Howdy! After recently switching powders from IMR 4064 to IMR 4166, I performed an OCW test using my Remington 700P. The test revealed that from 42.9 to 43.5 gave the closest similar POI; however, at 43.5, the bolt was getting hard to open as IMR claims 43.1 is the maximum. I chose the middle of those three at 43.2. I then tried that load at 200 yards. The group sizes went from .540 MOA down to .313 MOA being the best. My problem lies with vertical stringing, its causes,and trying to eliminate it. There are no signs of my barrel touching the stock. The bolt lugs both appear to be contacting the receiver equally according to wear marks. I did notice that at lower charge weights there was no vertical stringing. Is it possible that it is being caused by this particular powder? The 43.2 charge puts me at 2607 fps avg. If I drop the charge weight to 41.7, I'm at around 2500, but with no vertical stringing. What's your guys opinions on this. Thanks
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Range Report Vertical Stringing
- Thread starter fmaglin
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It definately contributes to the problem, yes. Is it the sole contributor to verticle dispersion? No, but an SD of 10 or under is usually the goal. There are quite a few things that effect SD, primer type, consistant neck tension, seating depth, powder type, runout, etc, including equipment problems, the list goes on & on. I usually just take each issue one at a time and address each on as I address the culprit. The SD on my handloads is 6 or less across all guns so for me the effort is worth the trouble. I'm sure others will jump in here with good input but getting your SD down under 10 will definately improve things.
Agree with fursniper here. If your SD is 19, your ES is probably at least twice that, so let's just say it's 40 fps for a nice round number. That means you have rounds leaving your muzzle at, let's say, 2500 fps to 2540 fps. At 300 yards, your looking at a vertical shift of over six tenths of an inch. At 1000 yards, the difference is now over 14". Get those ES and SD numbers down to eliminate the ammo as a cause.
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Vertical stringing is often times due to inconsistent ignition, inconsistent neck tension, a barrel that is not free floated, or a combination of the three. Firing pin springs need regular changing, neck wall thickness needs uniform, and a barrel should never have bedding contacting it.
Dan, what is your opinion on maybe 1 1/2 inches of bedding just forward of the recoil lug for very heavy and long barrels? I know a builder who does this and I have always had conflicted thoughts on this. Thanks for your input.....
Like I said, bedding should never touch the barrel. If the barrel and action were once piece, solid and same material, they would expand and move at the same rate with the heating of the assembly. But because they are not and never will be, the receiver, barrel, & stock (or chassis) expand at different rates. So the first place that one would expect to see that expansion is at the hottest parts of the assembly; right in front of the receiver face at the point of bullet entrance into the barrel. Thus, the first thing to expand is the barrel into said bedding contact and placing stress on the receiver and stock/chassis; pushing them apart. Not a combination that lends itself to accuracy to say the least. Many will disagree, but if a receiver is mated to the stock/chassis properly, there is no need for bedding under the barrel. And it doesn't matter how heavy the barrel is. Some would say that the heavier barrel need the support. Maybe, but if that's the case, bedding under the shank is not going to remedy that need. At that point, I'd say lighten the barrel or use a barrel clamp system instead of bedding the receiver.
Thanks everyone! After doing some experimenting with seating depth, I've cured my problem. My rifle chamber is deep throated and I usually seat my bullets. 010"off the lands. When I do this there is only about 1/8" of the bullet seated in the case neck not counting the boat tail. After seating the bullet .090 off the lands, the vertical stringing was gone and the deeper seating depth did not seem to critically effect the group size. I don't know why Remington reams their chambers so deep.
