TRG65 Posted March 14, 2004 Share Posted March 14, 2004 Do Ar's as a general rule like hotter rounds? Not to the point of cratering, but warm. Link to comment Share on other sites More sharing options...
George Posted March 14, 2004 Share Posted March 14, 2004 If it locks the action open on an empty mag every time, it is usually hot enough to be reliable, but making USPSA minor (160 pf) is another story. The following is a good range of velocities to settle on for a given projectile weight out of 18-20" bbls. 52's from 3200-3300 (166-171 pf) 55's from 3050-3150 (167-173 pf) 69's from 2700-2800 (183-193 pf) 77's from 2600-2700 (200-208 pf) Hope this helps. -- Regards Link to comment Share on other sites More sharing options...
warpspeed Posted March 14, 2004 Share Posted March 14, 2004 George, New USPSA Minor pf will be 150. Link to comment Share on other sites More sharing options...
TRG65 Posted March 14, 2004 Author Share Posted March 14, 2004 Sorry I wasn't clear enough in my post. I was looking at accuracy not function. Thanks. Link to comment Share on other sites More sharing options...
George Posted March 15, 2004 Share Posted March 15, 2004 I was looking at accuracy not function If you are using match grade bullets of the weights mentioned, those are the ranges of velocity that Sierra notes as optimum for accuracy (typically) with barrel twist rates appropriate for that bullet weight. Yes, much more, and some less can be accurate too. But, that is what finding barrel nodes is all about. You will typically get very close to optimum results within the velocity ranges mentioned. Even though a .224 projectile can be pushed really fast in longer barrels with larger capacity cases, most any 20" AR will "typically" perform well in both function and accuracy within these velocity ranges. Accuracy can usually be found across a fairly broad velocity range by identifying the velocity nodes where everything comes together vibrationwise at the muzzle and the groups tighten up on paper, but that's a lot of tedious work compared to using good components and techniques and just going with a load in the velocity ranges specified that shows low SD over a chrono. That method almost always results in MOA, or better groups if the rifle is capable of it without a lot of testing. The BC just doesn't get a whole lot better as the primer gets a whole lot flatter New USPSA Minor pf will be 150 Yeah, I know, but because I am not willing to change the great running rifle/load combo I have, I am just gonna flat out ignore the wussification of an already too low minimum PF for rifle. IMHO, this is just a concession to help all of the folks who can't hack full size barrels on AR's make power factor -- Regards, Link to comment Share on other sites More sharing options...
warpspeed Posted March 15, 2004 Share Posted March 15, 2004 New USPSA Minor pf will be 150 Yeah, I know, but because I am not willing to change the great running rifle/load combo I have, I am just gonna flat out ignore the wussification of an already too low minimum PF for rifle. IMHO, this is just a concession to help all of the folks who can't hack full size barrels on AR's make power factor I agree. Besides, what would a 69gr be like travleing @ 2200 fps? Link to comment Share on other sites More sharing options...
George Posted March 15, 2004 Share Posted March 15, 2004 I agree. Besides, what would a 69gr be like travleing @ 2200 fps? I think it would be like shooting an M1 carbine, but without all of the power that round delivers! BTW, the JP ACOG reticle is trajectory mapped for the 77gr at 2700 fps (207 PF), and the 69gr at 2800+ (193 PF). I'm standing pat at 2700 for my SMK69's (186 PF) and 2610 for my SMK77's (201 PF). The ballistics are great, the brake holds the rifle like it's in a vise, and the full case of powder chronos tight and shoots sub MOA. Why change anything chasing a ridiculously low power floor. It almost seems as if they are heading toward getting pistol caliber carbines into the game. At least my hits on mechanical flashers will be easy for the RO's to call -- Regards, Link to comment Share on other sites More sharing options...
TBF Posted March 15, 2004 Share Posted March 15, 2004 Just one guy's opinion. With real accuracy research on one barrel. Max loads usually do not deliver as much accuracy as those a little under max. Travis F. Link to comment Share on other sites More sharing options...
Patrick Sweeney Posted March 15, 2004 Share Posted March 15, 2004 My experience with .223 accuracy in AR's has been all over the map: I've had some shoot great whent he primers were practically falling out of the pockets, and some so wimpy it was embartassing to describe the load. I gave up trying to wring the best accuracy out of the hot-load gun (who really needs a 52 gr match HP @ just over 3300 fps?) but I still have some of the wimpy ammo. It is a Winchester 63 gr SP out the muzzle at 2350fps. Out of the 1/12" barrel it was developed for, it shoots like a bullseye gun to 100 yards (never tested it past that) and tipped over every pin at Second Chance I ever hit with it. Soft hardly begins to describe the recoil. Once you've exceeded the threshold for Minor, don't make yourself crazy trying to find that "best load." Link to comment Share on other sites More sharing options...
uscbigdawg Posted March 16, 2004 Share Posted March 16, 2004 George, I'm with you. 69 gr. SMK's at 2850. I hate it during load development that the load that I should have gone with was the, "Most Accurate" load in the Sierra manual. Rich Link to comment Share on other sites More sharing options...
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