Need help with Beretta 76 showing bulged cases - Page 2 - Pistolsmith
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Old 02-17-2012, 01:30 PM   #11
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More info.... I measured the headspace ( meaning...the "front-of-slide" depression dimension, where the cartridge rim sits being captured by the extractor)... is 0.044 ".

SAAMI drawings for 22LR show a "spec" rim thickness of 0.04"...so I would think this dimension is just about perfect....a bit more than rim thickness ( to avoid "slam-fire" if the dimension were too close to 0.040")...but not so much more than 0.04"... to be a headspace problem.....

.... right ??
 
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Old 02-17-2012, 09:11 PM   #12
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Okay, the headspace seems to be fine and new springs eliminated the other problems.

If you are determined to eliminate the bulging, I think either having the chamber sleeved OR getting a new barrel made OR adapting another make barrel are your best alternatives. How accuracy would be affected remains to be seen. If the latter, I suggest a faster than 1-in-16 twist if feasible/available.

IF you haven't already done so, make a mark on the case and manually feed it into the chamber, noting where the line is in relation to the ramp. Fire it and examine the spent case to make certain it is bulging at the ramp and not, for example, at the extractor cut. This might affect how the sleeve is made/chambered.

As far as finding a 'smith, three disciplines come to mind for accurized .22 pistols: Olympic Rapid Fire, Metallic Silhouette, and NRA Conventional Pistol aka "Bullseye".

BTW, I am impressed with your efforts, especially regarding measuring springs.
 
Old 02-18-2012, 04:37 AM   #13
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RetDAC (Dave):

Thank you kindly for the response. Yes....the cases are automatically "indexed" for rotation. The firing pin marks are always at 12 o'clock position (correspondong to the real firing pin location in the gun)...and from this....we can see the bulge is *always* in the general 6 o'clock location. Specifically...always around 4 0'clock to 6-7 o'clock. Matches perfectly with the "overly gentle" feed ramp entry into the chamber.

Thank you for you being seemingly impressed about me taking spring measurements ... however, it was not difficult if you take your time and you have a digital read-out electronic caliper. Easy-peesy.

Been trying to talk to a number of barrel makers....but no one keeps talking to me. Can you recommend someone who you think would be interested to fix this or make a new one?

I keep on coming back to this question...as I really don't understand why this couldn't work--> adding some silver solder to this very small area at the chamber entry...and sanding/grinding down to "cylindrical" shape again to regain case support that currently isn't there. I've worked with high-silver content silver solder in hobby gunsmith work before..and it ends up strong (repairing cracked mags and building up front sight blades,etc). I also can't see doing any real harm to this barrel anyway, seeing what it does now.

Aside.... have people ever relined a chamber ( only?). That sounds intriquing too.

Last edited by IPSC; 02-19-2012 at 08:33 AM.
 
 
Old 02-18-2012, 08:55 PM   #14
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Please forgive my oversight regarding the firing pin indent providing an automatic index mark. Momentarily forgot this is rimfire.

There was one possible smith, but it seems he is out of business, probably retired. The reason I mentioned the three disciplines was because there should be a smith for you in one of them.

As I sit here, a few other possibilities come to mind. One is mentioned in post #3 here: Re-boring a barrel, who does it?

A long shot is Karl Sokol at Karl Sokol Chestnut Mountian Sports Gunsmithing Services

Another long shot is here: Home
He said on his site he likes experimental work.

I suppose with a generous application of Heat Stop in, out, and around, your silversolder idea might be worth the risk. You might have to roughen an area or cut a slight groove to give the solder a better grip.

Regarding chamber inserts, what is generally done, after a lot of careful study, planning, and measuring, a short cylinder is cut, bored/chambered, and turned to fit inside a newly formed hole where the original chamber was drilled out carefully to leave a shoulder as a depth stop. In your case perhaps extra metal would be left for a new ramp. After several hours in a freezer - better yet a dry ice/acetone bath - the sleeve is quickly slipped inside the (preferably heated to about 350F) rear of the barrel keeping it properly aligned. If everything was done right, you won't need solder, epoxy, or other adhesive to keep the sleeve in place. If slightly undersize after temps normalize, I think you could use one one of those to keep it in place. It's only a .22 rimfire; they don't get that hot. That's why soft solder and epoxy (take your pick) have long been used for securing liners in .22 rimfires.

I haven't actually done this; just read about it.

If you already knew the procedure, please forgive my redundancy.

Another thought: have you tried contacting Reid Coffield or Alex Hamilton for their recommendations?

Last edited by retDAC; 02-18-2012 at 09:01 PM.
 
Old 02-19-2012, 08:25 AM   #15
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retDAC:

Great response....no need to be apologetic about anything.... just being clear that I had some way of knowing the rotational position of the fired cases....

Great set of suggestions.... I guess I have a number of phone calls and contacts to make.

Let me go through a number of these suggested possible contacts...and see where we end-up.

Thank you all for taking interest and responding to my little problem...
 
Old 02-24-2012, 02:32 AM   #16
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You have a headspace problem...and it's a dangerous one. If a case head bursts, the hot gases and brass shards will vent into the magazine. If a sympathetic detonation of 2-3 rounds occurs, it can get pretty ugly.

A heavier spring won't help it a bit. It's a locked-breech/short recoil operated pistol. You can fire it without a recoil spring.

The spring doesn't have any effect on timing. There's often a confusion between time and timing. Timing is mechanically fixed while time is a function of speed and distance. The timed event will occur at its appointed place in the cycle...whether the cycle is in slow motion or at full speed.
 
Old 02-24-2012, 05:58 AM   #17
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JohnnyT... I think you're coming in late with your comments....much apreciated..but we've found out some things since the thread started.

My only point in locking the slide, (an easy-enough and cheap "first-test" to do)....was to test the theory someone proposed.....that maybe weak springs were allowing the slide to open too soon (when casing pressures are incrementally higher)...making the unsupported end of the case bulge...or bulge more. A stronger spring (under this theory)...would keep the slide closed a fraction of a second longer, allowing peak pressures to dissipate a bit before the case gets extracted.

No....I am not confusing the timing issue.

As to headspace.... that also is not a problem (see post #11 here). The SAAMI dimensions for the rim thickness of a 22LR cartridge is 0.040" ... and the measured headspace (depression depth on the front of the slide) is 0.044". The slide otherwise closes unimpeded on the breechface. Doesn't sound like a headspace problem to me...does it to you? You need a few thou's more than 0.040", to avoid slamfire should the gun get dirty or a sliver of lead gets caught in there. And if it was a "headspace" problem (and not a feed ramp problem)....wouldn't we be seeing a bulge all around the case, a full 360 degrees ??? Yeah...I think so.

No....the bulge is ONLY around the case for 40-60 degrees...and MATCHES the overly-gently chamber mouth entry at that same 40-60 degree position. So it is most definately NOT a headspace problem, it is a problem that this portion of the chamber shows a portion that gives no (or somewhat less) case support. And is it truly a dangerous problem that you say it is? ... seeing 1.) the amount of the bulge and 2.) seeing that it does not "ring" completely around the case?

Recall too that this happens primarily with HV ammo. The very, very minor bulging that occurs in SV would be something I wouldn't haven't even noticed if I shot only such ammo.

Further follow up.....I asked another member of the Beretta forum who has the same pistol...to show me pictures of his chamber. Same thing. Then I asked for him to fire the gun and look at the cases. Hmm.... SAME....same bulging !!

Look at the pictures. It seems to be the way Beretta shapes the "funnel" of the ramp that enters the chamber....it is much different than any other 22 pistol I have. In these other guns, the "O" shape of the chamber is kept all the way-round and the feed ramp is a bit lower.

Last edited by IPSC; 02-24-2012 at 07:43 AM.
 
Old 03-02-2012, 08:09 AM   #18
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Quick update.... just a few days ago, picked up a pristine model 70S, mechanically-identical to this 76.

From the 99-100% bluing and other hints....the gun seems to be almost new. The barrel chamber entry looks almost the same as my 76, visually maybe a "tad" less chamfer on the lower edge where the feed ramp enters.

Result?..... bulged cases too !!! ...

Hmmm.... my 2 guns (100% of all Beretta 22's I own !)....plus Vins_CB's model 76 from Milan ( see Beretta forum link) ...all showing tendency to show bulged cases.

More and more I am thinking this is NOT a case of a PO going Dremel crazy. It's function of the goofy feed ramp design which has a much-too-gentle roll-over at 6 0'clock. And perhaps loose controls on the use of hand-held grinders at the factory..... causing some guns to have more material removed than others.

Look here at a Belgian Browning to see a notable difference in design philosophy---->


Last edited by IPSC; 03-02-2012 at 08:24 AM.
 
Old 03-02-2012, 09:34 PM   #19
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That's interesting. Wondered how your quest is going.
 
Old 03-03-2012, 04:50 AM   #20
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retDAC... well....it's where we're at. The topic of this thread is the original model 76. It shows almost no (very little) bulging with SV ammo....which the gun may have been designed for in the first place. A lot more bulging with HV.

A second "control" gun was purchased....a model 70S in almost new condition....to compare and contrast. However, it too is showing bulges, although a bit less. Same deal.... bulging is a bit worse with HV and almost none with SV.

Friend "Vins_CB" on the Beretta board checked and his 76 is also showing some degee of bulging. Gun was in his family since new, 30+ years ago, having been fired a few hundred rounds by his father when bought new...and then not used for 20+ years until recently by him. Meaning?--> not very used...fairly new condition.

So.....this may be a Beretta "70-series" characteristic. Most guys on the Beretta forum are advising if the gun shoots good, feeds and extracts perfectly (as it does).... then simply ignore it, or shoot more SV rounds through it. There is some perverse logic to this, as the bulge is only around a 40-60 degree circumference and may not pose a safety threat afterall.

If it goes toward a fix instead at some point.... I found a "great" pistolsmith who can do a chamber reline....a chamber plus barrel reline ( using premium TJ barrel liners)...or... can try applying some silver solder at the missing case support area (he's not too keen on this last option). John Taylor out of Washington state.

http://www.johntaylormachine.com/ ...I believe he even posts to boards like this one....maybe even this one.

For the time being....doing nothing except gathering more info from the Beretta gang to see how many more of these guns may do this.

Last edited by IPSC; 03-27-2012 at 04:41 AM.
 
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