some one please school me on aluminum

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sgms18
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some one please school me on aluminum

Post by sgms18 » Tue Aug 19, 2014 9:39 pm

So I wana make a a high volume 9mm smg can for a m11/9 & short barrel .300whisper. Both full auto. I know that 7075 is pretty tough. Should I be looking at any other grades? Should the tube, baffels & end cap be the same material?

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Re: some one please school me on aluminum

Post by john.t.little1 » Tue Aug 19, 2014 10:29 pm

We use 7075 on a lot of our aircraft components so I would guess it'll be fine I'm not sure tho haven't done aluminum cans yet. And from what I've heard it isn't always best to use same material for threaded areas because of the potential of them "meshing", for lack of a better word, together...
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Re: some one please school me on aluminum

Post by sgms18 » Wed Aug 20, 2014 7:57 am

I figure the threads will hold up better to screwing on & off the barrel if I use stainless. If I make the blast baffel stainless will 6061 be ok for the tube & other baffels?

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Re: some one please school me on aluminum

Post by BinaryAndy » Wed Aug 20, 2014 8:34 am

There's also 7068 and a handful of other 7000 series grades that may be marginally better, but 7075 is pretty much the best you can actually find and very nearly as good as it gets without going to exotics like lithium and scandium alloys.

I would tend to keep aluminum away from high-volume, full-auto cans though. A stainless blast baffle is a good start, if you want to use aluminum for the rest I would stay away from 6061. You want 7075 for baffles and 2024 for the tube (7075 for that too if you don't mind machining it from solid, 7075 tube is hard to find). Or Ti or SS.
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sgms18
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Re: some one please school me on aluminum

Post by sgms18 » Wed Aug 20, 2014 9:26 pm

Thanks for the responses guys. So 7075 is hard to find in tube? That sucks. I got lathes but no way to bore solid stock that deep. Obviously I want my can to be as light as possible & still be strong. How much will the grade of aluminum affect the wall thickness of the tube? How (other than trial & error) will I know how thick the tube needs to be?

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Re: some one please school me on aluminum

Post by BinaryAndy » Thu Aug 21, 2014 7:51 am

Yeah, I don't think I've ever seen 7075 tube, and that does suck. 2024 is really pretty good though, just a notch down in strength. In fact, in your application it might even be a better choice; it's supposed to put up with heat a little better than 7075. That's just hearsay of course, and I don't have a good guess about the temperature at which that becomes significant. Hopefully someone who has some experience with aluminum in full-auto cans will join the discussion soon.

In any case, I doubt the differences between 2024 and 7075 are enough to require any substantial change in wall thickness. 6061 is a different story, it's roughly half as strong as 7075. And don't let me catch you putting 6063 in a silencer!
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Re: some one please school me on aluminum

Post by Capt. Link. » Thu Aug 21, 2014 11:32 am

A high volume suppressor is large is that what you wish.
A old school MK-9 knockoff using a Ti tube with SS end caps and baffles would last almost forever.
This my favorite can on a MP-5 or UZI or Mac 9mm its about 2x12" in size.
Image
Even made of anodized aluminum it would last a very long time.The large internal volume decreases the gas pressure and heat so components last a very long time.7075 and 7068 are both good choices in 9mm.The 300 should get made of better materials.
Its a great design and surprisingly light on a buzz gun!
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Re: some one please school me on aluminum

Post by sgms18 » Thu Aug 21, 2014 5:41 pm

Thanks for the picture. I need all the ideas I can get. I like the dual tube design of the mk9 & mk9k. I really don't want a can that's a foot long though. I am thinking 8 -10in. long & 2in. OD. The 300 whisper is subsonic only so am I right to think that what will hold up to 9mm will hold up to 300whisper subs? If I go w/the 2024 tube & 7075 baffels what should I be looking at for tube thickness?

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Re: some one please school me on aluminum

Post by Capt. Link. » Thu Aug 21, 2014 9:54 pm

sgms18 wrote:Thanks for the picture. I need all the ideas I can get. I like the dual tube design of the mk9 & mk9k. I really don't want a can that's a foot long though. I am thinking 8 -10in. long & 2in. OD. The 300 whisper is subsonic only so am I right to think that what will hold up to 9mm will hold up to 300whisper subs? If I go w/the 2024 tube & 7075 baffles what should I be looking at for tube thickness?
The MK-9K was 9 or 10 long with the same basic design.The space between the muzzle of the host and the first baffle makes a world of difference in longevity.Built right I think it will work well on both calibers.Unless you have a full anodizing set up I don't recommend aluminum alloy even though it has the strength.There is a hidden cost as type 3 hard-cote anodizing is really what you want and that will be very expensive.I really think that Ti and SS are better values with better wear and strength.Ti tubing is not that expensive as cuts are available in sizes needed.I think the cost of anodizing would pay for the Ti tubing and 7075 is not cheap.Hoop strength analysis will determine the best thickness of aluminum if you go that route.I could only guess wall thickness at that large a diameter.PM sent.
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Re: some one please school me on aluminum

Post by CThomas » Fri Aug 22, 2014 9:05 pm

The MK9-K was 7.0" long and 2" in D with SS baffles all else was aircraft grade aluminum but for the mounts. It is viewed as one of the best sub guns cans of the day.

The Gemtech Raptor was made entirely from 6061-T6 and 2024 and it was a great performer @9.1"L x1.4" D. I use to hammer the hell out of my Raptor on my MP5's and never an issue.

Sure if your going to do a Form 1 why not utilize materials that will last longer,SS/Ti but aircraft grade aluminum has been doing it is sub gun cans for a long time.

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Re: some one please school me on aluminum

Post by sgms18 » Sun Aug 24, 2014 11:15 pm

Would there be any issues with heat expantion using alum tube & ss baffels? Im sure the two react to heat differently. I know it has been done but I don't know if tolerance between tube id & baffel od would differ depending on material.

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Re: some one please school me on aluminum

Post by sgms18 » Sun Aug 24, 2014 11:19 pm

Also, would it be legal for me to send my suppressor parts out to have them hard coat anodized? After my approved form 1 comes back of corse.

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Re: some one please school me on aluminum

Post by Bendersquint » Mon Aug 25, 2014 1:58 am

sgms18 wrote:Also, would it be legal for me to send my suppressor parts out to have them hard coat anodized? After my approved form 1 comes back of corse.
Yes, as long as the shop you send them to is a licensed as an 07/02 manufacturer.

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Re: some one please school me on aluminum

Post by doug hall » Sun Aug 31, 2014 5:47 pm

I won't offer any advice, I'll just share with you my experience. Made a monocore baffle in 5.56 from 7068. It has about 25 percent higher tensile strength than 7075 AT ROOM TEMP! Thread attachment and baffle in a single unit with a stainless tube pinned at the base. Ten or twelve rapid fire rounds from the AR and the core had streched about a quarter inch out of the tube. The increased heat changed the tensile strength of the aluminum and it softened. Check out the maximum operating temperatures for various grades of AL and you'll find none of them that like heat. I'll never make a full auto can with aluminum. There's just too much heat.

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Re: some one please school me on aluminum

Post by Bendersquint » Sun Aug 31, 2014 6:43 pm

doug hall wrote:I won't offer any advice, I'll just share with you my experience. Made a monocore baffle in 5.56 from 7068. It has about 25 percent higher tensile strength than 7075 AT ROOM TEMP! Thread attachment and baffle in a single unit with a stainless tube pinned at the base. Ten or twelve rapid fire rounds from the AR and the core had streched about a quarter inch out of the tube. The increased heat changed the tensile strength of the aluminum and it softened. Check out the maximum operating temperatures for various grades of AL and you'll find none of them that like heat. I'll never make a full auto can with aluminum. There's just too much heat.

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Thanks for posting your real life experience.

Finally someone besides a manufacturer saying what we have been saying all along.

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Re: some one please school me on aluminum

Post by maccrazy2 » Mon Sep 01, 2014 8:46 pm

I have a bowers cac9 can on my Mac. Next time I have it out I will measure it cold and hot after a mag dump. I am curious to see if it grows much.

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Re: some one please school me on aluminum

Post by Historian » Mon Sep 01, 2014 9:21 pm

Fun WWII Factoid on 7075 Aluminum from Wiki:

"Nakajima's team considered the new requirements unachievable and pulled out of the competition in January. Mitsubishi's chief designer, Jiro Horikoshi, felt that the requirements could be met, but only if the aircraft could be made as light as possible. Every possible weight-saving measure was incorporated into the design. Most of the aircraft was built of a new top-secret 7075 aluminium alloy developed by Sumitomo Metal Industries in 1936. Called Extra Super Duralumin (ESD), it was lighter and stronger than other alloys (e.g. 24S alloy) used at the time, but was more brittle and prone to corrosion[6] which was countered with an anti-corrosion coating applied after fabrication. No armor was provided for the pilot, engine or other critical points of the aircraft, and self-sealing fuel tanks, which were becoming common at the time, were not used. This made the Zero lighter, more maneuverable, and the longest range single engine fighter of WWII; which made it capable of searching out an enemy hundreds of miles away, bringing them to battle, then returning hundreds of miles back to its base or aircraft carrier. However, that trade in weight and construction also made it prone to catching fire and exploding when struck by enemy rounds.[7]"

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Re: some one please school me on aluminum

Post by sgms18 » Tue Sep 02, 2014 5:36 pm

So I been lookin around at production cans & almost all the 9mm smg cans are aluminum. It seem like an obvious bad idea for full auto rifle but seems to be the standard for subguns. The Thompson Machine SG is even 6061. Is the heat factor that much different between 9mm & 223?

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Re: some one please school me on aluminum

Post by Bendersquint » Tue Sep 02, 2014 6:53 pm

sgms18 wrote:So I been lookin around at production cans & almost all the 9mm smg cans are aluminum. It seem like an obvious bad idea for full auto rifle but seems to be the standard for subguns. The Thompson Machine SG is even 6061. Is the heat factor that much different between 9mm & 223?
Its not just the heat its the pressure, velocity of gases. The erosion from gases on a pistol is unbelievably lower than from rifles.

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Re: some one please school me on aluminum

Post by sgms18 » Tue Sep 02, 2014 7:21 pm

That makes perfect sense.

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