Introducing the AI Obsession Chassis

[samb300]

Some of you may remember a few years ago I drew a concept for an "AIAC" competition chassis for the current AI rifle platform. Nothing ever really came from that outside of some good conversation between fellow AI fans and competition rifle shooters. That concept has been a bug in my brain since then, and a few months ago I decided to make it a reality, taking into account current design trends and the overall design language of AI rifles in general.

Shown here is the final plastic 3D printed prototype of my 100% self-designed Obsession Chassis. The next real step is to complete the drawings and get one of these machined for testing. I'm not entirely sure where I will get one machined, and I know one-offs are very expensive, but I need to test an aluminum version before I would ever consider making more and offering them to other shooters.

My path to get this functional prototype was to reverse-engineer both an AT chassis and an AX chassis. Once I put those in CAD, I 3D printed the "bottom metal" to verify the dimensions, fit and function. Then I designed my chassis around the bottom metal and arrived at what I believe is the perfect AI rifle for competition-oriented shooters.

In order to do this I had to de-bond my factory AX. Doing that really de-mystified the bonded action interface, and opened my eyes to the possibility of some cool options for the chassis. The design intent of this chassis is to be epoxied to the action - just like the factory rifles are. I think that there is some magic in the bonded action, and didn't want to shoehorn something around it like the MPA chassis does with the AT. This chassis is designed to be completely functional when bonded to the action, and the accessories are designed around it. That being said, if bonded it will only work with the current generation of rifles that have the Quick-Loc barrel change system.

The feature list is long, and I think it encompasses almost anything a match shooter would be looking for:

• Single piece of machined aluminum (either 6061-T6 or 7075-T6)
• Compatible with AT and AX short actions, ambidextrous for either RH or LH
• Compatible with either AT or AX buttstock, fixed or folder (including thumb hole skins ?)
• Uses AW magazines and AT mag catch lever (AX mag catch lever is different and will not work)
• Generously flared mag well for easy magazine insertion and removal
• 12.75" forend (measured from action face)
• Forend length ensures the user can screw/unscrew a barrel as short as 16". A longer forend is certainly possible, but would increase the minimum barrel length.
• Integrated full-length RRS-dovetail
• M-Lok standard mounting interface on sides and bottom
• Proprietary dovetail-stop screw system
• Barrel channel and accessories allow 1.25" dia. straight-taper barrel with 0.050" minimum clearance per side
• Integrated non-rotating flush cup mount on both sides.

I also designed accessories to accompany the chassis, for an integrated system.

• Bipod spigot bolts directly to chassis, and adds 3" of length in addition to being 1/2" closer to the bore-axis. Spigot has an M-Lok attachment point for easy mounting of 3 or 5-slot picatinny rail.
• Internal weight system allows the user to add up to 1.25# of weight, without interfering with the M-Lok mounts or barrel clearance.
• NV bridge allows user to wrap "thumb over bore," and has mounting points for picatinny rails or other attachments. NV bridge can be positioned front to back via the side screw holes, and the orientation of the bridge itself can be flipped depending on user preference.

I hope you guys think this design exercise has merit - I've definitely put in a lot of late (LATE) nights working on this, and I honestly feel that this has been a culmination of many of the ideas floating around in my head. I understand this chassis won't be for everyone, since many won't want to de-bond their action and even more won't want to spend additional money over the AT, which is an admittedly awesome rifle. I'll definitely keep you all posted as I pursue getting one machined. If you have any questions (or own a CNC!) let me know!

Sam
Accuracy Obsession, LLC


AI Evolution

Comparison to AT

Comparison to AX

Flared Magwell

Internal Weights and Spigot

Full build

 

[Vargmat]

Very impressive work!

 

[thaflash_la]

Indeed, most impressive. Pretty clean print too.

 

[Dthomas3523]

Make the nvg hood holes like up to accept the finger grooves add on Dave Preston builds for the MPA chassis.

 

[Dthomas3523]

Also, I’d imagine MDT might be a good place to look to help with prototype.

 

[kthomas]

Badass

 

[M338]

Nice work man!

 

[samb300]

Make the nvg hood holes like up to accept the finger grooves add on Dave Preston builds for the MPA chassis.

Maybe the holes do line up? I don’t know.

The NV bridge is still a concept, I haven’t spent the time to finalize the pic rail and look at possible accessories. As it is it works to wrap your thumb around (which is what I do with the AX forend). I can certainly design a thumb shelf for it.

A big part of my process was designing it NOT to rip off or directly use other chassis elements. Nothing against Dave, but I might not want to design my chassis to use an accessory he made for another chassis lol.

 

[PBWalsh]

Super nice to see something I know we’ve talked about before. Looks wonderful Sam, what is the weight for the new chassis as you have it?

 

[BLKWLFK9]

you are the mother fucking man. Sign me up.

 

[BLKWLFK9]

I wish i could see what would look like on an AT. Tits, im sure, but i would love to be able to envision it. I feel you hit every design feature that people want in a competition chassis. I will take a shot of whiskey in your honor this evening.

 

[schlaiek]

very, very cool work.

 

[samb300]

Super nice to see something I know we’ve talked about before. Looks wonderful Sam, what is the weight for the new chassis as you have it?

I don't have the weight on the top of my head, but I can pull it from CAD tonight when I'm home. I want to put the de-bonded AX chassis on a scale and get the actual weight as well. The AX buttstock is definitely a heavy pig!

 

[Steel head]

That’s pretty sharp!
Me likely!

 

[samb300]

I wish i could see what would look like on an AT. Tits, im sure, but i would love to be able to envision it. I feel you hit every design feature that people want in a competition chassis. I will take a shot of whiskey in your honor this evening.

Pardon my crude "photoshop" skills in MS Paint haha. It's beginning to look like the FDE version of the SCAR 17S...how many shades of green can we fit on one rifle?

 

[BLKWLFK9]

That still looks awesome. Mine is a thumb hole stock but I get the idea.

 

[trob_205]

Super Cool. I’d also be interested in weight compared to Standard AX.

 

[Tx_Aggie]

Very cool.

 

[Lowlight]

Nice job on that

 

[Kiba]

Nice work, your prototype is pretty close to what I imagined you were working on.

I also see you made a lower cheek rest for the AX buttstock to allow the use of a lower scope rail and scope mount like the AT.

 

[samb300]

Nice work, your prototype is pretty close to what I imagined you were working on.

I also see you made a lower cheek rest for the AX buttstock to allow the use of a lower scope rail and scope mount like the AT.

The low cheek piece currently on my rifle is a very rough prototype. I'll have a final test version in hand very soon that will be available through my partnership with Anarchy Outdoors.

 

[rak187]

Damn sign me up, awesome work

 

[Mute]

Awesome work! I like the concept.

 

[dmtsc]

I didn’t see anyone offer but I could be talked into being a prototype tester, I’ll sacrifice for the others. That looks awesome.

 

[BLKWLFK9]

Lol^ yeah, I'm down too.

 

[kthomas]

Something like this could almost convert me to be an AI shooter. Would just need to get rid of that horrid pistol grip...

 

[brianf]

dont take this the wrong way, i might be missing it (which isnt unusual)

ill start off by saying that you must have put a GOOD amount of hours into it

what printer and material did you use?

what are the actual benefits of the chassis, unless you have a old school AI?

same action
same bonded chassis
same butt
same mags

would you be better off creating a better fore end than the AX or AT has (lighter/adjustable weight, different lengths etc)

or do you think the whole kit will loose a few pounds in comparison

dont want to ruffle feathers, just truthful questions

 

[BLKWLFK9]

The printed version is just a model, I'm sure. He wants to do it out of 7075

 

[brianf]

The printed version is just a model, I'm sure. He wants to do it out of 7075

thanks for the reply.
i got that much, just trying to vet out the differences regardless of materials it made out of etc.

 

[Adam B]

looks great, too bad I wont debond my AX

 

[samb300]

I didn’t see anyone offer but I could be talked into being a prototype tester, I’ll sacrifice for the others. That looks awesome.

Lol^ yeah, I'm down too.

Ha, I'll let you guys know if/when I get more than one made in the first batch.

 

[Badfinger]

I knew it, I knew you were sneaking around working on that chassis! Impressive as always

 

[samb300]

dont take this the wrong way, i might be missing it (which isnt unusual)

ill start off by saying that you must have put a GOOD amount of hours into it

what printer and material did you use?

what are the actual benefits of the chassis, unless you have a old school AI?

same action
same bonded chassis
same butt
same mags

would you be better off creating a better fore end than the AX or AT has (lighter/adjustable weight, different lengths etc)

or do you think the whole kit will loose a few pounds in comparison

dont want to ruffle feathers, just truthful questions

I use a Prusa i3 MK3 printer with PLA material. This is for prototype/proof of concept purposes only. The tolerances are good enough that I can test fit all the components, and threaded holes work with screws down to M3x.5 which is pretty impressive. The action is bolted to the chassis with the intended screws and the AI brass washers, the mag catch is installed in the bottom metal, and I have function tested live ammo by cycling them through the action (not fired though). The print bed only allows ~11" max length, so this was printed in 3 pieces and dovetailed/bolted together.

The main drawback of the AT and AX platforms are how high the chassis sits on a barricade relative to the bore axis, and a lack of a continuous flat forend. The pictures with the Obsession chassis on top of the AT and AX chassis show how much taller the bottom metal is on those. There's only so much I could do with the current AT or AX forend before you realize you're completely limited by the design of the factory bottom metal. I could design a forend for the AT that's half the height, but when you put the rifle on a Gamechanger it will still sit up really high because the bottom metal is so tall. Ever try to put an AX into a short barricade porthole? Not fun, especially when you see everyone else with a Manners or MPA fit it in with no issues.

My intention was to retain the solid, purposeful feel of the AI system. I could not (in any reasonable time or cost) design a better buttstock than the AX buttsock, same with the grip skins (for now). I could get a version to work with an AR grip tang, but it's likely not going to be pretty. I wanted the AT or AX user to debond their action and buttstock, then re-bond them to this chassis and think "this is how AI should've done it." Same ergonomics, for better or worse (again, for now).

This design is in no way about losing weight. It might even be heavier than the AT and AX factory chassis, I'll have to weigh them tonight and compare to the CAD model. But running a 1.25" straight taper barrel with internal and external weights is what the current competitor wants, and that's what this gives them.

Yes, this took a lot of time and there's still a lot more to do. And I'm doubtful that I'll make any money off it unless I'm surprised by a large number of people wanting to try it out. But my hope is to continue to push AI's forward, and ultimately I'd like to align my career with work like this rather than what my 9-5 is. If that means I'm up til 2am every night for another couple months getting this thing perfect, then I'm good with that.

Sam

 

[samb300]

looks great, too bad I wont debond my AX

I know that's going to be the rub with most people. De-bonding my AX was a simple affair, after I took the buttstock off I threw the action in my oven at 250F for an hour and it peeled right apart from the chassis. Putting it back together requires a $5 tube of Devcon epoxy, nothing special there.

There's always the option of buying a used AT to try it out. I thought about it, but being LH it made it harder to find a good example, and I didn't want to spend the $4k+ on an AT and AX buttstock for testing purposes when I knew I'd need that money to get parts machined.

AI's only have a 1-year warranty anyway, so I figured why the heck not do it with the AX?

 

[Adam B]

I will go the AT route. I can tell you right now, they say 1 year but they warrantied a 1995 AIAW that broke no questions asked.

 

[samb300]

I will go the AT route. I can tell you right now, they say 1 year but they warrantied a 1995 AIAW that broke no questions asked.

Fair enough. Maybe the AI overlords are watching right now and drafting up an offer to me, so no need to worry about the warranty

 

[samb300]

Something like this could almost convert me to be an AI shooter. Would just need to get rid of that horrid pistol grip...

Do you want an AR grip tang? Or a more traditional stock interface (i.e. Manners)?

There's only so much time in the day, but this is a possibility I mentioned a couple weeks ago.

 

[brianf]

Thanks for the complete reply
Makes sense from a competition standpoint as you suggested.
You might have just made a convert.
And thanks for sharing the 3D info.

 

[kthomas]

Do you want an AR grip tang? Or a more traditional stock interface (i.e. Manners)?

There's only so much time in the day, but this is a possibility I mentioned a couple weeks ago.

View attachment 7041734

I currently use JAE's and love those. The KRG Bravo's have an excellent grip as well IMO, a bit more upright than the JAE and works with small hands like mine.

 

[Notdylan]

I currently use JAE's and love those. The KRG Bravo's have an excellent grip as well IMO, a bit more upright than the JAE and works with small hands like mine.

I'm with you, the AI grip is pretty chunky. I'm surprised no one is making smaller grip panels/inserts.

 

[MarkLeupold]

I use a Prusa i3 MK3 printer with PLA material. This is for prototype/proof of concept purposes only. The tolerances are good enough that I can test fit all the components, and threaded holes work with screws down to M3x.5 which is pretty impressive. The action is bolted to the chassis with the intended screws and the AI brass washers, the mag catch is installed in the bottom metal, and I have function tested live ammo by cycling them through the action (not fired though). The print bed only allows ~11" max length, so this was printed in 3 pieces and dovetailed/bolted together.

The main drawback of the AT and AX platforms are how high the chassis sits on a barricade relative to the bore axis, and a lack of a continuous flat forend. The pictures with the Obsession chassis on top of the AT and AX chassis show how much taller the bottom metal is on those. There's only so much I could do with the current AT or AX forend before you realize you're completely limited by the design of the factory bottom metal. I could design a forend for the AT that's half the height, but when you put the rifle on a Gamechanger it will still sit up really high because the bottom metal is so tall. Ever try to put an AX into a short barricade porthole? Not fun, especially when you see everyone else with a Manners or MPA fit it in with no issues.

My intention was to retain the solid, purposeful feel of the AI system. I could not (in any reasonable time or cost) design a better buttstock than the AX buttsock, same with the grip skins (for now). I could get a version to work with an AR grip tang, but it's likely not going to be pretty. I wanted the AT or AX user to debond their action and buttstock, then re-bond them to this chassis and think "this is how AI should've done it." Same ergonomics, for better or worse (again, for now).

This design is in no way about losing weight. It might even be heavier than the AT and AX factory chassis, I'll have to weigh them tonight and compare to the CAD model. But running a 1.25" straight taper barrel with internal and external weights is what the current competitor wants, and that's what this gives them.

Yes, this took a lot of time and there's still a lot more to do. And I'm doubtful that I'll make any money off it unless I'm surprised by a large number of people wanting to try it out. But my hope is to continue to push AI's forward, and ultimately I'd like to align my career with work like this rather than what my 9-5 is. If that means I'm up til 2am every night for another couple months getting this thing perfect, then I'm good with that.

Sam

Prusa Mk3 for the win! I've been very satisfied with the one I've gotten to work with this semester designing my own AICS DBM system.

I'm not an AI owner, but this is what I would want if I was. Great looking work!

On a side note, what filament brand are you using and have you been noticing any thermal expansion/contraction from your material? Been trying to solve some slight print issues on mine and improve print accuracy.

 

[samb300]

Prusa Mk3 for the win! I've been very satisfied with the one I've gotten to work with this semester designing my own AICS DBM system.

I'm not an AI owner, but this is what I would want if I was. Great looking work!

On a side note, what filament brand are you using and have you been noticing any thermal expansion/contraction from your material? Been trying to solve some slight print issues on mine and improve print accuracy.

I've been using the MatterHackers Pro series PLA and really like it. Not sure if it's worth the 2x price premium over their standard PLA, but the green was only in stock in the Pro series when I ordered.

I've also done some more functional prints in the Prusament PETG, and those turned out OK. I haven't really had any expansion or shift issues, but the machine is really new (I've only had it for 2 months).

 

[tsu45]

Curious on what ballpark you think the cost would be on a metal prototype? Anything that can’t be hit with a 3D scan?

 

[samb300]

Curious on what ballpark you think the cost would be on a metal prototype? Anything that can’t be hit with a 3D scan?

I have a ballpark based on some rough quotes from the online CNC "hubs" that offer one-off machining, but I'm not sure how accurate those are because it's just giving numbers from an algorithm. My guess is one chassis with the accessories is going to cost as much as a really nice optic or rifle build. There isn't really anything about it that's not manufactureable, and my background in tool design lends me to think with real life manufacturing in mind. That being said, I have no experience with machining so I can't exactly say if my design is "easy" or not to fixture and machine.

 

[samb300]

For those of you interested in weights, here they are. All are without a buttstock attached. The Obsession Chassis numbers are from CAD, the AT and AX were weighed on a food scale.

• Obsession Chassis (bare) = 30.2 oz
• Obsession Chassis w/spigot and NV bridge = 34.6 oz
• Obsession interior weight kit = 22.9 oz

- AT chassis (no plastic skins) = 28.2 oz
--- I'm not sure how much the forend skins would weigh...another few ounces?

- AX chassis w/RRS auxiliary plate and top picatinny forend rail = 40.6 oz

They are very close in weight, the difference would be when you add a bolt-on full-length RRS forend rail to the AT and AX, or you add the factory NV bridge and metal side panels to the AT. Getting the functionality of the Obsession chassis with the AT or AX will require additional accessories.

 

[Ccollins02]

Nice job on that, impressive work! That has some real potential for the AI guys...

 

[morganlamprecht]

awesome work on that

 

[PBWalsh]

@samb300

The AT skins (total) are approximately 6-8 oz. The AT NV unit is about 7ish oz. as well. So it is about 45-50 oz. according to your number plus skins and NV unit. The pistol grip rear skin is about 1 oz LESS than the thumbhole, but 100% less sexy as well.

Is your posted weight WITH the AX rear portion or without?

Did you happen to weigh the bare action before assembly?

The “bottom metal” you machined, any chance you think it could be fitted to a MCS/MCM stock or is it too large in some dimension?

 

[samb300]

@samb300

The AT skins (total) are approximately 6-8 oz. The AT NV unit is about 7ish oz. as well. So it is about 45-50 oz. according to your number plus skins and NV unit. The pistol grip rear skin is about 1 oz LESS than the thumbhole, but 100% less sexy as well.

Is your posted weight WITH the AX rear portion or without?

Did you happen to weigh the bare action before assembly?

The “bottom metal” you machined, any chance you think it could be fitted to a MCS/MCM stock or is it too large in some dimension?

All the weights above are the bare chassis WITHOUT the AX buttstock. I can unbolt it all and get weights of the AX buttstock and action by themselves tonight.

As for getting the bottom metal to work in a traditional stock, I’m definitely no expert there. I have the AT bottom metal measured and in CAD, so if there was a way to make it work I have the ability to modify it accordingly. I know from a different thread about putting an AE action in a stock that @morganlamprecht mentioned someone was already working on the AT bottom metal. Not sure if that project is still going but I could certainly help if needed.

 

[morganlamprecht]

still in the works far as i know