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Why does the 18” M4 come stock with “Modified”?


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Did the military version have chokes? If not, is their 18” modified?


i just screwed in a cylinder choke for a class where I tested truflite 8pellet 00 for the first time - admittedly didn’t try with modified.

What are rationales behind modified on a fighting gun?

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This has been hashed out numerous times.... but yes the military barrel has a fixed choke.  Most of what I've seen, included order forms from benelli and benelli italy show it having a fixed modified choke... some web review says it has a fixed improved cylinder.  There were no citations in that article so I have no idea where they got that from. You can take the measurements of the barrel and determine what it is as it's the amount of constriction that determines what choke it is.



The testing requirements that the benelli was entered in for the trials back in 1998 required the use of 00 buck, other shotshells, and slugs.  So there is a compromise one needs to make for selecting only one choke.  It makes sense that you wouldn't want chokes coming loose in the middle of battle... and who would want to carry around extra barrels. 


With that information I'll turn the question back around... why wouldn't you want a fixed modified choke on a fighting gun?  But don't wake my word for it.  There's plenty of information out there with a little use of a search engine. 

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This does get confusing.  Mine came with a modified as well.

However, on the Benelli website they say not safe to shoot slugs through chokes tighter than improved cylinder or cylinder.

I thought to myself then why would they ship the M4 with a modified?

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Wasn't trying to be dense - first part of the question was preamble, to qualify what I'm after.

I've got the Modified, and I've got the cylinder, and have yet to set up extensive tests of this and that ammo.

I did the searches on Benelli/Modified/etc.; but it doesn't go to the heart of it.

I gather slugs can work through anything and everything needs to be  tested gun by gun. . .


What I couldn't find, if it exists, is some "The military tried Cylinder and Modified, took Modified because X and Y with ammo Z in ambush situations" etc.

Also interested in any insight, like 'Modified improves 00 but causes flyers', or 'modified was found to work *better* with this type of slug across all guns'.


Interested in any insights or generalities discovered along the way that may influence what I should try to leave on the gun. It's also general interest, given that I have to examine my own role (or recreational use cases).



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For the testing they really are not going to run "ambush situations" unless it is specified in the requirements (or desired characteristics).  This is getting into legal wording for what is required and unless it is spelled out there will be lawsuits.  What you are asking for is something you'll have to test yourself.  Besides you'd have to use the exact same type of ammo the military was using at that time for those results to be applicable to your situation.


The Combat Shotgun to be procured and fielded will be
required to satisfy the following operational and physical
requirements described in the Joint Operational Requirement
Document and further amplified in the contract Purchase
(1) Capable of semiautomatic operation.
(2) Capable of firing both standard Department
of Defense (DOD) 2.75-inch, 12-gauge
No. 00 buckshot, No. 7 1/2 shot, No. 9 shot,
and slug ammunition,3 and 3.0-inch 12-
gauge commercial ammunition conforming
to Sporting Arms and Ammunition Manufacturers’
Institute (SAAMI) standards without
adjustment to the operating system. The
Marine Corps Systems Command is unaware
of any DOD acquisition programs to procure
and type classify 3.0-inch, 12-gauge ammunition
for use by DOD components.4
(3) Have a maximum effective range of forty
meters (fifty meters desired) with the DOD
standard 2.75-inch No. 00 buckshot ammunition,
and 100 meters (125 meters desired)
with slug ammunition.
(4) Have a length of 41.75 inches or less and
be capable of being reconfigured to, and be
operated at a length of, 36 inches or less.
(5) Weigh no more than 8.5 pounds (six
pounds desired) unloaded.

6) Be equipped with Low Light Level iron
sights and a standard U.S. Military accessory
mounting rail integral to the upper receiver,
to permit use of other sight enhancement

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1 hour ago, Scout_21 said:

(3) Have a maximum effective range of forty
meters (fifty meters desired) with the DOD
standard 2.75-inch No. 00 buckshot ammunition,


Yeah, I'm guessing choke made a big difference in this part (albeit probably the difference between 0-1 pellets and 4).

And point (2) precluded some very special-cased tool by claiming it has to be handy with what's basically the full gamut of 12 gauge ammo. . .

Thanks for the info.

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