I have a nice Japanese box lock/extractor gun. Has chopper lump barrels and double underbite. Pretty typical stuff I think.

I noticed that at lock up there is a very small bit of wiggle. So after looking it over this is what I found. The wiggle seems to be up and down not side to side. When you put upward pressure on the barrels the fit is tight as a vault with no wiggle left or right and no gap at face. It seems the interface between the locking bolt and lug surfaces are not as tight as they should be thusly holding the barrel flats down tighter to the frame table.

The lever is just ever so slight left of center.

Does this make sense and what is the recommended fix?

Thanks

One more thing to consider….is your top lever spring strong? It’s it’s weak and is starting to have a little spring back…then that should be looked into.
If it’s strong, and the gun still snaps close with authority, then yes, you probably have some bolt work to do. If you can smoke it in and see where is not “biting” that’ll give you a good idea on how much material will need to be added. It won’t be much. Adding some material to the bolt locking surfaces via tig or laser welding and then refitting should give you plenty of bite.

When you push the barrels down is there any gap between the bottom of the barrel flat and the action ?

It may well be the bolt that needs attention, but note that the barrel flats should NOT be snug down against the action flat. There should be almost no daylight visible at the very front of the juncture, but an increasing amount visible towards the rear. This is by design. The "tightness" should be at the hook/pin relationship and the barrel breech/standing breech relationship. The barrels' breech faces should "seat" snugly and with much contact with the action breech, thus stopping the breech end of the barrel flats from contacting the action flats.

Of all the break action shotguns that I've had, the breech face has never been a component of the lock-up. And I have to admit that watching the best Perazzi 'smith in the US fitting a number of barrels for me revealed only his interest in the proper fitting of the flats and the bolt. Ejectors may rub on the standing breech but not the barrels proper.
IIRC you have a Perazzi that is mondo difficult to open. Lucio could fix that badly fitted barrel for you in a couple minutes. You'd be amazed at how easy a Perazzi is to use when it is right.

Just a thot

Of these two vastly different opinions, I'd have to agree with Stan rather than Dr. Wanker. Loss of contact of the barrels with the breech face is a problem. In fact, there is a commonly used term for it... "off face", or as the British say, "off the face". And the rear of the barrel flats should not contact the water table. All of the informed sources I've read on this subject also agree with Stan, including "Shotgun Technicana". Here's a link to a pretty good article on the subject by gunsmith Delbert Whitman:

https://shootingsportsman.com/re-jointing-a-gun/

On most, but not all double shotguns, the top lever going left of center is a clear sign that the bolting surfaces are worn. This is also covered in the link above.

Of course, Dr. Wanker also seems to think the gun in question is a Perazzi, when the OP clearly states that it is a "nice Japanese box lock/extractor gun". Who knew that Perazzi's were Japanese??? Another Mystery of the Cosmos Unlocked, I guess! Same intellect that says Biden is better than Trump.

Blacking to barrels down wanker. Fit the hook the circle and the face

Re the barrels fitting tight to the action flats, actually they should not. The fit there must give some room for the flexing of the action during firing, in gunmaking language the barrel flats should clear the smoke. The tight fit is between the breech ends, the bottom radius of the barrels and the breech face.

From the description, that the play is only vertical and the breech face tight, plus the leftward top lever, it seems that the wear is on the bold bite.

I guess that I need to get every one of my guns attended to since they all come down solid on the flats and the bolt holds them there. And what possible reason could there be to allowing flex in the lock up?
And just to be clearer, on face/off face is the Result of properly fitting the hinge pin/hook and the flats.
I'm fairly certain that Lucio Sosta, a Beretta factory and later Perazzi factory trained gunmaker, knows how to fit barrels and locking bars. And that's how he does it.
Good enough for me.

Thanks for the many replies and Links. I am going to do a little smoking this weekend and see what touches where. I am also curious about the fit on a couple other SXS's I have that seem to be fitted well and see what/where things touch on those.

I will report back

Wonko I think you just don't understand fitting barrels

I'm certain that you are absolutely correct in whatever alternative universe you live in

I live in the trained gunsmith universe,how bout you

Just read this thread, interesting. I was looking at one of my vintage British shotguns that had been rejoined back in the day, which is still tight on face but it does have a slight gap remaining between the barrel flats and the receiver flats. I had wondered about that.

But according to Larry Potterfield and the late great Jack Rowe, there should be a slight gap remaining between the barrel flats and action flats when rejoining. I think it might have to do with accommodating for future wear in-order to maintain it staying tight on face? Maybe some of the gun experts can way in on the reason for the leaving a slight gap?

Rejoining Off Face

The barrel flats touching the action flats when the barrels are closed and locked is improper and if Jack Rowe was still alive he would tell you that the "trade" refers to this condition as "banging on the flats".

Our colleague on this BBS, Vic Vinters discussed this very issue in his book GUN CRAFT beginning on page 11 --the chapter titled "Jointing & the Circle. I am going to ask Dustin to post page 13 of this book which outlines how a proper fitting double gun should clear the action flats/barrel flats.

Also for those of you interested in the entire process of Joining a Purdey, you can review the other 4 episodes of the video that I posted above.

To believe that the barrel flats should touch the action flats is counter intuitive to physical science and gunmaking basic principles.

Stephen Howell

Thanks for the reference and link Keith. I missed your post this morning for some reason. Good stuff.
___________

Tim

If the gun is off face the breach end and lumps drop down the bolt does not move it comes off the bite so off face can give other. Symptom s this isn't a big deal other them explaining it ,put the gun on face then check the bolt.

Salut,

En rouge, les points auxquels le canon et les crochets, ainsi que le verrouillage, doivent porter d'une façon absolue.

En vert, les canons ne doivent jamais toucher la bascule.
10 à 15 centièmes de garde au basculage est correct.

Great drawing,if the gap between barrels and action closes the lump goes down and allows for play in the bolt.the end

For Bushveld:

Although the copy of the page above is a bit "cloudy", the arrow pointing to the action/barrel flats in figure 2 reads .002" to .004" clearance between the flats of the barrel and the action body at this point. This is a statement from the famous Birmingham gunmaker Robert "Bob" Turner. He further notes that the clearance between the circle of the lumps and the draw of the action is .0005" to .00015".

The clearance is for shotguns, not double rifles. Twice as much clearance between the barrel/actions flats and rubbing between circle and draw for double rifles.

Stephen Howell

I am trying to figure out how the headspace on wonko perrazi is maintained if barrel isn't fitted to action

I looked at the two Perazzi guns I currently have, a MX8 and a DC12. Both have blued actions and have been shot a lot so it is easy to see where the bbls bear on the action due to blue wear. Both were bought new, are still tight on the face w/ the top lever well to the right & have never had any adjustment on the bbl to action fit since leaving the factory.


On the MX 8 the back of the top barrel bears on the face of the action from about the 9 to the 3 o'clock position & there is no indication of the monoblock bearing at all on the flats that is visible from the blue wear.

On the DC 12 SxS both barrels bear from approximately the 8 o' clock to the 4 o'clock position including the rib between the bbls & approximately .200" of the front edge of monoblock is bearing on the action flats.


As mc posted, I don't see how you can keep the hook tight against the hinge pin (for long) unless the back of the bbls are bearing against the action face.

In one of the Purdey videos, the barrel fitter talks about that joint as being gas tight at the breechface.
If I recall the video correctly, he stoned it in.

Stoning is the last phase, after filing, when fitting a set of barrels. The ideal is 100% contact between the barrel breech faces and the action breech. But, that is virtually impossible. The higher the percentage of contact, determined by smoking in, the better. There are very few men in America that are capable of doing this job right, IMO.

Gough Thomas had written (cannot remember if it was in a book or ST article) of a way to prove action flexing and the need to make room for it by relieving the contact between between barrel and action flats. It involved the use of a small lump of plasteline (play dough in American I think) on the flats and closing the gun. Open and measure the diameter of the flattened plasteline. Now load and fire and remeasure. The plasteline dot grows in diameter after firing, proving that it has been subjected to further deformation due to the flexing of the action bar.

That is a neat experiment but there is no need to go that far. Close any SXS and slide a thin paper, cellophane or feeler gauge between barrels and action flats. That should convince that there is a gap there.

One mechanical phenomenon rarely, if ever, discussed in barrel fit is the Poisson effect. It concerns the behavior of thick wall cylinders (walls thicker than 1/10 of the diameter). Under pressure such a cylinder shortens and expands radially. Presumably that happens to the chamber end of barrels under pressure and this is followed by an equally fast recovery. This process must involve some considerable slamming of chamber ends against the breech face and the hook on the cross pin, and all this is in addition to the flexing of the action bar.

Simply holding the barreled action to a strong light source will reveal the tapering gap without the need for paper or other "devices". A .004" gap at the rear, with strong light behind it, looks big enough to throw a dead chicken through. An exaggeration, certainly, but it does look bigger than it measures, IMO.

So I checked four of the Perazzis, one MX8, two Mirages, and a MT6, and a 682 Beretta. All wearing their original factory fitted barrels. On every one the barrel shoulders (barrel flats) solidly engaged top of the action walls (action flats). The 682 has a replaceable block in the barrel shoulder at the breech end to accommodate wear. Those blocks as well solidly engaged the top of the action walls.

Someone best be getting those two manufacturers informed about how to do things the proper way.

The thinnest feeler gauge that I have is 0.001" and the action of my GR3 will not close if that is between the flats at the breech. It will also capture a human hair. What a POS. Looks like Beretta can't fit a SxS either.

I appreciate all of your comments about the fitting stuff. Gotta tell ya that I'm pretty disappointed in the quality of the factory work on my guns. Not even going to check the others, they're certainly just as crap.

Maybe all those guns were made in an alternative universe.

Pretty sure that if I had some way to travel out of this particular hellhole I wouldn't have bothered to return. And if the guns are floating in I'd be looking for that entry point.

Maybe the confusion Wonko is due to most posts being about SXS and the shotguns you refer to are OU.

As for Beretta action shoulder fitting, I heard from a Beretta fitter at the factory that the shoulder must have a relief of one tenth of a millimeter, about four thou, and that is also included in the instructions to service gunsmiths who go to the factory for training in repairs.

In an alternative universe .004" will not allow daylight to pass through.

I have read all the posts about clearances and lack thereof. About 40 years ago, I fitted a set of barrels to my K-32 Krieghoff. There was a gap at the breech face as big as a fried chicken wing. I asked the chief gunsmith at Krieghoff USA, Ottsville if he could replace the trunnion with a bigger size. His statement was similar to "It's a shotgun, don't worry about it." End of story is that this has been my main competition gun for that 40 years and has been problem free. Obviously, the fit of the forend lug has drawn the barrels into the trunnions and made everything work without a close fit at the breech face. How does this fit in with previous posts on this thread?

Gee ,,eightbore and the primers stay in ? What about headspace I have a k32 I think I'll check it out today also my Beretta that wonko say can be off face by design and function.i will report what I find.

Yes, the primers stay in, in all four gauges. I don't take any pains to install the small gauge tubes out a bit, so they meet the breech face. In fact, I have never thought to do that. I don't expect your gun to have excess headspace like mine because you probably have the original barrels. In a previous life, back to 1967, my gun was an ATA trap gun and I traded the trap barrels for my tubed skeet barrels years ago. For your information, all the Beretta barrels that I have fitted are tight to the breech face. As a side note, Wonko describes the replaceable gizmo at the rear of the monobloc as a wear item. Only the high end Berettas have that feature, 680 series guns less than 682 don't even have them. I have hundreds of thousands of rounds through a 682, have replaced locking pins after the lever went to the left, but have never replaced one of those "gizmos" nor do I know of anyone else who has. They are absolutely not necessary in keeping the gun tight. I have read that they pull the barrels away from the trunnions, for whatever reason I don't know.

My 32 and 686 both have trunions I blacked the action face on both put the barrels on with the forend opened and closed the guns viola both barrels have pressure on the trunion and breach face a clear outline in the smoke reside so they are on face, both guns have a metal piece machined on the barrels that contact the top of the actions the Beretta has locking pins the k32 a sliding hood .what I have learned is on these model guns the barrels rotate on trunions that hold the breech face to the action and metal machined on the barrels keep the barrels on the top of the action tight when the locking device is engaged.so they are on face in a traditional way but don't seem to have the gap required on a sxs.the end