View Full Version : 870 SuperMag Barrel on 870 Mag

February 7, 2011, 11:02 PM
Are there any issues with mounting a Remington 870 Exress Super Magnum barrel on a Reminton 870 Express Magnum receiver? Will it even fit? Can the receiver cannot take the stress of a 3-1/2 Magnum shotshell? What if it is only used with 2-3/4" and 3" shells?

Accoridng to the Remington website, "Model 870 Super Magnum barrels chambered for 3 1/2" shells cannot be used on non-Super Magnum Model 870 receivers. However, Model 870 magnum barrels with 3-inch chambers can be used on Model 870 Super Magnum receivers, but only with 2 3/4 or 3-inch shells. Super Magnum receivers have serial numbers that end with the letter "A"." I wonder if this is because Remigton doesn't want to held accountable should somone fire some 3-1//2" in a barrrel mounted on a regular Express.

February 8, 2011, 12:26 PM
Gets a little confusing doesn't it?, my 3in magnum has a 26in vent rib barrel that is marked as capable of firing 3 1/2 in shells as long as its on a supermagnum receiver. I know the non-supermag barrels (3in) will work with an 870 supermag as long as you only use up to 3" shells.

I have also read that supermag's do not perform as well with the 2-3/4" to 3" shells due to the exta spacing in the chamber as the shot has more room to become deformed before leaving the barrel and that makes me wonder why Remington would ship out standard 3" expresses with a supermag (3 1/2")barrel.

This leads me to believe the only really difference between the express magnum and the supermagnum(other than some internal parts and a longer cycle) is the strength of the receiver, eyeing both the receivers seem the same size. I guess I would prefer a barrel that was specifically designed for 2-3/4" and 3" shells versus getting a barrel that has blanket coverage for all 870's.

Anyone have any input on this?

February 8, 2011, 02:05 PM
There are several issues when using a different chamber or shell than the gun is designed for. Let's start with the easy one: shooting shells shorter than the gun's chamber. The most typical application of this is when you use a 2-3/4" shell in a gun chambered for 3" shells. This happens all the time, these days it's hard to find a 12 ga field gun that doesn't have a 3" camber. Performance may be degraded a pinch because of pressure loss in the slightly longer chamber, but who's aware of it?

Now let's turn this around. Suppose you have an old 879 or 1100 with a 2-3/4" action and a new Remington barrel has 3" chamber. Despite all the warnings, someone is going to manually feed a 3" shell into that 3" inch chamber. What happens? Nothing except you may have to manually remove the hull because it doesn't eject by itself. Why didn't the gun blowup? Because it's excessive pressure that causes shotguns to self-disassemble, and 2-3/4 and 3" shotguns are designed to operate at the same maximum average pressure.

Okay, enter the Supermag: Shooting short shells is the same as with the 3" chamber. But, with the 2-3/4" shells you may suffer a pinch more performance degradation. Also, you may encounter some feeding problems with that short shell on the long lifter. Next, what happens if you theoretically fit a Supermag barrel on a 2-3/4" or 3" action. Nothing (except performance degradation) as long as you shoot the shorter shells. But, when that same guy tries to manually fit a too-long-for-the-action 3-1/2" shell into that Supermag chamber, he may get a nasty surprise. The Supermag barrel is designed to operate at higher pressures than the non-Supermag action. As a general rule of thumb, if it will function via the magazine, then you're okay. Don't try to force a longer shell into a short action gun just because the barrel has a longer chamber.

Here are the SAAMI specs for Shotshell Maximum Average Pressure (MAP) in PSI.10 gauge 11,000
12 gauge 11,500 (except 3-1/2")
12 gauge 3-1/2" 14,000
16 gauge 11,500
20 gauge 12,000
28 gauge 12,500
.410 bore 2-1/2" 12,500

February 8, 2011, 02:34 PM
klawman are you related to superdave?

February 8, 2011, 04:08 PM
Is the bolt design the same for both guns? With the extra pressure of the
3 1/2" the bolt/reciever may need to be beefed up a bit to handle the thrust on the bolt. My second question would be if the ejection ports are the same.

February 8, 2011, 04:19 PM
Kind of sucks that Remington throws the 3-1/2" barrel on the 3" shotguns, new from the factory, specially if you mainly shoot 2-3/4".

February 8, 2011, 07:37 PM
Not related to Superdave. Per someone with a great deal of expertise as a Reminton LE armorer, the only problem will be that the Express Magnum receiver isn't going to eject the 3 1/2" hull. What Zippy says about the shell being to long for the elevator (if that is the proper term) makes sense and just looking at my Express withut having any 3 1/2" shells, I don't know if you could load through the loading port. I think you could top load one into the chamber. Anyhow, it looks lilke I found a 28" Express barrel. Regardless of the fact he says there is no dange, I don't like the idea of putting a 3 1/2" barrel on a 3" receiver

February 8, 2011, 07:40 PM
razo, I don't believe that Remington sells the Express with the Super Magnum barrels. My quetion was if I could put one on an Express, if I didn't shoot any 3 1/2" ammo with it.

February 9, 2011, 01:26 PM
I would assume you would be fine Klawman, my 870 came NIB from the factory with a barrel marked ok for 3-1/2" if used with a supermag receiver, I was just curious why Remington would ship a 3" gun with a supermag barrel when it seems the 2-3/4"-3" only barrels would seem to be better with the 2-3/4"-3" barrels.

February 9, 2011, 01:35 PM
I was just curious why Remington would ship a 3" gun with a supermag barrel when it seems the 2-3/4"-3" only barrels would seem to be better with the 2-3/4"-3" barrels.
I suspect Remington is trying to reduce the total number of barrels in their inventory.

February 9, 2011, 05:43 PM
I guess Razo's Express Magnum came with a Super Magnum barrel, which sounds all wrong given that Remington states that "Model 870 Super Magnum barrels chambered for 3 1/2" shells cannot be used on non-Super Magnum Model 870 receivers." If I were him I would call Remington for an explanation as to what is going on. I think I saw something somewhere about the 26" being special.

February 12, 2011, 01:59 PM
Zippy. You opined that Razo may have received an 870 with a Super Magnum barrel because Remington may want to reduce barrrels in its inventroy.

Are you thinking Remmie just wants to use up a temporary over supply of 31/2" barrels, that it is going to stop producing the 3" and sell all Magnums with Super barrels, or both? It seems there are few new ones even on the market.

I am having trouble finding a 3" Magnum barrel but I suppose I would be wise to be patient. From what I have read 3-1/2" loads are a flop to begin with, and it just seem dumb to put a barrel on my receiver that (1) may invite some poor fool (perhaps me) to load a 3-1/2" shell, (2) there is the shot deformation issue, ande (3) some think the extended chamber may affect barrel pressure.

February 12, 2011, 04:18 PM

I wasn't thinking they were trying to reduce their inventory of a specific part number barrel; but, are trying to minimize the total number of different barrels available.

If you have an older 2-3/4" action, new replacement barrels will have a 3" chamber -- they no longer offer the 2-3/4" only as 870 spares. So, Remington has already set a precedence that they will sell barrels with chambers too long for the 2'3/4" receiver in order to minimize the number of barrel types to catalog.

Following precedence, there's the possibility that all future barrels may be chambered in 3-1/2", if contour compatible. As to your potential problems from such a practice:

Someone putting a too long shell in the barrel: Perhaps the Remington engineers (and legal staff) don't see this as a problem. We don't know what safety factor was used when the action was originally designed for 2-3/4" shells. We don't know if the locking lug is made from higher strength steel these days than 60-years ago. Perhaps our fears of forcing a Supermag shell in a 3" (or 2-3/4") receiver are unfounded.
Shot deformation: Since the advent of plastic shot cups, shot deformation is no longer a real problem. If you check the old shooting records you'll notice that top scores sky rocketed with the transition to plastic hulls and one piece wad cups. IMHO, shooters worried about shot deformation are very old school.
Performance: Yes, there will be some slight performance degradation from pressures drops shooting shorter shells in long chambers. Typically, only the hard core target shooters will notice. (That's why Remington still makes 1100s with 2-3/4" chambers.) If a field shooter is worried about a pressure drop, he can go to a longer hull.

February 12, 2011, 04:33 PM

The last two new 870 Expresses I purchased came factory with 28" 3 1/2" capable barrels on non-supermag actions. My thoughts are the same as Zippys in that they are trying to streamline their supply chain.

Also as you heard from the armorer Klawman, there's no danger from firing a 3 1/2" shell in a 3 1/2" chambered barrel on a non-supermag action. The shell won't likely eject, but the gun won't go boom either. Now, if someone crammed a 3 1/2" shell in a 3" chambered barrel you may have some pressure problems. Maybe not, but......

By making this change Remington is actually in one way making their guns safer in that it's no longer possible to cram too long a shell into a barrel. Unless someone decides to start marketing 4" 12 gauge shells :eek:.


February 12, 2011, 04:51 PM
zipp13 & rantingredneck, Thank you both for explaining those points. I don't think I will be too concerned about pressure drops and shot degradation at this point. If I ever get that far into target shooting it will be time for an entirely differnt gun. Given everything, if the deal on a used 3" that I am working on falls through, I have a deal on a used 3-1/2" that may be go gold and, if not, a good price on a new 3-1/2".

As for the Magnum breech handling the pressure should a 3-1/2" be fired, the police armorer says the breech is so over designed it isn't a problem.

February 12, 2011, 05:49 PM
>Unless someone decides to start marketing 4" 12 gauge shells :eek:.Mama Mia! That would be one spicy meat ball!

February 12, 2011, 06:23 PM
As for the Magnum breech handling the pressure should a 3-1/2" be fired, the police armorer says the breech is so over designed it isn't a problem.

It is. And the 3.5" shells really don't have THAT much more oomph in most cases than a 3" to begin with. Going from a 3" 15 pellet 00 load to a 3.5" 18 pellet 00 load at you gain payload weight, but you lose some velocity as they drop the powder charge a bit to compensate. I think there's a 100-150 FPS drop in velocity going to the 3.5" load in most cases.

Now, there are some high velocity 2oz Turkey loads and Winchester markets at least one high velocity 3.5" 15 pellet 00 load at ~1400 fps if memory serves. Those probably spike the pressure just a tad, but there's that overdesigned thing again............

February 12, 2011, 06:24 PM
Mama Mia! That would be one spicy meat ball!

Makes me hurt and my Orthopedist see $ signs just thinking of it...........;)

February 12, 2011, 06:30 PM

There was a video on Youtube (and I think a thread about it here somewhere) some months back of a test where they obstructed the bore of a 12 ga. 870 with a 20 ga shell.

(One of the classic dangers of shotgunnery in mixing 20 ga and 12 ga ammo. A 20 ga shell will drop far enough into the forcing cone to allow a 12 ga shell to chamber behind it. You fire 12 ga shell into 20 ga shell not realizing it's there and boom!)

Well, someone tested this with an 870 on video. They remote fired it of course. It did not visibly damage the 870 in any way. No barrel bulge, no split, no KB. Would have been no injury to the shooter.

Now, they may have just gotten lucky with that one. There have been people injured by that mistake in the past.

And again......DO NOT TRY THAT AT HOME WITH YOUR 870!!!!

February 12, 2011, 08:30 PM
I took the easy way out and bought a used 3" chambered barrel a private party in Ohio this past hour. There goes one good excuse, the 18" unchoked barrel, for missing those mud birds.

February 17, 2011, 05:02 PM
I got a PM from someone, who is welcome to post about it here if he wishes, but he called Remington and was told, which some suspected, that Remington is putting the 3.5 inch chambered barrel on everything but the Wingmaster and the Police models. He couldn't get them to say why and they repeated the safety instructions stamped on the barrel.

Meanwhile my used 28" Express barrel is due in the next 2 hours.

April 11, 2012, 11:23 AM
I have both 870 mag and 870 supermag. I interchange the barrels on both 3.5 to 3 or 3 to 3.5. The only difference in the 2 receivers is that the supermag receiver is longer to allow the use of the 3.5" shells. The shot pressure is a barrel and chamber thing, the receiver is nothing but a device to hold it all together. While excessive chamber pressure could cause some receiver damage most likely the damage would be to the barrel. I have shot 3.5" shells in my 3" barrel several times with no damage to the gun at all. The shorter chamber in the 3" will result in more recoil however. It also can cause higher pressures which could damage the barrel. Usually by a bulge and crack in the barrel (if it doesnt' blow up) just ahead of the chamber. So it's not a bad move by Remington to put the 3.5 barrels on their shotguns, since the 3.5 shells won't function in the shorter receivers. If you can get the shell into the barrel it will shoot fine, you will just have a single shot shotgun. Just saying