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Posted: 2/18/2010 6:39:02 PM EDT
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So I managed to get to the range with a buddy today and took the Rem 700 VS out.
I had picked up some winchester WLR primers, because there WERE some. My load(.308) is 46.5 gr of H-380, 168 Sierra Match Kings, Rem brass and CCI BR2 primers. I had run out of CCI's (have since replenished my stash) So I loaded up some with WLR primers. It's amazing to me that I could actually see the difference, not only in the group size, but it actually looks different where it punched through the paper. I can't figure that out? But I did learn for sure that there is a difference in this particular load. The WLR primers are the target on the lower left. Actually a larger group than my clean-out shots on the top right. Ignore the errant .223 hole on the left of the page 
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| Is your brass as well uniformed as posible? Flash holes debured, necks turned, cases sorted by weight and primer pockets uniformed. How do you size cases as well? Did you use the same lot of brass for both loads? Which group did you fire first and did you foul the bore before shooting for groups? Are the bullets picked for culls and are they uniformed for length? Did the wind conditions change from the time one group was fired to the next? How much time did you take between shots and was one group fired faster thasn the other one? |
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You could easily have destroyed your rifle. Some primers will yield 5,000 or more psi than others. You should always rework your loads when changing components. I own testing equipment and can actually pressure test loads and I have never seen a primer change chamber pressure more than a couple hundred psi. I also would look at H-48945 as well as IMR 1 4895 or 4064 to tighten the groups up. |
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Is your brass as well uniformed as posible? Flash holes debured, necks turned, cases sorted by weight and primer pockets uniformed. Yes to all of these except I do not turn the necks. Cases sorted...I try to keep them around .5gr or so..That is about where I started anyway.... How do you size cases as well? Neck sized with Neil Jones dies, sent fired cases to them so they could make the dies pretty close, I expect?. Full length re-sized when they get a little too tight, trimmed as needed... Did you use the same lot of brass for both loads? You got me there?? I'm going to bet they're not, but the weights are in the ~.5gr tolerance I've decided on.. Which group did you fire first and did you foul the bore before shooting for groups? Clockwise from the top right...top right was right after I cleaned it.... Are the bullets picked for culls and are they uniformed for length? No sir. Right from the box SMK's Did the wind conditions change from the time one group was fired to the next? Yes sir, the wind was blowing like a sonofabitch all day. I am completely stupid when it comes to figuring wind drift. How much time did you take between shots and was one group fired faster thasn the other one? I would guess less than 20 seconds between shots....approximately 5 minutes(one cigarrette) between groups. And thank you, by the way....You have helped open up my eyes a little wider, to take in more of the big picture....there is a vast amount of knowledge here to soak up. There are so many variables, it's mind boggling at times, as I try to take in so much at once. This is why I keep coming back here to ask questions. |
| I have an old article in an old magazine from a few years back where the author, an authority on reloading, I think he was with RCBS, used pressure trace equipment and changing only the primer brand, measured differences of several thousand psi. It has been a while, so he may have substituted a magnum primer for a standard in the test when he recorded that much difference though. I will have to find the article and report back to you. I'm curious now. I haven't used that powder OP, so I'm not sure where you're at at the pressure level. I generally ran IMR 4064 with 175 and 168 SMKs. I had used blc2 as well. I still would recommend backing the load down some when making any component change, even different bullets of the same weight, since some may have more material in contact with the barrel. 1903pa gave some very good advice. Keep working, you're doing great, good shooting. |
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I have certainly seen changes or improvements in grouping with a primer change. In my case a change from Win WSR primers to Rem 7 1/2 BR primers in .223 made a noticeable difference.
The CCI BR2 is a milder primer in brisance than the WLR which is the hottest standard LR primer, by most accounts. Competition rifle shooters often favor mild primers i.e. primers that produce just enough heat to properly ignite the powder. They feel that as primer brisance gets higher, it also gets less repeatable from primer to primer. Another train of thought is that the powder is ignited a tad more gently. When this happens, the front slope of the pressure curve is less steep. Which means the bullet is pushed a tad more gently into the rifling which tends to deform it less. Whatever the scientific reason, competitive rifle shooters seem to feel that the milder primers give both better velocity uniformity and accuracy. In addition, as regards the BR2 primers - CCI states that Benchrest cups and anvils are selected for exceptional uniformity. During the assembly operation, the operator who meters the primer mix into the cups (or "charger") is chosen from the most experienced workers with an outstanding record of consistency. The BR line runs at a little slower pace to provide time for extra inspection. I think that all these things added up so they gave you your best groups. The gun likes the powder charge and powder type, the bullet is concentric, and the barrel is pretty good, plus the sparkplug is a good match. All of this things make up the biggest accuracy difference. Matching case lots, weighing cases, flash hole deburring and primer pocket uniforming make only very a minor difference and many times no difference at all, unless the cases are grossly out of whack. |
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The Winchester primers may be as accurate as the CCI, you just need to rework the load for them, until then there's no way to tell. I concur with this thought. The load you used was worked up with CCI primers; there are subtle differences between one brand of primers and another, which may affect velocity, pressure, and most importantly the curve that both velocity and pressure increase along. While I wouldn't say that changing form one primer to another would necessarily make a load unsafe, it does change things-you have evidence in your targets. Try working up a similar load with the Winchester primers and see if those groups don't squeeze down noticeably. |
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Quoted:
The Winchester primers may be as accurate as the CCI, you just need to rework the load for them, until then there's no way to tell. I concur with this thought. The load you used was worked up with CCI primers; there are subtle differences between one brand of primers and another, which may affect velocity, pressure, and most importantly the curve that both velocity and pressure increase along. While I wouldn't say that changing form one primer to another would necessarily make a load unsafe, it does change things-you have evidence in your targets. Try working up a similar load with the Winchester primers and see if those groups don't squeeze down noticeably. I will do that. The CCI primer availability around here is very spotty....The WLR's are generally more accessible. I've had very good results with the WLR primers in a different powder/ rifle combination. I hope no one took my OP to mean that I thought the CCI was somehow better than the WLR....It was certainly not meant that way. Really, I was just surprised by how easily I could see the difference in the two different primers. I actually think a load tailored to the WLR primer would be excellent....far more options in components. |
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