Jump to content

Measuring internal barrels


Reeceknight
 Share

Recommended Posts

I am selling my 1880 side by side, with Damascus barrels and I keep getting the same question. what's the internal measurements coming up at? I work for an aerospace company who can measure these but how would I know what they was to start? The gun was reproofed in the 60s. someone's asked to measure it at the 9" point?

 

 

Any help would be good.

 

 

Thanks

Link to comment
Share on other sites

They are asking for the internal bore size measured 9 inches from the breech. They are interested in that because it gives an indication of how much enlargement may have occurred in the intervening half century. When it was last proofed a nominal size is stamped on the barrel flats by the Proof House, expressed most probably as a decimal of an inch, say .729".

 

If the internal bore measurement has increased by more than the next proof size (which will be roughly 10 thousandths of an inch greater than that stamped on the flats) then the gun is "out of proof" and can't legally be sold - leaving aside the arrangements for a gunsmith to purchase it with a view to re-barrelling/sleeving/reproof. An increase in the bore size probably won't be caused by simply shooting it, more likely by pitting being removed, which of course is done by removing the surrounding steel.

 

If it's "out of proof" it can be submitted for reproof; far better to get a gunsmith (a proper one) to do this. If the bore is too big inside it may have gone too far to be considered.

 

You may be asked for a wall thickness measurement, too. This is usually expressed as the thinnest barrel wall measurement for each barrel. The walls get thinner as pits get lapped out, they get thinner sometimes when a some types of choke work are done, and they get thinner when the exterior is re-browned. This measurement doesn't affect the proof, but can affect the value.

 

The very best answer is to take the gun to a decent gunsmith. That's going to be one who actually works with English guns, has the right gauges, knows his way round the rules and requirements of proof, and has a good reputation.

 

Perhaps the very first step is to have a good look at the gun, its overall condition, maker, type and quality, and compare it to similar examples that have passed through Holt's salerooms. That'll give you an idea as to a range of possible values. Sadly damascus barrels and age alone don't necessarily mean valuable!

Link to comment
Share on other sites

Wow thanks for your help plenty of info there. Iv just put the gun in for sale section. By the condition of it I would say it's been extremely well looked after but I will get it to a gun smith to measure internals as it will help towards it selling 👍🏼 Really appreciate that mate thank you.

Link to comment
Share on other sites

A shotgun is only as good as its barrels, good current bore sizes in relation to original and any subsequent proof sizes (as stamped on the barrels/barrel flats) and good barrel wall thicknesses are critical to the value of an English gun!

Once you establish these measurements you can start looking at the rest of the gun....pretty is an indication.......but does not mean valuable!

Link to comment
Share on other sites

A shotgun is only as good as its barrels, good current bore sizes in relation to original and any subsequent proof sizes (as stamped on the barrels/barrel flats) and good barrel wall thicknesses are critical to the value of an English gun!

Once you establish these measurements you can start looking at the rest of the gun....pretty is an indication.......but does not mean valuable!

 

the gun was reproofed and checked at some point in the 60-70s. Would this have been checked before the shop was allowed to sell it ?

Link to comment
Share on other sites

The right hand barrel was stamped 18.4, which is a metric measurement, of course. The original bore measurement when the gun was first proofed is 13, meaning nominally a 13 bore (this system pre-dates the fractional imperial measurement, which would have been .710")

 

I can't read the other one.

 

Mr Hadoke explains it all better than I ever could - https://www.vintageguns.co.uk/articles/proof-sizes/

Link to comment
Share on other sites

As has been stated above, looks like the right barrel was proved at 18.4 mm which would be 9" (I presume there is a metric 'near' equivalent to this at which the measurement was actually made) in from the breech end. If it still measures 18.4 (or close) at this point, it is well in proof; however - if it is larger diameter here (e.g. from lapping, fine boring etc.) then it may be getting near (or even past) the point at which it is deemed 'out of proof'. There used to be 10 thousandths of an inch between proof sizes (0.719, 0.729, 0.739 for 12 bores), but I'm not sure what the metric version of this is.

Link to comment
Share on other sites

Ok so turns out the aerospace measuring section have a calibrated bor tool. 👍🏼 and one for he wall thickness so they will measure 9" in and also wall thickness. we build helicopters and fighter jet parts so I trust them lol

 

E5B187F4-E1C6-4AA0-A826-F2528CFBC985_zps

 

 

2F7E079C-481A-43D3-9B1D-F42A0E57CE1B_zps

 

 

 

Appreciate all the advice and helps guys thanks

Link to comment
Share on other sites

Just as a by the by, what is the Anson and Deeley's Patent number, stamped on the action flat. I bought a similar boxlock earlier this year and mine reads 6270, again with a replacement stock although nowhere near as nice a piece of timber.

4336 mate, is yours the same maker? or just anson and deeley action same as mine?

Edited by Reeceknight
Link to comment
Share on other sites

Well who knows, was Michie and Crockart actually a maker or did he finish supplied boxlocks? Mine says Blissett and Son but I'm fairly sure they didn't physically MAKE the action. I was told mine was circa 1880 although it may be later going by the patent number

http://forums.pigeonwatch.co.uk/forums/uploads/monthly_10_2016/post-75973-0-47578300-1476183701.jpg

http://forums.pigeonwatch.co.uk/forums/uploads/monthly_10_2016/post-75973-0-06663300-1476183737.jpg

Edited by Mr.C
Link to comment
Share on other sites

You don't measure the minimum wall thickness at 9" You measure the minimum wherever it is. Again I refer to Holt's, who provide wall thickness measurements. I have seen barrels there listed as having as little as 12 thousandths of an inch minimum wall thickness, which is OK at the muzzle but you wouldn't want half the thickness of a poistcard a mere 9" from the breech, would you?

 

The 9" measurement is for proof gauging.

Link to comment
Share on other sites

You don't measure the minimum wall thickness at 9" You measure the minimum wherever it is. Again I refer to Holt's, who provide wall thickness measurements. I have seen barrels there listed as having as little as 12 thousandths of an inch minimum wall thickness, which is OK at the muzzle but you wouldn't want half the thickness of a poistcard a mere 9" from the breech, would you?

 

The 9" measurement is for proof gauging.

 

But that's what I'm going for. I'm checking inside bore for proof? I'm assuming wall thickness is harder to measure as they will always be thinner at the muzzle end?

Link to comment
Share on other sites

The walls are usually thinnest in the middle of the barrels they then stay thin to where the choke starts to taper. Some early 1900's guns were made very thin for light fast handling.

Gunman is the one to give you all the info you need.

Edited by figgy
Link to comment
Share on other sites

Internal bore measurement 9" from breech and wall thickness 9"from muzzles.

Bore is 9" from breech (for proof defined as that point). Note it will decrease again where any choke is (near muzzle).

 

Wall thickness is the minimum wall thickness - and is wherever the wall is least thick - which could be anywhere, but is likely to be a few inches from the muzzle behind the choke. Note that this could be quite a small 'patch' anywhere around the circumference because a locally thinned area may have been caused by previous work, typically a dent having been raised.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...