doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com how to check chamber length

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.

Simple, and it works
http://www.lcsmith.org/faq/chamlgth.html

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