Author Topic: Gunmetal designs questions  (Read 13240 times)

Offline laffinz

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Gunmetal designs questions
« on: January 21, 2012, 07:30:55 PM »
Me and a friend are about to start machining a pair of Gunmetal designs 50's and we have a handfull of questions I'm hoping you guys can help us with. 

1. First off.. SAFETY.  If we make it to specs and out of the steel and heat treating called out on the print theres no reason this thing would turn into a pipe bomb correct??  Is the .614 of material in the receiver enough to keep the bolt from blowing backward into our face?

2. The prints call for 4130 for a lot of the pcs like the receiver and bolt. We have a lot of prehardened 4140 laying around.  Would it be safe to make it out of this or???? Suggestions on any other material that would be better yet are welcome...

3. Where do you get the trigger and misc. springs from?

4. What are our options for a stock?

5. Does anyone have any pics or video of a completed gunmetal designs build? We'd love to see em!

Here is a link to the prints we are using.  Thanks in advance, we're lookin forward to your input!!
http://garagegunsmithing.com/index.php?option=com_jfusion&Itemid=54&jfile=viewtopic.php&f=23&t=1585

Offline laffinz

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Re: Gunmetal designs questions
« Reply #1 on: January 21, 2012, 07:34:15 PM »

Offline tlagnhoj

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Re: Gunmetal designs questions
« Reply #2 on: January 21, 2012, 11:29:32 PM »
DELETED BY Tlagnhoj:
« Last Edit: May 10, 2012, 02:20:51 PM by tlagnhoj »

Offline laffinz

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Re: Gunmetal designs questions
« Reply #3 on: January 22, 2012, 11:44:41 AM »
Thanks for the input!  As far as the .614 dim, you can back that 45 up almost .250 before you get into the receiver opening.  Seems like you'd just have to back the 45 on the bolt up the same amount that you do on the receiver and all would be good.

I haven't looked into how much meat you have to work with between the ID and OD of the bolt along that area, but even if you just backed it up .150 that doesn't sound like much but its almost an additional 25% of material in the receiver to support the bolt when fired.

As far as material used, It seems like there wouldn't be any drawbacks to going from 4130 to a tougher prehard 4140.  But we honestly aren't educated enough on the differences between the two to feel comfortable making the decision.  Machining it isn't a problem.

Offline tlagnhoj

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Re: Gunmetal designs questions
« Reply #4 on: January 22, 2012, 02:40:58 PM »
DELETED BY Tlagnhoj:


« Last Edit: May 10, 2012, 02:21:31 PM by tlagnhoj »

Offline Delw

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Re: Gunmetal designs questions
« Reply #5 on: January 22, 2012, 09:56:15 PM »
Sence you are building a pair this is what I reccomend.

buy enough material to make 3 actions ( cause your going to screw up one).
rough cut all your action pcs, and send out to heat treat ie normilize harden temper to around 36-40rc. also send out your other parts as well that are the same material.
then finish the actions.
Soft material will gall.

the reason for the o1 is because it will harden harder than 40 series material.

if you short cut on the heat treating process you will more than likely kill or injure yourself.
you wont find CHEAP already heat treated material to do this JOB. your going to easily have a few hundred bucks in material and another 100 or so in heat treating.

There was a really cool build thread  on this gun last year or the year before floating around. I wish I could find it. its how I found this forum so it might be linked or in here. It was an absolutely AWSUM thread on the gunmetal build. I believe the guy was a retired airforce sergent.


Delw



« Last Edit: January 22, 2012, 10:00:53 PM by Delw »

Offline tlagnhoj

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Re: Gunmetal designs questions
« Reply #6 on: January 22, 2012, 11:40:03 PM »
DELETED BY Tlagnhoj:
« Last Edit: May 10, 2012, 02:22:15 PM by tlagnhoj »

Offline Delw

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Re: Gunmetal designs questions
« Reply #7 on: January 23, 2012, 08:19:29 AM »
Not only do I disagree, but I strongly disagree with most everything you posted

Sence you are building a pair this is what I reccomend.

buy enough material to make 3 actions ( cause your going to screw up one).

Perhaps you will.  I would not and I make no such assumption of the OP

I make the assumption for a few reasons. 1 its cheaper to buy anough material for 3 actions as it is 2 actions.
2 mistakes happen its a fact of life.


rough cut all your action pcs, and send out to heat treat ie normilize harden temper to around 36-40rc. also send out your other parts as well that are the same material. 

Rc30 - Rc35 is "generally considered" to be as hard as can be machined by normal methods.  This is the reason 4140 Pre-hardened is only hardened to Rc27 - Rc32.  It remains "workable".  If you get steel much harder you will have issues cutting it.  4130 may well require Rc40 to get the yield strength where it is needed.  But you will find that it is a problem to cut it at that hardness.
30-35 is like cutting butter 36-40 is also pretty easy.
I do it everyday in my real job
then finish the actions.
Soft material will gall.

Bologna! If you have galling issues with 41XX annealed steel your not cutting it correctly!!  I cut 1018 frequently, 4140 occasionally and have no problems and it doesn't get much softer than 1018! 

The other issue with cutting first and heat treating after is the steel WILL warp.  4130 more so than 4140 but both warp.  Then you have to go back and repeat all of the setups and re-cut hardened steel...  Much easier to read the article I linked and do the math for the 4140 you have. 

your rough cut first then send in to heat treat and finish the rest, if not you will have a warped action due to stress. drill a hole cut the scale off then send to heat treat.
Galling happens on all soft materials its like velcro.
if your worries about set up for a rgh finish than you shouldnt be building anything as your too much in a hurry. an extra 2 set ups on a lathe takes what 10 mins?
again I do this every day in my real job

the reason for the o1 is because it will harden harder than 40 series material.

For an ejector pin???  WTF??  1018 CR would work.  4140 pre-hardened would be excellent.  There is NO point in using fully hardened O-1 for an ejector pin.  Even the extractor should not be fully hardened.  I would make the extractor from a tool steel IF I were to make it.  However, I see no point in making one either when I can buy one "off the shelf" any day.  They are cheaper than my time is worth and it is not an easy piece to make.
you can use alum and hard anodize it if you want. fact is 01 ie tool steels, gets harder than 40 series

if you short cut on the heat treating process you will more than likely kill or injure yourself.

This I do agree with.  The heat treat is in many ways more important than the steel used.  4130 and 4140 are both widely used by firearms manufacturers for making actions, bolts and such.  But if the heat treat is not what it should be VERY VERY BAD THINGS WILL HAPPEN!

you wont find CHEAP already heat treated material to do this JOB. your going to easily have a few hundred bucks in material and another 100 or so in heat treating.

What rock do you live under?  4140CFHT is not very expensive.  I have less that $80 in steel to make my action, bolt head, bolt body and blot handle.  $0.00 in heat treating as it is already heat treated. and ZERO warpage!!!

See: https://www.speedymetals.com/ 

https://www.metalsupermarkets.com


Again expensive to some is different. I usually see guys who post looking for alternitive maters the main proble being cost.


There was a really cool build thread  on this gun last year or the year before floating around. I wish I could find it. its how I found this forum so it might be linked or in here. It was an absolutely AWSUM thread on the gunmetal build. I believe the guy was a retired airforce sergent.


Delw

You (and others) may find builds of the GunMetal and Maddi "cool" but I cringe.  The GunMetal design is not a very good design.  There are dims missing from the drawing that are CRITICAL to safe operation.  Fill them in correctly and you may do well.  Get them wrong and you have a problem.  Construction methods are critical and not noted in the "plans".  The the bit about fillets above.  Get this wrong and the steel can and will develop stress cracks over time.  Some day it will fail for wand of a .005" fillet on the bolt.  The bitch is no one can say when it will fail!!  Maybe on the 10th round...  Maybe one the 10,000th.

I don't discourage anyone from making a bolt action rifle.  I STRONGLY suggest that you really know what you are doing before you start.  If you can't see the shortcomings of the GunMetal design than you should do more home work before starting one.  I can assure you there are a few that you need to understand.

I never said the gunmetals was a awsum design. never said it was a bad design. there are flaws in it that I dont feel comfortable with.

I been working with 4130 -4340-9310-1045 for about 25 years I run about 5000lbs a month used to run 20klbs a month before 911

a 50 I wouldnt go changing anything if you have no clue what your doing or be guided by someone whoss does other than someone on the internet. there is way to much false information out there, and guys WHO take short cuts and THINK they know what there talking about.


The org. poster I think is the same guy that posted on weapons guild. asking for cheaper material and heat treat. or its a buddy of his or coinsidence as the exact same questions was asked 2-3 weeks ago.

Delw

Offline tlagnhoj

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Re: Gunmetal designs questions
« Reply #8 on: January 23, 2012, 09:46:03 AM »
DELETED BY Tlagnhoj:
« Last Edit: May 10, 2012, 02:22:33 PM by tlagnhoj »

Offline Delw

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Re: Gunmetal designs questions
« Reply #9 on: January 23, 2012, 12:02:53 PM »
Quote from: tlagnhoj
Then one would think that you would know how to machine it without galling.  I will admit that I have far less experience with 4140 than you but I don't have issues with galling.  What more can I say about that?

One would also think that with that much experience you would know how readily available 4140 CFHT is, how much it costs and the quality of the material available.   Firearms manufacturers and barrel makers use pre-hardened 4140 regularly.  Pre-hardened 4140 is cheaper than many other steels bought in the annealed state and hardened after working for MANY applications.  It also solves ATFE issues with sending out "Firearms" for work by 3rd parties, a PROPER temper for firearms can not be achieved at home by most people. 

I think I said a few hundred bucks for materials? remember he is building 2 firearms. not one.

I use fry steel, emj, castle and  copper and brass sales, I dont use internet sales on my material due to you dont know exactly what your getting. All my material comes with certs.
Then I use a quality heat treater why because I cant rely on the fact that Its good enough, it has to be exact.
I wouldnt reccomend HOME heat treating to anyone. but thats me I know guys that do it and are good at it but again thats me.
we have places local that will do a lot charge for under 100 bucks sometimes if you need a pcs they will throw it in with some other stuff for 25-50 bucks.

roughing a action in does NOT VIOLATE any laws as its not a firearm with just a hole and some scaleing removed or lugs cut.

Hope that helps clear some things up.

Remember this anyone building a firearm that hasnt done so in the past, should follow secific REPUTABLE instructions.
The gunmetal and other prints out there are specific, wether you or I think they can be made better or not. Dont deviate form them unless you have experiance in it. Gunmetal and some of the other ones people have built a bunch of firearms with. there pretty reputable.

Look at ar-15s for example. guys building lowers and uppers out of 6061 instead of 7075. theres a reason for 7075.
Yes 6061 does work fine.
buy some junk chinese 6061 off the net and you may have some problems, but then again you maynot.

As far as galling
I can take 2 ground finishes ID and OD  perfectly round and it will gall on pressing them in, where as if one or both is heat treated you wont get galling Ie  due to soft  material
its like rubbing 2 pcs of velcro together.


Delw







Offline tlagnhoj

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Re: Gunmetal designs questions
« Reply #10 on: January 23, 2012, 02:04:32 PM »
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« Last Edit: May 10, 2012, 02:22:51 PM by tlagnhoj »

Offline Delw

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Re: Gunmetal designs questions
« Reply #11 on: January 23, 2012, 08:16:37 PM »
Quote
And your letter from the ATFE to this effect is where?  Let me explain something to you.  Unless you have submitted a piece of metal and gotten a determination letter SIGNED by a DIRECTOR or ABOVE...  A bit of steel is a firearm when the ATFE says it's a firearm.  There was a guy a few years back who was selling "funny pipe" (drilled and lug ways broached, NOTHING more).  He went to jail for that.  He never bothered to get a determination letter, someone in the ATFE decided he was making "firearms, he went to jail...  It's was in fact that simple.

I guess I am going to jail then.
 I cut 2.5" 9310 gear steel and run a 1" bore through it 12-14 inchs long,all the time then send it to heat treat.
 looks like the guy a few years back had a little more than a pc of metal , I am guessing it was more of a firearm not a piece of metal.
your exageratting a tad much.

Quote
If the receiver is not finished enough to be able to fire, then no, it's not a receiver yet.

ATF defines a receiver as a "firearm" when it will: hold a barrel or firing chamber, hold an ammunition feeding device, and hold a firing mechanism. Since a single shot has no feeding device, only the other two would apply.
Can a barrel be attached, and the breech closed and a round fired? If not, then it is not yet a a receiver, and you're GTG.

The final finishing, however, is on a completed receiver, and would require an FFL shop.


ETA: your local ATF office cannot answer such questions, 9 times out of 10. You'd need someone in Martinsburg.

hope that helps. I dont have time for the rest as its jibberish and opinion nothing more

Offline tlagnhoj

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Re: Gunmetal designs questions
« Reply #12 on: January 23, 2012, 09:21:19 PM »
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Offline Delw

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Re: Gunmetal designs questions
« Reply #13 on: January 24, 2012, 12:58:04 AM »
Quote
And your letter from the ATFE to this effect is where?  Let me explain something to you.  Unless you have submitted a piece of metal and gotten a determination letter SIGNED by a DIRECTOR or ABOVE...  A bit of steel is a firearm when the ATFE says it's a firearm.  There was a guy a few years back who was selling "funny pipe" (drilled and lug ways broached, NOTHING more).  He went to jail for that.  He never bothered to get a determination letter, someone in the ATFE decided he was making "firearms, he went to jail...  It's was in fact that simple.

I guess I am going to jail then.
 I cut 2.5" 9310 gear steel and run a 1" bore through it 12-14 inchs long,all the time then send it to heat treat.
 looks like the guy a few years back had a little more than a pc of metal , I am guessing it was more of a firearm not a piece of metal.
your exageratting a tad much.

Actually nothing left out....  The only thing he did that you are NOT doing is cut the lug ways. 


Quote
If the receiver is not finished enough to be able to fire, then no, it's not a receiver yet.

ATF defines a receiver as a "firearm" when it will: hold a barrel or firing chamber, hold an ammunition feeding device, and hold a firing mechanism. Since a single shot has no feeding device, only the other two would apply.
Can a barrel be attached, and the breech closed and a round fired? If not, then it is not yet a a receiver, and you're GTG.

The final finishing, however, is on a completed receiver, and would require an FFL shop.


ETA: your local ATF office cannot answer such questions, 9 times out of 10. You'd need someone in Martinsburg.


I have no clue who or what you are quoting here but it is not what the law says.  The law does NOT say WHAT has to be completed, it is VERY subjective.  However, in the case of an AR lower the one line that can not be crossed is the FCG...  If the FCG is STARTED it is a firearm even if nothing else is done.  If the FCG is not started but everything else is completed BATFE has repeatedly sent out determination letters stating that it is NOT a firearm.  That does not square with the what you quoted above.

So I go back to what I said before: 

Quote
Unless you have submitted a piece of metal and gotten a determination letter SIGNED by a DIRECTOR or ABOVE...  A bit of steel is a firearm when the ATFE says it's a firearm.

hope that helps. I dont have time for the rest as its jibberish and opinion nothing more

Nope... more of the same stupidity and nonsense IMHO.

Theres more to the story if he went to Jail..  if you dont have the actual true story and FACT your point it useless as its just another story/myth. save that for another topic ( As I would really like to read about it Seriously) but reguardless.

like I said in my first posts there is NOTHING WRONG/Illegal with drilling a hole in stock and takeing scaleoff and sending it to heattreat. its 100% legal as it is not a firearm.
 I never mentioned cutting a FCG in it nor lugs nor threads. just drill a hole and cut scale off then send out to heat treat, then finish the firearm.


I was told if my state couldnt answer it to call the AFT Office Martinsburg. it was explained perfectly and I was left with NO doubt.


 

Offline TehVice

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Re: Gunmetal designs questions
« Reply #14 on: January 24, 2012, 06:18:51 AM »
Fight! Fight! Fight! Fight!

Offline tlagnhoj

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Re: Gunmetal designs questions
« Reply #15 on: January 24, 2012, 06:47:50 AM »
DELETED BY Tlagnhoj:

« Last Edit: May 10, 2012, 02:23:25 PM by tlagnhoj »

Offline Delw

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Re: Gunmetal designs questions
« Reply #16 on: January 24, 2012, 10:04:57 AM »
man dude you got a bug up your ass or what.

CR/CF ie cold roll/Cold finish does have what machinist call scale, not like Hotroll where its brown and looks like bark. but we have been calling it scale for years.

The outside surface is slightly harder then the inside surface. you cut it off so it takes stress out. it comes that way from the foundry.

BTW this is machine shop 101.

Now get back in the Kitchen were you belong ;)
 
Delw

Offline Delw

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Re: Gunmetal designs questions
« Reply #17 on: January 24, 2012, 10:06:15 AM »
Fight! Fight! Fight! Fight!

Naw dude the guy is menstrating, it will be over in a few days.

Delw

Offline j_blankenship

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Re: Gunmetal designs questions
« Reply #18 on: January 24, 2012, 11:30:12 AM »
I doubt it.

Offline tlagnhoj

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Re: Gunmetal designs questions
« Reply #19 on: January 24, 2012, 12:36:13 PM »
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