doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com question for those familiar with 24 gauge guns

Quite some time ago (at least 6 or 7 year now) I purchased a beautifully built St. Etienne box lock with like new case colors, gorgeous wood with super finer checkering and when I went to shoot it with my newly purchased RST light 2.5" shot shells, the gun wouldn't close. It won't close with my 20 bore snap caps either. The snap caps appear to fit fine, but I can see that the they stay slightly proud of the barrels. The RST shells stay out about 1/4". So I was thinking that the bores are a bit tight and I needed to send it off to Mr. Orlen for a bit of chamber polishing. While I had the barrels out - and access to my British proof house book, I notice the the barrels are marked with the number 15 in front of the barrel flats. So I research a bit and see that this should be the bore size in MM on French guns. Well, 15MM is a lot closer to a 24 gauge (14.7 MM, thus 2% over) vs. a 20 gauge (15.6 MM, thus 4% under). So, even though I thought that I was purchasing a very nice 20, I now think that I have a very nice 24! For those of you with 24 gauge guns, do 20 gauge nickel plated brass snap caps mostly fit into your guns? I don't own any 24 gauge shells (yet) to see if they are a good fit. I'll try to post photos in the future. Thanks in advance for your help!! Perhaps I shouldn't sell my proof book after all.

Old Colonel hopefully will chime in as he picked up a beauty of a French 24 last year. In the meantime, photos of it would be nice to see. Gil

PS: If for some reason the gun is neither fish nor fowl, RMC will make custom brass hulls to fit the gun. However, I suspect you will get an answer regarding bore size markings from a 24 ga. owner. Kirby Hoyt of Vintage Doubles may be of some help but he is not a board participant. He was at the Shot Show last week but should be back this week should you choose to call him.

Wouldn't call myself an expert on 24's, but if the RST 20's don't fit, there's something amiss. Shooting the only 24ga I ever owned at skeet, my last shell of the round slipped past the ejectors but chambered fine. And shot fine. One I got it out, I discovered that I'd somehow mixed in a 28ga with the 24's.

I do not have chamber dimensions for the 24 gauge off hand. In most gauges the small end of the chamber are approximately .070" above nominal bore diam. & the chamber then tapers, bigger toward the breech, @ .005" per inch. thus .0125" for a 2�" chamber. Nominal bore for the 24 is .579" thus about .662" for the big end of the chamber.
Small end of 20 gauge chamber runs around .685", thus you have .020"+ to account for. I have not measured the little end of a 20 gauge shell but certainly would not think it would have .020" worth of Slop in the chamber.

I have two 24 ga. guns. I use Fiocchi 24 ga shells and they fit properly

Never tried any 20 ga caps in the guns,

John Boyd

I have not tried 20ga snaps in my 24 gauge gun, but it would seem to me they would fit. As 2-piper has pointed out that 20ga chambers that are different from 24 gauge chambers.

I do not believe that 20 gauge snaps would fit anymore than 16 gauge snaps in a 20 gauge gun.

For snaps on my 24 gauge gun I salvage hard plastic primer inserts from a cheap set of snap caps and put them in a 24ga hull which I blued to ensure they looked very different.

Joe U,
Before you spend any money, redoing the chamber, check the rim/rim recess fit. If the rim recess has a radius and the rim is "square", it will act as you describe.
Mike

Joe U, PM sent

You could bracket by testing with 20 & 28 ga shells. The 20 should not fit and the 28 should be loose in the chamber.

Per my PM I can send you two 24 gauge hulls to test the chamber.

See this website for chamber dimensions, note manufacturers have some variance. I.E. the RMC brass shot in my 16ga Christophe will not chamber in my German 16 BLNE or Purdey 16 SLE as those chambers are a couple of thousandths tighter. They will chamber almost completely but stick out the last 1/8 inch.

http://www.dave-cushman.net/shot/shotshellloads.html

Bores can be slightly under or over sized. Can you measure the chambers? If they measure .698 just past the chamber rim cut you have a 20. If they measure .661 then you have a 24. If they check out as a 20 then measure the front of the chamber area, check to see if the chambers are short, tight or normal.

The chart of Dave Cushman is an excellent source of date to check if chambers have been buggered. I was looking at a nice Ithaca 12 Graded NID until I figured out not only had the bores been honed but the chambers as well and worse they were out of round. Must have had pitting in the chamber, used a round file or drill motor to get the pits then honed to cover the work. Dead give away for me was a very narrow shell rim cut that was thicker on one side than the other. Second barrel was normal.

Just to complicate things a bit; the 24 bore has two cartridge types, the thin rim and the thick rim. Most modern ones plus modern ammo are for the thin rim type. I had a Belgian one made for thick rimmed ammo and someone had fitted longer firing pins to reach thin rimmed rounds low in the chamber. It has been sorted out now. Lagopus.....