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Posted: 5/2/2009 10:04:57 AM EDT
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I reloaded soime 55gr and 69gr bullets. All my reloads consistently go 1 in left at 100yards compared to factory loads.
I have a 1:7" twist barrel. Using Win748 ball powder. What would cause that? Also, the 69gr fell about 1 in low. Could that be the difference in trajectory already? (Also, brass is ejected forward of the firing line with the heavy bullets.) I read here that slower burning powder is better for heavier bullets. http://www.shootingtimes.com/ammunition/st223_120606/index2.html |
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The factory ammo is "Black Hills Ammunition". I have some Remington stuff I should try to compare. But none of my handloads were more accurate than the Black Hills ammo.
I'm just very surprised to see two tight groups with a horizontal separation. Obviously one or the other is deviating from the true bullseye in a very consistent way. |
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Quoted:
300 FPS difference between loads is about 1/2" at 100 yards. Harmonics, not bullet drop. Also dynamics, the rifle MOVES before the bullet exits. This makes slower bullets hit higher at 100 yards. However, I tried four different powder loads (from min to max) with the 55gr and two with the 69gr. They all shot consistently to the left to about the same spot. In other words, no difference horizontally by either powder load or bullet weight but only by handload vs. factory. Also, the heavier bullets shot lower. Could it be the powder? |
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Unless the testing was done with a lot of heavy sandbags and a 10x-20x scope I would chalk up a consistent 1 inch to the left as error on my part. We need more info about your setup. I used sandbags and a scope. The individual groups themselves were very nice, . I went back and forth between the factory and handloads. Even though I didn't do a double blind test, I don't think it's an error. The results were too consistent and obvious. I do have a bore laser sighter. If I can get that working that would at least tell me which loads are off boresight. Also, I'll try some other factory loads. |
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I just checked with the laser bore sighter. The bore sighting is to the left of my sight alignment which means my handloads are going to bore center and it is the factory loads that are going right. (I had previously sighted in to the factory load.)
So the question, perhaps now more properly framed, is why are the factory loads going right of bore center. |
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I just checked with the laser bore sighter. The bore sighting is to the left of my sight alignment which means my handloads are going to bore center and it is the factory loads that are going right. (I had previously sighted in to the factory load.) So the question, perhaps now more properly framed, is why are the factory loads going right of bore center. 
Adjust your sights 4 clicks right (if it is a 1/4 moa scope) for the handloads. If you go back to factory loads, 4 clicks left. How hard can it be? ETA: Almost EVERY load shoots just a bit different. This pic, 100 yards the group on the left is 25.5 of BLC-2 the group on the right is 26.0 of BLC-2. No adjustments were made. Same brass (Win) same bullet Nosler 69gr (53065) same primer (CCI400) Now somebody convince me a little powder dosen't make a big difference. ETA: Calm day, no wind at all. 
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Adjust your sights 4 clicks right (if it is a 1/4 moa scope) for the handloads. If you go back to factory loads, 4 clicks left. How hard can it be? ETA: Almost EVERY load shoots just a bit different.
Not hard at all except for the fact that it doesn't answer the question. |
| There were already half a dozen posts with the answer to your question. Adjust your scope it is easier than trying to adjust your ammo to match factory POI. Or go buy some other factory stuff and see where it shoots I recommend a federal gold medal match, or whatever you find that will give you a sub inch group. |
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The answer has already been given.
It is due to barrel harmonics. Barrels whip and not in a perfectly horizontal or vertical direction. Chances are the nodes for BHs and your reloads are different. I don't think you mentioned what bullet weight the BH Match ammo was. It's hard to tell you what is going on without barrel length and velocity readings. |
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It is due to barrel harmonics. Barrels whip and not in a perfectly horizontal or vertical direction. Chances are the nodes for BHs and your reloads are different.
Barrel harmonics that vary between handload and factory but not between different handloads (from min to max powder, hence fps, and different bullet weights)? I don't think you mentioned what bullet weight the BH Match ammo was. It's hard to tell you what is going on without barrel length and velocity readings.
I should probably invest in a chronograph but the BH bullet weight is 55gr and the barrel length is 20". (The BH is not match ammo, though.) |
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What people are trying to tell you is that there are thousands of unquantifiable variables that affect where a certain load will impact at a given range.
It's not worth trying to figure out "why"; just accept that they DO shoot differently, and adjust your sights for whatever load you prefer. |
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What people are trying to tell you is that there are thousands of unquantifiable variables that affect where a certain load will impact at a given range. It's not worth trying to figure out "why"; just accept that they DO shoot differently, and adjust your sights for whatever load you prefer. OP, you got lots of good answers, this one was my favorite. |
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I just checked with the laser bore sighter. The bore sighting is to the left of my sight alignment which means my handloads are going to bore center and it is the factory loads that are going right. (I had previously sighted in to the factory load.) So the question, perhaps now more properly framed, is why are the factory loads going right of bore center. Every different load is going to shoot to a different point of impact for a dozen or more reasons. You won't be able to sight your gun in to have every load hit to the same point of impact Pick a load, sight your gun in for that load and buy components accordingly, then make a concerted effort to produce exactly the same load every time you pull the handle. That's how I do it. 
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Quoted:
Maybe your dies are crooked  
Also, is your rifling right or left hand twist? Did you buy the correct right-spin or left-spin bullets? Are your primers all spun the same way? Was it low tide or high tide when you went to the range? I'm sure the coriolis effect plays into this too. Which hemisphere are you in? 
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Quoted:
It is due to barrel harmonics. Barrels whip and not in a perfectly horizontal or vertical direction. Chances are the nodes for BHs and your reloads are different.
Barrel harmonics that vary between handload and factory but not between different handloads (from min to max powder, hence fps, and different bullet weights)? I don't think you mentioned what bullet weight the BH Match ammo was. It's hard to tell you what is going on without barrel length and velocity readings.
I should probably invest in a chronograph but the BH bullet weight is 55gr and the barrel length is 20". (The BH is not match ammo, though.) Think of the muzzle of the barrel moving in an elliptical shape when a cartridge is fired. When a cartridge is fired, this is analogous to hitting the rifle with a hammer, and the barrel response changes according to how hard it is hit. You can experiment with this idea by taking a metal object and rapping it in the same spot with hits ranging from soft to hard. You'll be able to hear differences in items such as a pan or coffee can that respond at low frequencies, as various harmonics are added or subtracted. A piece of metal tubing is an even better object for this experiment. So, the motion of the barrel depends on how it's rapped by the cartridge. Only very tiny changes in the angle of the bore centerline are needed to move a bullet inches at 100 yards. What you've discovered is not particularly unusual, and if you change something, such as free floating or hanging a weight on the barrel, expect the bullet to strike a different point. |
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