3.5" barrels?

[Silvio55]

Hi! I just bought my first 870, it's an express magnum (3") with a 26" barrel. But on the barrel says it can shoot 3.5" shells with a super magnum reciever. What's that? All 870 express come from the factory with 3.5" barrels even if it's not a super magnum?
Thanks!

[cwebb]

I've read about this at another site and almost posted here about it, but held off. Interesting to have confirmation from someone who has purchased one.
Think I'll give Remington a call.

[Synchronizor]

I've also heard folks say that Remington manufactures all current 12ga 870 barrels with 3.5" chambers to save money. Seems to me that an extra half an inch of chamber reaming would increase manufacturing costs, but perhaps the difference is made up in process streamlining & simplified tooling. Or maybe it's just all internet hogwash - that's always a possibility.

In any case, if your barrel is engraved as having a 3.5" chamber, then I would guess it does indeed have a 3.5" chamber. Obviously you don't want to shoot 3.5" shells if you only have a standard magnum receiver; while the gun can probably handle the increased pressure & bolt thrust (it is an 870, after all), the standard-length action will jam up trying to feed & eject the longer shells.

[Silvio55]

The barrel markings reads "2 3/4 or 3", 3 1/2" only with super mag reciever".
The reciever only says "remington 870", it doesn't says "express", nor "magnum".

[Synchronizor]

Remington currently makes 12ga 870s in either Magnum (3" & shorter) and SuperMag (3.5" and shorter) forms. Non-magnum 12ga 870s also used to be offered, which shared the same receiver design and most internal parts with Magnum models, but had slightly different ejectors & ejector springs, and barrels with 2.75" chambers. These non-magnum models are no longer being currently produced however, it's either 3" or 3.5" for 12ga 870s now.

Externally, 870 SuperMag receivers can easily be recognized by their lengthened ejection ports, and the spring-loaded sliding port cover on the rear of the bolt. Other 12ga 870s have shorter ejection ports, and no moving parts on the outside of the bolt. That is the most foolproof way to tell SuperMag models apart from others, as engravings vary, and no single serial number format applies to all 870 variants and production runs.

[Silvio55]

Thanks synchronizor! Yeah, I know it's a magnum reciever, but the magnum recievers are no longer marked as such, not even in the stickers on the box or the back of the user's manual says it's a magnum, neither says the Chamber lenght, maybe they change it when they started putting 3.5" barrels on every model.
I was worried about having a 3.5" Chamber since I never even shoot 3" shells, always use 2 3/4, and many people says that a longer chamber degrades patterning using shorter shells, and the problem is worse when the chamber is even longer or the shell is shorter.
By the way, I saw all your youtube videos, great job!!!

[Synchronizor]

Yeah, I know it's a magnum reciever, but the magnum recievers are no longer marked as such, not even in the stickers on the box or the back of the user's manual says it's a magnum, neither says the Chamber lenght, maybe they change it when they started putting 3.5" barrels on every model.

It's probably because they stopped making 2.75"-only models. 870 Magnums were and are called as such because 3" and 2.75" models were offered side-by-side for so long. But now, it's just normal 12ga 870s and 870 SuperMags. Calling out a standard 870 as a Magnum is only really necessary when talking about older guns.

I was worried about having a 3.5" Chamber since I never even shoot 3" shells, always use 2 3/4, and many people says that a longer chamber degrades patterning using shorter shells, and the problem is worse when the chamber is even longer or the shell is shorter.

Having a chamber that's longer than the shell can affect patterns, but it's probably only going to be really noticeable in extreme cases, like a 1.75" or 2" shorty shell in a 3.5" chamber (and 870s don't cycle those reliably anyway). With standard shells, an extra half-inch really isn't that much more of a jump. Remember that even if the chamber is exactly the same length as the shell, the payload still has to jump through the forcing cone. You might think that you're tripling your freebore shooting a 2.75" shell in a 3.5" chamber instead of a 3" chamber since .75"/.25" = 300%, but if you add the length of the forcing cone in, the actual difference in total freebore is far less. I don't know offhand how long a stock 870 forcing cone is, but if we assume 1/2", the difference is (.75+.5)/(.25+.5) = 166.67%. And if the forcing cone is 3/4", the 3.5" chamber only gives you 150% the jump to the bore you get with a 3" chamber.

I think freebore was a bigger deal back when shotshells used stacks of simple disk- & cylindrical-shaped card and filler wads between the powder and shot, which let the mass of shot spread out to the sides in the larger-diameter chamber, before slamming into the forcing cone and being violently squeezed back into a bore-sized column. These types of wads also let a fair amount of gas leak around them, and this gas could blow into the shot and stir it up even more before it got all the way into the narrower barrel bore. The longer the trip to the bore, the more opportunity there was for the shot to get disrupted.

If you look back at guns and ammo from those days, you see trends and fads aimed at reducing this effect. Things like longer shells that could hold more filler wads for better sealing, very short forcing cones, and even slightly short chambers that let the mouth of the hulls extend a little ways into the forcing cone to reduce the jump to the bore.

Nowadays, however, one-piece or multi-piece plastic wads have largely taken over. Modern wad columns incorporate obdurating over-powder cups that expand under pressure to provide very good sealing even in the hull & chamber, and shot protecting cups on the front to hold the shot together and keep out gases during the jump, and protect it from direct contact with the forcing cone and barrel. With these advantages, modern shotshells can handle a little extra freebore without a problem, and we're even seeing a trend toward elongated forcing cones that supposedly make for a less abrupt transition from the chamber to the bore. Some low-end or specialty shotshells skip the plastic over-powder cup and/or shotcup, and may be more affected by the extra chamber length, but if you're after the best long-range patterns, you shouldn't be using those shells anyway.

And as has always been the case with shotguns, if you really care about your patterns, you need to do some experimenting and testing to find load and choke combinations that your particular shotgun shoots well. No shotgun ever made patterns well with every load out there, and even a $40,000 shotgun won't produce a good pattern from a low-quality shotshell and the wrong choke.

[Silvio55]

Thanks Synchronizor!!!!