Barrel length needed ??

Discussion in 'Rimfire and Airguns' started by Alfred Crouch, Oct 4, 2011.

  1. Alfred Crouch

    Alfred Crouch Well-Known Member

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    How long does a barrel need to be to get maximum (or maybe optimum would be a better word) performance from a 22 long rife?
     
  2. 6mm Remington

    6mm Remington Well-Known Member

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    Now I've never chronographed .22 LR's in any of my rimfires yet........, but my understanding, and this makes sense, is that with the small powder capacity, the .22 LR actually starts to slow down after anything longer than a 22" barrel. Based just on that it would seem a 20-22" barrel would be about the perfect length.

    I was given a Remington Model 41P single shot .22 by my father when I was 10. It had a 27 1/4" barrel and shot like a house afire! It's the most accurate .22 I've ever shot. I decided to give it to my son when he got old enough so I took and had the barrel shortened to 22", it was reblued, and I had him drill and tap it for scope mounts so I could put a rimfire scope on it. It still shoots the same, lights out!

    I've really cleared that question up now haven't I! I"d be curious to know what the rimfire competitors use for lengths on their barrels. That would probably tell us more.
    David
     

  3. Alfred Crouch

    Alfred Crouch Well-Known Member

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    Thanks David. That is some very interesting and meaningful info. Maybe some others will add to it as well. Al
     
  4. top predator

    top predator Well-Known Member

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    don't think of barrel length and powder burn when thinking performance or accuracy, think barrel twist. you at least want to spin the bullet 1 complete turn. for example a 1 in 16 means 1 complete rifling "spin" in a length of 16".

    the rifling twist helps to spin the bullet, which centrifigul force helps to stabilize the bullet in flight once it leaves the muzzle, just like throwing a football.

    if it is a 1 in 16 twist as most .22lr manufacters have, a 16" barrel + chamber length will give you that 1 full complete spin of the bullet.

    just like a centerfire, a longer bullet heavier (such as the 60 gr aguila) will work better in a "faster" twist like a 1 in 9 compared to one with a shorter lighter bullet (40 to 29 grains) that a 1 in 16 twist.

    a wiki explaination and equations for the best twist rate for any given projectile
    Rifling - Wikipedia, the free encyclopedia


    Rifling twist rates and bullet accuracy

    if you want to think powder burn, it'll depend on the powder charge / FPS of the ammo used. again, most powder in high velocity will be burnt up in that 17 to 20 inch range, standard velocity / subsonic / match ammo will burn up in the 14" to 18" range.

    i cut a 20" barrel down to 16" and chronied both HV and match velocity ammo. at 19" there was a noticable drop in FPS, but after that the amount of FPS was barely measurable. i've further cut it down to 16", and same FPS range as the -1 and -2 inch readings.

    from a post elsewhere:

    Whether you call it a 20" barrel as advertised, 19.75" measurement from the muzzle to receiver, or 21 1/8" by inserting a cleaning rod into the barrel againt a closed bolt, then marking and measuring the rod, we'll call it the "stock length barrel", -1", and -2".

    Rifle used: Savage MKII "F" sporter barrel - 2lb 12oz trigger - shot of harris bipod and rear bag - 12x on the optic. Used 2 ammos, CCI blazer (high velocity) and Aguila Golden Eagle Match rifle. 10 round groups were shot, barrel was dry swabbed "clean" before an ammo change. At 50 yards, 1" bull was used, at 100 yards 1.5" bulls.

    Groups with the stock length barrel - weather 65 deg. F., 35% hum., 3-7 mph wind from 8:00, mostly sunny.

    Groups with the -1" and -2" - weather 45 deg. F., 47% hum., 3-10 mph wind gusts 3:00.

    FPS per length - Chrony was set at 10 ft away from muzzle:

    Stock barrel
    Blazer - 1241 FPS avg., (range of 1221-1256 FPS)
    Aguila Match Rifle - 1101 FPS avg., (range of 1080-1126 FPS)

    -1" shortening
    Blazer - 1216 FPS avg., (range of 1207-1221 FPS)
    Aguila Match Rifle - 1083 FPS avg., (range of 1062-1095 FPS)

    -2" shortening
    Blazer - 1217 FPS avg., (range of 1173-1239 FPS)
    Aguila Match Rifle - 1082 FPS avg., (range of 1062-1111 FPS)

    50 Yard groups - stock length top, -1" middle, -2" bottom
    [​IMG]

    100 Yard groups - stock length top, -1" middle, -2" bottom

    [​IMG]

    It appears (in general) that the groups of both the ammos shrank at both 50 & 100 yards. From stock length to -1" there was a 25 FPS drop in the HV Blazer, and 18 FPS in the Match velocity Aguila. When shortened another inch to 2", no significant drop in FPS, but more consistant on paper. Oddly the -1" and -2" barrel length RAISED the POI an average of 1.5" in the HV and remained the same for the match ammo at 50 yards. On the contrary, at 100 yards the POI on the match ammo changed about 1.5" higher - STRANGE!

    BULLET DROP - (shooting at 100 yards with the 50 yard setting) the amount of bullet drop changed, but only slightly by about -.75" with the shorter barrel.

    OVERVIEW:
    1. Shortening the sporter barrel decreases group size with HV and match ammo.

    2. FPS was reduced with the initial -1" (around 20 FPS), but the second inch reduction didn't show much more as i would have expected (I figured it would be -40 FPS, but was nearly identical to the -1" FPS).

    3. Balance and handling was improved.

    So will further shortening the barrel decrease group size more, stay the same, or actually hurt?

    After the initial drop in FPS, would FPS stabilize until a more "extreme shortened barrel" length is reached?

    Is it that the shorter barrel is "stiffening" up the sporter styled barrel by reducing "whip" and harmonics producing better groups?

    I'm not sure at this point, but shortening my sporter barrelled rimfire by 2" actually improved my groups at both 50 and 100 yards, high velocity and match / standard velocity.
     
  5. donw

    donw Member

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    i seem to recall a test done by Ruger (?) and for some reason i seem to recall that the ideal length was 16" or 19" for max FPS from the 22 LR cartridge.

    many, if not most, of today's M4/AR carbines and ruger 10/22 barrels come in 16" lengths. (My Spikes ST-22 M4 has a 16" barrel)
     
  6. Kevin Thomas

    Kevin Thomas Well-Known Member

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    Alfred,

    are you asking about top velocities, or best accuracy? Top velocity in rimfires will usually be achieved with barrels not more than about 18"-20" at most. After that point, most longer barrels will actually reduce velocity to some degree. Accuracy is another matter, and is (to a large degree) independant of barrel length. Assuming identical quality and chambering, a short, stiff barrel will give better accuracy than a longer and "whippier" one. Most of hte longer barrels used in target rifles are selected for reasons other than accuracy per se. Balance, sight radius, etc., all come into play here. That said, there are a great many match/target rifles that use very short barrels, and shoot phenomenally well. I have a S&W M41 that will (with select ammo) hold a half inch at 50 yards for a 10 round group, time after time from a machine rest. That's a mere 5" barrel, but it shoots better than most inexpensive rifles, no problem. That said, I use a fairly long (24" heavy") barrel on my silhouette rifle, fluted, to get the balance where I want it. The price for this is more barrel time, meaning that follow through becomes even more critical.

    All depends on what you want to use it for, and how you want to configure the rifle.
     
  7. Alfred Crouch

    Alfred Crouch Well-Known Member

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    My main concern is accuracy. I have a Savage Mark II BTVS with a 21 inch barrel. My goal is shooting squirrels through the head.

    Don't laugh...... Doesn't hurt to try.
     
  8. Bart B

    Bart B Well-Known Member

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    .22 rimfire free pistols, such as the single shot ones shown here:

    free pistol - Google Search

    will shoot about 1/4 inch at 50 meters, same as .22 caliber free rifles. By "free," I mean they are virtually free of restrictions. They have those longer barrels to make them front heavy so they can be held better and easier to align the sights.

    High Standard and Smith & Wesson both made target pistols with shorter barrels that shoot almost as good. Ruger semiautos were also rebuilt and did very well in competition.

    For rifles, .22 rimfire target rifles originally had 26 to 28 inch barrels so their front sight woud be far enough away. But it takes a long time for those slow bullets to leave the barrel after the round fires. Rimfire compeition is a holding game; you have to hold still while the bullet goes down the barrel. It takes 3 times as long for a rimfire bullet to clear the muzzle than high power rifles. Anschutz finally did something about this and made their top target rifles with 19 inch barrels with a "bloop tube" on the muzzle to extend the front sight an exta 6 to 8 inches. That bloop tube's about 3/4 inch inside diameter.

    For a rifle, a 19 to 20 inch barrels is probably optimal for accuracy as well as holding when they have a scope on them.
     
    Last edited: Nov 21, 2011