Chamber depth

[Charlie Diehl]

I have a 28 ga Parker vintage 1917-18 with a chamber depth (?) of 2-3/4” and need to know if I can use 2-3/4” RST shells. I based my assumption of chamber depth on the fact I measured from the breech to a definite ridge in the bore that can be felt as well as seen. After reading about chamber depths and the use of gauges to do so I am wondering if I may have measured incorrectly as it appeared maybe “too simple”.

[Researcher]

At the time your gun was made, our North American Ammunition Companies were offering 28-gauge shells in two lengths. The "standard" shell was 2 1/2 inch, and carried a load of 1 3/4 drams of bulk smokeless powder or 14 grains of dense smokeless powder such as Infallible or Ballistite, pushing 5/8 ounce of shot. A longer shell of 2 7/8 inch with a slightly hotter load of 2 drams of bulk smokeless powder or 16 grains of dense smokeless powder such as Infallible or Ballistite, pushing the same 5/8 ounce of shot was also offered.

28-gauge Bulk Smokeless Powder Loads 1915-16.jpeg

28-gauge Dense Smokeless Powder Loads 1915-16 Infallible or Ballistite.jpg

NITRO CLUB 28-ga 1 3-4 dram, 5-8 ounce.jpg

FIELD 28-ga 1 3-4, 5-8 ounce.jpg

Early Long 28-gauge Peters TARGET.jpg

FIELD 28-gauge, 2 dram, 5-8 ounce.jpg

With Parker Bros. policy of holding chambers about 1/8 inch shorter than the intended shell, a 2 3/4 inch chamber would be about right for the 2 7/8 inch shell.

The progressive burning powder, high velocity, 28-gauge load with 3/4 ounce of shot was introduced in a 2 7/8 inch shell in the 1931-32 time frame.

28-gauge Super-X #6.jpg

The 2 3/4 inch 28-gauge shell first appears as Skeet loads, just before WW-II. Shortly after the War the 28-gauge was standardized at 2 3/4 inch.

Whether your gun was rechambered to 2 3/4 inch at some time or came from Parker Bros. with longer chambers may be impossible to prove.

[Charlie Diehl]

Dave, thank you. Can you help me with determining if I have measured the bore correctly? I can shine a light into the breech and see a definite ridge. I can also insert a very thin metal blade into the breech and it hits this ridge at a depth of 2-3/4”. After reading many posts concerning chamber depth measuring methods am I accurately measuring the chamber depth? I have been using a 2-1/2” RST shell with 5/8” of shot and assume that if I use a 2-3/4” shell with 7/8 oz of shot I would improve my chances of hitting quail.

[Big D]

Be careful. A chamber measuring 2 3/4 is for a 2 1/2" shell. Remember - Shell length is measured as unfired. When it is shot, it opens up about another 1/4"

[Charlie Diehl]

John, thank you for your response. Am I correct in assuming the bore is 2-3/4” based on the method I used to measure it? Many other posts I have read on this subject suggest it is very difficult to determine chamber depth.

[John Davis]

Originally Posted by John Dallas

Be careful. A chamber measuring 2 3/4 is for a 2 1/2" shell. Remember - Shell length is measured as unfired. When it is shot, it opens up about another 1/4"

I believe that is a misstatement.

[Charlie Diehl]

John, thank you for your comment but now I am even more confused.

[John Davis]

A 2 3/4 inch shell when loaded measures approximately 2 1/2 inches. When shot it measures 2 3/4 inches. Parker chambered their guns 2 5/8 inches to shoot 2 3/4 inch shells. The thought was that the 1/8 inch overlap created a better gas seal.

[Garth Gustafson]

Charlie, Galazan (Connecticut Shotgun) sells a combination chamber length and choke gauge tool that is fast, easy to use and 100% accurate. It handles all gauges from 10 to .410. Its a wise investment at $45. There may be other less expensive ones out there too.

[Charlie Diehl]

If I encountered a shoulder 2-3/4” from the breech using the very simple method of inserting a small metal ruler, have I accurately determined that my 28 ga Parker has a 2-3/4” chamber? Based on this measurement can I use a 2-3/4” shell which would allow me to shoot 7/8 oz of shot instead of 5/8 oz of shot?

Why have so many members comments for years regarding chamber measurement methods make it sound complicated IF the manner by which I determined chamber depth is accurate?