carrier slot milling ?

[roland3]

does the slot that gets milled in the bottom of the carrier for the semi auto conversion,match the slot that is in the bottom of the bolt? I saw the diagram on the tutorial, but there is no dimensions.

[hulygan]

read that a little closer but i believe that you don't need to cut the slot in there. Plz someone correct me if i am wrong.

[Teyvareb]

That slot is cut into the carrier to prevent the FA FCG from being used with that carrier. If you've already got a SA FCG, you don't need to make that cut. The shelf welded on behind the magwell is what's supposed to prevent you from using the FA FCG, so that's the real safety.

To clarify, whether it's there or not, the function will not change, as long as you have a semi-auto control group.

[DAA1]

Is just another compliance related issue to keep folks from getting any ideas. It makes it impossible to trip the sear if it were to somehow get installed by an accident. It is not worth messing with a trigger pack to make any other mods then converting to semi. slot is about as wide as the existing slot in the carrier, does not have to be perfect, and can be as wide as the other slot.

YMMV and the above is provided soley as guide, subject to correction by those more knowledgeable.

[roland3]

I understand what the slot does, i just thought it was a ATF reguirement to be compliant in case someone did put in a FA trigger pack. I already made all the mods to the trigger pack parts and put the shelf in the trigger cage. i have the shelf made to go in to the trigger housing, just waiting for the reciever to get here to fit it in the right spot.

[DAA1]

Roland,
We will have to see what the more experienced folks have to say. My guess is that it may not be a "by law" requirement but may have something to do with how Century got the approval to make these. They may have included the carrier slot as a "demil" of the FA parts. Cutting the slot would make the carrier a semi only part that could not be used in a FA cetme.

The slot is a cheap way of "demilitarizing" the carrier. The bolt on the sten gun kits comes to mind, as they have to be completely reworked so as not to function in a FA sten.

[rustypirate]

Not to be contrary here, but a properly converted semi-auto receiver cannot accept a full auto FCG. It will not fit.

The slot in the bottom of the bolt carrier prevents you from running the rifle in full auto even with a registered sear. This is not really a semi auto conversion compliance issue.

Also the bolts in the Sten have to be reworked because the RECEIVER must be modified to no longer accept the full auto bolt, not the other way around.

[Perro]

it most definately IS a compliance issue in my opinion, and needs to be done unless you have an autosear - why??

when these firearms were sent to tech branch for approval as a semi auto, these features were required back then. Do you really think HK was going to take the time to mill those slots out of there bolt carriers if the atf didnt require it?

the semi auto approval includes milling that slot - show me even an opinion letter from the atf stating that that slot is not needed, and ill change my mind.

now, WHY would they require that slot if the shelf blocks the parts?? Cause it takes anybody with a dremmel tool and a fiber cutoff tool 5 minutes to take a full auto fire control group and notch the front of it to fit over the top of the shelf built into the receiver on the back of the magazine well - you just utilize a grip frame that doesnt have the compliance shelf welded into it, and notch the front of the pack, and whalla, you have an illegal FA MG

adding that slot in the carrier removes the spot on the carrier that trips the full auto safety sear dropping the hammer again for full auto fire.

of course, you could just swap in a new carrier and youre restored again, but thats not the point

the point is that you cannot be "readily restorable to a machine gun"
the GREY area of that phrase is what is readily restorable?? It has never been officially defined by the .gov
one thing is for sure - 5 minutes with a dremmel tool is beyond readily restorable

your mileage may vary - my opinions only which doesnt mean im correct



Mike

[rustypirate]

I deferr to your wisdom.......

[Teyvareb]

I just realized noone answered the original question. Oops.

On mine, it's about 1/4 to 3/8 inch taken out starting at the inside of that groove. Just make sure everything's in line with the flat of it.

[Perro]

first off
century arms didnt invent this conversion

Heckler and Koch invented this conversion when they first started importing HK41s as semi autos into the US

Mars equipement corporation imported semi auto cetmes in the 60s from Spain that had that same exact slot milled as the HK41s

Century just copied what HK already had approved

In the beginning HK could have pin on grip frames - the atf came back and said that having a pin on grip frame made it a machine gun so they had to change that part of there design to the shelf system you see to this date.

One thing you will find on ALL ATF approval letters no matter which gun it came from is that if ANYTHING is changed on the design, it must be resubmitted to tech branch for reclassification. To my knowledge, nobody has ever re submitted an HK, or CETME with that slot NOT cut, so TECHNICALLY speaking, you really must have that slot cut if youre manufacturing things or you can get into hot water.

Being a civilian, no ATF approval is needed for any firearm you build, but im here to tell you, its not worth it not to cut that slot.
If your gun is spot on built EXACTLY the same as an already approved firearm, then you have no problems cause you can say "well, you approved HK for this, why are you not approving me?" and you have a case.

If you dont have something already approved, and they take it, and they WANT to get you for something, they are going to get you and there aint nothing you can do about it, and you have no insurance policy to fall back on cause you cant say "well, thats how HK did theres, and they are approved as semi auto"

See what im saying?

its a judgement call - everyone is big enough here to make up there own minds on how to handle it. If you dont think its a problem, then dont mill the slot. If you prefer to take 10 minutes to cut it for an insurance policy, then you have a few things the other guy doesnt have
#1 piece of mind that its right
#2 the ability to compare your gun thats identical to an already approved semi auto design.


im not saying im right, or that anyone else is wrong
im saying these are my opinions which doesnt mean im correct.


about the slot
its made on a mill with a 3/16 end mill, and you are removing the area that trips the auto sear. The cut is made in the z axis to the height of the existing carrier.
If you have your carrier indexed on your X axis so that the tube faces the right of the tables travel, and the back end of the carrier faces the left, then it is cut flush with the raised island in the center of the carrier. you only need to remove the area that the safety sear rides in.

USE CARBIDE END MILLS!!! THE CARRIER IS HARD

[roland3]

I have a feeling it needs to be there also, if anybody could give me some more accurate dimensions that would be great. my original question was. is the slot that is getting added. a continuation of that slot that is in the bottom of the bolt head, I already cut my auto sear down to use as a spacer bushing on the trigger pin, so I cant use that for a location guage. if not no big deal I can figure out where to put it after the gun is more together.
Also what spring are they talking about that needs to be rebent? I mad a minor adjustment to the trigger spring and got it back in hooked under the hammer after my shelf was added. not sure what that spring that the tutorial diagram was refering to.

[Perro]

it doesnt have to be precise
these should help

and Roland, do you go by the moniker of lucky on other firearm forums?

[Perro]

one more thing
if its a CETME you are building, than the photo below shows you which spring

if its a g3 you are building, refer to gunplumbers website in his notes section
arizoneresponsesystems.com or something along them lines

[Arizona Ranger]

I believe the spring being referred to is on this photo. This is a G3 trigger pack and no spring bending is required for the CETME. Do not follow this diagram for the CETME.

[roland3]

got it thanks. and no I only go by the name I have here on this forum. the only other forum i go on is ar15.com. yes it is a cetme im doing. and ya the spring i bent a little and got it to fit. one more ?
modifing the trigger housing to go on the reciever. I understatnd you can either mill it out so it slides on or cut the tabs that stick out with the throug hole off? is that correct and what is the most popular way of doing it? I dont have the reciever yet so maybe it will be more clear when I get it.
also while were at it, the 1/8 dowel they say to weld in the trigger cage, from what i can see it will do nothing, is this also somehting to prevent fA parts from going in?

[rustypirate]

The dowel in the triger cage is only for the G3 trigger pack conversion and it prevents the trigger travelling into the full auto position.

[MWDG3]

Both of these at one time were in my possession. The left is from an SW3(Special Weapons) and the right an aluminum SAR8.

http://mwdg3.homestead.com/files/G3_91_carriers.jpg

[ocharry]

Hi Arizona Ranger, do you think you could e-mail me a copy of that print or picture? I'm building a G3 and it would be helpful to have some dimensions to do the mods to the parts that get it.

Or could you direct me to a place to get the details for a build, with prints or pictures of what needs to be changed?

I knew about bending the spring and cutting the cage for the FCG, but i never heard of the slot in the bolt. Thanks

ocharry:newbie: