Sporter upper and lower from Polymer or similar material?

[G.Mitchell]

This is a LONG shot I know but here goes.

Any chance ATRS might make a plastic upper and lower specifically for rimfire builds?

I really would like to build a dedicated rimfire trainer and was thinking a polymer or similar upper and lower might be less expensive and complicated to make?

I know you all are swamped but thought I’d see what you thought just the same.

[Aniest]

Just my opinion from my research on the polymer AR15 lowers...

The polymer really needs certain points to be embedded with aluminum blocks, almost like a "sub-frame" inside the polymer. On the AR15 lower the pin locations, magwell and definitely the buffer tube threads become weak spots that need aluminum. I could see an upper needing aluminum in the barrel thread, take-down pins and some other areas. You just have to look at, was it OMNI? that ended up putting the aluminum into their 2nd Gen lowers due to issues in the full polymer Gen 1 lowers. Lots of my research seemed to point to people saying not to use full polymer AR-15 lowers on any cartridge larger than .22LR, but not to buy them because they could be made into .223 / 5.56 / 300 BLK / 50 Beo / etc. Again, just a "majority" opinion.

So if they need to make special jigs and such to embed the aluminum into the polymer, why not just make a dedicated full aluminum .22LR and/or pistol caliber set instead? Would you buy an aluminum upper and lower set with barrel attached if it was a good price?

Overall, polymer sounds great but when you are producing small numbers the machining and jigs needed becomes expensive. Might be better to use the machining they have to make a modified full aluminum... but that's just my opinion. ATRS can weigh in...

[G.Mitchell]

Just my opinion from my research on the polymer AR15 lowers...

The polymer really needs certain points to be embedded with aluminum blocks, almost like a "sub-frame" inside the polymer. On the AR15 lower the pin locations, magwell and definitely the buffer tube threads become weak spots that need aluminum. I could see an upper needing aluminum in the barrel thread, take-down pins and some other areas. You just have to look at, was it OMNI? that ended up putting the aluminum into their 2nd Gen lowers due to issues in the full polymer Gen 1 lowers. Lots of my research seemed to point to people saying not to use full polymer AR-15 lowers on any cartridge larger than .22LR, but not to buy them because they could be made into .223 / 5.56 / 300 BLK / 50 Beo / etc. Again, just a "majority" opinion.

So if they need to make special jigs and such to embed the aluminum into the polymer, why not just make a dedicated full aluminum .22LR and/or pistol caliber set instead? Would you buy an aluminum upper and lower set with barrel attached if it was a good price?

Overall, polymer sounds great but when you are producing small numbers the machining and jigs needed becomes expensive. Might be better to use the machining they have to make a modified full aluminum... but that's just my opinion. ATRS can weigh in...

All great points! Thank you for the well thought out reply.

I’ll be building a couple ATRS Sporters just was wondering if a less costly option might be possible for a dedicated rimfire build.

[shredon]

If you want to pay the $300 grand for the molds i'm sure they will build you a couple sets for free!

[biologic]

If you want to pay the $300 grand for the molds i'm sure they will build you a couple sets for free!

Thats ridiculous molds for plastic is in the tens not hundred of thousands

[Shorerider]

3D printer. You can print with some very exotic materials and you could leave space where you could epoxy aluminum into the plastic after its finished printing. If it was a dedicated 22lr lower you wouldn’t need to worry about buffer threads as the buffer tube is just for the stock at that point and shouldn’t have any load from firing. The barrel interface would be a very tricky part. You’d likely have to print the upper over a thin walled aluminum piece that was part of the barrel threads and gave the bolt somewhere to ride without chewing up the plastic. Best bet would be keep the existing upper and just print a poly lower.

[alberta tactical rifle]

Thats ridiculous molds for plastic is in the tens not hundred of thousands

True but the injection molding machines we lack DO cost a small ton of cash. I have not priced 1 out but can't see 1 being much different from purchasing another milling machine.

OP Not likely as we are a machine shop 1st and foremost, injection molding is a totally different thing.

[matm]

3D printer. You can print with some very exotic materials and you could leave space where you could epoxy aluminum into the plastic after its finished printing. If it was a dedicated 22lr lower you wouldn’t need to worry about buffer threads as the buffer tube is just for the stock at that point and shouldn’t have any load from firing. The barrel interface would be a very tricky part. You’d likely have to print the upper over a thin walled aluminum piece that was part of the barrel threads and gave the bolt somewhere to ride without chewing up the plastic. Best bet would be keep the existing upper and just print a poly lower.

3d printers are a really cool way to make certain gun parts. I'm working with my dad on a custom chassis for a rem 600 that takes AR mags. If you use a good strong material like a carbon fiber impregnated plastic it takes a beating and costs next to nothing (after printer of course) Its easier for bolt actions, the barrel interface would be an issue for sure though.

[G.Mitchell]

True but the injection molding machines we lack DO cost a small ton of cash. I have not priced 1 out but can't see 1 being much different from purchasing another milling machine.

OP Not likely as we are a machine shop 1st and foremost, injection molding is a totally different thing.

Thanks for your reply, guess I’ll just need another upper/lower for a dedicated rimfire build.