If you have short chambered gun, 2 1/2” finding proper length shells can be an issue. Looking at some British shell boxes and CIP rules, they say safe for guns chambered for 2 1/2” or 65mm and the shells are 65 or 67mm. 2 3/4” chambers use up to 70 mm. 2 1/2” converts to 63.5mm. But they consider 65 and 67mm as still, ok which tells me a few mm is less important than chamber pressures. Sounds reasonable.

Measuring a large number of Remington 20 gauge hulls most came up with an average just over 2 9/16 “ = 2.5625” = 65.1mm. Weird because we consider them to be 2 3/4”=2.75=69.8mm. Might just be one lot but it is about four thousand, so not just a short box. My Remington 20’s were closer to 2 1/2” than 2 3/4”. A few were 2 3/4” but most nearer 2 9/16”. Winchester AA were closer to 2 3/4”. Length can be different from lot to lot and some of my hulls are old. But as a group the Remingtons measured under 67mm. I just need to sort the longer ones out.

So I’ve decided to use hulls which have an overall length under 67mm and have built a simple gauge for go or no go. Once measurements are confirmed I intend to just keep my pressures down to the 8,00-9,000psi levels for 20 gauge loads. In the end, this eliminates trimming hulls, eliminate special wads and simplified reloading. Have not decided to trim all hulls down to 67mm but I might.

Next I am going to look at a 12 gauge hulls and see if Fiocchi, B&P, Remington, Federal or AA has a similar hull as a starting point. If not, I’ll just trim one group down to 67mm and load as normal.it would be nice to just reload instead of making so many special trips, special shells, wads and adjustments. And I think getting things to fit into a 67 mm shell might be a lot easier than finding things to fit into a 2 1/2”= 63.5mm shell. Going from 70 to 67 has got to be easier than going from 70 to 63.5mm.

or, when in doubt shoot 7/8 oz light target loads in 20 ga guns and 1 oz light target loads in 12 ga gons...ammo mans. are now providing fps data on boxes...most anything under 1200 fps should be fine...

and if you really wanna resolve your worries, have chambers opened to 2 3/4, so long as gunsmith agrees it is safe to do so...

american made gons, usually no problem...

but be extra cautious removing metal from barrels of light weight foreign made gons...

what ever you do, remember the 90 - 30 guidelines...

STFU Ed.

I'm in the process of making a chamber length gauge. I've been trying for fit in all of my doubles and it is pretty clear to me that chamber length is a bit arbitrary. Some guns are a little longer than stamped, some seem to be a little less. Some are quite different from one bore to the next on the same gun. I imagine at least some of this is due to the particular method and tools used to cut the forcing cone, but in any event, there is a lot more variation that I expected.

no reason to reinvent the wheel...

been using one of these for about 30 years now...

https://connecticutshotgun.co/professional-shotgun-chamber-length-gauge-with-integral-choke-gauge/

Says a lot ed. You keep it.

Ed you really area a moron aren’t you? Have you every looked up what factory pressures are? They all run high enough to operate a dirty, semi auto. Even the 3/4 ounce loads are running 9,500 to 11,900 psi. Saying light loads, or low brass shells is a completely dumb thing to do. It is pressure, not the pay load, not the velocity, not how tall the brass is. By your logic the old Active loads ought to be best because they had the very least brass height you possible could have, none. Payload and velocity might be important to recoil but have zero effect on pressure. Please block me and stop responding to my post. You are becoming a waste of keyboard clicks. You bring nothing to any post that I can see. Go back to whatever board you came from, assuming they will have you.

KY Jon - Brent,
I've been in same boat since the disappearance of RST shells and the like. Kent shots hells had some 2 1/2" available, but with only 3/4 oz. of shot. I've recently scored a bunch of Fiocchi and Rio 2 3/4 " shells loaded with 7/8 oz. shot at 1200 fps. I've shot them in my 2 1/2 " chambered Churchill with great results. The hulls show no harm at all to the ends, and they feel better than the RST's did. Perhaps just reloading the shortest 2 3/4 " measured shell to the 20 gauge equivalent would work. I have to admit, I haven't missed the 1 oz. that I normally shot.
Hope this helps,
Karl

careful karl, you too could be labeled a moron, for offering safe solutions to simple problems...

well ky, i have been a member of this fine forum for longer than you have...

if you dont like my posts here...well, then... thats too bad for you...

To know the exact measurement of the chambers in a quick and easy way, without tools, there is a way that I imagine many of you know.

We need a stick, a wax candle and a ruler. We will make the measurement in one of the two chambers, if the shotgun is SxS or O/Y. First of all, we will make a block with newspaper and we will put it in the barrel at a distance of about 10 cm from the extractor. This will act as a stop for the wax.

The first thing to do is to place the barrel vertically with the breeches facing upwards. Tape both barrels, leaving a gap in which to test. Optionally, the inside of the barrel can be lightly oiled.



Fill the barrel with wax.


Wait for it to cool and solidify.


Cut it so that it is level.



With the help of a stick and through the front barrel, we will remove the wax candle with small blows.

Measure the length of the chamber.


This is the chamber length of my W&C Scott & Son, that surprise me with 70 mm!

PD: Sorry for my bad english and regards!

campero, I love it. Never thought of using candle wax. But I think it would be a little tricky on the floor of a gun show with a gun I have not yet bought.

I'll post a photo of my solution, though it has a few more coats of finish to go and it needs to be cut from the stock yet. Marks are for 2", 2.5", 2.75" and 3". The shoulder is 3.5".

The idea for this came from a photo texted to me, by another member here. Many thanks for that.

Karl, I have 1 flat left of those same RIO loads. They are really nice to shoot and I don't suffer any damage to my scores either.

I have been reloading near equivalents of that load as well using American Select powder and some others. I'll be adapting that to the 2" gun, if and when I find one.

Crude, but it works for me

Gauge by FGP1154, on Flickr

Brent,
Loaded as such, the pressure feels low and the ends of the hulls in 2 1/2 " guns have no burns/splits or damage what so ever. I suspect that the shot string is improved as well. The solution for your proposed 2" gun would be quite different I'm sure.
Karl

Brent, your solution is great and very usefull but hard to do for all gauges. Mine is easy and it show how is the chamber and the first part of barrel, but as you said is not for do in a gun show.

Regards!

Edd how would you check the barrel for the 30,,90 measurement at a gun show .??????????

A very easy way to check chamber length on any shotgun is to use a index card, roll it lengthwise and insert it in the chamber and let it conform to the chamber size. Then gently slide it until it stops, mark it and try it again. Works every time and is simple to do anyplace.

Jon, years ago I only shot 20 gauge and started reloading for skeet. I used only Winchester AA compression formed 2 3/4" hulls. They all seemed to be consistent in length. I shot them out of a Winchester 101. Since then I have not reloaded any 20's but still have components to do so, but again they are 2 3/4". Since I started shooting and collecting doubles, mostly L.C. Smiths, the chambers for 20 gauge until sometime in the middle 1930's was 2 1/2", after that they went to 2 3/4". So I cannot say anything about loading short 2 1/2" 20 gauge, however I do reload 2 1/2" 16 gauge. The chambers for 16 gauge L.C. Smith's until late 1939-40 were 2 9/16" chambers. I use a Mec 600 Jr. and use a 1/4" spacer under the 3-5 stations to raise the hull for powder/shot, start crimp and final crimp. I use mostly Cheddite hulls, some Federals and a few black Remingtons cut to 2 1/2" .
From all the shooting you do you probably use a progressive machine like the Mec 9000. Not sure how short 20's are done in that.

Brilliant!

Well I now have about 3,600 Remington 20 gauge hulls that are at or under 67mm. Measured and sorted. I adjusted my Spolar loader last night and loaded 800 with 7/8 ounce shot, 8,000 Psi, 1150 fps. I was more interested in keeping the pressure under 8,000 than getting velocity up to 1,200 fps. I have used this load in the past and know it patterns beautifully. All with standard wads and powder on hand. If the weather hold Sunday I’m going to shoot these in my 20 bore, 2 1/2” Pape hammer gun.

I am a happy fellow. Next up will be finding a 12 gauge equivalent hull and load. Goal will be 1 ounce, 67mm, with pressure under 7,500, maybe 6,500 for Summertime use and anything around 1100-1150fps. Again it has to be with common available wads and powder on hand. I know I could just load 2 3/4” and most likely never worry about shooting them in my guns, but 67mm in a “65”mm chamber is easier to accomplish than I thought. I have 5,000 Fiocchi and 3,000 B&P hulls to start with. I might just load up a couple loads and have them tested if I can’t find a listed load. But I think there are plenty to pick from, between the two. If not, I still have Remington, AA, Federal paper and Federal plastic to look at.

wow...thats impressive...

tell us more about your pape hammer gon...

i too have a pape, but its a mere hammer less gun...but, wid fluid steel barrels...

bet your pape has twist barrels?