Shotgun 2. 3/4' vs 3'

Discussion in 'Shotguns' started by BigJohnx13, Sep 3, 2019.

  1. BigJohnx13

    BigJohnx13 AH Veteran

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    I need your expert opinion please.

    Will this Slug and AAA rounds fire safely and flawlessly in a 2.3/4" chamber semi auto. I get conflicting answers because a shotgun shell is measured in the open position which in theory means the first 2 rounds is too long. The 70 marking states that is is actually a 2.3/4" round.

    I Have the following rounds that measures as follows
    Slugs 63mm (2.52") closed- Open position 73mm- markings- 70mm (plastic casing)
    AAA 63mm (2.52") closed- Open position 73mm –markings- AAA 70/35 (plastic casing)
    No 7 58mm (2.35") closed- Open position 68mm- markings- 7-70-7 (paper casing)
    No 3 58mm (2.35") closed- Open position 68mm- markings- 70/35 no3 (plastic casing)

    All rounds are crimped at the top like a pizza )

    Chamber length 2.3/4" = 68.7 mm
    Chamber length 3" = 75 mm

    A shotgun shell length is measured in the open position. So 63mm closed shell + 10mm extra in open position depending on crimped type = 73mm

    From this info I can conclude that the AAA rounds in plastic casing overall length is 73mm and needs a 3" chamber. Although all four rounds state 70 mm (2.3/4) the first 2 is considerable longer than the other 2 rounds. Is this info correct


    shotgun shells (1).jpg
     

  2. Hogpatrol

    Hogpatrol AH ENABLER SILVER SUPPORTER AH Legend

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    3" chamber for all of those.
     

  3. Ridgewalker

    Ridgewalker AH ENABLER LIFETIME BRONZE BENEFACTOR AH Legend

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    Last edited: Sep 3, 2019

  4. Hogpatrol

    Hogpatrol AH ENABLER SILVER SUPPORTER AH Legend

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  5. IvW

    IvW AH Elite

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    These should all be fine in a 2 3/4 inch Nitro gun, semi auto I don't know.

    70mm devided by 25.4mm(1 inch)=2.7559 inches which is slightly longer than 2 3/4.

    I think you may be over estimating the length of the crimp which woul be closer to 8mm rather than 10mm.

    I have shot thousands through my Brno sxs without issues.
     
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  6. rookhawk

    rookhawk AH ENABLER AH Legend

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    What your ruler says doesn’t matter, only what the saami/ cip stamp says.

    3” slugs may not even be 2-3/4” when opened, but how it’s stamped matters.
     

  7. Ridge Runner

    Ridge Runner AH Enthusiast

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    I presume these are 12 gauge?(referring to the photo)

    The low/short brass shell and high brass shell on the right look to be 2-3/4 inch, the 2 high/long brass shells on the left look to be 3 inch shells. Both will work in a shotgun chambered in 3 inch or 3-1/2 inch. The 3 inch shells will not work in a shotgun chambered for 2-3/4 inch only.

    (If ) / These look to be factory loads and they look to be 2-3/4 and 3 inch shells. All 4 shells will work in single, double, pump and semi-automatic shotguns. Again, Proving the shotgun is chambered for 2-3/4 & 3 inch shells or in barrels chambered in 2-3/4, 3, & 3-1/2 inch shells.

    It is possible to force feed a 3 inch shell into some single and double barrel shotguns, BUT THIS IS A SAFETY HAZARD(!!!) for the shooter and anyone standing near by.

    I would NOT recommend shooting that or any slug through a screw in choke or fixed full choke shotgun. Slugs should only be used in modified, improve cylinder, open bore/ no choke, slug, or rifle slug barrels.

    The mm thing you are over thinking, just use a standard American ruler to measure.
     

  8. Red Leg

    Red Leg AH ENABLER LIFETIME BRONZE BENEFACTOR AH Legend

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    Assuming they are factory loads, all are marked 70mm - 2 3/4 inch. They are designed to be fired safely in a 2 3/4 inch chambered gun proofed for 1 1/4 ounce loads (virtually all - otherwise they wouldn't be chambered for 70 mm).

    As Rookhawk notes, shell length is not an exact science, but pressure and payload are much more so.

    Traditional slugs will work fine through almost any constriction. The groves (or "rifling" as it is often incorrectly called) on the Brenneke design like the one in the picture on the left, allows the slug to be constricted as it goes through the choke. They are, for instance, often quite accurate from the left full choke barrel of a drilling. The right shotgun barrel will often contain an insert barrel, the left can be used with shot or a slug and of course the rifle barrel is slide push away. On a drive hunt for wild boar, the rifle is normally enabled, allowing a second immediate shot with a slug from the rear trigger and left - full choke - shotgun barrel. Been that way for a century.

    However, Ridge Runner is correct, never use shells intended for a 3-inch chambered gun in a 2 3/4 or 70mm chambered gun. But the shells you have pictured are marked for 70mm use regardless what your ruler may say.
     
    Last edited: Sep 3, 2019
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  9. rookhawk

    rookhawk AH ENABLER AH Legend

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    Shells lie, intentionally. I don’t know how to be clear about this.

    65mm to 67mm May be 2-1/2”, or 2-5/8”, or 2-9/16”.

    70mm is usually 2-3/4”

    75mm is 3”.


    But if I make a shell as a CIP manufacturer, and I write 3” and 75mm on it, and it is in fact only 1” long, and you put it in a 2-3/4” or 2-1/2” proofed gun, and it blows up....who’s fault is it?

    The operator.

    Put the ruler away. Don’t attempt to outsmart the proof house.

    Proof marks say what the gun shall shoot. The box of shells says what it is. Those better match.

    3” 20 gauge remington Accutip slugs at 1900fps are no where near 3” long. They lie for your safety and tell you 75mm/ 3” so you don’t fire them in a 2-3/4” / 70mm chamber which is not proofed for that PRESSURE LEVEL.

    It’s not as simple as asking if the hull will unfold into the forcing cone causing barrel obstruction on the wad, bumping up pressure.(it will)

    Please don’t try to outfox the proof rules, particularly CIP and the two English proof houses. Don’t measure your hulls, conclude the measurements are different, then ignore the stamped nomenclature on the hull and the gun.
     

  10. IvW

    IvW AH Elite

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    They are all 2 3/4 and safe to use in 2 3,4 Nitro guns.

    Why can you not shoot an original Brenneke slug through a fixed full choke?
     

  11. Ridge Runner

    Ridge Runner AH Enthusiast

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    Not all full chokes are the same.

    Different slug (ammunition) manufactures have a variety of slug options.

    Shootin slugs through a tight full choke; may create excess pressure, expand the choke from full to improved modified, or worse split the muzzle.

    '...Threaded chokes can be damaged or dislodged....ending in possible injury or death to shooter or bystanders....'. para phased from one of the owners manual of one of my shotguns, either Remington, Winchester, or Mossburg. I'll try to find the manual and post the warning.

    That said, according to Stoeger, I am able to shoot slugs through my screw in chokes out of the P350. But why chance it? Just replace 11-87 that was also stolen from me and use the slug barrel with rifle sights the thieves left behind.
     
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  12. BigJohnx13

    BigJohnx13 AH Veteran

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    Thanks for replies. I sold my 3” shotgun and is busy checking out some 2 ¾” semi auto. Most of them is Berratta/Franchi’s about late 80 or 90 models or so

    I still get some conflicting info here according to this answers here.

    3" chamber for all of those.

    3” slugs may not even be 2-3/4” when opened, but how it’s stamped matters.

    Assuming they are factory loads, all are marked 70mm - 2 3/4 inch. They are designed to be fired safely in a 2 3/4 inch chambered gun

    They are all 2 3/4 and safe to use in 2 3,4 Nitro guns.

    I know a shotgun shell (chamber) is measured in the open position. Hence the measurements of the rounds. All the rounds fit easily in the 2 ¾ “ chamber. A 2 ¾ chamber length measures 68.7 mm. The AAA round measure 73 mm in the open position. So the opening of this cartridges extends into the forcing cone which may up the pressure level. Although it states 70 mm.

    CIP and SAAMI standard for

    12/70 indicates 69.80 mm or 70.10 mm open position (UNCRIMPED)

    12/73 indicates 72.80 mm

    12/76 indicates 76.00 mm

    One gunsmith advise it is safe to do so and the other one says no. Maybe best is to look for a 3” chamber and play safe, although in 2nd hand semi auto’s they are rare.
     

  13. Red Leg

    Red Leg AH ENABLER LIFETIME BRONZE BENEFACTOR AH Legend

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    Choke tubes are one thing. But Brenneke style slugs are designed to be fired through any constriction to include full choke. They have been used that way for a hundred years in Europe and are still used so. Indeed, a full choke tube often shoots them more accurately than a more open choke.


    I am still not sure what your confusion is BigJohnx13. Your 2 3/4 inch or 70 mm chambered shotgun will handle any load designed for a 2 3/4 inch or 70 mm gun. The box of shells and the shell itself will be clearly marked. The answers are not in the least conflicting. Throw away the ruler. This is pretty simple.
     
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  14. Ridge Runner

    Ridge Runner AH Enthusiast

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    BigJohnx13, where are you located?

    You are WAAAYYY over thinking this mm stuff: Open, closed, this, that....you are giving me a headache.(y)(n)(y):D:D

    Here in the USA, 2-/34 & 3 inch chamber, shotguns are as common as a dog to getting fleas :D. New and used in semi auto. Brands like Remington, Winchester, Mossburg, Benelli, Stoeger, Savage, Beretta, Franchi,...others.

    Measure a factory loaded shotshell or slug, convert your mm to inches, if the shell is closer to 2-3/4 than 3 inches it's 2-3/4, if it's closer to 3 inches than 2-3/4 then it's 3 inches.
    i.e. 2.72 to 2.78 = 2-3/4 inch : 2.90 to 3.10 = 3 inch.
     
    Last edited: Sep 4, 2019

  15. rookhawk

    rookhawk AH ENABLER AH Legend

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    I consider myself somewhat familiar with the rules of proof and shotguns in general...I'm getting confused by this conversation.

    The OP's questions were not really his questions, he has other designs on what he intends to do and it adds to countless problems.

    First suite of questions, answered succinctly by one and all. If you put a shell (as stamped on box and shell) into a chamber (as stamped on chamber) in any configuration that there is a mismatch, loss of life is a possibility.

    Second unstated/implied/inferred questions seem to allude to things like slugs, used guns he doesn't have anymore, new to him old guns he wants to buy, etc. A slug isn't a slug isn't a slug. They are highly calibrated, purposefully designed items. So are the guns that go with them. Your ideas of buying used autoloaders and having it all come together may fall apart, or at least be horse-sh&t accurate. Then it was into chokes. Too many loose ends... How accurate do you need? What do you want to kill? Is it a rifled barrel or a smooth barrel? Scoped or not scoped?

    If you're in the States and you want a world-class custom slug rifle that will kill to 250+ yards, send me a PM. I've built several and have an unfired custom spare I'll let you have for my cost of fabrication. If that's not what you're after, please start with the actual statement of what you're trying to accomplish, rather than getting deep into the technical minutae of CIP and the worshipful proofhouse rules.

    I don't mean to come off as frustrated, none of us are, we're just getting more and more confused by the OP. The people on this thread will give you the 100% gospel-best-in-the-world answer to your questions if you can get right to the point instead of focusing on the sidebar curiosities...this isn't really what you want to know anyway. (we just don't know what you REALLY want to know or do)
     
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  16. Ridge Runner

    Ridge Runner AH Enthusiast

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    Red Leg,

    Brenneke slugs and some other types of slugs may be shot through a full choke, BUT they may be of smaller diameter, by .001 compared to other slugs manufactured for use in slug barrels.

    There are sabots, buck and (mini) ball, round ball (home defense), types of "slugs", that shot through a full choke barrel could cause No harm.

    Not to demeaner BigJohnx in any way, but he does not seem to have the knowledge about shotguns as you or I and others have. THUS let's not overwhelm him with what we know and keep him safe until he gains more experience.

    Let all of us here on AH with our experience and knowledge get BigJohnx, safely into a modern shotgun shooting modern slugs and shotshell, before we start with older guns, damacus barrel guns, rifled and smooth bore slug barrels, bead sights, rifled sights, balliastics, various types of loads, various types of shot, high brass, low brass, light loads, heavy loads, field loads, small game vs upland bird vs waterfowl loads, etc, etc, etc...

    I have no clue where BigJohnx lives, what hoops he has to go through to purchase or even own a shotgun, or any type of firearm or what more hoops he has to go through to buy X number of shells.

    A $200.00 USD shotgun may cost him $2000.00 USD.

    He may or may not be able to purchase over the counter a standard USA $4.00USD (low end) box of 25 shells or USA standard $5.00 USD box of 5 slugs, like we can.

    I don't want invade BigJohnx thread so I'll title a knew thread "Should this guy be allowed a gun?" later today. It's about experiences I have had at 2 local ranges, 2 different people, both knowing nothing about the firearm they had just purchased or why they purchased it.
     
    Last edited: Sep 4, 2019

  17. Ridge Runner

    Ridge Runner AH Enthusiast

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    +1
     

  18. Ridge Runner

    Ridge Runner AH Enthusiast

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    Why did you sell a 3 inch chamber that also shoots 2-3/4 inch shells?

    A 3 inch chamber will safely shoot 2-3/4 shells!!!

    A 2-3/4 chamber IS UNSAFE TO SHOOT 3 inch shells!!!!.
     

  19. Red Leg

    Red Leg AH ENABLER LIFETIME BRONZE BENEFACTOR AH Legend

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    I don't believe anyone has moved off on a tangent. The OP showed a photo of a 70mm Brenneke style slug and questioned was it (along with the other pictured shells) safe to shoot in a 2 3/4 inch chambered shotgun. Typing slowly - Yes they are. Someone else began a dialogue about slugs and full-choked guns - The slug he showed a picture of is a 70 mm Brenneke style that is perfectly safe to shoot in a 2 3/4 inch gun - full choke or otherwise.

    He has followed that initial post with a second that shows he is still hung up on mm's and fired casing length. Those two posts have been his sole contribution. Any tangents have been provided by those responding.

    Back to the OP. I am repeating myself, but regardless of shot size, load, etc, assuming your shotgun is a modern gun in good shape, I repeat - Your 2 3/4 inch or 70 mm chambered shotgun will handle any load designed for a 2 3/4 inch or 70 mm gun. The box of shells and the shell itself will be clearly marked. The answers are not in the least conflicting. Throw away the ruler. This is pretty simple.

    But I will move on. Everyone has answered the base question consistently and accurately.
     

  20. Ridge Runner

    Ridge Runner AH Enthusiast

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    I just realized, No Photo of BigJohnx13 in avatar...HHMMMM?

    Yeeeaaahh, rather bluntly put to a new fellow to firearms, but, well put.

    How about we encourage him/her (no photo) and help him/her to become a better shotgunner, rather than alienate him)her???
     

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