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Post by Timber Butte Outdoors on Mar 23, 2011 11:59:59 GMT -7
If you have ever wondered about bullet weight/twist rate ratios, here is a chart to use in selecting a bullet that will shot well from your rifle. If you are reloading, this chart will also help you in choosing the correct bullet weight for your caliber rifle. Good Hunting! Gary Attachments:
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vmaster59
Full Member
Coyote One Production
Posts: 112
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Post by vmaster59 on Mar 24, 2011 14:43:08 GMT -7
Yes that is good to know when you are reloading.
Clint
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Post by 72camaro on Dec 20, 2012 19:49:02 GMT -7
Next question, it usually shows what the max bullet weight is but it does not have minimum weight, should there not be an amount?
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Post by 72camaro on Jan 1, 2017 20:15:53 GMT -7
I can answer that, somewhat, the minimums are not as much as a concern as the max for a twist rate. For instance, my 24" 1:12 barrel shoots 40 grain around .25 MOA if I do my part and .375 is a norm. The last 3 shots of my wife's AR with a 16" barrel with that same 40 grain load did a .25 MOA too with a 1:7 twist. The rumor had it that the fast twist may blow the 40 grain into little pieces before it even got to 100yds, didn't happen. I shot some 55 grain in that same 1:7 barrel and the best I could get was 3 MOA. It is the load more than the bullet weight.
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Post by broper on Jan 2, 2017 6:16:32 GMT -7
And the length and shape of the bullet has a lot to do with it.
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Post by Timber Butte Outdoors on Jan 2, 2017 8:47:20 GMT -7
It is neither the load nor the bullet weight!
It is the length of the flat land of the bullet that makes contact with the grooves of the barrel. The shorter the land of the bullet (light bullet), the faster the twist, the longer the land of the bullet (heavier bullet), the slower the twist.
I guess I should not say the bullet weight has nothing to do with accuracy, because the length of the land is determined by the weight of the bullet! In the 22 cal bullets, a 40 gr bullet has a short land, where say a 55 gr has a longer land, and a 75 gr has an even longer land, and so on!
If you will notice that a bullet that has a Boat Tail, will be 1 gr lighter than one without a Boat Tail, which means that the Boat Tail bullet has a shorter land area to contact the rifle barrel grooves!
That is the reason that there are so many twist rates in barrels! You decide on the load and bullet that you want to shoot, and you purchase a barrel specifically tailored to launch the bullet you want to load to shoot with accuracy! If you do your homework and work up a load that will shoot MOA or even SubMOA, then you have done your job and made that barrel live up to it's potential!
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Post by broper on Jan 2, 2017 12:11:03 GMT -7
But they can change the shape and length of the same weight bullet i.e., hunting bullet vs match bullets in same weight. Berger is well known for this. It all comes down to ballistic coefficient.
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Post by Timber Butte Outdoors on Jan 2, 2017 18:57:36 GMT -7
Ballistic Coefficient only tells you how aerodynamic the bullet is. In other words it is how well it travels through the air! Like an airplanes wind resistance performance!!
Bullet stabilization is a whole other ball game! That is determined by how much of the bullet is in contact with the rifling's of the barrel, and the twist of the barrel rifling's that determine if the bullets will shot in the same hole or the bullets will shot in a shotgun pattern or if they will keyhole.
I have seen a friend, try to make his 6mm-284 shot 55 gr bullets, at a high velocity, in a slow twist barrel meant for heavier bullets. The bullets would not group, at all, let alone hit the target at 100 yards, in fact we determined that the bullets were not long enough, and the twist in the rifle were not sufficient (fast enough) enough to stabilize the bullet as it left the barrel.
My Remington 22-250 has a 1-14 twist, my gun will not shot a bullet over 55gr, and it doesn't shot them very well, I might get a 1 inch or 1 1/4 inch groups with them, but if I drop down to a 52 or 53 gr bullet, I get 3/8 inch groups! But my rifle will also shot a 40 gr bullet as well as it does the 52 gr bullets.
Loren reloaded some rounds for a friend for his 220 Swift. The guy wanted to shot 62 to 65 gr bullets with it, so Loren did as he asked, Loren took the reloads out and tried them, they would not shot a group at all, in fact he got some keyholes with them. When he told me his problem with the bullets, I asked him what the rifle twist rate was, so he looked it up and sure enough it came from the factory with a 1-14 twist barrel, so I told him that the rifle will not shoot anything over 55gr bullets, so he goes home reloads some 52-53 gr bullets and he got groups of a SubMOA size right off the bat!
Because bullets can not get bigger around (determined by size diameter of the bore of the rifle), the difference in weight has to be utilized by making the bullet longer. Which in turn determines the length of the land surface between the base and the shoulder of the bullet where it begins to taper to the point.
So, if you try to shot a heavy bullet in a fast twist barrel, all you are doing is plowing the bullet through the barrel, because the bullet is not rotating or spinning, because it requires a slower rate of twist to get the heavier bullet spinning, compared to a lighter bullet! Even with loads that are at Max velocity, the right barrel will stabilize the correct weight bullet! I load my 22-250 to Max Loads, to get the max velocity from it, and it still shoots the right bullet very well!
I hope that is more clear than mud!
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Post by broper on Jan 2, 2017 20:48:13 GMT -7
A bullet won't be stable if it doesn't have good b.c. That's why the most accurate match bullets have very high b.c.'s. Also the new long range hunting are long, aerodynamic and high b.c. And that's why the 6.5 m/m's are so popular for long range, they are long, slender and high b.c. for caliber. Also, they can change the length of the land surface by changing the shape of the ogive. Again, refer to Berger and the newer Hornady's. Look at their bullet charts, you will see different shapes and lengths in the same weight and caliber. Also, most people don't realize that caliber and weight have nothing to do with wind "bucking" ability. It's all about bullet length and b.c. That's why 40 gr. .204 is flatter shooting and will "buck" wind better than a 40gr. .223 and the .204 also starts faster to begin with and will get there with more energy.
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Post by broper on Jan 3, 2017 13:56:53 GMT -7
It all boils down to this; longer bullets need faster twist bullets, shorter bullets can use slower twists. The longer high b.c. bullets will be more accurate and better for long range. They don't use short light bullets with low b.c.'s at long range bench rest for a reason.
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Post by 72camaro on Jan 3, 2017 19:13:52 GMT -7
I hear what you are saying, really, but I've yet to find a bullet that so far has grouped as well as the 40 grain in every .223/5.56 rifle it has been tried in with a particular load that I and my son-in-law have tried, probably 6 different guns from 1/7 to 1/12 twist and have some terrible loads for a 55 grain in the 1/7 though it really should group better it was 3MOA, though I've finally found one that is a little less than .40 MOA, finally. It is way more than bullet weight and length.
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Post by broper on Jan 5, 2017 6:27:33 GMT -7
Well, I put a lot of store in ballistic coefficient. I don't think it matters so much in varmint bullets unless you are shooting prarie dogs at 5 or 600 yards or something like that. My 22/250 is a 1/14 twist, it shoots 55gr. and under super accurate but the 60 gr. V-max hits the target side ways. But if I shoot 70gr. Speer they are really accurate. That bullet is a semi spritzer, shorter than most 60gr. I don't know why factories insist on 1/14 twist for 22/250 and .220 Swift. They do better with 1/12 or even 1/10. You are right in that there are other things that make a barrel accurate or not. Every gun/barrel shoots different and has it's own quirks. Some barrels are smoother, straighter, whatever. Some are just hard to figure why they won't shoot. But if I was goin to hunt big game at long range I'd be looking for high ballistic coefficient in the caliber and weight I wanted to use. High b. c. will also penetrate better.
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Post by dogdown on Oct 30, 2018 11:30:02 GMT -7
There is a definite confusion in this conversation between internal and external ballistics. BC (mathematical computation) and bullet form (ogive, length, weight). Also confusion with "accuracy" vs "precision". Accuracy referred to hitting what you're aiming at and precision related to size of group. Let me throw something in the mix here. IF it was all so definitive on some of the subjects discussed i.e. bullet baring surface, length, design weight, then how does one explain why a bullet of the same caliber, weight and design but of different manufacture will shoot tight groups in your rifle but the next one won't. If you have done much load development I know you have seen this. It's not a phenomenon, it does occur and on a regular basis. As my friend Frank C. Barnes used to say, "it gives the typewriter shooters much to sell copy with"... I hope you all realize firearms, bullets, barrels, loading components all vary from gun to gun, barrel to barrel, lot to lot. That is why we reload, we don't accept mediocracy, at least we shouldn't. I believe, at least in my case, that's what makes reloading/shooting precision rifles and handguns makes it so intriguing. A challenge one gives him/herself. The other thing is, at some point one has to realize this hobby is very, very complicated. The firearms are as individual as the people shooting them and loading for them is the same. These subjects are what add the fuel to the fire of conversation and as long as they have been debated they will continue to be subject of debate as long into the future. Just remember there is no solidified one size fits all answer!
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Post by 72camaro on Nov 25, 2018 19:39:14 GMT -7
More food for thought. I do wish I had more time for load development, that's for sure. I believe there is at least one load for every gun that shoots better than it should but sometimes it takes a lot to find it.
My deal is I have mostly inexpensive rifles but have found pretty good loads for most around .75 MOA or better. The only exceptions are a couple AR's that have been escaping me and I'm thinking it is more of a bullet issue as I've not done well with 55 grain flat bottom cantalures with any powder combination. V-max, almost always find a load.
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Post by broper on Nov 26, 2018 6:03:54 GMT -7
Precision is accuracy. The better the b.c. a bullet has is going to make it more accurate and closer to precision, shoot flatter, less drop, less drift, and hit with more energy when it gets there. That's why everybody is going to heavy for caliber bullets these days. Of course the shooter has to do their part too. Everybody seems to be worried about long range accuracy these days. Personally I think it's being carried just a ittle to far. Unless you're a bench rest shooter trying to set a new record.
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