Posted: 7/6/2015 5:57:32 PM EDT
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I am trying to figure out a load for a rifle that has not been cooperative in the past shooting sub MOA groups. The rifle in question is a Remington 700 sps varmint in 7mm-08. I have replaced the stock with a B&C medalist, upgraded to a timney trigger and a Sightron S3 scope. I checked torque and used locktite on all scope mounting hardware. This rifle has a long throat that cannot be reached with mag length rounds.
The latest load that i am trying because i didn't think i was getting anywhere else before consists of, Speer 130 flat base spitzers H414 CCI LR primers Twice fired neck sized brass with primer pockets and flash holes uniformed. The charges are (green targets) top left to right 1, 2 and bottom 3, and 4, 47.8, 48.3, 48.8, and 49.3. The brass looked good after firing. I noticed a lot of vertical aberrations that I also cannot explain. It could be me but i am not sure that it is. I may not have enough torque on the action screws which is causing the vertical random dispersion. The bottom metal is factory and i only used 45 inch lb IIRC. Maybe I should step up to 55 or 60? Any insight as to random vertical flyers? I loaded up 2 batches of these rounds and overlayed the 3 shot group targets so each of the 4 targets is 6 shots, black sharpie circles are round 1 and holes are round 2. Groups 2 and 4 look the best. There seems to be 2 nodes at these charges, but i am not sure which one to pursue further. 49gr is the book max recommended load for this bullet, so I don't think i want to try anything higher. 48.3 seems to be the better one of the two. Any suggestions or comments? Thanks for looking. ETA: I was shooting off front and rear bag rest at 100 yrds. 
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I don't know anything about your caliber. So all I can offer are the things I did to my (50yr old) Rem 700 when I OCW'd groups like that. IOW, couldn't find a node. At least two you have already done.
1) Replaced stock to float barrel. 2) Dropped in a Timney trigger. 3) Discovered that the yardage markers on my side focus dial weren't accurate. I don't think any of them are, and parallax error isn't helpful. Had to make sure the eyepiece was focused and then adjust side focus until moving my eye produced no movement of the POA. 4) Discovered powder charges thrown by the RCBS Chargemaster are rough approximations. Bought a mag force restoration scale. IOW, my powder charges varied. 5) Used only the same batch of brass acquired new for load development, not a collection of range and other brass. 6) Chose a bullet most likely to be accurate in that caliber. 7) Chose the closest matching bullet weights for each OCW charge set. Bullets that weigh the same seem more likely to shoot the same. 8) Made certain the rifle was held on target by the front/rear bag not me, then shoulder/hand pressure even and consistent. Yeah, I know, basic shooting. Eventually I could tell by the direction of recoil whether I did it right or not. Once I found the node(s), they were more forgiving of normal reloading variation. But they were hiding behind a lot of stuff for me. GL. |
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Target labeled with a 4 is distinctly horizontal, while target labeled 5 is distinctly vertical. This is trying to tell you that either a node or an anti-node exists between these two targets.
The target at the bottom left has the best shape (to my eyes). I would do another set of loadings near this set in 0.1 gr increments and see if they shoot the same/better/worse. Be sure to tune up the scale before doing this reload set (i.e., clean the bearings and fulcrum of the scale.) As to 3 in the first response:: it is optically impossible to make the parallax adjustment accurate with an eyepiece that can be adjusted for focus. It is harder for second focal plane optics than first focal plane optics. |
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By chance, did you have a reference load that you liked before the re-stock and new scope? You mentioned the rifle has not been cooperative in terms of getting below 1 MOA.
What loads did you run and what was their performance? Do you have velocity data for those? 7-08 is usually easy to work with. I am just guessing, but I think something else is wrong here and interfering with your load development. This rig has a twist of about 1:9 or 1:10, correct? It helps to have a known good reference point, like going back to the original configuration and running a known good load for comparison. Then, make one set of changes at a time, for example, first the trigger, then the scope, then the stock. This way, we can tell if something is amiss with the assembly. Do you have a loading procedure or experience with any other rig that performs sub MOA, even if it is a different design? If something obvious doesn't turn up between the scope or the stock, then we would have to investigate the velocities, the bullets and loading techniques. |
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This rifle has never really performed up to my expextations. Maybe 1.5 or 2 moa with factory ammo and never really better than 1.25 with handloads. I have tried 4 or so different handloads with different powders and bullets from the 140 to 160 class range. I did upgrade the trigger and stock at different times and the results have been negledgable.
I am leaning to the chamber of this rifle and the long throat as causes. The 130 flat base was an attempt to see if longer bearing surface bullets would group better. When i restocked the action there was slight interference in the bolt handle notch which i clearanced but maybe there is contact somewhere else i didnt see. I am going to try a few groups with the 2nd and 4th loads up and down a tenth of a grain or 2, and check for any clearance issues with the stock and action again. Thanks for the advise and suggestions. |
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Region Rat:
I believe that the barrel has a 1:9.25 twist. I have been reloading for a few years now(5+?), and am pretty meticulous about building things that go boom next to my face. I SS tumble the brass after every loading. I checked the concentricity of the outer necks of the brass that i just shot and tumbled and they are all within .002. I also checked a batch of 223 that I loaded last weekend and fired in the bottom 2 targets in the top picture, and they are all within .002 bullet concentricity. So i think that the brass prep and loading is GTG. I believe that I am loading ammo that while not benchrest quality, is more than capable of getting .5 moa. I also check loaded rounds for datum to case base length when loading so as to keep them all the same length to the lands and not just the tip OAL. I individually weighed these loads and trickled up to the charges when i made them. What is screwing me up is the random nature of the horizontal centers of the different loads.Group one is higher vertically than group 2, and group 3 appears to be lower than group 2. I would think that they should get higher the greater the charge, but they seem to be up and down with random levels of vertical spread. I am leaning towards a rifle problem more than anything else. maybe the crown? recoil lug off center? maybe just the jump to the lands is too great? Just for reference i shot this group the same day, savage 12 223 200 yards 10 shots. 7 of the 10 are in 3/4 inch 
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Quoted:
. . . As to 3 in the first response:: it is optically impossible to make the parallax adjustment accurate with an eyepiece that can be adjusted for focus. It is harder for second focal plane optics than first focal plane optics. If it's optically impossible to get the parallax adjustment correctly, what do I call it when the POA stops moving? |
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Quoted:
Don't understand you. If my eyepiece is in focus, I can see the crosshairs well. Then I can adjust the side focus until movement in eye position doesn't change the POA. If it's optically impossible to get the parallax adjustment correctly, what do I call it when the POA stops moving? Quoted:
Quoted:
. . . As to 3 in the first response:: it is optically impossible to make the parallax adjustment accurate with an eyepiece that can be adjusted for focus. It is harder for second focal plane optics than first focal plane optics. If it's optically impossible to get the parallax adjustment correctly, what do I call it when the POA stops moving? What I mean is:: a) that if you took a scope with parallax adjustment b) and had someone with perfect (20/20) vision (also no astigmatism) c) focus it perfectly and d) perfectly adjust the parallax and d) give the scope to someone with 1 diopters of nearsightedness (also no astigmatism) and e) have him refocus the scope for his eye (without adjusting the parallax), f) you would find that the parallax adjustment is no longer perfect. The parallax adjustment is co-dependent with focus. This is one of those :: 1/f = 1/f1 + 1/f2 optical anomalies. What they do is to give you a parallax adjustment and label the scale so that it is close and then graduate the scale coarsely enough that most people never figure out that the scale can never actually be perfectly set. |
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Speer's 130 grain bullet is a hunting bullet and may not give you the best accuracy.
Sierra's 168 or Hornady's 162 is a better bet using slower powders. Try some single base extruded powders. Not every rifle is capable of sub-moa groups. This is especially true of rack grade rifles. I have been astounded by the accuracy of some Winchester M70's and Remington 700's I have owned when using match grade bullets. I have been frustrated by some as well. Some barrels just won't shoot better than 1.5" to 2.0" no matter what you do. Your stock has an aluminum bedding block if memory serves me well. Use up to 65 inch pounds, tightening it 5 lb. at a time, starting with the bolt under the barrel lug first. Sometimes a sweet spot can be found by doing this. I own a Savage .308 with a light barrel that my brother loved because it shot so well. I can't get it to shoot anything acceptably. Different people have different expectations. It's fine for hunting inside 200 yards but a disappointment at the target range. |