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16" Vs 20"


Kyle Norris

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Pretty sure this has been covered before, but I can't find any post relating to it in a search. Which do you perfer for 3-Gun applications. I seem to recall in previous discussions that 20 was perfered over 16, with 18 being considered the perfect comprimise. Also, any issues with making minor, or downrange energy with 16"?

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i think it depends on how far you have to make shots. i only have to make it 100 meters at the only local club that holds 3 gun matches, so i bought the colt match target m4 (16in barrel). however, if i was out west or anywhere that required a shot farther than 300 meters then i would go with the 20 in barrel.

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The 18" is perfect. For out east here the 16 is fine. Most of the courses are 150 yds and in. I'm sure the 16 would work fine out west too. It will give up some ballistic efficiency out past 200-250 but it still comes down to the shooter's ability to put hits on paper or steel. The difference comes in to play much more in limited with the longer sight radius of the 20".

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I have shot 16" & 20" AR's with standard bolt & recoil spring systems, and with the JP Lo-mass bolt & recoil spring systems and find the 16 inchers to be a harsher rifle to shoot either way. Not harsh as in lot's of recoil, but harsh as in not smooth in recoil recovery. After the shot I find the 20" rifles exhibit a lot less "sproing" from the bolt slamming into the end of the recoil tube like a freight train. The violence of the bolt carrier travel in a 16er causes an extended period of sight dance before the next shot can be taken. I have heard that a trick lengthened gas tube (pigtail?) can fix this on the 16er but I haven't tried one set up like that so I can not put experience to this issue.

The real root problem here is the fact that the gas pulse from the closer gas port location on the 16" barrel is getting to the bolt carrier earlier than it should and causing a slightly earlier unlock than desired hence the all extra violence in bolt cycling from the extremely sharp pressure pulse. An adjustable gas system will lessen this a tad on a 16, but functioning can then be a real problem if enough gas is bled off to slow the bolt down to where it doesn't reciprocate the rifle too much.

My 20" JP is ready for a steady follow up shot on the same target before I am. On all of the 16's I have tried I feel I am actually waiting quite a bit for the rifle to settle down (this includes a 16" JP lo-mass bolt carrier equipped rifle). Comp or no comp, the cycling pulse is responsible for a lot of the delay in getting off accurate repeat shots on the same target. I have only heard that the 18 incher is as good as a 20 incher in this regard.

BTW, I find a 20" rifle length is of no hindrance to me in any course of fire I have ever faced. I hear folks say light weight and fast handling are why they use a 16" barrel. Yet a lot of the 16" rifles I see are fitted with heavy & even bull barrels to help tame the recoil and they wind up weighing lots more than my just over 8 lb, 20" JP, and then handling like a heavily loaded barge in the fast stuff. Also, why have a rifle that can't reach out to it's full potential?

As far as the PF issues go, I have never found a factory 55gr ammo that won't make minor in a 20". In the 16 inch barrel you will probably have to chrono to verify as not all ball makes minor if it doesn't burn all of the powder in the barrel (16ers make great fireworks displays in the dark because of all of the still burning powder coming out the muzzle). Another issue is the fact that a 55 grainer not doing all the speed it is capable of doesn't fly as well as it should even out to 300 yds, so wind bucking is gonna be at the low end of that projectiles envelope. Heavy bullets with their optimum powders will not work as well in a 16" tube as they will in a 20".

Regards.

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Kyle,

I'm definitely in the minority, but I like the 16" barrels. They still make minor relatively easily. The are more manuverable and if you use a setup like the Bushmaster Dissipator's you still get the full length sight radius. Yes, the 20" guns cycle a little smoother, but the rifle compensator helps tame and smooth that out. The only time that smoother cycling may help you is on a long range course, but your going to slow down regardless so I don't think you lose any recovery time. Where the shorter guns really shine are the up close hallway/house stages. Your transitions and movements are much faster, IMHO.

Erik

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i shot my new colt match target m4 on tuesday. i was disappointed with the accuracy at 100yards, it was about a 6in group. at 25yds i could cover a quarter.

if i have to shoot anything out to 200 yards i'm going to be screwed.

i think i'll shop for a 20in top end.

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If you want to shoot a quantity of match-bullet ammo, you have to reload because factory match ammo is prohibitively expensive. There are a bunch of accurate bullets from 52 gr to 77 gr. You can run them through a ballistics program to find the trajectory and wind-bucking properties that suit you. I use 69 gr MatchKings with a 60-yard zero so I don't have to change my sight or hold from 60-220 yards. But in close range stages I just use 55 gr FMJ.

You might find something like Black Hills 68 gr reloads would be cost-effective

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Limited 40, each rifle is different but my JP 1:9 twist prefers Sierra 52 HPBT for 100 yds and Sierra 69 @ 300. Hornady 52 and 68 are the equivalents. Some like the longer Sierra 77 and Hornady 75 but the 69s shoot better for me. All mentioned can be loaded to magazine length.

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I saw it first hand last weekend at the RM3G match in Raton, a 16" AR didn't have enough to swing the heavy flash targets at 304 yds. We could hear the hits, but no flag. The 16" barrel really doesn't gain much in quickness on the open terrain courses. Get 2 ;) , or just stay with the 20" and practice, practice, more practice.

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The 55's werent moving the flash targets very well. Granted Pueblos (the ones used at Raton) are a little heavy, but more speed is always better.

I shot our flash targets with 55's, 60's, 69's and 77's at 420 yards. The 69 and 77's elevated the flash card 12-16 inches.

We are going to order new targets that are 3/8 thick for use past 300. The ones right now are 1/2.

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The 150 Sierra Match King rang them just fine! :P

Limited 40, be sure to use a scope when shooting for groups if you really want to test your rifle. Iron sights with a short radius (like the M4) make it tough to shoot groups. And remember barrel length has nothing to do with accuracy.

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