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Discussion Starter · #1 ·
I am looking for members who might be able to corroborate Tony Ben's number of 0.00027 as the amount of material needed to be removed from the barrel face to cause the barrel to rotate one degree further into the receiver. My barrel times in at 26.7 degrees when hand tight.

The shoulder on the barrel face is very square. I am intending on removing enough material to allow 20 more degrees of twist into the receiver. That would leave 6.7 degrees of crushing rotation after the barrel was hand tight.

See the attached picture with very square shoulder:

Thank you guys.

P.S. Didn't find a thread with a clean, "Barrel Timing", name so I started one.
 

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Forum Jester
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if you screw up and need shims,
carl lesinger
2140 Pennington Rd
Ewing, NJ 08638-1432
609-883-3729
[email protected]

5 bucks each
 
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Discussion Starter · #4 ·
That's It. Excellent !

Thanks, JayKosta for your knowledgeable replay.

Your provided formula produced the same result as Tony's value listed in his video:

(1 / 10tpi) / 360 = 0.00027

Or 2.7 thousandth of an inch equals 10 degrees of addition rotation. I will need to remove 5.4 thousandth of an inch to get to 20.

Is 6.7 degrees of crushing rotation enough to create adaquit torque?

Thanks again, guys.
 

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Slow down. Something doesn't sound right here. I know this has been beat to death around here.

Edit: Where are you getting the 26.7 degrees?
 

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bigger hammer won't work?
 

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Discussion Starter · #8 ·
big hammer won't work?
LOL. Yeah, I wish. I was surprised to see the barrel time-in so early at what looks like more then a clock value of 7:30. When I put a digital angle finder on the receiver I get a delta angle between the receiver and the front sight plane of 26.7 degrees. At 26.7 degrees the clock value should look more like 8:30. Don't know what to think.
 

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Discussion Starter · #9 ·
Thanks MemphisMachinists

Thanks for writing how the shims don't hold up. Hopefully I won't need them by having too much material removed. I'm looking at 4.5 thousandths now. That would give my 10 degrees of crush rotation. I do not have a lathe. I will take the barrel to a local gunsmith.
 

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Discussion Starter · #11 ·
A really nice Bula Defence receiver and -
" A reproduction of the classic Saco-Lowel national match barrel which was used by US Military on XM-21 and M14-NM rifles. Made in USA exclusively for LRB by Criterion using the original Saco blueprint #9345206 dated 81-06-20 "
 

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LOL. Yeah, I wish. I was surprised to see the barrel time-in so early at what looks like more then a clock value of 7:30. When I put a digital angle finder on the receiver I get a delta angle between the receiver and the front sight plane of 26.7 degrees. At 26.7 degrees the clock value should look more like 8:30. Don't know what to think.
This looks about right to tighten up. Some barrels have a slight taper machined into the shoulder so it can "crush" some. Some do not. Personally I would try tightening this barrel up with out any metal removed. If it would not work, then I would cut the shoulder. I like the taper in the shoulder. It seems a bit more forgiving. I set the compound of the lathe on 1 degree and make the cut with the compound. If you do it this way you probably will not need more than a thousandth or two removal. My bet is that it will not need anything. The feed ramps are just an indicator and probably not the most important part to be aligned. The alignment of the front to rear sight is more important. She will feed with a slight alignment issue on the ramps. If everything is right everything will line up, but not all will.
 

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I installed a Criterion barrel purchased from LRB two years ago. It also timed way early. I also recall a thread where someone else noticed the same thing. Perhaps the Criterion barrels just have a tad more "meat" on the shoulder.
 

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Discussion Starter · #14 ·
Great Info MemphisMachinists

I like your idea about the 1 degree cut with the compound. I'll discuss with any gunsmith I work with. Copy on the front and rear sight alignment being most important. Much appreciation for all your responses. Definitely helps me out.
 

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Discussion Starter · #15 ·
Thanks To smooth8500 About Criterion Barrels

That is super interesting. Glad to know my parts are not a fluke. Definitely more meat, as you put it, on the Criterion Saco reproduction. Thanks a bunch.
 

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It, from the photo appears past C/L, the shoulder can be rolled and it may give you the "crush" you need.
Or, you have almost one turn to go, unless yours is a left handed thread..

Why are you attempting to calculate material removal if you are not doing it?
The numbers you presented are wrong, unless it is the new math.
You posted .00027" should be .0027", you not working in millionths of an inch here.
As I said it is over wound as it is.
In all the M1 and M14 barrels I have replaced, I never tried to number them out.
Just wound them in and saw where they stopped then cut what I thought I needed to at a one degree shoulder angle not 90..
 

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I've installed barrels that time around there. Some guys like it to be closer to 6:00, but I've gotten it done from where yours is at before. As long as the timing gauge says you're good, then you're good, as was mentioned earlier.
 

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26 degrees is not really excessive. You really should have no problem tightening it as is. But if you must, take off 0.002" and that's all you need. That will put you between 10 and 15 degrees which is where I like them to be. If you're shooting for 5 to 8 degrees, use red Loc-Tite.

Tony.
 

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I just finished my first build, with a criterion barrel.

Hand tightened, it looked like this from the receiver...



Roughly speaking, that is about 7:00 versus the approximate 6:00, one 'hour' of rotation to go, which if you divide 360 by 12, would be 30 degrees. Looking at the feed ramp, it looked more like 6:45 to me. The Assembly guide said, if I recall, that I wanted about 7:00 to 7:30 or so, so 30-45 degrees.

The guys on the forum assured me both not to take the feed ramp as an indicator, but also that it would likely be plenty of draw pressure. They were correct. I rigged up a contraption to do slow rotation via turnbuckle pulling the receiver wrench against the barrel vise in a total steampunk abomination, referencing the receiver's sight shelf and the bottom of the front sight mount via Easton aluminum arrows, and it seems to have worked out pretty well.

I wouldn't take off anything. I would guess that if you do, you'll need those washers.
 

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26 degrees is not really excessive. You really should have no problem tightening it as is. But if you must, take off 0.002" and that's all you need. That will put you between 10 and 15 degrees which is where I like them to be. If you're shooting for 5 to 8 degrees, use red Loc-Tite.

Tony.
Why do you prefer 10-15 degrees? I'm not going to undo anything now that it's working, but it's always nice to learn more

GI1
 
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