22TCM 1911 and odd problem...

[onelight]

If the barrel is fit to the gun correctly and the headspace is in spec it would seem the only way for the shoulder to move is if it is unlocking while under a good bit of pressure.
Will the gun return to battery with a fired case in the chamber ?

[mattw]

Will check this weekend, fired cases at my reloading room... 75 miles away. No place around home to test fire 1. My gut says no.

[onelight]

Will check this weekend, fired cases at my reloading room... 75 miles away. No place around home to test fire 1. My gut says no.

They sure don't look like they would.

[35remington]

The gun cannot unlock when the barrel is pressurized, so do let that idea go. Since the 22 bullet imparts so little momentum to the slide, a small radius firing pin stop is the wrong fix for something that is not occurring. The gun does not need a “delay” in opening because “early unlocking” is not happening.

If anyone is unclear on that point I can explain in detail.

Anneal some brass, size such that the shoulder of a fired case is set back very little (best done with die setup with a comparator) and compare fired case dimension from head to shoulder with a SAAMI spec drawing if you can find one.

It would be good to quantify any difference between fired case size, which may tell you something about the chamber, and the SAAMI dimensions if you can find them.

[35remington]

I just reread where you say you used factory new brass, which means the sized case shoulder is where the factory sets it, not where you set it.

The fired case has a notably shorter neck and the shoulder is further forward by a considerable amount than factory brass.

Likely poorly annealed brass that gives way when it has to stretch a fair amount to fit the chamber.

Suggestion.....since you use factory new brass, try annealing before loading.

Further, anneal the surviving fired brass and set your sizing die so it does not move the shoulder back and try them again.

[onelight]

The gun cannot unlock when the barrel is pressurized, so do let that idea go. Since the 22 bullet imparts so little momentum to the slide, a small radius firing pin stop is the wrong fix for something that is not occurring. The gun does not need a “delay” in opening because “early unlocking” is not happening.

If anyone is unclear on that point I can explain in detail.

Anneal some brass, size such that the shoulder of a fired case is set back very little (best done with die setup with a comparator) and compare fired case dimension from head to shoulder with a SAAMI spec drawing if you can find one.

It would be good to quantify any difference between fired case size, which may tell you something about the chamber, and the SAAMI dimensions if you can find them.

I am not questioning what your knowledge of how this thing works just trying to learn something .
Does the pressure on the breech face create enough friction on the locking lugs to keep the slide and barrel locked together until the pressure drops enough for them to separate ?

[35remington]

Yep, mostly so with a caveat. Think of it as the pressure that is forcing the bullet forward and the friction between bullet and barrel is pulling the barrel “forward” seating it hard into the lug recesses in the slide. Meanwhile the rearward moving slide is tugging the slide/barrel assembly rearward...which is why I put “forward” in quotes in terms of barrel motion, which is actually moving rearward as it is being pulled that way by the slide.

It is like hooking your hands together and pulling in opposite directions. That is what keeps the lugs in solid contact. This force is not trivial.

The forces holding the barrel lugs in contact with their abutments in the slide very actively resist separation while the bullet is in the barrel. Which is why it is very undesirable to have the barrel link trying to disengage the barrel from lockup while these forces are applied. A skinny link is too weak to stand up to these forces, which is why the gun is timed such that those forces are gone before the link starts pulling the barrel lugs out of engagement.

The distance the slide travels while the bullet is in the barrel is a ratio of the mass of the barrel, slide, hammer, and about half the weight of the recoil spring, all of which are set into motion when the gun fires. (This discounts any spring effect for simplification and springs are certainly not the major player....mass is by far). The gun has been carefully designed such that this ratio sees to it the bullet (always!) exits and pressure drops to zero before the link starts pulling the barrel out of engagement.

Always.

Further, for the case to back out of the chamber, the slide has to back up far enough that not only the lugs disengage, but it also has to go rearward enough that the link starts to arrest the barrel’s rearward motion and the barrel is stopped from moving rearward by contacting the frame. Only then can the breech start to back away from the end of the chamber.

The bullet and pressure are not only gone at that moment, they are long past gone.

The barrel separates not because pressure goes away and allows unlocking. The barrel separates because the mechanical timing of the event ensures the pressure is gone first, and then it separates. The separation occurs when the link drags the unpressurized barrel out of engagement with the slide because the slide and barrel has traveled rearward enough to make separation happen.

[onelight]

Thanks for the explanation .

[StrawHat]

Learn something new every time I sign in to this site.

Kevin

[onelight]

It will be interesting to hear if the fired cases will chamber and the slide return to battery with one chambered.
Cause they sure look like they would not, but the pictures may not show the position of the shoulder clear enough.

[1006]

It the gun’s barrel fit is improperly setup, I believe it could begin to unlock prior to the bullet exiting the barrel. Here is some info on the very small amount of unlocking that occurs in a properly setup 1911.

It took me a while to find this, but here is an old photo that shows the 1911 slide does move -ever so slightly- before the bullet exits the barrel.

This is not intended to disagree with the physics as explained by 35Rem. It just shows that the slide is pushed rearward-slightly- just as the round is ignited, This is when full lockup begins, it then remains locked up until the bullets exits the barrel.

Here is a link to the page that I found this old image on.

https://rangehot.com/full-length-guide-rod-1911/

[Texas by God]

IMO RIA owes you a new barrel. That one’s no good. OR it’s bad brass but Armscor is the only brass you can get, right?

[onelight]

It the gun’s barrel fit is improperly setup, I believe it could begin to unlock prior to the bullet exiting the barrel. Here is some info on the very small amount of unlocking that occurs in a properly setup 1911.

It took me a while to find this, but here is an old photo that shows the 1911 slide does move -ever so slightly- before the bullet exits the barrel.

This is not intended to disagree with the physics as explained by 35Rem. It just shows that the slide is pushed rearward-slightly- just as the round is ignited, This is when full lockup begins, it then remains locked up until the bullets exits the barrel.

Here is a link to the page that I found this old image on.

https://rangehot.com/full-length-guide-rod-1911/

Thanks for posting that , Interesting.

[35remington]

The photo shows no unlocking whatsoever. Note the lugs are fully engaged as the bullet is nearly out the barrel. This supports what I posted above. I also mentioned the slide is moving while the bullet traverses the barrel.

The gun cannot unlock “early.” A 1911 shooting a lightweight bullet, even vastly more so.

[35remington]

Note the measurement of slide motion is about 0.075”. The bullet is almost out of the barrel. The link does not start to pull the barrel out of the lugs seats until around 0.110-0.120” of slide travel, this with a 230 grain bullet. The bullet and pressure, as stated, is long gone by the time the barrel starts to unlock.

A light 22 TCM bullet means the barrel is even less likely to be pressurized when the barrel is pulled out of battery. Which is to say no chance whatsoever. The info in the posted link shows no amount of unlocking is occurring. To the contrary....the gun is locked up as much as it can be.

[35remington]

Note also the link has to go well past the vertical to start pulling the barrel out of engagement with the slide. The link is not close to that.

I do agree that the photo is useful for supporting my explanation, so it was helpful to post it.

[1006]

I agree, 35, your explain has been very well put, and that is why I said that the photo does not disagree with the physics you explained. I should not have used the word “unlocking” as soon as I did in the description. I should have just referenced the rearward motion of the slide.

It just shows that a properly setup gun’s slide does move before the bullet exits the barrel.

I put the picture on the post to show that if a properly setup gun’s slide moves a little bit, an improperly setup gun’s slide may move too far. And, I believe, that the possible excess movement combined with a poorly cut chamber, might cause the brass to rupture.

[35remington]

An improperly setup gun in terms of barrel fit also cannot see the slide/barrel move too far while the bullet is in the barrel because the weight of slide barrel and hammer dictate how far the slide moves while the bullet is in the barrel. Not how the barrel is fit.

Just clarifying that point as well. Unless there is obvious evidence the barrel and slide have areas milled away to lighten them excessively when used with a heavy bullet the gun will not unlock early....doing so would be pretty dumb. With a 22 TCM the gun could have considerable lightening of the slide and barrel and it still would not be subject to early unlocking.

Barrel fit will influence lug engagement and this can be poorly done but barrel fit does not influence when the link starts pulling the barrel out of battery. Just a point of clarification here as well FWIW. It would be pretty much impossible to fit a barrel to have zero lug engagement as they do not make links and barrel lug feet that short....only standard and oversized long ones. As long as some amount of lug engagement is present, however undesirable minimal engagement is, unlock timing will be largely the same, and in any event well later than when the bullet and pressure has left the barrel.

[35remington]

The other thing not completely understood in the midst of all this “early unlocking” postulation is the lugs don’t instantaneously disengage once the link starts pulling on the barrel. The slide must move further still for the link to get the lugs to disengage from their seats in the slide which approximates 0.2” of slide travel.

This is way, way past the time the bullet has left the barrel and has pressure remaining.....and this with a heavy 230 grain bullet. The gun cannot unlock early. The timing of the event absolutely precludes that from happening. When he lugs disengage from the slide the pressure is long past gone.

[mattw]

Ok, got to spend much more time with the 22TCM this weekend. Problem found, and sorta solved. So, the chamber is cut to deeply and I am not sure that it is not cut at a slight angle as the formed brass still looks odd. I was able to drop my 40 grain cast loads down to 1675 fps with 8.8 grains of LilGun. The action still cycled, but really did not feel right and the cases came out with soot down to and sometimes into the shoulder. I was able to fire 52 rounds of factory new brass and only had a minor split on one!

I now know why she splits nearly 50% of factory rounds shot in it. I am going to call RIA and try and get the barrel replaced. It was in once for feeding issues and once later because it split so many cases. They could not spot this issue? I have only fired a couple of boxes of 2 out of 2 cases as it just was not worth the waste. I have not looked for the problem in so long because I was just flat ticked over the split cases, as a reloader that is something that sets me off. I have fired a bunch of 9mm with it and it performs very well.

Someone asked if the fired case would go back in... heck no. they go about half way back in without sizing.

This is a factory loaded round in my barrrel, notice the bad headspace? Factory new brass fits this way as well.


This is one of my fireformed and sized empties in the same barrel.


Notice the geometry of the center case? That was formed in my chamber and sized.