Barrel pin location challenge.

[drine]

I removed a trunnion from an extra front stub I bought for other parts. I have my ruined Spanish barrel sitting here so I decide to see up close how these things go together.
On my CAI CETME, the Spanish barrel pin slot was no good. About 1/8 or so short leaving the barrel face well inside the trunnion. This barrel I gaulded(see previous posts) so it slips fairly easy into a trunnion.
So I have this newly harvested trunnion sitting here and I decide to see how close it is. Well I can't measure bolt gap obviously but lining up the slot leaves the barrel ever so slightly out of the trunnion. I'd bet it would close enough.
The point is there must be different trunnions. I used the old piece to measue my receiver with to find the pin holes and I drilled a hole into oblivion, the hollow space between the ends.
I can lay this trunnion next to my receiver and there is obviously differences in location.
I see now why some folks can and have pinned using the slot provided. I guess I'm challenging the notion that the NEW BARRELS provided with kits now are slotted wrong. Maybe right for some trunnions and not for others.
Hey I LEARNT some'in on my own!:lol2:

[tomoshenko]

I removed a trunnion from an extra front stub I bought for other parts. I have my ruined Spanish barrel sitting here so I decide to see up close how these things go together.
On my CAI CETME, the Spanish barrel pin slot was no good. About 1/8 or so short leaving the barrel face well inside the trunnion. This barrel I gaulded(see previous posts) so it slips fairly easy into a trunnion.
So I have this newly harvested trunnion sitting here and I decide to see how close it is. Well I can't measure bolt gap obviously but lining up the slot leaves the barrel ever so slightly out of the trunnion. I'd bet it would close enough.
The point is there must be different trunnions. I used the old piece to measue my receiver with to find the pin holes and I drilled a hole into oblivion, the hollow space between the ends.
I can lay this trunnion next to my receiver and there is obviously differences in location.
I see now why some folks can and have pinned using the slot provided. I guess I'm challenging the notion that the NEW BARRELS provided with kits now are slotted wrong. Maybe right for some trunnions and not for others.
Hey I LEARNT some'in on my own!:lol2:
drine,

I read your post and it sure enforces what else I've read on the subject.
There used to be a post with pictures that Mike put up that showed the X and Y coordinates for locating the barrel pin on an undrilled CAI receiver.
Subsequent to that post, a builder reported that when he finally located his
barrel pin "they weren't any where near" those posted by Mike.

Sounds like not all trunnions are created equal...

Is there a surefire way to acurately locate the pin? X-ray maybe, like they do on critical welds?

I hate to think that the only way is to start doing exploratory drilling....

[SSwee]

The dimensions Mike posted were from an uninstalled trunnion. The differences people get are from the differences in the receivers. The different types and manufacturers. The depths of the trunnions installed can be different from one gun to the next. I'd be willing to bet that if measurements were referenced off the trunnion instead of the receiver, the pin hole would be within a few thousandths each time.
SS

[tomoshenko]

The dimensions Mike posted were from an uninstalled trunnion. The differences people get are from the differences in the receivers. The different types and manufacturers. The depths of the trunnions installed can be different from one gun to the next. I'd be willing to bet that if measurements were referenced off the trunnion instead of the receiver, the pin hole would be within a few thousandths each time.
SS
Yes, but then how do you explain drines's comparison?

[Perro]

the measurements i took were from a CNC mill with a mitutoyo dial indicator mounted to it to confirm true measurement.

it was taken off of a trunnion that was not installed into a receiver.

i know the measurement from the front of the trunnion is right - it was sloppily clamped down in a hurry to get the bottom measurement so im not 100% positive that measurement was dead nuts correct, but close enough for sure.

ive never sat and compared trunnions - that measurement was asked for, so i took a barreled trunnion and clamped it to the table of the mill

indexed zero to the front of the trunnion and jogged over till an end mill fit over the top of the pin good to go from eyesight. compared the reading on the computer to the dial indicator, and then posted the information.

if there are different trunnions where pin holes are in different spots, that might explain alot of things including why someone couldnt find there pin hole off of my measurements, but ive never sat and compared a pile of trunnions to each other, so i cant say for sure

that is why i posted all the disclaimers that it was just a guide, and could be off - your mileage may vary, etc etc

thats why i also hate posting that information cause if your parts are different than mine and you ruin your stuff, im the Mother Fer


Mike

[SSwee]

It was my understanding that on drine's post the barrel pin groove location was what was in question. I have three bare trunnions from different sources all identical. This is not to say that there may not be some with a different design. Just for curiousities sake, here is a pic of the style I have. The diameter with the pin hole in it is approx. .462" wide with .175" straight knurl on the outer edge. This doesn't leave much room for variation in the hole positioning. Does anyone have a trunnion that is very different?
SS

[tomoshenko]

the measurements i took were from a CNC mill with a mitutoyo dial indicator mounted to it to confirm true measurement.

it was taken off of a trunnion that was not installed into a receiver.

i know the measurement from the front of the trunnion is right - it was sloppily clamped down in a hurry to get the bottom measurement so im not 100% positive that measurement was dead nuts correct, but close enough for sure.

ive never sat and compared trunnions - that measurement was asked for, so i took a barreled trunnion and clamped it to the table of the mill

indexed zero to the front of the trunnion and jogged over till an end mill fit over the top of the pin good to go from eyesight. compared the reading on the computer to the dial indicator, and then posted the information.

if there are different trunnions where pin holes are in different spots, that might explain alot of things including why someone couldnt find there pin hole off of my measurements, but ive never sat and compared a pile of trunnions to each other, so i cant say for sure

that is why i posted all the disclaimers that it was just a guide, and could be off - your mileage may vary, etc etc

thats why i also hate posting that information cause if your parts are different than mine and you ruin your stuff, im the Mother Fer


Mike
Mike,
I think you have long, long, long passed from being regarded as a misinforming M-Fer!
I know you have always qualified your posts.
I think this discussion is geared only to rebuilding the lost body of knowledge
on pin location and everyone is aware of the caveats...
I didn't mean to point fingers at anyone.

[jfowl31]

Drine, if you pressed a barrel into the bare trunnion, and were able to pin it in that spot, then you CAN measure bolt gap. It wont necessarily be all that easy, but you can do it, and just try to get it as steady as possible.

If you have apicture of the other trunnion to compare it to SS's, maybe it could shed some light on it all.

I guess there could have been 2 different types.... was there a different trunnion utilized for the modelo B?

what model is the one that you stripped that trunnion from? The cocking tube has thinner lines, and the front sight isnt just plain on the modelo B...

Ill see if I can find some up close pics of my Cetme, as its built on a Model B unissued parts kit.

[Perro]

I guess there could have been 2 different types.... was there a different trunnion utilized for the modelo B?
not to my knowledge - i have a complete modelo B and its the same from what i can tell


what model is the one that you stripped that trunnion from? The cocking tube has thinner lines, and the front sight isnt just plain on the modelo B...
the modelo B had the standard large rib cocking tube - so did the model C
the model 1969 C cetme had the small rib cocking tube with the cast triple frame


Ill see if I can find some up close pics of my Cetme, as its built on a Model B unissued parts kit.
your cetme was one of the select 500 special edition ones if i recall correctly - if thats the case, those were not built on model b kits
those were built on modelo 69C kits

[jfowl31]

hmmmmm... I coulda sworn you told me a while back that it was a B kit... Ill take your word for it Perro. Thats all I thought I was doing before. lol.

So whats the difference between the normal C and 69 C?

[Perro]

i told you before you had a 69c kit as well - thats how i remember you having one of the special 500 edition cetmes

the model B has a standard large rib cocking tube - the cocking tube is 100% exactly like the large rib cetme C cocking tubes - stamped on the same machinery im sure. The only difference is that the end of the model B tube is made to accept a carry handle swivel where there is no provision for this on the C
the B also has a triple frame that has mill cuts on the top ring, and its slotted hollow on each side of the triple frame to allow light in to the front sight post
the model B uses a different fire control box - ejector spring in back instead of side.
it uses a Y style safety sear - totally different trigger components
it uses a different lower receiver with the safety selector on the right
it uses 2 piece pistol grips
instead of the left - safety selector is different as well.
it uses a different buttstock housing
different buttstock
different buttpad
metal clamp on handguard, and attached bipod
different flash hider
and slightly different receiver.
milled bolt carrier instead of the tube being welded on - the carrier also has lightening cuts for the csp-003 ammunition
im sure im leaving some out


the standard model C cetme has large rib cocking tube without provision to accept carry handle. It also has a milled triple frame with no slots cut into the side of it, and it is not cast.
it uses an improved flash hider
wood hand guard
clamp on bipod that fits on the grenade rings
new buttstock housing shaped more like HKs
new buttstock style
new thicker butt pad
new lower receiver with selector on left side
new selector lever that is angled to help change positions
1 piece pistol grip
most of the early Cs have the modelo B style fire control box, but they were all updated with the trigger improvements of the 69c.
the trigger set improvements of the 69C allowed you to cock the rifle on safe and not damage anything - the old style trigger parts had a problem breaking parts if you tried cocking it on safe. This doesnt mean it was able to cock on safe, just that no parts would break.
more im sure, just off the top of my head


the modelo 69C improvements were as follows
1. small rib cocking tube - im sure to ease in manufacture - probably takes less pressure to stamp the small seams than it does to stamp the really large ones?? Maybe the jig is easier to manufacture with the small ribs instead of the really large oval shaped domes?? Not sure really why they changed this, but they did

2. cast triple frame - obviously saves time, money, and material - before the milled triple frame had to be cut from a billet of steel.

3. improved trigger parts / safety sear that prevented the thing from breaking when trying to cock it with it on safe.


those are the 3 differences of the 69C from the standard C

and here are some photos for you :)

first we will do modelo B

[Perro]

modelo B features that make it unique

first, the cocking tube, and triple frame
notice it has large ribs, and it has the mill cuts in the side of the triple frame for light to enter into the hood.


then after that the modelo b flash hider
it also doesnt use a bayonet lug, but instead uses a cap like HK later utilized on there g3s
the semi permanently attached bipod that bolts to the triple frame instead of clamps to it like on the C


after that, the carry handle of the B - the handle attaches to a ring of stamped sheet metal that is riveted around the cocking tube

after that, obviously it has a tangent rear sight that has been riveted to the top of the receiver with solid rivets - countersunk outside, smashed flat inside in the top rib of the receiver


after that the different lower with 2 piece grip set, safety selector on the right hand side of the lower, and different safety selector - the lower receiver is different to accomodate the 2 piece panels, and the right hand safety


after that, the different profile of the buttstock housing, and buttstock


lastly, a full shot of the B showing the thin buttpad, and all the other differences as a whole

one more last thing - a manual cutaway showing the early trigger parts with the Y shaped sear, and the later parts showing the dogleg shaped sear

onto the C next

[Perro]

i give up
it will not allow me to post any images, and i dont know why

maybe tanker has a setting to approve images or something?

all i know is i cannot post photos

i even deleted images inside of my user CP to see if that was it? it aint allowing me to upload the images i want for whatever reason

sorry bout that

[Perro]

here, here is a quick comparison of photos i had uploaded to my old server already - best i can do till we find out why i cant post photos with the attachment device built into the forum

first, a model b - notice the large ribs - also notice the triple frame is completely different with side cuts
http://www.cetmerifles.com/comp/1.jpg

here are the other 2 C cetmes - the one on the left with the bobbed barrel has the standard milled triple frame and large ribs
the one on the right made from new parts has the small ribs and cast frame.

the early century guns were all made on unissued parts kits with the small rib/cast combo - they also sold for $800.00
they had unissued small rib parts kits that sold for $400.00 as well
all the early guns were marked differently on the magwells than the later cai guns.

http://www.cetmerifles.com/comp/2.jpg

[weasel_master]

Mike, just out of curiosity do you sit down whenever you get a gun or kit and find the last bit of info for it? I am truly amazed at the knowledge you and some of the other members have here. I've got a lot to learn.

[MID]

For finding the hole,
Could you take, your rifle, and put it in a fridge or freezer, leave it there over night.

Then the next day take a pot of water, and gett it to a boil, so theres lots of steam.

Now take the cold rifle and hold it over the steam.
Watch the condinsation.
At first all of the trunion will have condinsation on it.
WIpe it off, and then hold it in the steam.
Keep repeating this untill you cn see the outline of the barrel pin.
Eventauly the part of the trunion thats over the barrel pin will have less condinsation, beause it will heat up faster. Thus leaving an out line of the pin.

[Perro]

Mike, just out of curiosity do you sit down whenever you get a gun or kit and find the last bit of info for it? I am truly amazed at the knowledge you and some of the other members have here. I've got a lot to learn.

i try my best at it, thats for sure.

ive been involved with the cetme intimately since around 9/11/2001 - that was the time i bought my first cetme. i dont remember exactly when, but i believe my cetme arrived at my FFL a day or two after the world trade center attacks. I believe i joined gunboards cetme forum on 10/11/01 - i remember this cause Kim Youngblood joined the same day. Ive been seriously studying the gun for almost 6 years now. Ive built them, messed with parts kits, made parts for them, and seriously collected everything cetme i could find for 6 yrs.

so i have alot of information about the cetme - 6 years worth as a matter of fact :)

i do save everything to my hard drive - i have so much stuff on it that i cant remember what i even have anymore.
add to that a stack of about 20 different backup dvd sets that each hold more information than the last, and you can imagine how hard it is to find what im looking for when i want it. One day i need to sit down and catalogue it ALL correctly so i can browse to the correct folder to find what i want. then i need to make a set of backup dvds and everytime i make a new set of backup dvds, i need to throw the old set away.

[drine]

I got it stirred a little. Here's the trunnion I have and just by looks a little different than swee's picture.
I was asking questions and noting differences. BTW, my CAI pinhole is huge(not pictured). The 5mm pin slides right through. I don't know if there is a difference, or if they actually cared and reamed it over for a tight, all be it "0" gap, fit. This pup(pictured) will start a 5mm pin and it would have to pressed/hammered to finish. Which takes me back to CAI work. They just welded the trunnion and barrel and all in to the receiver hence we have no access hole, correct? Then this came from Spain like this. Just putting 2 and 2 together. It doesn't always equal four though.
Perro,
FYI, I did drill into the hollow behind the trunnion pin hole. You know why? Because I used this stub(pictured) to go by and NOT your measurements. Had I used your measurements, I would have been dead on. I can cover the hole over easy enough and learned a little something in the process. AND please, never, get tired of sharing or giving pointers. I work with/for a man with a PHD in Nuclear power generation. A humble soul who will teach as well as listen.
For all the true experts here, I greatly appreciate you sharing your knowledge. It is my philosophy that no matter how smart you are if you can't teach someone your knowledge then maybe you AIN'T so smart. You guys teach us something new all the time.
Well enough leg humping here. Let's see the pic!
Oh yeah, the receiver did say Modelo C in case anyone wondered. And yes, I cut the cocking tube support completely off cause I got in a hurry. I'll know how next time! I didn't need it anyway, I wanted to give it to the next person who ruined theirs.

[jfowl31]

Its all coming back ot me now.... Thanks Perro.

The more I learn about the first Century rifles, and the Limited editions, the more Im thinking they were just the exact same rifle, just produced at 2 different times. Same unissued parts kit, same cast receiver... only difference is the US made barrel really.

Mine won't cock on safety though, if the hammer is dropped. If the hammer is already cocked, I can pull the charging handle back, but not otherwise.

Thanks again for the reminder of the info youd already given me though.

[jfowl31]

back to the subject... those are definitely 2 different kinds of trunnions...

look at the difference in length from the hole to the ridges...

[jfowl31]

also, the steps inthe middle arent at the same positions.

Maybe one of them is an HK trunnion???????

Perro?????

[MID]

The rifle wont charge on safe, and that is the correct function.

[SSwee]

Not much difference but there was at least two different blue prints. Maybe a revision, maybe a screw up. I'd like to know just for my own curiousity.
SS