OK Gents,
Please forgive the stupid question, but how do I check the length of a chamber? I recently purchased a Midlands Gun Co, BLE, 12 bore. I've been shoting 2 3/4" shells through it, but just realized it may have 2 1/2" chambers. How do I check? I do not have an english speaking gun smith anywhere around.
Patrick, Obviously you don't have a chamber gauge. Brownells sells them. They are easy to use and any collector needs a set. If skilled, you could use a caliper. There may be other ways to measure too.
Easiest way is to take an unsharpened pencil and carefully slide it along the chamber's wall until the first resistance is felt [check it w/a strong light, if you question your feel] pull it back out & take the measurement against a ruler .. you then have your answer and no need for buying anyhing not already on hand.
Gents - thanks - your answers were just what I was looking for.
My merthod is to use a 6" machinists acale. One of the flexible 6" scales available at home improvement centers for $2.00-$3.00 will work just as well for this. As a retired machinist I just happen to have a Starrett. Look through the bbl from the breech, held up in front of your eye toward an indirect light sourse. An uncurtained window is a great sourse. The forcing cone will appear as a shadow. Slide the scale in alongside your eye contacting the chamber wall. When the corner of the scale just touches the shadowline STOP & mark at the breech, then read chamber depth directly from the scale. With just a small amount of practise this can be a very accurate method. Many older chambers have some variation of actual diameters. I have personally witnessed a chamber which was only .001" smaller than the end of a chamber gauge show that chamber to be more than 3/16" short, IE a 2 3/4" chamber read 2 9/16" on the regulation chamber gauge. In this case the scale was more accurate than the gauge.
Personally I have found this method of watching the shadow line to be both easier & more reliable than trying to Feel an indistinct break between two tapers.
While having a chamber gauge as sold by Brownells or Parker Hale is a good option I have discovered they are not failsafe because different manufacturers have different standards for how they cut the chamber.
I have noticed that my German made guns have slightly tighter (smaller) chambers than my Belgium and Brit guns and the Brownells 16ga does not fit my German Gun marked 16/70mm 2 3/4in. So a chamber gauge that works perfectly in a modern Browning Citori 16, 1920's Greener 16, 1920's Belgian 16, may not tell the full story and you need to measure as 2-piper has described.
That said numerous traffic has been posted on shooting 2 3/4 in 2 1/2 guns with immunity. As a general rule I try to do what the manufacturer intended and believe you should too.
For a 12ga, I use a 6" metal machinist scale (ruler) like Miller does. You slide it in along the chamber wall and it will lift off the chamber wall when it rides up the forcing cone. A little finesse and you will see the light under the scale where it lifts from the chamber wall. Then read the scale. That's it.
On the smaller bores, I use the depth measuring blade that is on the back end of vernier, dial, and digital 6" calipers to do the same thing.
What are the barrel markings 65 is 2 1/2 or does it have a 16 in a circle?
My GECO has these markings
If you do not have a chamber gauge use this
This is for 16 gauge
I can give you the diameter for 12 gauge if you still need it.
My chamber gauge reads .728 and the marker .718. It should get you in the ball park.
My 2.5 inch gun measures to between the A & J in MAJOR putting the marker in butt first. And that is 2.62" in actual measurement but remember the marker is a tad small in diameter. You can build up the diameter with masking tape.
Hope this helps
Mike
Here are the markings on the barrel flats. The mark on the far left is a 13 over 1
Patrick,
According to the markings on your gun, it was indeed a 2 1/2" 12 ga. with 1 1/8 oz. Birmingham nitro proofs. The bore diameter at the time of proof was .719" The right barrel has no choke and the left does.
Now you just need to check and see if the chambers were lengthened with one of the methods above. The small machinists slide rule works well and is cheap to acquire.
Blue Grouse,
Thanks. So, I understand the 1 1/8 is the proof load (I thought that marking might be the load). What tells you that the chamber was originally 2 1/2"? And that the bore diameter was .719"?
Thanks again for the help.
Patrick;
There is nothing on your gun that tells you it had "Exactly" .719" bores when proofed. The 13/1 tells you it would accept a .719" diameter gauge 9" down the bore, but would not accept a .729" (12ga) one. It could have thus been anywhere from .719" to .728". 1 1/8oz was the standard proof for the nominally chambered 2˝" gun. The chamber actually likely measured from 2 9/16" to 2 5/8" (65-66.7mm) but the Brits called them 2˝". This 1 1/8oz was the service charge, not the proof charge. A gun of this era carrying 2 3/4" (70mm) chambers was required to pass the heavier proof for 1Ľoz of shot. The former was essentially a 3-ton proof & the later a 3Ľ-ton proof. These amount to approximately 8960psi & 9800psi as service loads.
The marks relate to the 1925 Rules of Proof. The 1 1/8th. ounce service charge denotes it has 2 1/2" chambers. They started putting chamber length on after 1954. I suggest you use only European ammunition that has the CIP mark on the box with 65mm. or 67.5mm. length cartridges. I know the 67.5 is longer than 2 1/2" but they are o.k. for that chamber length. The U.S. does not have comparible proof standards on either guns or cartridges and U.S. 2 3/4" stuff is generally a lot hotter as to pressure than European stuff. Please don't strain the old girl!
Midland guns are quite interesting in that a great many were as per the catalogue; although they did make one offs to order, if you can show a picture of the side of the action and let me know the type of fastening to the action and the forend I may be able to say what it is. They had very fanciful names for their guns. Sadly no records exsist. Lagopus.....
Gents, Thanks for the great help. I really enjoy the gun and have been shooting 2 3/4 shells through it. I'm thankful to have realized it may have 2 1/2 chambers and asked. I'll measure just to verify and then stop shooting it until I get back to the states and get correct ammo.
Lagopus, I'll put the info on the action and lock up in my other thread on this gun "Trying to date a Midland SxS"
Thanks again to all.
Patrick,
Bell showed in his studies published in the Doublegun Journal that there was only a slight pressure increase of a few hundred pounds shooting 2-3/4" shells in 2-1/2" chambers. As long as you're not shooting "magnum" loads, I wouldn't expect you'd have a problem.
Steve
