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Posted: 5/3/2009 10:15:07 AM EDT
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Well I've worked up a load for .308 for my 20" remington 700 with 168gr SMK, 46.0 gr Varget, and CCI BR2. All groups shot with this load so far have been sub-MOA at 100 with an average group size of 0.6". Average velocity is 2652. However, I've noticed that some of these groups have velocity extreme spreads of up to 59 fps. The groups with higher ES are predictably larger. When ES are under 20 group size averages 0.4". I'm using neck sized WW with uniformed primer pockets and deburred flash holes. I know I could try a different primer to see if that helps but given the current situation with primer availability I was lucky to get the 1000 BR-2s that I have. Anything else I can do to decrease extreme spreads?
Thanks, DOC |
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Clean the insides of your necks down to the bare metal, then with acetone on a q-tip. Metal-on-metal contact will improve the case neck's grip on the bullet and lower your ES. Also use the same brand of brass per batch. Trim brass to same size. Weight the brass and put them into like batchs. Turn the neck to to same thickness. Bullets batched by weight, length (using a bullet comparator), type and brand. Use bench rest primers. Use the same powder lot # per batch. Measure c.o.l. using a bullet comparator. Use the same amount of bullet crimp per batch. In other words make ever round the same per batch. That's IMHO. Mike |
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Clean the insides of your necks down to the bare metal, then with acetone on a q-tip. Metal-on-metal contact will improve the case neck's grip on the bullet and lower your ES. More detail on how to clean the necks please? I know the nylon brush in a rcbs case prep station doesnt do a thing... |
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Clean the insides of your necks down to the bare metal, then with acetone on a q-tip. Metal-on-metal contact will improve the case neck's grip on the bullet and lower your ES. More detail on how to clean the necks please? I know the nylon brush in a rcbs case prep station doesnt do a thing... +1 on more details, I use a plastic brush too. Maybe a bit of 0000 steel wool wrapped around something and spun in a dremel tool would do the trick? |
| I wouldn't use steel wool. If some got left in a case? Might burn up and might not.I would take some green scotch brite and roll it so it fits tight in the neck and chuck it in a drill. Yes you can chuck up on it , just don't get nuts with it. Use a short piece or it will get interesting. Will clean those necks quick. |
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Clean the insides of your necks down to the bare metal, then with acetone on a q-tip. Metal-on-metal contact will improve the case neck's grip on the bullet and lower your ES. More detail on how to clean the necks please? I know the nylon brush in a rcbs case prep station doesnt do a thing... I use a bronze brush chucked in a cordless drill at low speed. It won't damage the neck. Plactic will not get the neck clean to the bare metal. |
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I'll probably get flamed for this but I've had better E/S on my loads when I used cheap Wolf primers. I don't know why but it's just the way it's been so far  Primers are a significant variable in load development. Wolf is different than Winchester, FC, etc. |
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Clean the insides of your necks down to the bare metal, then with acetone on a q-tip. Metal-on-metal contact will improve the case neck's grip on the bullet and lower your ES. Also use the same brand of brass per batch. Trim brass to same size. Weight the brass and put them into like batchs. Turn the neck to to same thickness. Bullets batched by weight, length (using a bullet comparator), type and brand. Use bench rest primers. Use the same powder lot # per batch. Measure c.o.l. using a bullet comparator. Use the same amount of bullet crimp per batch. In other words make ever round the same per batch. That's IMHO. Mike i do everything execpt crimp  still get the occasional flier
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I'll probably get flamed for this but I've had better E/S on my loads when I used cheap Wolf primers. I don't know why but it's just the way it's been so far No, from what I hear those Wolf primers are very consistent. They're used by quite a few top level competitors. I think David Tubb uses them. DOC |
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Doc, I may have missed it, but did not see your "Jump-to-Lands" figure. Jump-to-lands seems to be one of the more important parameters for BR shooters.[/quote CCW, I measured using the honady OAL tool how long the bullet had to be seated to touch the lands and it was long. The bullet was barely in the case. The maxiumum OAL that will feed through the magazine on this 700 is 2.810". So I loaded some 2.795, 2.800, 2.805, and 2.810. 2.805" OAL is the optimum OAL in terms of accuracy for my gun. However, all the lengths tested had high extreme spreads in velocity. Average group size with 2.805" OAL was less than the others. I also threw out any groups shot with all lengths that had over 20fps ES and then calculated average group size. 2.805" was still the winner. It also seems to tolerate the high ES better than the other lengths although things still tend to open up a bit. DOC |
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DOC:
20 FPS ES or even 59 FPS ES may not be so bad, depending on population or number of shots fired. The more important parameter is SD. If you have Microsoft Office or Open Office, you can use the standard deviation function there to get an SD relatively easy. For instance, if your 3 x SD = 59/2 or close, that would demonstrate a very good repeatability. I notice you used the SMK's. I just got in my Widener's Bulk 168 gn. FMJ HPBTs. They measure .309 in dia. consistently, and weigh 169 gn. The .309 is on the upper limit of SAAMI specs. Any comments on that? |
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DOC: 20 FPS ES or even 59 FPS ES may not be so bad, depending on population or number of shots fired. The more important parameter is SD. If you have Microsoft Office or Open Office, you can use the standard deviation function there to get an SD relatively easy. For instance, if your 3 x SD = 59/2 or close, that would demonstrate a very good repeatability. I notice you used the SMK's. I just got in my Widener's Bulk 168 gn. FMJ HPBTs. They measure .309 in dia. consistently, and weigh 169 gn. The .309 is on the upper limit of SAAMI specs. Any comments on that? The SMK's I have measure .3086 on the micrometer. I'd say if it's within SAAMI specs then shoot it and of course watch for pressure signs. I've been shooting multiple 3 shot groups instead of 5 shot groups so I've been using ES. My chrony does calculate SD though. I write it down as well but I'm recording each 3 shot group seperately so ES has been working for me. It's really helped me see how variation in velocity affects my 100 yard groups. I am going to enter all velocities individually into excel and get a good average and standard deviation with a large sample size. I'll probably do it when I have 100 shots recorded. Are the bullets you have Sierras? What did you pay for them. These 100 round boxes of Sierras are about to 35 dollar me to death. DOC |
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Clean the insides of your necks down to the bare metal, then with acetone on a q-tip. Metal-on-metal contact will improve the case neck's grip on the bullet and lower your ES. Also use the same brand of brass per batch. Trim brass to same size. Weight the brass and put them into like batchs. Turn the neck to to same thickness. Bullets batched by weight, length (using a bullet comparator), type and brand. Use bench rest primers. Use the same powder lot # per batch. Measure c.o.l. using a bullet comparator. Use the same amount of bullet crimp per batch. In other words make ever round the same per batch. That's IMHO. Mike i do everything execpt crimp still get the occasional flierI use a ligh crimp with a Lee FCD to make sure the bullel is seated true in the brass in my match grade rounds. In my target and hunting rounds I use a medium crimp. I just got some Wolf primers to test, I read that they really work well in 223 REM. That's IMHO. Mike |
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DOC, Mike,
It is good to compare notes. Thanks. I went back and used my 4 pos. outside mike, got .3089. The Widener's bulk price is $359 / 2000 plus shipping. They go to smaller quantities for a little more per round. They list the Mfgr as "Mil-Spec". Typically, they do not reveal their sources for the bulk deals. [www.wideners.com]. These are no cannelure bullets. I am going to try to get by without crimping at all. I don't use acetone, but do use the Q-tip / Isopropyl Alcohol. I have resized some 1X WWC '05 and LC '05 & '07. The neck ID is .3035. |
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I'll probably get flamed for this but I've had better E/S on my loads when I used cheap Wolf primers. I don't know why but it's just the way it's been so far You aren't the only one; I get crazy low ES (under 10, a lot of dupe velocities) with my LC Match Brass, WW748 powder, Wolf standard LR primers, and various Hornady and Speer match bullets. To say I was a little surprised when i saw my numbers is an understatement. |
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DOC, Mike, It is good to compare notes. Thanks. I went back and used my 4 pos. outside mike, got .3089. The Widener's bulk price is $359 / 2000 plus shipping. They go to smaller quantities for a little more per round. They list the Mfgr as "Mil-Spec". Typically, they do not reveal their sources for the bulk deals. [www.wideners.com]. These are no cannelure bullets. I am going to try to get by without crimping at all. I don't use acetone, but do use the Q-tip / Isopropyl Alcohol. I have resized some 1X WWC '05 and LC '05 & '07. The neck ID is .3035. I've never crimped rifle rounds even the cannelured ones. From everything I've read it does nothing positive for accuracy. Just load a round measure the OAL and push the bullet tip into the side of your bench with moderate force. Remeasure, if it still measures the same then neck tension is sufficient. DOC |
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