Gunsmithing AICS recoil lug slot; why can't I go deeper?

[glock24]

I'm preparing for the arrival of my new AICS stock by outlining the mods I'll have to make so it accepts my Stiller TAC30 action.

I've been reading that the recoil lug area will need to opened up (front wall) around 0.070" to accept my thicker recoil lug. Fair enough.

I'm also reading however that the bottom of the recoil lug itself will need to be shortened by about 0.050" to fit the depth of the chassis.

My question is, why can't I simply mill the recoil lug slot deeper at the same time I'm making it wider?

I've never seen one disassembled up close, but I found this picture thanks to <span style="font-weight: bold">03rangerxlt</span> over on ARFcom.

Thanks

 

[9H_Cracka]

Re: AICS recoil lug slot; why can't I go deeper?

Because the mfr said not to. Have the smith machine down the bottom of the over-sized lug instead. You still have to machine the slot wider for most oversized lugs to fit, so both need machined with a mill.

 

[glock24]

Re: AICS recoil lug slot; why can't I go deeper?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: NineHotel</div><div class="ubbcode-body">Because the mfr said not to. Have the smith machine down the bottom of the over-sized lug instead. You still have to machine the slot wider for most oversized lugs to fit, so both need machined with a mill. </div></div>

Interesting. Thanks.

Can you elaborate on the manufacturer's warning? Are we talking integrity problems?

 

[9H_Cracka]

Re: AICS recoil lug slot; why can't I go deeper?

Sure. I called them on the phone and asked and they told me not to do it. That is as elaborate as I need.

 

[glock24]

Re: AICS recoil lug slot; why can't I go deeper?

Thanks again.

And I assume at the time you also explained to them that you'd be opening up the front wall of the chassis? And they were okay with that modification?

I'm sorry if it sounds like I'm second guessing you or the manufacturer. I'm really not. I have just dealt with enough OEMs to know that the "don't modify our product" line is the easiest answer over the telephone.

Assuming there is a good reason, I still appreciate the info. This means that enough care should be taken when widening the slot to keep the end-mill from even touching the bottom of the recessed area.

One can see from this angle that the recoil slot is somewhat of a "hinge point" for the entire chassis. Maybe they're worried about someone going too deep and the stock cracking in half!

 

[300sniper]

Re: AICS recoil lug slot; why can't I go deeper?

take a look at the picture you just posted. if you go deeper, you have significantly lessened the amount of material connection the front of the chassis to the rear. i did deepen mine a little bit and also removed some of the recoil lug on my first one. the more i thought about it, the more removing material from the recoil lug only made sense. now i remove material from the front of the chassis and the bottom of the recoil lug.

 

[glock24]

Re: AICS recoil lug slot; why can't I go deeper?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300sniper</div><div class="ubbcode-body">take a look at the picture you just posted. if you go deeper, you have significantly lessened the amount of material connection the front of the chassis to the rear. i did deepen mine a little bit and also removed some of the recoil lug on my first one. the more i thought about it, the more removing material from the recoil lug only made sense. now i remove material from the front of the chassis and the bottom of the recoil lug. </div></div>

I understand, but 0.050" deeper? Damn! It sure seems like it wouldn't hurt anything.

<span style="font-style: italic">(How many times have you heard that one?!)</span>

And yes, I'm trying to be cheap and lazy. It will be less expensive and faster if the 'smith only has to perform one setup on the mill for the chassis compared to one setup for the chassis and one for the barreled action.

Thanks for you insight.

 

[300sniper]

Re: AICS recoil lug slot; why can't I go deeper?

it shouldn't take more than 10 minutes to set up the barreled action some vee blocks and mill the bottom of the recoil lug.

yes it is only .050". if you are cheap and lazy and willing to deal with the consequences if it does fail, then go ahead and give it a run. i probably deepened my first one about that much and it has not failed. that does not mean i will recommend someone else do it that way as i know it is not the best method. i will not do mine or anyone else's that way again.

 

[Don Black]

Re: AICS recoil lug slot; why can't I go deeper?

The old axiom of "modifying the least expensive part" has always made sense to me.
I'd hazard a guess that the recoil lug would more'n likely fit that criteria.

 

[9H_Cracka]

Re: AICS recoil lug slot; why can't I go deeper?

You need clearance under the lug, so you'll go deeper.

On the width of the cutout, we cut front and back as I was going to bed the rifle in the stock and wanted more bedding compound on the back side of the lug than just a skim coat for durability.

 

[JRose]

Re: AICS recoil lug slot; why can't I go deeper?

I carved mine out with a Dremel b/c I don't have a mil, and had to make the Cup...

 

[Hateca]

Re: AICS recoil lug slot; why can't I go deeper?

Cut a $30 lug or a $900 stock, I'll cut the lug. There's really no reason all those aftermarket lugs need to be that long anyway.

Honestly it would probably never have any problem cutting the stock deeper within reason but there is always that one time that it ends up in the trash. Cutting the lug shorter just makes more sense to me anyway.

 

[RADcustom]

Re: AICS recoil lug slot; why can't I go deeper?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: HateCA</div><div class="ubbcode-body"> There's really no reason all those aftermarket lugs need to be that long anyway.

</div></div>

...or wide either for that matter

 

[Wild_Bill]

Re: AICS recoil lug slot; why can't I go deeper?

hi the reason not to cut the lug deeper is because if you relieve the lug more the stock might close up at the top as is usual if you cut a slot through an alloy square bar.

I make up lots of bedding blocks to use a recoild spiggot on rifles and when prople want to make a block for a rifle with an integral recoil lug and have a spiggot fitted we cut a slot for the recoil lug to free float in and then re cut the top surface because the cutout will close slightly at the top and also the deeper you go the strength can be comprimised. if you are using sompthing smaller than a magnum calibre the remington recoil lugs that have been surface ground are fine we have had the standard recoil lugs crack with large calibres like ultramags so a thicker one is better in those applications.

Just have 50 thou milled off the lug and widen the front only.

 

[DAVETOOLEY]

Re: AICS recoil lug slot; why can't I go deeper?

I had this discussion with AI this week and they are going to address the width of the slot. Bottom line is if any mods are done the warranty is voided. Also I've never felt like my shoulder, even 20 years ago, was strong enough to flex a standard lug under recoil.

 

[SpotcheckBilly]

Re: AICS recoil lug slot; why can't I go deeper?

If you're gonna have the lug mortise milled in an AICS follow the advice given by Accuracy International.

But one question comes to mind. If you're using a Stiller TAC action why are you going to an oversize recoil lug anyway? The recoil lug that Stiller supplies with these actions has standard M700 dimensions and fits the AICS mortise with no modifications. This is not speculation. BTDT!

 

[300sniper]

Re: AICS recoil lug slot; why can't I go deeper?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SpotcheckBilly</div><div class="ubbcode-body">If you're gonna have the lug mortise milled in an AICS follow the advice given by Accuracy International.

But one question comes to mind. If you're using a Stiller TAC action why are you going to an oversize recoil lug anyway? The recoil lug that Stiller supplies with these actions has standard M700 dimensions and fits the AICS mortise with no modifications. This is not speculation. BTDT! </div></div>


stiller also offers a .300" recoil lug with their tac series actions. btdt a few times. it sounds like the op already has the barreled action in this configuration so changing recoil lugs is not a valid option at this point.

even with a barreled action, it shouldn't take more than a few minutes to machine the bottom of the lug to a height that will work with the aics.

 

[Shady_Jay]

Re: AICS recoil lug slot; why can't I go deeper?

I milled mine out for my Surgeon and then fully bedded the lug. I have had no issues over 2 years and a lot of heavy use.

 

[glock24]

Re: AICS recoil lug slot; why can't I go deeper?

Gents,

I appreciate all the feedback and advice. I guess I'm still just wrestling with the fact that I already have to mill on my AICS chassis, why not go one last step and make a 0.050" cut at the bottom of the lug? And for the record, not only do I have to mill the slot wider for the 0.300" lug, but I also have to cut room for my Jewel trigger. I'm told it won't fit in the current condition. And I believe it because I had the same problem with a Jewell and my Manners stock. And if the AI warranty gets voided due to this work, then it won't matter if I cut the recoil lug slot deeper . . .


300sniper is right, my completed barreled action already has this 0.300" lug installed, and it already has some nicely finished metal. I'm not overly anxious about letting someone set it up on V-blocks and torque it into a vise. Yes, I know a good gunsmith can do it, but if I'm only working on the chassis, my options just increased tenfold. Hell, I could take the chassis to work and buy a machinist lunch for performing the work for me. I certainly can't to that with the barreled action!

Again, I appreciate all the info. This is why I'm asking the questions first. I appreciate doing things "the right way", but I'm also open to alternative solutions if they appear logical.

Besides, I'm sure some of you will enjoy giving me the "I told you so" line when I screw it up!

 

[bigwheeler]

Re: AICS recoil lug slot; why can't I go deeper?

I would just mill the chassis. Looking at the photo it doesn't appear there is a lot of force put on the forearm ahead of the lug. Ask aics if they can give you the load specs
on the front and how they arrived at the amount and shape of the material they left
there. It's not something I would have paid an engineer to cal out. And in the industries I worked in we re-engineered a lot of stuff in the field to make it work
anyway. Paper and numbers only go so far. I would take heed on the warning
of the slot closing up as it means the front of the chassis has to lift a bit.

 

[BLANKSGUNS]

Re: AICS recoil lug slot; why can't I go deeper?

Ok, from the manufacture stand point:
1. DO NOT mill or remove any material from the bottom or rear of the recoil lug access area.
2. When installing larger recoil lugs than the factory, removal of material on the FRONT side only, of the recoil lug channel is acceptable, will void your warranty and this is your decision.
3. All larger recoil lugs, after market and custom, are thicker and deeper due to working with composite and fiberglass designed stocks providing essentially more surface space and contact point for obvious reasons. There is no need for this on the AICS due to material and structural design.

Note to glock24: You asked the question, members here have provided you with excellent feedback but you continue to disregard and argue with each warning and recommendation. Do as you wish, no one is wanting to say “I told you so”, see you purposely damage or degrade safety of any product I assure you. We are simply providing you with the information requested, but your decision seems to be made, so best wishes. If you have any further questions feel free to contact me directly.