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9/22/2017 12:11:25 AM
Posted: 8/14/2003 10:06:39 AM EDT
From Tatjana's fragmentation experiment #6 thread.


Originally Posted by Forrest
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Originally Posted By ArmdLbrl:
Wonder how much further the 18.5" SPR barrel or even the plain 20" M16A4 (USMC DMR rifle) would shove the fragmentation threshold out? Maybe 400m for the 20"?
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Not much - if you look at the velocity numbers for the 18" & 20" you don't gain a significant amount for the extra barrel length.



If the SPR barrel doesn't gain a lot on the 16" then what was the point of making the SPR instead of the SEAL's pet Recon Rifle which had a 16" barrel.

What does the 18" barrel give if not velocity?
Link Posted: 8/14/2003 11:24:36 AM EDT
better gas setup?
Link Posted: 8/15/2003 6:32:05 PM EDT
Link Posted: 8/16/2003 8:20:56 AM EDT
We just use the M14 to fill the void they are nice maybe one day i'll own one.
Link Posted: 8/16/2003 1:30:50 PM EDT
Better Acuarcy and Precision at longer ranges. I thought it was more of an accuarcy issue than a problem with the rounds and fragmentation and velocity. I thought thats why the SPR 18" and the Marines stayed with the 20". Flatter trajectory I would assume? You dont see many 14.5 or 16 inch barrels on the "Ready" line at shooting matches which is more along the lines of the SPR. DoNt ya think? I could be Biased though, I spent to many years on the Army Reserve Rifle Team, hahahaha, cp
Link Posted: 8/16/2003 2:03:51 PM EDT
I think the reason you don't see the 14.5" and 16" barreled rifles at the matches is probably because they are not authorized for service rifle match or because they don't have the sight radius of the 20" barreled rifles. The shorter barrel rifles shine when you put optics on them. They are lighter and less cumbersome in the field. I have had a 24" heavy match, an 18" match medium profile, and a SS 16" match Oly barreled ARs. They all shot sub 1/2 MOA with the right ammo, but the 24" heavy was just that, too heavy. I still have the 18" and the 16" rifles. I think once you get out to the ranges they are using these rifles at none of them are going to have the velocity for the bullets to fragment. I do think poking holes in people at those ranges still is going to get the job done. They may not die right away, but at those distances the average issue rifle in not really effective. The best I have been able to hit an 18"x18" gong with an 7.62 AK on a fairly regular basis was 350 yards. I was shooting clay pigeons at that range with my 18" AR last weekend. IDHunt
Link Posted: 8/16/2003 2:12:13 PM EDT
[Last Edit: 8/16/2003 2:31:07 PM EDT by Green0]
I had a M1A supermatch from SA and I just got sick of the wierd kick that would send the rifle skipping what seemed like 2 inches to the left when I fired from a bi-pod. It seemed like it was actually unlocking before the bullet left the bore and the sideward kick was opening groups to about an inch to 1.5inch at 100yds. I could put 2 in the same hole but before I got to 3 a flyer would always kill the group. If they could lengthen dwell time significantly (and fix a few other difficiencies- like stock bedding and scope mounting) the M1A would be nice. Maybe the TROY M1A doesn't have any of those problems? [b]I know the difference between 10.5 and 11.5 is a lot of velocity but it seems to taper off around 16-18 maybe CRANE felt it passed the point of diminishing returns. < the suppressor makes it long so they probably want to keep it as short as possible.[/b] Now if only they could get 14.5 velocity out of a 10.5............ Where is M2 CORP when you need them? didn't they promise a round that would make the 6 and 7inch 5.56 uppers attractive? [b]62grain M855 info from KKF's site[/b] 10.5" 2627 FPS 11.5" 2738 FPS (add 1" for 111FPS) 14.5" 2907 FPS (add 3 in for 131FPS) 16" 2989 FPS (add 1.5in for 82FPS) Notice the difference between adding 1.5 to 14.5in and 4 to 20in? big gain in length for little gain in velocity when the 2 are compared. 20" 3095 FPS (add 4in for 106FPS) 24" 3158 FPS (add 4in for 63FPS) 26" 3231 FPS (add 2in for 73FPS I'ld bet most of the 106FPS from 16-20 is before 18inches. just look at 20-24in if you doubt it- averaging 15FPS per inch (pitiful gain).
Link Posted: 8/20/2003 11:35:45 AM EDT
[Last Edit: 8/20/2003 11:39:52 AM EDT by eaglecp]
IDHunt You really think a 14.5" barreled M4 is as Accurate as a 20" barreled M5 out to say 3-500 meters or even 1-200 meters? Optic or Not? The velocity and Flatter Trajectory of the 20" I would think would translate into a more accurate/ precise platform. I really cant believe a 14.5 or even a 16" could hang with a 20" barrel rifle "off the shelf" at a Local CMP match. Im not talking about hanging with a CMP rifle set up Im talking like say a 14.5-16" against a 20" Bushy for example. Barrel for barrel. I know they are not allowed normally in competetion for record but I still cant beleieve they are as accurate. Even if you scoped them both. Now Im not talking about beyond 500 , because I think the 223 is useless pretty much out past that. Pretty much!! Dont flame me guys! hahhaha. I think for people like myself who like "rifles" the 18" platform is an excellant variation, I just wish their were more barrel manufacturers making them. Armalite , Bushmaster are you listening??? cp
Link Posted: 8/20/2003 3:17:52 PM EDT
Actually the shorter barrel should be more accurate. Shorter is stiffer, will have better harmonics, and will not flex as much. I have learned that accuracy is not dependent on velocity or barrel length. Many of my most accurate loads out of my bolt guns have not been their fastest loads. As long as the barrel is of good quality and you have enough length to stabilize the bullet and get a good powder burn the shorter barrel will win. I have a Rem PSS than came with a 26" barrel. I lopped 5 inches off the barrel and my groups shrank. I just changed my loads to compensate for the velocity loss. When you are talking about a difference of 106 fps when going from a 16" to a 20" it is less than 5 inches of drop difference at 400 yards. As long as you get your come-ups right and can read the wind the 16" will do just fine. If we where talking an elk rifle where a guy was pushing it for a clean kill I would say try to get the extra velocity, but these guys are just trying to poke holes in people at those ranges. People are very delicate creatures. Also psychology plays a big part in whether a person lives or dies. For a military rifle trying to put some lead in the enemy with the bullet weights they are shooting the 16" rifle will do just fine. IDHunt
Link Posted: 8/20/2003 4:10:25 PM EDT
IDHunt Thats interesting, Ive never heard this before but its interesting. I guess it makes sense even though its contridictory to everything I've ever read or learned while shooting with the Army Reserve Rifle Team. Id like to here the opposing argument if there is one? cp
Link Posted: 8/20/2003 8:26:58 PM EDT
The only reason for better precision in longer barreled rifles is a longer sighting plane with iron sights. The same effect can be attained with a dissipator setup in something like a 16" carbine. Optics make the matter irrelevant. Lower amplitude barrel vibrations account for better precision in short length barrels. A bullet's path will not be affected by a patch of barrel 4" behind it, 2" behind it, or any bit behind it. Its last point of contact is all that matters to its path.
Link Posted: 8/20/2003 8:46:02 PM EDT
Long barrels do increase velocity, which in turn flattens trajectory... But I am not sure that this applies to 5.56 which seems to have speed to spare. The other thing velocity helps is penetration, so the long barrel might help hunters using 5.56, but that doesn't mean that it would transfer to use against people in combat.
Link Posted: 8/20/2003 8:51:27 PM EDT
[Last Edit: 8/20/2003 8:52:26 PM EDT by Green0]
"I really cant believe a 14.5 or even a 16" could hang with a 20" barrel rifle "off the shelf" at a Local CMP match. Im not talking about hanging with a CMP rifle set up Im talking like say a 14.5-16" against a 20" Bushy for example. Barrel for barrel. I know they are not allowed normally in competetion for record but I still cant beleieve they are as accurate. " The NRA types just don't want to let smaller non-traditional guns polute the firing lines. It's all about sight radius. Just like the llama guy above said I noticed it in about 2 minutes when I first fired my 11.5- the sights are harder to use. My next rifle whenever Bushmaster makes my barrel is going to be a Dissipator with Rifle length RAS. And PRI flip sight to complete my A2 sight radius. really the best groups are attained using 20inch bull barrels and a tubed sight settup so you can get the sight radius of a 36inch barrel but still get the bullet out of the bore before you move and screw up your group. That's why a lot of 3 position match shooters use Anshutz .22lrs with 16in barrels and aluminum tubes to extend sight radius. [b]I wonder why they ruled out using a PRI gas tube and a 16in dissipator.? maybe it would be "wrong" to use a civilian designed weapon? Redundant to use 2 gas blocks? Hard to change the gas tube in forward areas (with people not qualified to take off the FF RAS to get to it?) [/b] I got really pissed off when I saw 6 M16's with yellow tags for months waiting to be repaired when all that was wrong was: 1 bent gas tube 1 Bad hammer spring 4 loose buttstock screws I offered to repair them but they told me that these parts have to be" fixed by a qualified individual per the TM" I have the TM and am a qualified individual but that doesn't matter to lemmings. If my guns had those problems I would have all 6 fixed and good as new in 45minutes.
Link Posted: 8/21/2003 2:19:54 AM EDT
Tyhe M16A2 is my baseline. I dont want any rifle that weights more than an M16A2.
Link Posted: 8/21/2003 5:09:48 AM EDT
GreenO Will the Bushy Dissapator fit under the M5 RAS? that sounds like an interesting combination. One I might like. cp
Link Posted: 8/21/2003 6:26:57 AM EDT
Originally Posted By eaglecp: GreenO Will the Bushy Dissapator fit under the M5 RAS? that sounds like an interesting combination. One I might like. cp
View Quote
It will fit, but you've got to be sure the gas block doesn't touch the RAS as the rail could flex when the RAS is tightened. Alternatively, just do what I'm doing. Take a 20" and have it cut to 16" and have the gas port opened up.
Link Posted: 8/22/2003 5:51:11 AM EDT
Don't forget that the 16" rifles are louder than the 20" rifles, and the shorter length is either going to put the shorty shooter up closer to the line, and closer to the muzzle blast of his competitors, or will put his muzzle inside of the line, and hence his muzzle blast right next to the guys shooting on either side. All this talk about bullet fragmentation I think focuses on FMJ ammo. If you're that worried about it, use a V-max round or one that is going to disintegrate on impact due to bullet design and materials. It may not be exactly NATO, but if you're not a military shooter in official combat, that's not a problem for you now is it? If there were armed conflict on this soil requiring guerilla warfare tactics from the civilian population, I think you'd be seeing a lot of nosler partition soft-points and V-maxes and Speer TNT's flying around out there. Personally, I always thought the AR should be chambered in .221 Rem Fireball. Since it's a pistol cartridge, it develops most of its velocity in shorter barrel lengths. With the right powder and bullet, ammo up to 55 grains can outperform same-weight .223 rounds from barrels less than 16"... Or so the reloaders guides seem to say.
Link Posted: 8/22/2003 7:25:43 AM EDT
[Last Edit: 8/22/2003 7:33:10 AM EDT by Green0]
A bushy dissipator will fit under a rifle length FF RAS (I don't know about regular rifle RAS with the stock gas block but I doubt the stock block and FF RAS will work together). If you opt for the FF RAS you need to use the KAC low profile gas block under the RAS. Same if you want the rifle length RAS to fit for sure (Kac gas block will work.) also a little dremel work will mod the existing block to the point where it will fit under both for sure. (IE grinding what used to be the sides of the front post off of the V-match gas block). Why didn't I think of that a week ago?
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