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Posted: 6/6/2011 12:33:44 PM EDT
I swear, I was intending to post this before I saw the "Horizontal stringing" thread. Just a coincidence. 
I've noticed over the last few range trips that I'm getting a lot of vertical stringing with my 75gr BTHP loads. 23.5gr of Varget, Hornady bullets, LC brass trimmed to 1.750", Wolf primers. The groups are acceptable with regard to the horizontal dispersion but the vertical stringing really opens them up. I shot a group at 200 yards over the weekend and it was very noticeable - it was probably 2.5" wide by 7" top-to-bottom. I know about breathing and all that - the groups I shot before and after the reload group didn't exhibit the vertical stringing, and I was using the same rifle (free-floated barrel), same distance, same sandbags, same technique and everything, so I think we can eliminate the shooter as the problem. What I'm trying to find out is what factors inherent to the reloading process can account for vertical stringing. Too much crimp? Too little? Primers? COL? I've read that vertical stringing can be found around a "sweet spot" in powder charges, and going up or down a few tenths can eliminate it and result in good groups - is there any truth to this? And no, I don't have a chronograph, so unfortunately I can't give info on velocities. |
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Breathing, heart rate, just having a bad day, too much caffeine and/or inconsistent velocities are all suspects.
Without a chrono, look to the first few examples above. Bullets can be weird. A few years back, I loaded up some new Nosler 150gr .308 BT bullets. Shot half a box one day at the end of my visit through a Savage bolt gun. Couldn't get on paper (targets along left edge of backer) and I ended up wasting 25 shots trying to figure out where they were landing, before I ran dry of this combo and left scratching my head. Fast forward two years, when I reloaded up the other 25 and fired them with the same Savage 10FP LE2b rifle. This time, I was aiming at targets in the center of the backing board. Low and behold, they all shot low 6" exactly and like 3" to the left. The 5 shot groups were sub MOA and near MOA, so they were all accurate, they just shot completely away from my normal-ish POA. I shoot a lot of different bullets and combos, so I'm familiar with typical shifts, but this was weird. I even took a picture of target just for reference. Sometimes ya just never know... Chris |
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If I were you, go and buy a box of Sierra 69gr SMK's. They are far more consistent.
The Horady 75gr porjectiles got to be a bit frustrating for me. One group all of them will be touching, then the next group right after that will be huge. I realise some of this was me, but this doesn't happen with SMK's for me. I don't want to clutter your thread with pictures, but my first 20 or so shots with the 69 SMK's gave me amazing groups, infact my best group yet at around .4moa (5 shots), on the same target I only fired 3 groups with horady 75gr and one was really small and the others were huge. ETA: Also Hornady prjectiles have a larger weight variation too which could cause verticle stringing. I have sorted the rest of my hornady projectiles (several hundred) and 95% of them fall in two groups 75.2-75.3gr and 74.9-75.0gr |
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Quoted:
... I've read that vertical stringing can be found around a "sweet spot" in powder charges, and going up or down a few tenths can eliminate it and result in good groups - is there any truth to this? ... Yes, an untuned load will string vertically. This is the classic sign. You may need to change the powder charge more than just a few tenths to bring everything in line. With 7 inches of vertical, I would check everything else first. Which 75 grain bullet are you shooting? Tighten everything, try a different scope, even make sure the float tube and barrel are tight. Clean the barrel down to bare metal. Check for a ding on the barrel crown. I had a M-4 contour 14.5 inch barrel that wouldn't shoot, and the only solution was to get a different barrel. |
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Quoted: are you weighing each and every charge? Make a batch of your load, but weigh/trickle each charge then go test it... Process of elimination! Even if he was +/- 1.0grs, I'd be amazed if it added more than a half inch to his groups at 200yds. Weighing charges for short range is highly overrated. Highly. OP: what do you have for sights? |
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Quoted:
Yes, an untuned load will string vertically. This is the classic sign. You may need to change the powder charge more than just a few tenths to bring everything in line. With 7 inches of vertical, I would check everything else first. Which 75 grain bullet are you shooting? Tighten everything, try a different scope, even make sure the float tube and barrel are tight. Clean the barrel down to bare metal. Check for a ding on the barrel crown. I had a M-4 contour 14.5 inch barrel that wouldn't shoot, and the only solution was to get a different barrel. Hornady BTHP. As far as the rifle, this is happening solely with my reloads - factory ammo shoots nice round groups, so the barrel and scope seem to be fine. Turns out it's actually 5 inches of vertical dispersion, and 2 horizontal - I measured the target when I got home from work, I was going from memory before. I thought I had a pretty decent load worked up, but maybe something went sideways in the process. I think I'll experiment with some different charge weights (again) and see if I can work it out. Thanks to all for the input. |
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There are lots of potential reasons for vertical stringing.
Are your cases all trimmed to uniform length? Are your powder charges consistent? Are your bullets all seated to the same depth? How many rounds have already gone down your barrel? Is your shooting position consistent? Is your eye relief consistent? Is your parallax dialed out? |
| I have seen it in marlin lever guns 30/30 and .35 rem.(quite common as the barrel heats up);and only once again in a 722 that was a .222 and that was because of the scope.It was a very old weaver that had seen its better day.For some reason when people have talked about it they always say powder charge first;but I have seen bullets that will print differently from some makers but not the SMKs.Also,wolf primers can be weird some times try the same load with another brand;I noticed a strange occurance with them and H335 and some dude told me they did some almost milisecond stalling on ignition with some loads he had worked up like they seemed to retard on ignition). |
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Just curious how you arrived at your load specifics. Did you run a ladder test to ascertain your powder charge/barrel harmonics match? Have you checked the jam/jump of you overall length? You may want to check this factor as it can make a difference. I'd also get some match primers to use. I have never used Wolf primers, but have shot a lot of their .223 ammo. I can't imagine they would be very consistent. |
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Quoted: Quoted:I'd also get some match primers to use. I have never used Wolf primers, but have shot a lot of their .223 ammo. I can't imagine they would be very consistent. A lot of competition guys swear by them. Shows ya what I know.  I worked up my precision loads using CCI Benchrest primers and never had a reason to change. |
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I have a similar issue with a similar load. I was trying loads with the Hornady 75 gr BTHP, and would get good groups with Varget, but was getting consistent vertical stringing when I switched to TAC.
I could shoot both loads back to back, and would get the same stringing with the TAC every time.... I need to go back and re-evaluate my TAC loads and see if something needs to be done different to get them in line. |
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The new gold color Wolf primers are not near as good as the older silver ones, in fact I know a guy that just finished working out a problem load that was shooting 100 fps slow with several powders and turns out the Wolf primers where the problem, he went to CCI #41 and gained the 100 fps in velocity back and the extreme spread went to high down to single digits, the 41's are very consistent primers.
Also powder charge variations and velocity spread are the worst causes of vertical stringing for me, some people say +/-1.0gr of powder doesn't matter but they are crazy, thats +/-100 fps difference in velocity or more and will make a huge difference even at 100 yards(+/-.6" if the load stays accurate). I can see the difference in +/- .2gr so I try to keep all my target loads at least +/- .1gr and closer than that on most loads, the loads that shoot best have single digit SD's and that takes a very consistent charge weight. |
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