after a stop at the sporting goods store. A box of 5.56 cost less than the box of WMR did. Crazy. But off we went. He had one box of 193 and a box of Hornady 35gr. The Hornady advertised almost 4000 FPS. Well he ran down the 193 supply in no time and switched over to the Hornady while I was plinking away at a paper bad guy at 75 yards. There were a few times that he'd fire at the target and I'd watch through a binocular, but it never hit the target, and I didn't ever evidence of the bullet hitting the dirt berm behind it. I figured his old eyes were just worn out..didn't matter since he was having some fun. He handed it to me, I threw another mag loaded with 10 rounds of Hornady and I took a stab. Same deal. Like I couldn't hit the target, so I walked down range within about 20 yards of the paper target, fired, and really didn't see a cut & dried bullet hole. Ran out of ammo, went home.

But it got me to thinking the spin rate of the bullet. At 4000 FPS (advertised for the Hornday NTX 35gr) and a 1:7, I came up with 411,000 RPM. It very well could be coming apart at that RPM; I don't think they're balanced or anything so anything that is even .001g out of balance is going to have a big affect. I work on a few turbo's and balancing them, just a tiny bit makes a huge difference at "only" 100k RPM. 411,000 RPM is a little over 6,800 revolutions per second.

Interesting.

 

[sdk1968]

thats not the bullet Revs.

the twist rate you listed of 1:7.. thats 1 Rev for every 7" of barrel.. so on a 20" barrel you had 2.8 Revs total as its leaving the barrel.

take your 7" for a rev & divide total distance of inches to the target..(75 yards is 2,700inches) making your total revs to target= 1,080 revs & that should have taken about .05 seconds to cover that distance.

then you have to assume that everything was stable & there was no +/- at the exit point of the barrel... no wind affect...

that particular bullet is a good varmit load & better at long distances, but you still should have been able to see it go thru the target, aka= punch the paper.

 

[lugbolt]

Might not be accurate. But when I was much younger and shooting competitively, we used the following formula:

MV x (12/twist rate in inches) x 60 = Bullet RPM

 

[sdk1968]

Might not be accurate. But when I was much younger and shooting competitively, we used the following formula:

MV x (12/twist rate in inches) x 60 = Bullet RPM

its all how you look at it: as RPM vs RPD or RTT.

never really looked at it as RPM on small arms because we are always talking sub second delivery time.

lets run it again just for fun...

yes, the math you listed would give you 411,428 as a number per minute.

with that math it would be 6,857 revs per second.. or 685.7 revs per tenth of a second..

your distance is still only 225'... & your flight time at 4,000fps is still less than .056 seconds at that distance.

making your flight time almost non existent to the naked eye. that formula actually gives you a much lower RTT than the one i used did. actually comes out to be way less revs to target ...

good info & a nice comparison on what sounds like a totally crazy number verses how that number works out to be applicable in the actual distance involved.

hee hee... i can now start telling people that the guns i build can stand almost 500,000RPM.. LMAO

 

[twomany]

I can't think of a single reason why revs to target would be part of any consideration regarding bullets coming apart.

When inertia forces exceed centripetal forces, the object "comes undone". Even if for the merest instant of time.

Perhaps you were speaking on some other aspect of this deviation from the OT

 

[Lil Foot]

The only experience I have with bullets driven so fast they disintegrate was with a guy I used to work with. He would load 110gr FMJ 30 carbine bullets in a 300 H&H Magnum with a compressed powder load. He was trying to achieve 5000fps.
Bullets would vaporize before they got to the chronograph, or the target. That guy always was a little nuts.

 

[bucktail]

There are a couple of writers that I believe that say they've had bullets designed for 22 hornet come apart in fast twist 22-250's. I have a couple of boxes 22 hornet bullets that I plan to run in my 1:9 twist .223. I expect them to hold up, but if they don't, I'll try some faster powders to slow the muzzle velocity down until they start to hold together.

 

[sdk1968]

I can't think of a single reason why revs to target would be part of any consideration regarding bullets coming apart.

When inertia forces exceed centripetal forces, the object "comes undone". Even if for the merest instant of time.

Perhaps you were speaking on some other aspect of this deviation from the OT

lugbolt was thinking maybe his bullets were coming apart from the amount of RPM being excessive for that bullet.

i was saying they werent turning that "fast".... so we were looking at 2 different aspects of it.

he's thinking overall RPM... im thinking RTT.

RPM sounds way cooler & is a ridiculously high sounding number.

RTT is not nearly as flashy sounding & is all about when the bullet stabilizes in flight.

this became more of a conversation/research thing among us when keyholing bullets started becoming an issue a few years back in the gunbuilding community in several calibers.


on the topic directly: that particular Hornady bullet is a proven commodity as a groundhog killer, designed for 4,000fps+ & is highly unlikely to be "spinning apart".

oh & the recommended twist for this bullet is even SLOWER at 1/12..