doublegunshop.com - home Forums Thread Like Summary - On face but barrels not tight to frame at lockup

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

Maybe all those guns were made in an alternative universe.

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.

For Bushveld:

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

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.

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.

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

Wonko I think you just don't understand fitting barrels

I live in the trained gunsmith universe,how bout you

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.

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

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.

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.

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

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.

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.