Investment Cast Receivers

[laurencen]

machining lexan to be clear is difficult, we machine lexan and one way to get it clear is fine pollishing to remove machine marks, there is also a process using vapor but it gives distortion, saying that I have a 3d plastic printer and it would work great for a dummy reciever if it had enough travel, would make a 3/4 scale one.

[buzz]

Ruger specifically designs their guns from the ground up to conform to their manufacturing methods.

[gunhistorian]

Interesting discussion. Wasn't an experimental TSMG (or two) made in aluminum? I believe there were problems with this material -- either receiver stretching or cracking. While this is a SWAG, I suspect that the problem with building a TSMG receiver in aluminum (if it was legal) would be the fact that you have stresses from the recoiling bolt that aren't found on the AR series or in bolt action rifles. I might be all wrong on that but I noted the comments on the WH Thompson forum regarding changing the buffer from the WH to a more modern buffer to prevent receiver cracking (and maybe stretching?).

[Jrickard81]

Ruger specifically designs their guns from the ground up to conform to their manufacturing methods.

Worked for their 1911 i bet well made cast Thompson parts could be great. Well made of course

 

Too bad we have that silly NFA law or else we may see a good bit of Thompson clones, i mean just look who all make 1911's now . Be awesome to have new Thompsons!

Sorry for folks who paid though. But our freedom should be worth more than their return on $$$

Edited October 26, 2014 by Jrickard81

[MARK2112]

I run a 3d printer at DS ARMS, they are rather crude as far as a display reciever and the toughest material we use is abs....bar stock in my opinion for this reciever is the easyest and best way to manufacture it.most military recievers are forged and for those applications they work great . Other than the feed ramp on this reciever there is nothing really difficult to program.

id love to see turnbull make a '21 clone like he did those 1911s.........in semi and full.....semi for those of us in a communist republic like illinois.

Edited October 27, 2014 by MARK2112

[mnshooter]

 

Ruger specifically designs their guns from the ground up to conform to their manufacturing methods.

Worked for their 1911 i bet well made cast Thompson parts could be great. Well made of course

 

Too bad we have that silly NFA law or else we may see a good bit of Thompson clones, i mean just look who all make 1911's now . Be awesome to have new Thompsons!

Sorry for folks who paid though. But our freedom should be worth more than their return on $$$

If You want a Thompson with cast parts, just buy a West Hurley.

[Paladin601]

Cast and investment cast are different. Besides didn't someone mention that the WH dimensions are different.

[buzz]

I just don't see the point in casting a Thompson receiver.

 

What advantage would there be?

 

How much money would be saved by using a casting instead of bar stock?

[laurencen]

using bar stock requires the middle being removed, then finish cut every surface, if its cast all one does is finish cut, still needs every face machined but that would be less than 1/64", it all comes down to machine time,

Edited October 27, 2014 by laurencen

[buzz]

How much would that come out to in dollars for a Thompson receiver?

 

Reconbob's 80% receivers are around $350

 

So if you set up an operation across the street from Reconbob called "Cast Thompsons R Us", what would your 80% receiver cost?

 

Serious question

Edited October 27, 2014 by buzz

[laurencen]

based on my skill level a upper from solid would take 5 to 6 hours on the CNC, just to skim the surfaces 2 hours, this is assuming it is made using jigs not 5 axis CNC

[full auto 45]

I would love to have a clear polycarbonate receiver for display. We use it everyday in our CNC machines for underwater housings. Hit them with a torch after machining and they clear right up. Also SC125 cleans up small spots. Also a clear lower would be nice to show working parts.

[MARK2112]

I BELIEVE THE RECEIVERS FROM BAR STOCK NEED TO BE NORMALIZED PRIOR TO MACHINING,THIS REDUCES TWISTING DURING THE MILLING OF THE INSIDE,BOB MAY KNOW MORE THAN I ON THIS SUBJECT THOUGH BEING HE HAS MADE THESE BEFORE.

[gunhistorian]

While this is a LITTLE off the subject, it should be kept in mind that a number of parts for the Browning m.g.s made during WWII were cast in order to save material and machine time. I suppose that is the benefit to casting -- particularly investment casting. On a similar off-subject (sort of) issue: Was the NFA amended to prohibit the manufacture of full automatic weapons, or with this a part of the Gun Control Act? I'm not sure that the NFA should be blamed for all evils -- though I do question the effectiveness of it.

[buzz]

I'm wondering what kind of dollar cost savings are we talking about for a cast receiver.

 

This is the key question to this whole topic.

 

Certainly nobody would take a cast part over a billet part if the cost was identical.

Edited October 28, 2014 by buzz

[MARK2112]

Imho......no gun part should be casted or MIMed.

[MARK2112]

Just watched a Youtube Video from Jay Leno's Garage and he is making parts for his cars as I said scan-print- investment cast. Even intricate parts.

 

Now I just need the money.

saw that machine at the international tooling show, it uses a laser to melt powdered metal into a 3D model...cost..... $2,000,000.

[buzz]

I once made a 100% USGI M14 clone with all new parts from the wrapper and an LRB forged receiver.

 

I wonder what it would cost to find those NIW parts now? A fortune.

 

Anyway, the M14 guys are constantly debating forged vs billet vs cast.

 

It's hard to pin down because none of the makers uses standard blueprint dimensions. Like SA makes a cast receiver but the walls are real thick. but LRB uses the thin wall USGI dimensions.

 

 

 

But anyway, this company (see link) prices their forged vs cast receivers $100 apart.

 

So that's a 20% price difference between cast and forged.

 

 

http://www.762mmfirearms.com/receivers/

Edited October 28, 2014 by buzz

[Paladin601]

James River Armory also makes a Forged M14 Receiver for a great price I have 3 Fulton's that I like. But, Civilians are not going to shoot the rifle as much as the military.

 

My idea was to use a 3d printer to make a plastic copy, use that as the pattern for investment casting, then finish it up on a CNC mill.

 

thanks every one for the reply, even though I doubt I could do it, it still gives me directions in the thought process

[MARK2112]

The M14........my second favorite rifle......those LRBs are exquisite.

[GUNGUY45]

Some of our customers use 3-D printed models as sample patterns, they can sometimes spend as much as 1/3 of the tooling cost for 1 model.

Just remember, Investment Casting uses a consumable pattern, 1 pattern =1 casting.

They do however allow them to get exact shrinkage rates to hit their dimensions on the tooling.

[Paladin601]

Mark2112, one would have to make a lot of Thompsons to pay off a $2 million dollar machine like that.

 

Gunguy, just what I was thinking, but I guess could not get across. Investment casting is very cost effective. The cost of the pattern, I think would pay in the long run for reduced machining.

 

BTW, A kid in Japan was arrested the other day for making workable guns with a 3d printer. How workable, the article did not say, but we all know that the press will over embellish his accomplishments.

[reconbob]

If the call ever goes out for 100,000 Thompsons we'll find out what would be considered the most cost

effective manufacturing technique. You could certainly make Thompsons the way they made G-43's in WW2.

Forgings and castings which are machined only where it counts - sliding and mating surfaces - but the exterior

left rough. The gun would still shoot the same. But of course, it would not be thought to be a "real" Thompson.

Back when they made the Colts they were not doing anything special. Machining forgings and bar stock was

the way you made guns back then.

The bar of steel you make a receiver out of has to be stress relieved - which is different than normalizing -

so that the front of the receiver does not bend upward due to the thin cross section where the mag cutout and

ejection port are.

 

Bob

[Paladin601]

You are right Bob, but don't think that will ever happen. I think it's days have past as a front line weapon. Maybe an update of the design, might work.

[Paladin601]

Unless a 3d printer can use Wax to build the pattern, this process is not feasible, sadly to say. A little research on my part found that the material used in the used in 3d printing would not leave the mold clean enough to make a sound casting.

 

Back to the drawing board.