Advice needed please!

[artech]

OK, here's my dilemma. Got the Yugo 53 kit about a year ago, got .308 and other parts from RTG, got drums from Marstar, belts and cans from Aim, barrel bushing from Wiselite, .308 barrel from Numrich, more parts from Angola Dan, and ammo here and there. Finally got the CS receiver blank, now the real work starts.

Printed out most of the relevant stickies, threads, and pics from this site, searched, searched, and searched again, asked questions, printed, put it all in a 3-ring binder. Bought the HF TIG welder as everyone recommended, learned it is really very close to the gas welding I did way back in high school shop class.

Practiced my way through a few tanks of Argon, now reasonably confident that I can make some types of metal stay together. Have a drill press and small lathe with a milling attachment in the garage, probably the equivalent of a HF mini-mill machine. Too stupid to know this is impossible, so there's a major point in my favor as well.

My particular demil has the front of the t..t..cam piece slot(thought I was going to say trunnion, din't cha! ) remaining, so it's not as bad as some others, but the joint will wind up being under the cam piece, so it's pretty close. My dilemma is how to locate the entire gun off this one single reference point.

Here's my initial plan of attack. Using the existing barrel stop in the shroud and the 'dime trick' at the muzzle, locate the proper depth and alignment and weld in the barrel bushing per Pirate's tutorial. Using the 37 11/16" receiver length guideline and the existing reference point, locate and weld up the rear section to the correct length, and then lay out the rest from the rear in the hopes that this should put everything in the receiver somewhere near where it's supposed to be.

Opinions, comments, concerns? Any 'land mines' in this plan I should be watching out for? Any advice would be appreciated.

[sdk1968]

dont worry about the barrel bushing part until the very end.

get your rear section perfect and matched up to the camming area, then the barrel bushing will pretty much set itself at Pirates length.

you need someone who did the CSS section to help you with the pointers on it.

[xano]

I built my kit from a cold steel reciever and did it just like you described without a problem. I welded in my front bushing first in the same location as the original. I'm not saying this is the best way but I am testifying that it will work out ok. I also used as may reference points as possible for the rest of the measurements. I did screw up and set my gripstick almost 3/8" to far forward and had to make adjustments for this in the fire control and recuperator but the gun runs perfectly.

[xano]

Sorry my memory is starting to fail me. My gripstick is 1/4" too far to the rear. Not a good thing but it works fin e.

[TbcSEOD]

If i understand your question then I had to figure this out just last week - fortunately I had a MG42 receiver on hand that wasn't cut thought the camming area.

Heres the measurements I came up with - they are based from the rear edge of the cam stop (the bump behind the rear site base) to the rear of the side opening and to the front of the cut out where the bolt strips the round from the feed tray.

(Clicky for full size)

if thats confusing then let me know and I will take a picture of the receiver I am welding up and will get a better angle and label it with the measurements.

Hope that helps
~T

Also for what its worth I welded my bushing 1st to the original specs and then worked the measurements back along the receiver trimming and lengthening where needed to get them to the correct specs - I am using a BRP receiver on this one and its got extra meat in every dimension, so its all been cutting and trimming to make it fit the original specs.

~T

[TbcSEOD]

Also - once I was completed in trimming - I tacked it all up and measured it out, and it came in at 37.7 inches - the spec is 37 11/16 ( or 37.685). So all in all I would say that working from the front to rear and taking time and measuring 2, 3, or 4 times works - it also made me feel confident that I got accurate measurements from the 42 receiver that wasn't butchered through the camming section.

~T

[sdk1968]

i retract my weld the bushing last statement. LOL

on the WLA it works really good that way, but evidently it doesnt matter in the long haul.

there is a great picture on the site with every dimension of the barrel shroud labeled and put on it for you. it helped me alot. you may wanna go get it??

[TbcSEOD]

Here is a few pertinent threads with measurements that could help.

viewtopic.php?f=39&t=2919

viewtopic.php?f=39&t=5431

viewtopic.php?f=39&t=11

~T

[artech]

That's awesome! That 382 mm measurement from the receiver rear to the rear of the cam window is exactly what I was looking for! So it needs to be 15.038", plus zero, minus .008". Excellent! That is a huge help!

And I read on here that the receiver print floating around is not accurate. I received what appears to be a copy of that same print along with my CS receiver blank. Can anyone enlighten me on the accuracy of that print before I use any of the dimensions off it? Some of it is right, is that correct?

And although I am a on this board, I'm still going to throw in my two cents here. I simply cannot accept that the shorter mainspring we want is not a stock item for some other application. Probably some garage door opener or pogo stick or something is running the exact spring we need. Has anyone tried an M60 spring? How about a Remington 1100 spring? An AR15 spring? A Sten spring? Or failing that, can someone provide a tutorial on how to close and grind one end of the cut-off stock spring?

[blackreichswehr]

Artech, you sound like a very nice fellow, and to show you how much i like you---- i'm going to give you a 5 gallon bucket full of information. Call a spring manufacturer of your choice, they will be sitting by the phone waiting for you to call. First tell them who you are, they like that, next tell them you would like them to design and make you a compression spring for a firearm. Sometimes spring companies are funny,if they ask how how you came to call them,you can tell them it was me. Be ready to answer some simple questions-- i'll give you an advance on those questions so you won't feel stupid when they ask. question 1 Your free lenght will be 17"- question 2, installed height- i don't know the lenght of bolt your extention-but put your bolt in and push it in till it locks in the Cam, now measure from the back of you bolt to the buffer were the srping will sit, OK good. Some of these i'll let you do because i don't want to take all the credit. question 3, the mean diameter, measure the o.d.of your coils on the stock spring because this will not change, very good now question 4 i.d. of spring ,ok good Question 5 wire diameter measure one but tell them its braided -x2. question 6 right helix question 7 finish- your call . they may try to throw in a trick question in, so be ready. here is what they'll do to make your spring--- elastic limit,endurance limit( thats B.S. but they wont tell you) free lenght, gradient, load,MCD, Soild height.spring index, stress and lastly total numder of coils. after all it was you that said, I simply can't accept that shorter main spring is not stock.No more looking at pogo sticks and garage doors for a spring . GOOD LUCK YOU on you build and welcome aboard.

[Bil]

It is hard to tell if you are being sarcastic,helpfull,or that is just your personality.Whatever,I like it!Thank you for the info,that is more than we have gotten so far,I would have never thought of those questions or answers.If no-one has started this before mid Feb.,I will look into it.Thanks again. ---bil

[bolex]

And I read on here that the receiver print floating around is not accurate. I received what appears to be a copy of that same print along with my CS receiver blank. Can anyone enlighten me on the accuracy of that print before I use any of the dimensions off it? Some of it is right, is that correct?

I simply cannot accept that the shorter mainspring we want is not a stock item for some other application. Probably some garage door opener or pogo stick or something is running the exact spring we need........ Or failing that, can someone provide a tutorial on how to close and grind one end of the cut-off stock spring?

I found that the CS print was lacking and searched out dimensional information on this forum similar to the posts above. I doubt you find a spring that will work. The cut one I have seems to work just fine. The major issue is to get the rails level and inline with the barrel. I took a ground tool steel rod with a tappered end as a fixture to insure that the weld between the barrel shrould and CS receiver permitted the bolt to mate with the barrel trunnion.

[blackreichswehr]

Bil, i know my words came off harsh towards Artech, and you noticed it.Its obvisous he read some of the post as he recall the nomenclature. when he was talking about possibly mixing springs from this and that, it threw up a flag. I had a vision of this fellow putting in an over powered spring and driving the bolt through the barrel. I would just hate to see someone get hurt experimenting with springs in a firearm. were all here to help each other----- Sorry for my behavior, and I apologize to you Artech. off subject i dont how to open an inbox or where its even at

[artech]

Well, I asked for some advice and I guess I got some. No sweat BRW, no blood no foul. I was being facetious about the pogo sticks, but that's neither here nor there. Thing is, I'm not trying to get a spring made, and I'm not trying to duplicate the factory spring. I'm trying to find a stock item that will work, and that's a different thing entirely.

Now I ain't the sharpest knife in the drawer, but I do understand that the factory spring rate can be figured by compressing the stock spring to 20% of it's total deflection and measuring the weight necessary, call that P1. Measure the height at that weight, call that L1. Now load the spring to 80% of the available deflection, make sure no two coils are touching, and call that weight and height P2 and L2.

Your spring rate is the change in weight divided by the inverse of the change in height, or R=(P1-P2)/(L1-L2) Gives you the weight in pounds per inch. No idea what this is on the factory spring, but a hunk of round stock and some free weights should provide the answer pretty easily. Take that rate, the desired solid height, the OD and ID, and free length, and go shopping.

Recall that the spring weight can change a little since the bolt carrier weight is now different, the diameter can change a little since we got some room in there to play with, the rate can change a little since we got different sizes of booster nozzles to play with, and the wire size and twist don't matter anyway except as how they relate to the solid height. There should be a range of springs that fit the range of build configurations, and probably several different ones may work depending on the individual gun, the ammo, etc.

Find something close, buy it, stick it in and try it. That's the only way to know for sure. Then post the damn part number and company here so everyone else can get some too.
Hey, how the hell did we wind up talking about springs anyway? This ain't a spring thread! Hey Bolex, what taper did you use for the rod in your jig, and did you locate off the chamber or the bore?

[bolex]

Taper of the chamber/cartridge.

[mdm2]

could anyone tell me the distance from the barrel gate stop to the front of the barrel bushing

[42rocker]

Did this one ever get finished???

Some interesting stuff to review from 2007

Later 42rocker