[cgebhard]

I understand the legal importance to keep your barrel at or above 18.5 inches. I also understand a short barrel is more maneuverable in tight spaces, less for someone to grab onto in close quarters, etc.

But is a 20" or 21" barrel that much of a difference? I cut my m37 down to 21". I like the thought of a little extra length for slugs (in hunting applications too). I know it's kind of a preference question, just wondering if the 18.5 inch thing isn't a "mythical" and a legal number more than anything.

 

[papillonkirby]

The legal limit is 18" not 18.5"

 

[Ezra Smack]

Many prefer a 20" barrel simply because it allows the use of a longer magazine tube and increased the capacity by one more shell. The reason Remington makes 18 1/2" barrels instead of 18" is so that their magazine tube does not extend slightly past the end of the barrel.

Most every gunsmith or barrel maker is very careful to cut barrels just slightly longer than the legal minimum just in case.

 

[JMcDonald]

Between the common lengths of defensive-type shotgun barrels, there is little to no measurable difference in velocity:
http://forum.saiga-12.com/index.php?showtopic=19103

Looks like some of the links throughout the thread are broken, but there is still enough at the beginning to get the point across. The other links just showed the same stuff.

But yeah, the difference in spread and velocity between an 18" and 20" barrel is immeasurable, and both remain very practical until you get to about 7" or so (slugs that go 1600fps in a 20" barrel will be about 1100ish in an 8" barrel, IIRC), and the spread starts to get bad largely due to the lower velocity. The shot will move in radial directions at a given speed, so the faster the shot travels toward the target, the less spread will develop before the shot cloud impacts.

 

[cgebhard]

Edit JM- I posted this before I read your link info. That's kind of wild - it seems like the 20" length actually looses a little velocity. I would have thought the longer length would at least marginally increase. thanks...

Yeah, I know the 18" vs 18.5" thing.

I guess what my question boils down to is there any "proof" or validity that an 18-18.5" barrel is better than a 20-21-2x" inch barrel in a defensive/HD situation? To me it seems that people and vendors get stuck on the legal length "issues" when I see really little dis-advantage to a barrell that's 2-4" longer than the legal limit. I mean a 21" barrel doesn't really give the guy on the other end of the barrel much more of an advantage over a 18" barrel.

In reality there is probably more of an advantage to a longer barrels as long as it isn't 28-30"s. Just curious why most defensive guns try to take advantage of the 18-18.5 length other than to go below that is illegal in most applications. I know there are some 20" barrels as an alternative but generally those are older "riot gun" type of applications. It seems to me the legal length is more of a "holy grail" and that longer lengths are just a well suited or better.

 

[Ezra Smack]

Between the common lengths of defensive-type shotgun barrels, there is little to no measurable difference in velocity:

But yeah, the difference in spread and velocity between an 18" and 20" barrel is immeasurable

Barrel length has nothing to do with spread. That is a function of the choke.

18" barrels are just a little bit more maneuverable and 20" barrels allow one more shell in a flush fitting magazine tube. That is the difference.

 

[papillonkirby]

I don't know if Remington still makes 18" Police barrels but they made them at one time.

 

[T-TRAIN]

I don't know if Remington still makes 18" Police barrels but they made them at one time.

I bought an 18.5" cylinder barrel for my 870 from Mossberg. I just got it from Fed-ex yesterday and tested it out. Put about 15 rounds buckshot, 9 slugs, and 20 birdshot, and did not jam once; qualtiy seems very good, equal to the remington bbl my 870 came with. I perfer the 18" over the 20" because the shorter length, and I will never put an extended magazine on mine anyway.

One question about this barrel though. The part that is between the barrel and the ring that goes one the magazine has a small button that pushes in; what is this for?

 

[papillonkirby]

That is a detent ball that keeps the mag. cap from backing off. Some of the newer guns have a ratching detent inside the mag. cap. And I think that the 870 turkey barrel that is 21" with rib and Remchokes is a very good all around barrel.

 

[JMcDonald]

Cgebhard, the reason for the shorter barrels is just to get the most compactness as possible (within legal limits) for manueverability, swingability, and weight. I went for the 20" barrel because the extra 1.5" of length of 18" got me three extra shells over the 18.5" 590A1.

Adding two inches to the mag tube and barrel, and adding another shell, all together will add a few ounces on the end of the gun, slowing the swing and making it feel even heavier than that.

Ezra, yeah I do know length doesn't iself affect spread, which I explained in my post (that velocity is the largest factor in determining spread for relative barrel lengths). I was just saying from a practical perspective, one doesn't lose much velocity between common defensive shotgun barrel lengths, and a shorter barrel doesn't inherently increase spread as some believe (not necessarily anyone in this post, was just putting that info out there).

 

[T-TRAIN]

Adding two inches to the mag tube and barrel, and adding another shell, all together will add a few ounces on the end of the gun, slowing the swing and making it feel even heavier than that.

That's why I like mine with just the 18" barrel.

I do know length doesn't iself affect spread,

When I was patterning my 18" barrel, I noticed that at 35 yards I was getting roughly the same patterns with 9 pellet 00 buck as I was with my 26" bbl with IC. I guess I found a handy little barrel for shooting coyote's with! :wink:

 

[luke6-31]

Have you considered these advantages of the 20" bbl:

Available with interchangable chokes.

Increased distance between the front and rear sight.

 

[cgebhard]

Have you considered these advantages of the 20" bbl:

Available with interchangable chokes.

Increased distance between the front and rear sight.

Yes I cut mine to 21" for several reasons. It's good enough for HD but also should work fine as "slug" gun for hunting. Interchangeable chokes may or may not be a factor, I mean just because it's 20" doesn't necessarily mean it has chokes. Sight plain does make a difference. There are a lot of factors to consider. I think until I saw the link on one of the post above this I just figured the velocity would be the same or marginally better. The data in the link (JMac post I believe) says the 20" actually looses some velocity, seems wierd. So while velocity may be a negative you have to weigh the positives also.

 

[JMcDonald]

There is no logical reason a 20" barrel would actually have a lower velocity over marginally shorter and longer lengths. I think its just an anomoly.

 

[mattsbox99]

The legal minimum without paperwork is 16". I find it funny that a short rifle is a $200 stamp and a short shotgun is only a $5 stamp.

 

[FiveseveN]

The legal minimum without paperwork is 16". I find it funny that a short rifle is a $200 stamp and a short shotgun is only a $5 stamp.

16" for rifles and 18" for shotguns. The $5 is for a transfer of an AOW, but you still have to pay $200 to manufacture one.

EDT I have no idea what an AOW is, the internet is full of conflicting info and I'm having trouble finding info from the ATF

 

[LS240]

The legal minimum without paperwork is 16". I find it funny that a short rifle is a $200 stamp and a short shotgun is only a $5 stamp.

No, minimum length for a shotgun barrel is 18", rifles are 16". Also, a short barreled shotgun still costs $200 to either manufacture or transfer, same as a short barreled rifle. AOWs(all other weapons) cost $200 to manufacture and $5 to transfer. In order for a shotgun with a barrel length less than 18" to be considered an AOW it must be equipped with a pistol grip, not a stock, and can never have had a stock on it at any point in it's life. In other words, something like a Mossberg Cruiser could be converted to an AOW but it would still cost $200 to do so, and if you have ever put a stock on it for even a single moment you're breaking the law, before or after you made it into an AOW.

The reason the 20" barrel doesn't gain velocity over an 18.5" barrel is because shotgun shells use very fast burning powder, so most of the energy from the powder is expended quite early, typically in the first 14" or so. This means a 20" barrel wouldn't even have a significant advantage over a 14", let alone an 18.5" barrel. So basically anything over 14" and the projectiles are just kinda cruising down the barrel, not being pushed, and any length beyond that has nothing to do with velocity or patterning. The length is there for various other reasons such as legality, weight and swing for different types of shooting, mag capacity, etc.

Unless you like the swing and balance of a 20" over the 18" or 18.5", or have a need for another round in the tube, there just isn't much point to go for the longer barrel. The 18" does everything the 20" can but is obviously slightly more maneuverable. That's not to say 20" is a bad thing, it just doesn't do anything better than the 18-18.5" barrels. That's why most "tactical" shotguns are shorter.