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Posted: 2/8/2011 11:48:22 AM EDT
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I am working on a 77gr load for my SDM rifle.
I am looking to buy some more bullets and was debating between cannelure and no cannelure. However, on midway's site it shows the 77gr smk with cannelure has a BC of .362, while the non cannelure version is at .225. Is this correct? How can basically the same bullet have such a higher bc when it has a cannelure. I was thinking the cannelure may not be needed and may lead to less accuracy than a bullet with out it. FWIW I have shot this rifle to 700yds using SSA 5.56mm 77gr(w/ cannelure) ammo. Drop was 18.5moa. I am trying to get a load with a trajectory close to this, but I realize 5.56 pressures are hard to do for the reloader. I have a chronograph and plan to test powder charges until I find acceptable velocity with good accuracy. |
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Quoted:
I am working on a 77gr load for my SDM rifle. I am looking to buy some more bullets and was debating between cannelure and no cannelure. However, on midway's site it shows the 77gr smk with cannelure has a BC of .362, while the non cannelure version is at .225. Is this correct? How can basically the same bullet have such a higher bc when it has a cannelure. I was thinking the cannelure may not be needed and may lead to less accuracy than a bullet with out it. Not according to Sierra's website. |
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Quoted:
Quoted:
I am working on a 77gr load for my SDM rifle. I am looking to buy some more bullets and was debating between cannelure and no cannelure. However, on midway's site it shows the 77gr smk with cannelure has a BC of .362, while the non cannelure version is at .225. Is this correct? How can basically the same bullet have such a higher bc when it has a cannelure. I was thinking the cannelure may not be needed and may lead to less accuracy than a bullet with out it. Not according to Sierra's website. Sir, according to the Sierra website the BC for the cannelured bullet is the same as the one without cannelure, ie: .362 for MV between 2500 and 3000fps. Regardless the needs of the military I've used this bullet without the cannelure for many years with an MV slightly above 2800fps with excellent success in a service rifle legal AR-15. In my humble opinion for distances beyond 300yd there are much better choices with BCs significantly higher than .362. Regardless the drop in trajectory at extended distances your ballistics program will indicate a significantly reduced terminal velocity at 600 yd and beyond. HTH, 7zero1. |
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Thanks for the replies. I didn't find the chart on sierra's site until reading replies to my thread. Turns out both are the same BC.
7zero1, What bullet would you suggest to try other than the SMK? I am looking at this 75gr Berger VLD hollow point that has a BC of .423. Midway usa If there are other bullets out there that fit in an AR mag, I am open to suggestions. |
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Quoted:
Thanks for the replies. I didn't find the chart on sierra's site until reading replies to my thread. Turns out both are the same BC. 7zero1, What bullet would you suggest to try other than the SMK? I am looking at this 75gr Berger VLD hollow point that has a BC of .423. Midway usa If there are other bullets out there that fit in an AR mag, I am open to suggestions. Sir, since you require that the cartridge fit into an AR magazine I know of no VLD type bullets that can be made to fit without some modification of the magazine or other means of adapting the longer bullets. In high power competition slow fire stages are all single loaded which facilitates the use of cartridges that are longer than what will fit in the magazine. There are a lot of high power service rifle shooters that use the 80gr SMK that IIRC has a BC of .44. My personal choice is the JLK 80 gr VLD with a BC of .5. Some experimentation with powder charge and seating depth are required to successfully use these bullets but neither can be made to fit such that they can be fed from an AR magazine. HTH, 7zero1. |
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Quoted:
Thanks for the replies. I didn't find the chart on sierra's site until reading replies to my thread. Turns out both are the same BC. 7zero1, What bullet would you suggest to try other than the SMK? I am looking at this 75gr Berger VLD hollow point that has a BC of .423. Midway usa If there are other bullets out there that fit in an AR mag, I am open to suggestions. The Hornady 75 grn HPBT match bullet has a BC of .395 if my memory serves me correctly. That's what I decided to use instead of the SMK. Higher BC, lower cost and just as accurate... -ZA |
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I am fairly new to reloading and have decided to go with the 77gr smk for the time being.
However, how do you find out over the internet if a certain bullet will be gtg at ar mag length? I am guessing by the overall length, or is this just something that you just gain knowledge of through experience? |
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Quoted: I am fairly new to reloading and have decided to go with the 77gr smk for the time being. However, how do you find out over the internet if a certain bullet will be gtg at ar mag length? I am guessing by the overall length, or is this just something that you just gain knowledge of through experience? Design. Bullets designed for single loading have longer ogive length. These would be most bullets 80 grains in weight or more. The Hornady 75 grain A-Max is also one of these. From the left Win 64 PP, mag length Sierra 69, mag length Hornady 75 A-Max, single load M856, mag length Sierra 30, non-catalog  Can be fed through magazine Sierra 77, mag length Sierra 80, single load Swift 75, mag length  |
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Quoted:
I am fairly new to reloading and have decided to go with the 77gr smk for the time being. However, how do you find out over the internet if a certain bullet will be gtg at ar mag length? I am guessing by the overall length, or is this just something that you just gain knowledge of through experience? Over the internet is a bad way to find load data. A book will contain mostly correct information. Another way is to load them up, pay attention to the funny looking cartridge, and then think through the cause. Ask someone else for confirmation. This is not a good way to go, but it might be all you have stuck out in the wilderness. |
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