Norinco barrel question (s)..

[saltydog452]

I have a question about Norinco barrel demensions, and what may/may not be acceptable for reliability, longevivity, and (again) reliability.

LENGTH..Looking at the 1911 barrel hood and slide breach face area, lets define 'length' as a distance from the face of the barrel toward the breech face of the slide.

WIDTH...Again, looking at the 1911 barrel hood and slide brech face area, define 'width' as the possible horizontal contact area of the barrel hood with the centering slot machined into the breech face area of the slide.

(Its times like this that I wish for a 'puter version of the kids toy "Etch A Sketch)

The pistol is recoil operated, and if I understand that correctly, as the bullet starts to move forward and engage the rifiling of the barrel, there would be some 'torque' forces applied to barrel to twist the barrel into the direction of the rifiling of the barrel.

Thats going to apply rotational twist forces to the barrel link, pin, and slide stop pin.

What kinda relieves this rotational force is the fitting of the barrel hood 'width' into the milled in centering slot of the slide. Some of the twisting force is directed into the slide and some to the lower area of the barrel.

Barrel hood fit into the breech area of the slide has to have room for grit, unburned powder, etc. But it also needs to contain some of the rotational forces exerted by the barrel under recoil.

Factory Norinco hood 'width' is considerably smaller than that in either my Colt factory barrel, GI Nat'l Match, and Kart 'E-Z Fit'.

Where would you draw the line between reliability in the top areas of barrel hood/breech face area and that of keeping the rotational torque of the barrel from damaging/changing the external geometry of the lower area of the lug involving the feet, radius, slide stop pin and the link? (Long sentence, but I didn't know how to divide the question)

I hope I've made my question clear.

Thanks,

salty.

 

[1911Tuner]

Torque

I have a question about Norinco barrel demensions, and what may/may not be acceptable for reliability, longevivity, and (again) reliability.

LENGTH..Looking at the 1911 barrel hood and slide breach face area, lets define 'length' as a distance from the face of the barrel toward the breech face of the slide.

WIDTH...Again, looking at the 1911 barrel hood and slide brech face area, define 'width' as the possible horizontal contact area of the barrel hood with the centering slot machined into the breech face area of the slide.

(Its times like this that I wish for a 'puter version of the kids toy "Etch A Sketch)

The pistol is recoil operated, and if I understand that correctly, as the bullet starts to move forward and engage the rifiling of the barrel, there would be some 'torque' forces applied to barrel to twist the barrel into the direction of the rifiling of the barrel.

Thats going to apply rotational twist forces to the barrel link, pin, and slide stop pin.

What kinda relieves this rotational force is the fitting of the barrel hood 'width' into the milled in centering slot of the slide. Some of the twisting force is directed into the slide and some to the lower area of the barrel.

Barrel hood fit into the breech area of the slide has to have room for grit, unburned powder, etc. But it also needs to contain some of the rotational forces exerted by the barrel under recoil.

Factory Norinco hood 'width' is considerably smaller than that in either my Colt factory barrel, GI Nat'l Match, and Kart 'E-Z Fit'.

Where would you draw the line between reliability in the top areas of barrel hood/breech face area and that of keeping the rotational torque of the barrel from damaging/changing the external geometry of the lower area of the lug involving the feet, radius, slide stop pin and the link? (Long sentence, but I didn't know how to divide the question)

I hope I've made my question clear.

Thanks,

salty.

Hey Jerry! Sorry I didn't see this one 'til just now.

The length between the face of the hood to the first lug face, as opposed to
the mating slide breechface to lug location is the first consideration. You want minimal play there and still allow a little space for dirt and fouling. To much barrel fore and aft play causes slap-seating of the lugs, and possible rearward deformation of the barrel lugs...which increased live headspace in the dangerous direction. Sometimes, there can be a lot of gap between the hood and breechface without excessive endplay. It's in how the barrel and slide lugs match up that determine it. You can get zero play there, and not achieve horizontal engagement on the first lug...which is the strongest one.
In other words, a tight fit between hood and breechface doesn't guarantee
ideal barrel fit. Gauging the slide lug locations is the only real way to know for sure which lug the barrel is locking on.

The clearance at the slides contributes to rotational torque resistance...but that's not the only consideration. If the lower lug is cammed up tightly by the
slidestop pin, and it's supported evenly across the width of the lower lug, that will do more to resist torquing of the barrel than the fit of the hood at the sides. The hood fit on the sides do more to guide the barrel straight into battery so that the incoming round will chamber consistently. This is why long-linking the barrel go get tighter lockup or more vertical depth into the slide is usually couinterproductive. When the barrel locks on the link instead of on the lower lug, it's standing on one narrow point instead of having a wider base of support.

Most factory-fit barrels don't offer all that. They either lock on the link...or they don't have full vertical depth...or they have a lot of horizontal end-play...or they have a lot of clearance at the sides of the hood...or all the above. I've found that the typical Norinco barrel fit leaves a lot to be desired,
but to give the devil his due, they do seem to be very reliable and surprisingly accurate given the amount of slop. Some, however, are just plain bad, and
have not only too much end-play and slap-seating, but insufficient vertical depth of lug engagement...and they deform quickly and badly.

To understand the term "Slap-Seating" a little better...understand that the
1911 locks horizontally when it fires. The pressure holds the barrel hard forward, while the slide is slammed backward until the lugs engage. When there's a lot of slop, the slide moves farther rearward before they engage...essentially giving the lugs a longer running start at each other before they hit. On the opposite end of the scale, when the hood is fitted tightly to whichever lug or lugs that achieve the horizontal lockup, there is no clearance, and the lugs begin to bear immediately...and there isn't a running start. Think of pressing two hammer heads together with gradually increasing pressure up to say 1,000 foot pounds of force...and then imagine starting them from a foot apart and slamming them together with the same force.
Which will deform the hammers more quickly? Steady pressure or impact?

Now, add another factor. Slap them together on-center...and then off-center. Which will cause quicker/worse damage?

 

[saltydog452]

Thank you sir.

I got it. (Ithink)

Another question. Its regarding the obligatory distance of approx 1/32" from the end of the frame feed ramp and the beginning of the barrel continuation of the feed ramp. With the slide removed and the barrel and slide stop cross pin inserted onto the frame, the barrel held down on its 'bed' by a thumb, I can induce a bit of 'fore and aft' movement of the barrel.

With OEM 'Rinco barrels, there is no measurable distance from the frame feed ramp to the barrel feed ramp (much less 1/32") when the barrel is held down and pushed toward the rear of the frame. This is true for both 'Rincos ( serial #s 502xxx and 503xxx).

However there is a bit of space when the barrel (again, held down with the thumb into its 'bed) is pushed forward toward the muzzle.

So, the question is, where do we measure to determine if the requisite 1/32" exists, 'fore' or 'aft'???

I am trying to paint a picture with words here, and it ain't easy. Joseph Conrad I'm not. Try to bear with me.

Thanks,

salty.

P.S.

Since everyone and their cousins, and their cousins' neighbor makes/markets 1911 pattern parts, do you have any personal experience with aftermarket oversize slide stops that are made with 'the right stuff'?

thnx,

sd.

 

[1911Tuner]

Fore and Aft

The endplay is measured between the slide and barrel by closing the slide on
increasing feeler gauge thicknesses between hood and breechface to push the barrel as far forward as it will go. When you find the gauge that won't slip out easily, note any further movement toward battery of the slide. If there's any...even an amount so tiny that you have to place your thumb at the rear of the slide frame junction to "feel" it move, go the the next thinner gauge until you find one that slips out with a little drag, but doesn't hold the slide back. That'll put your measurement within +/- .001 inch...close enough for gub'mint work.

Again, this doesn't tell you WHICH locking lug is setting the endplay. It could be any one of the three, or any two if you're lucky...which usually isn't the case with Norinco barrels.

To determine which lug is hitting, color the front faces of the lugs with a Sharpie marker and install the barrel. Cut strips of paper which combined thicknesses exceed the endplay by about .004 inch. Place the paper shims
between the hood and breechface and let the slide go to battery hard 2-3 times, so that drawing the slide back is a little sticky. That forces the barrel fully forward as it locks up, and the ink will be removed from the face of the lug that hits. It may only take ink off the corner to a shallow depth, so look closely.

Wilson Combat markets the only aftermarket machined slidestop that I know of...Pin diameter .199-.200 inch. Also, understand that no matter what the slidestop pin diameter, there's no guarantee that both sides of the lower lug are bearing evenly across the pin.