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Posted: 8/3/2003 12:33:02 PM EDT
[#1]
Since every barel wil have it's own inconstancies, these are ment as guides. The best way it to see what works best in your own rifle.
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Posted: 8/3/2003 3:22:56 PM EDT
[#2]
A 1:9 barrel will absolutely stabilize a lead-core bullet of up to 72gr. Beyond that, you are entering the ragged edge of its capabilities, and there's no way to know for sure. Some folks have reported success with 75/77gr bullets out to as far as 300m (though with some accuracy loss compared to a 1:7 barrel), and others report in-air tumbling, keyholing, and missing the target entirely at 100 yards.
Many things affect this. With the button-rifling process, some 1:9 barrels will really be more like 1:9.5, and others more like 1:8.5. Also, environmental factors play a big part, as higher velocities will stabilize a heavier bullet than the same barrel will at lower velocities. Temperature, humidity, altitude, BARREL LENGTH, and other factors affect velocity. For this reason, I normally recommend the 68/69gr match loads for 1:9 barrels. Performance is only slightly less than the 75/77gr bullets, but accuracy will be much better. -Troy |
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Posted: 8/3/2003 3:28:09 PM EDT
[#3]
Just to clairify, weight has nothing to do with it. The factors that matter are caliber and bullet length. Since your caliber will be consistent on the gun, people refer to the different weights of the bullets. Since they're all the same diameter, a heavier bullet will be longer. Different bullet construction (i.e., solid copper vs. copper over lead) would also affect this.
That said, the 75 grain bullets are questionable in 1:9. Some members have reported they work fine; others get keyholing. 68/69 grain should work, though. I suspect the 77 and 80 grain loads wouldn't work, but give it a try if you want. I just ordered a box of 68 and 69 grain stuff to try. I'm leery of trying the heavier stuff, just because it ain't cheap! So, I'm trying the ones that [i]should[/i] work to see how it goes before I spend more $$$ on stuff that may or may not work at all. |
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Posted: 8/3/2003 4:09:52 PM EDT
[#4]
Just my 2 cents.
Just got back from the range after all day testing of BH 60's , 68's and 75's. Out of my 20" RRA and my 20" bushy and also a friends 24" bushy we couldn't see any practical difference in poi.They all shot good. No problems of any kind. We shot from 25 yrds to 200yrds.It is my opinion that the changes in point of impact where so minor as to only be of importance to a bench rester.They where all "Minute of ground hog" out to 200 yrds. To tell the truth I didn't see much difference in this "heavy" stuff and the way M193 or 3131A shoots in our guns, even though this is "match ammo" I'll be the first to offer that this was in no way a conclusive test of any kind,just my experience |
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Posted: 8/3/2003 4:10:48 PM EDT
[#5]
If 1/9 will stabilize 72's okay, then who's tried them and wouldn't that be better than 68/69's?
Would love to see some one post trials with a bushmaster 1/9 chrome barrel using various bullets and 300yds or better. All the AR books talk about competition shooting with 1/8's and 1/7's but for most of us here 1/9 is probably the most common one owned here. I can see the heading now. Maximizing long range results with a 1/9 barrel. Film at eleven. Hope someone will post. M4-AK |
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Posted: 8/3/2003 7:57:53 PM EDT
[#6]
Ye old formula for figuring the "optimum" rifling twist is as follows:
L x t = 150 Or, 150/L = t L (length of projectile in calibers, OR Length of projectile divided by caliber) t (rifling twist in calibers) So a .224" diameter procectile that is say 1.155" in length would have an "L" of 5.15625 150 / 5.15625 = 29.090909 calibers (remember .224? ) or a optimum twist of 1 in 6.5" (rounded off) I had read this in an article and I figured I had to use in in a conversation at some point! [beer] Tex78 Edited cuz i cant spell |
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Posted: 8/3/2003 9:12:03 PM EDT
[#7]
Quoted: L x t = 150 Or, 150/L = t OUCH math!! Me brain now hurts. I'm thinkin' I'll just have to do some testing to see what I come up with. I'm hoping to try some of the 75gr TAP ammo, is this available to civilians? Mike |
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Posted: 8/4/2003 2:45:23 PM EDT
[#8]
Quoted: OUCH math!! Me brain now hurts. I'm thinkin' I'll just have to do some testing to see what I come up with. Your right on this one, just be sure you get to test to the max range you'll use it for, so you'll know in advance if your going to have a problem! I'm hoping to try some of the 75gr TAP ammo, is this available to civilians? I believe it is. Georgia Precision offers the widest variety off ammo I've seen, and would probably be a good place to start. Tex78 |
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