How reliable are internal parts on rifle that are cast?

Had some trigger work done on my rifle to bring the pull from 9.5 pounds to 3.9 pounds. The gunsmith said that it has a little travel but a crisp break. (I'll try it out soon) He also said that a few of the internal parts which were cast metal need a little flashing cleaned off.

My question is, how many rifles typically have cast parts in their internals and how good is their structural integrity.

 

They're equal if they've the same metal formulation and heat treatment, in my opinion. I'd guess most rifles have a lot of cast parts. Some will be milled and polished for functionality specs.

A metallurgist will have a better answer on structural properties.

 

How reliable do you find your car's engine block? It's cast.
Highly unlikely there'd be any flash left on any part. A burr, maybe, but not flash left over from manufacturing a MIM part.
Internal parts aren't cast like an engine block. They're usually MIM parts these days. That'd be Metal Injection Molding. Most MIM parts made from compressing powdered metal mixed with other stuff(That's highly simplified.).
Discussed here, at length, in the past. This is one.
https://www.thehighroad.org/index.php?threads/whats-the-story-on-mim-parts.3725/
Here's another.
http://www.chuckhawks.com/metal_injection_molding.htm

 

Sunray, kudos to you for updating my old metal casting to injection moulding. That's what I meant but didn't put it in words. That became popular in firearms back in the early '60's.

 

The hammer, trigger, and bolt stop of an M16 are cast . . . .

 

The receivers on Ruger m77s are cast. Cast items can be well made or they can be poorly made.

Injection molded parts can be made poorly or be just as good as machined parts. But, if it's not, it's usually an engineering problem.

Years ago people used to talk about stamped steel parts the same way. The trigger of a savage 110 is injection molded and most other parts on the savage's FCG is stamped steel, including the sear.

 

Not necessarily. There's also the issue of density & voids - especially with MIM. MIM parts will pretty consistently weigh somewhat less than a part made from a forging or barstock of the same dimension, metal composition, and subsequent heat treat. I don't know if this has improved, but for a long time many gunsmiths would not checker the frames of MIM handguns due to the likelihood of hitting a void.

Some manufacturers like Ruger have had reasonable success with investment cast parts.

 

I thought their success with investment cast was high.

 

As a purchasing manager for large manufacturing companies I was charged with buying castings as specified by our engineering staff.
The tools and machines that we made were the best or optimum design to have the best performance while being profitable in the market place.
Of these castings some were investment castings that used the 'lost wax' process or 'Investment Casting' that goes way back.

https://en.wikipedia.org/wiki/Investment_casting

One of my suppliers was owned by Sturm Ruger. I toured their foundry The Pine Tree Co. in New Hampshire!

http://www.ruger.com/casting/F-Overview.html

 

In terms of the parts not breaking, yes. However in many cases they have arguably had to design in larger parts than would have been required otherwise.

I think it's safe to say that if money was no object and the goal was simply to produce the most desirable end product, there would be very few investment cast parts (only for certain very hard to machine shapes) and no MIM parts in firearms.

 

@Llamabob: Thanks.

 

It is high. Ruger investment casts for other arms manufacturers and other industrial applications. As I understand it, the same is said of their MIM production as well. Their M77's catch a lot of flak for being oversized, but the "prone to cracking" myth is simply that. Much of why the M77 is so heavy and oversized is necessary design strength due to the MASSIVE ejection port compared to the lighter, smaller, almost completely enclosed Remington 700, and added weight inherent to a flat bottom receiver. Ruger also uses cast frames for their revolvers and cast cylinders - find a revolver of equal size which is stronger than a Ruger... They're also having high success with their MIM internal components in their revolvers - despite all of the fear-mongering by luddite naysayers who despise any change.

The voids/pockets issues in the past are largely not applicable for any modern production model by a reputable manufacturer. Not sure how much MIM is really done (cast, sure, not MIM) out of country in low quality import firearms, since the equipment is rather expensive, but it's pretty easy to avoid those issues by simply avoiding low quality import firearms altogether.

Modern models by reputable manufacturers use MIM parts where such a process is applicable and appropriate, and don't use it for parts where it's not. 50-80yrs ago, that may not have been as true as it is today.

 

Ruger's MIMs are outsourced, no in-house MIM production capability.
Denis

 

MIM is not applicable to larger parts like frames.

No cast cylinders. Ruger cuts their cylinders from barstock like everybody else.

 

In theory this is not true. While MIM production is sometimes said to be limited at 1 pound or the size of a golf ball as the max size, it's not a hard limit and is more dependent on parts/mold and furnace capability than anything having to do with the MIM process.

In practice, I believe at least Armscor and perhaps others have made batches what were advertised as MIM frames. It's possible this was a misnomer and they were in fact investment castings I suppose, but whatever they were they had voids. I can't speak to current Armscor production.

 

Gimme a break with this condescending blather. One doesn't have to be an "expert" on any given subject to have an intelligent conversation about it.

 

Sturm Ruger's casting business (aka Pine Tree Castings) makes military and aerospace parts, a lot of which are much more demanding applications than firearms parts.
IMHO, if a cast gun part will fail, it will be in the first few rounds and there is no company that stands behind their stuff better than Ruger.

 

The issue with the use of MIM is that it's a complicated process with many steps, any number of which can be less than optimal resulting in bad parts. Machining from bar stock that has been ultrasonically tested and certified free of cracks, seams, folds, laps, pipes etc. is much more forgiving since if the part is designed correctly, and the steel certified and the proper hardness, there's much less to go wrong.

 

Thanks all, for your replies.

 

For some reason this possiblity piqued my curiosity so i went googli g. Ive found no reference to ruger casting its centerfire cylinders, but i did run across a few that stated the blackpowder revolver cylinders were, atleast at some point, cast. Good discussion guys ive learned stuff, i call that a good day.

 

Making a cylinder from round bar stock would be simpler, faster, and cheaper than making one from a casting.....

 

I'd have to disagree. I work for a mfg. company that machines and assembles brake components, and it is usually not cheaper, faster or simpler to machine components from bar stock. With castings (which most of our product is machined from) or forgings, you are machining from a piece of metal that is "near net shape". You are spending much less of your expensive machining time taking away metal as compared to bar stock (machining costs includes amortization of the cost of a Mazak VMC for instance, hourly rate of operator, benefits, manufacturing overhead for the plant, etc.) . Our tool room will spend the time and money machining from bar stock if we're making a few prototypes that wouldn't pay to have casting or forging tools made for a run of ten pieces for instance. One we're producing in-line product, we'll pay to have casting or forging tools made and get in castings or forgings that need very little machining.

Additionally, casting vs. forging is too simple a premise. Depending on the forger or casting house, whether a casting for instance is done via lost wax, investment cast, gravity cast, etc. and what materials are used, either one could be superior to the other. Some materials (one type of aluminum vs. another type) lend themselves better to casting or forging, and you can tailor the material to the forging or casting method to get better results.

As someone else also mentioned, things such as aircraft landing gear are often cast items, and have much more in the way of stresses input to them then our relatively simple firearms.

If the manufacturer knows what they are doing, I would have no issues with casting, forgings or machining from bar stock for firearm parts. Castings always being better or worse than a forging is too simple a premise.

 

Ruger did indeed cast Old Army cylinders, that's the only exception.

In this case, it is easier to machine cylinders from round barstock than to cast them. Manufacturers buy barstock but Ruger would have to create a casting.