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 2½" 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.....
I just tried 20 gauge snap caps in my 24 gauge gun - they won't enter the chamber at all.
I also tried 28 gauge snap caps and they dropped in and the rims, while loose, were held by the rim cuts of the chamber. I'm pretty sure if a 28 gauge round has the same rim size as A-Zoom snap caps they would fire.
You just found what I found when I fired a 28ga shell in a 24ga, FlyChamps--by accident in my case.
Okay, adding answers to some questions here...
Top of bore measures .680, which is basically right between the 20 and 24! My 20 gauge snap cap measures exactly .680 as well. Measuring the rim diameter "A" on the recommended chart is difficult as they walls are not straight but radiused.
I'm taking the kind old colonel up on his offer to send me a couple of spent 24 bore to see how these fit.
I'll try to get some photos on line, but likely not until this weekend. Thanks to All!
Joe, hoping that it is a true 24 and not the world's first documented 22 gauge.
Gil
If you can not measure A you should be able to measure B. If your "top of bore" means C then it sounds like you have a 20 with tight chambers unless the shell rim is poorly cut. A 20 gauge chamber should taper from .698 (measurement B) down to .685 (Measurement C), bore should be .615 which is measurement F. A 24 gauge has a bore of .579 which is much tighter than .680.
I will measure my 24 later this evening and post what I find.
Joe, PM me your address
Tested my 24ga.
Like Fly hamps the chamber will not let a 20 hull in at all. Also tested 3 different sets of snap caps and none would make it past the rim recess into the chamber.
The rim recess measured .727, the top of the interior of the chamber measured .694.
If you can get a 20 gauge snap almost all the way into the chamber i suspect it may be a 20 with a very tightly cut chamber, similar to the difference between two of my 16s one of which will only let a fired all brass shell into the chamber to the last 1/8 of inch or so
I took a picture of my tight 16ga barrel to illustrate my point about chamber difference making I t not possible to fully chamber at shell.
The actual amount of shell length that would not chamber is .57 not the 1/8 I earlier describe. The difference between the two RMC brass shells in diameters at the point .57 is the difference of .0025 (.7350 & .7325)
The gun with the wider chamber is a Belgian Gun from the 1920, the narrower gun is a Purdey from 1898 (I also have a German 16 BLNE with narrow chambers similar to the Purdey.
I will see if I can dig out my Belgian 20 gauges tomorrow in order to measure their chambers rim recess and top of chamber.
If would really be good if you could either take a picture of the barrel flats or tell us what the stampings are.
Possibilities are:
1. You have a 20 gauge gun with tight chambers and slightly smaller bore for shooting fibre wads from thin walled brass shells (similar to the 13 bore 12 gauge guns)
(are measuring the muzzle or the bore, if muzzle you may be getting a way off number because you have a tight choke?)(also how accurate is you measuring tool, you may not be accurate on the .680)
2. You have a 24 ga gun with oversized bores and chamber ?
3. You have a custom gun of a very odd gauge like 22 etc.?
If you have very tight chambers with an undersized bore your best course is to cast the chamber and have RMC make you shells.
Before you know the answer you really need to post the barrel flat and barrel stamps and you really need someone with a proper bore gauge to measure the chamber, forcing cone, bore, and choke.
y 20 gauge snap cap measures exactly .680 as well.
I only have a dial caliper but it measures my two 20 gauge A-Zoom snap caps at .667 and ..666 and they will not chamber in my 24 gauge.
Many European guns have tight bores for their gauge, is there any proof mark indicating the chamber gauge?
If it is a 24 gauge welcome to the club of oddballs - yes, I am definitely an oddball. But the gun doesn't care because it's broken clays and killed quail and woodcock for me because I definitely don't deserve any of the credit.
I Agree with all the Old Colonel said on this except for one thing which I will take exception to. That is that most guns which were intentionally made for use with all brass shells were bored oversize not undersized. At the time these guns were made all shells were using card & felt or fiber wadding. The brass shells have thinner walls requiring larger wads, thus the oversize bores. Commonly a 12ga brass shell was loaded with 11 gauge wads, a 16 with 14ga & a 20 with 18ga etc. Note also that ion the very early days wads were essentially bore size so in those days brass shells used 2 sizes over as 10 ga wads in a 12 while a paper shell used 1 size over as an 11.
At some point the makers began making the wads larger than actual bore size so for a 12 ga paper case you used 12 ga wads, for the brass 11 etc.
Admitting you cannot measure the small end of the chamber down at the forcing cone with a dial caliper you can certainly measure it just ahead of the rim seat. This should be ample to determine the gauge. Remember we are looking at a difference of 036" between nominal 20 ga & 24 gauge. It doesn't have to be read to within 0001" to determine whether its a 20 or 24. That could be determined with an inside spring joint caliper & a 6" machinist scale.
By Top Of Bore, I meant diameter B in the referenced chart. Again, the whole thing that changed my thinking that it was a 24 vs a tight 20 was the 15MM proof mark, which is much closer to a 24 than a 20. I am using a RCBS dial caliper to measure, which obviously isn't the most accurate as I initially cam up with a measurement that was .001 under that of the snap cap, which isn't possible!
I Agree with all the Old Colonel said on this except for one thing which I will take exception to. That is that most guns which were intentionally made for use with all brass shells were bored oversize not undersized. At the time these guns were made all shells were using card & felt or fiber wadding. The brass shells have thinner walls requiring larger wads, thus the oversize bores. Commonly a 12ga brass shell was loaded with 11 gauge wads, a 16 with 14ga & a 20 with 18ga etc. Note also that ion the very early days wads were essentially bore size so in those days brass shells used 2 sizes over as 10 ga wads in a 12 while a paper shell used 1 size over as an 11.
At some point the makers began making the wads larger than actual bore size so for a 12 ga paper case you used 12 ga wads, for the brass 11 etc.
Per 2-Piper, you are correct I misspoke, traditionally if different sized the bores would be undersized not oversized
If the bore proof mark is 15mm (0.591 inches) That number would make sense as the original choke marking for a 20 gauge which would be .025 from a classic 20ga bore of .615 and makes sense.
The fact the gun near chambers the 20ga snap but not quite, when my 24 won't admit into the chamber any part of a 20ga shell or snap cap. Makes me think it can't be a 24ga.
Really need pictures of all marks and barrel stamps
20 gauge in chamber snap caps in chamber Hopefully my attempt at uploading these photos work!
That looks like a 20 ga gun with either extra tight chambers or rim cuts which are not deep enough. Since 20 ga empties are easy to find I would try several to see if any close. Perhaps you have just hit on two combinations of shell and snap caps which don't work. I suspect you'll find nothing closes and you will need to have the chambers recut. It is a minor issue to the right gunsmith. Had this been a 24 the odds of anybody having a chamber reamer or rim cutter would be low.
Okay, quick update, I just fished out some old unfired 20 Gauge Remington Kleenbore shells from the sixties and they do chamber...but are tight (I need to pop them out. So i obviously have a 20 and not a 24. I'll send the barrels off to Michael Orlen this week to have the chambers sorted out (without lengthening them). Sorry for the false alarm and hopefully Old Colonel has not yet mailed me 2 24 gauge shells. Many thanks to all.
True, you can get tight chambered guns. I have a John Fry of Derby double 16 bore that needed slight skim out as factory load ammo was a push fit and the black powder re-loads that I need to make for the gun were very difficult to get in. Simple job to sort out. Lagopus.....
Before altering the chamber it might be easier to resize down a batch of 20ga shells to fit the chambers. Plastic shells are not hard to down size.
You can set up the barrels with a wood mallet or piece of 2x4 cut down gently (very gently) tap an empty 20 gauge hull (slightly lube the metal base with either cartridge lube or pledge) into the tighter of the two chambers. Then use a wood cleaning to gently tap it out of the chamber.
Note I believe it is safer to assume it is a 2 1/2 in chamber and not 2 3/4. It is easy to trim a 2 3/4 hull to 2 1/2 then load it and roll crimp it.
Once sized load the with a good 7/8 oz low pressure sub 8,000 PSI load. You can use 2 3/4 inch data, most of which will fit in a 2 1/2 roll crimped hull.
Based on the "65" mark on the barrels it has 2 1/2" chambers if they haven't been altered.
If originally 2 1/2 doubtful they are altered as the same cutter to lengthened the chamber would likely have opened the chambers up width wise as well.
