Measuring shotgun shells


#1

was wondering whats the best way to measure shotgun shells? because not all 3 1/2" shells, for instance, are exactly 3 1/2"
frogbert


#2

Specified lengths for shotshells are taken when they are uncrimped/fired. Your 3-1/2" shells will measure approximately 3-1/2" when fired. I measure loaded shotshells with a tiny ruler and kinda measure the rolled in portion the best I can. There may a more precise way to do it. I am sure a more ‘seasoned’ shotshell collector will help. Cheers!


#3

Thanks Roundsworth, so in other words if a shell is unlabeled or unfired it is pretty hard to know the length as in 2 1/2" vs 2 9/16.


#4

2 1/2" vs 2 9/16
all depends :
the country of the shell
the gauge
the period of time

in the old time :

  1. in usa and in europe (except england) 2 1/2 are real 2 1/2 for 20 gauge and lower (16, 12, 10, aso)
    in england what they call 2 1/2 is in fact 2 9/16
  2. 24 gauge and higher were real 2 1/2

nowadays:
you have to check carefully because it can be either

jp


#5

The lengths of Shotshells is derived from the length of the cylindrical part of the Chamber (from Breechface to the beginning of the “Throat”, which guides the wads and shot column into the correct gauge of the barrel).

Since the shell has to be fully exapnded and cylindrical to allow the wads and shot column to pass through without any excessive pressure peaks, the crimped section (whether rolled or petaled/folded) has to be completely cylindrical.
Thus the chamber length is the actual “measurement” of an “Uncrimped” shellcase. ( actually, the chamber is fractionally longer than the factory made shell case)

Thus firing a 2&3/4 shell (70mm) in a 2&1/2(65mm) Chamber , leads to high pressure, because the Shot column has to “swage down” to pass through the now Tapered section of case (in the throat of the barrel). Since shell cases are about 1-1,5mm thick in the walls, that is a 2-3mm “choke” right at the Mouth of the chamber…NO BONO ( as the current day Romans would say)…and usually ( if a Damascus Barrel ) —Ka-BOOM!!!. A Bored-steel barrel would probably take once or twice this abuse, before either Bulging or letting go.

That is the Importance of the correct shell to chamber lengths.

Of course, one can fire a short case in a long chamber, wqith no ill effects, except maybe a loss of velocity ( windage blowby)

Regards,
Doc AV
AV Ballistics.


#6

Shooting a shell shorter than the chamber is not good also
(not as bad as shooting a shell longer than the chamber)
Indeed the shot expand in the chamber, before to be again squeezed in the barrel cone, meaning a lack of accuracy because of shot deformation.

funny is the fact the 1939 (or close) us saami standards allow (and even promote) to shoot 410 shells longer than the chamber !!

It is stupid but not surprising when you see how bad designed and thought are the us standards about guns and ammo, even nowadays.

Perhaps one day the us goverment will oblige the ammo and gun manufacturers to comply with the CIP standards and this will be a very good thing
jp


#7

Were the all-brass shotshells made to match the “unfired” length of paper shells so they would feed properly, or did they use the full “fired” length of the case since there was little or no folded material making their fired and unfired length nearly unchanged?


#8

jp

The last thing we need in the U.S.A. is more government regulation. More regulations mean more government employees to oversee the regulations which means more taxes to pay the employees which means . . .

While it’s true that most firearms, including shotguns, work best with the ammunition made for them, using short shells in a shotgun or short cartridges in a rifle seldom result in much change in ballistics or accuracy.

Ray


#9

all depends
the heavy all brass cases when they are loaded almost keep the same length as when they are unloaded
light all brass cases are often shorter loaded than unloaded because the thin walls allow a crimping which, depending of the kind of crimp can have a consequent length
jp


#10

jp

The last thing we need in the U.S.A. is more government regulation. More regulations mean more government employees to oversee the regulations which means more taxes to pay the employees which means . . .

While it’s true that most firearms, including shotguns, work best with the ammunition made for them, using short shells in a shotgun or short cartridges in a rifle seldom result in much change in ballistics or accuracy.

Ray[/quote]

hello Ray,
I don’t know which way the CIP and its employes are paid.

In Europe the goverment just says : “all the guns and ctges must be proofed by CIP”, CIP been independant from ctges and guns manufacturers.
It is not like that in the US.
Guns and ctges can be sold without been proofed by an independant organisation, and even can be sold without proofing at all.

About shooting a 2 1/2 shell in a 3 1/2 chamber changes a lot the accuracy;
It would be better to say the efficiency and the pattern of the shots.
you don’t see that very well nowadays because most the shotshells use a sabot to hold the shot. but if you use no sabot there is a difference (here again not as much as before because nowadays the chambers have a cone , which was not always the case before).
JP


#11

I have noticed differences in fired shell lengths from different manufacturers, reason being is that I have had to adjust my shotshell reloading press crimping die setting for length to get correct full crimp closure when using different shell types and brands.

I have a very early production (1912) Model 12 Winchester pump shotgun in 20 Gauge (as all the first ones were - other gauges came later). At that time the standard 20 gauge chamber length of the Model 12 was 2-5/8" which is an uncommon shell length today. After I bought it, I found this out, so I did not want to fire normal 2-3/4" shells in this gun. I considered rechambering it, but found that Winchester plastic shells had a fired length only very slightly more than 2-5/8" so that is what I have used in this gun with no ill effects. Fired Federal 20 gauge plastic shells were measured to be somewhat longer, just slightly less than 2-3/4", so I cannot use those. I have also found that empty Federal shells will not eject properly due to the shorter ejection port of my Model 12, whereas the Winchester shells eject perfectly without hanging up in the port. A Federal empty must be pried out.

I don’t believe shooting 2-3/4" shells in a longer chamber creates either a safety or performance hazard. I’ve yet to see any cautions from shotgun manufacturers about this practice, and also because many, if not most, new 12 gauge and 20 gauge shotguns have 3"chambers and are advertised as being for either 2-3/4" or 3" shells without reservation.


#12

[quote=“DennisK”].

I don’t believe shooting 2-3/4" shells in a longer chamber creates either a safety or performance hazard. I’ve yet to see any cautions from shotgun manufacturers about this practice, and also because many, if not most, new 12 gauge and 20 gauge shotguns have 3"chambers and are advertised as being for either 2-3/4" or 3" shells without reservation.[/quote]

i didn’t say it will create a safety hazard.
but a performance loss;
try without a sabot and check the patern of the shot

jp


#13

[quote=“DennisK”]I have noticed differences in fired shell lengths from different manufacturers, reason being is that I have had to adjust my shotshell reloading press crimping die setting for length to get correct full crimp closure when using different shell types and brands.

[/quote]
Oh yes, very much so. Very noticable on occasions. But if they can clip a bit off the length they can save themselves a bit of wadding and it all adds up over time.