Tag Archives: M203

M203 9″ vs 12″ barrel velocity

B.L.U.F.:  Negligible difference in muzzle velocity between the 9 and 12 inch M203 barrels.

About 2 years ago I decided I was going to buy a M203.  I had the extra cash and realized if I didn’t then, I never was going to.  Not to mention I had wanted one for years.  I searched out dealers in my state that had one in stock, and both dealers that I found wanted about $400 over MSRP.  MSRP being about $1600 for a LMT M203.  I went to my local NFA dealer, talked to them, and they ordered me a M203 and sold it to me for far less than MSRP.  Dealer made a profit, I saved a good bit of money, we both were really happy.

Still it took a while.  Took a long time for my dealer to receive in the M203, then with the 43P changes making things confusing for me, and the like, it took about 2 years from when I decided to buy a M203 to when I was able to take it home.

I tell you, going around and telling all my friends that I own a M203 was worth the cost and weight right there.  The fact that I get to shoot it just icing on the cake.

I ordered a standard mount M203 with a 12 inch barrel, while I waited I picked up a 9 inch barrel.  Really glad I did.  Also got the LMT stand alone stock for it.

Now to cut down on the rambling, I will get to the point.  I was recently contacted by someone from AR15.com forums asking about muzzle velocity on the M203.  Military manuals claim that the 14.5 inch barreled M79, the 12 inch barreled M203, the 11 inch barreled M320, and the 9 inch barreled M203 have the same muzzle velocity.  That seems a little hard to believe.

The muzzle velocity is said to be 250fps.  So, I have both barrel lengths and a chronograph so it is easy enough to test.  I fired a chalk round though each barrel length.  Lot Number on the ammunition is MTL13G614-034.  The Chronograph was set about 10 feet in front of the muzzle.  Rounds were fired into a 50 yard berm.

These training round consist of a zinc “pusher” base, a blue plastic cap filled with chalk.  The case is polymer with a .38 blank inserted into it.

From the 12 inch barrel, I got a result of 238.6 FPS.

For the shot from the 9 inch barrel, it was 233.5 FPS.

Now a sample size of 1 shot from each barrel is far from statically relevant.  But with only a difference of 5.1 FPS, I’m ready to call the difference between the two barrels negligible.

The picture doesn’t show it well, but these training rounds are horribly dirty.  Crud, sealant, unburned power, and all manner of gunk are left in the barrel after a single shot.

In any event, shooting a M203 is fun.  Little less fun shooting off the bench.  I used to own a .45-70.  I loved shooting that gun off hand, but when I shot it from the bench it would recoil straight back and be rather uncomfortable.  The M203 is similar.

M203 Information

I was asked by someone on AR15.com to find some information about the M203.  I am posting it here so it will be available for everyone.

I weight a 9 inch and 12 inch barrel on a precision scale.  Both barrels had grease on them which I did not clean off.  I can’t tell you how much the grease threw off the measurements, but this should still give  you a fair comparison on weights.

The 9 inch barrel is 14.7 oz, or 416.6g.

The 12 inch barrel is 17.54 oz or 497.5g.

It makes me think that since the 12 inch barrel is so close to 500 grams that may have been a target weight for the barrel.  When I first put the 12 inch barrel on the scale it said 500 flat, but when I moved it and wiggled the barrel it ended up settling down to 497.5g.  So in the end, the 9 inch barrel is about .18 pounds lighter than the 12 inch barrel.

LMT M203 with unknown brand 9in 40mm barrel.  LMT Stand Alone Stock, Daniel Defense Front Sight, and unknown rail mount leaf sight.

Also, the Army says that the muzzle velocity of the M320 is 236.22 fps, and the M203 is 250 fps.  But I don’t know what barrel length they are referring to in that.

On the Side Sling swivel

Occasionally questions arise about the side sling swivel for the AR15/M16/M4.  This will answer a few common questions.

It is normal for the sling mount to move.  it will wear and make marks on the barrel.

Side sling swivels come from the factory mounted so the loop faces the rear of the rifle.  This is fine if your using CAR or M4 plastic hand guards.  However if you are using a Knights M4 RAS this loop will interfer with installing and removing rail panel covers.  The Army authorizes mounting the sling loop forwards to negate that issue.

If you are mounting a M203 underbarrel grenade launcher on a M4, the side sling swivel will need to be mounted so the loop is on the ejector port side of the rifle(same side as used for left handed shooters).