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Extreme spread

 
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  #1  
Old 04-22-2007, 10:04 PM
 
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Extreme spread

What do you look for when your looking for extreme spread. I ran some loads thru the crony today looking for a node. Not looking for group but looking for the smallest extreme spread. Its worse than looking for the right combo of load, bullet, Col.
of the # rounds I fired I got the following info.
#1, 3210
#2, 3142
#3, 3177
#4, 3190
#5, 3182
#6, 3160
#7, 3174
#8, 3150
#9, 3148
The crony didn't record the actual #5 so I ended up with only 9 acutal recorded round.
3140- Low
3210+ High
3170 Average
68.36 Extreme spread
21.00 SD
yesterday I shot 10 rounds thru the gun, A 700 Remington, blue printed, 26" Hart barrel .300 Ultra Mag with all the bells and whistles and I ended up with an 82.XX ES 93 grains of Retumbo, Nosler AB Federal 215M primer and Remington Case.
I'm using 93.3 grains of Retumbo, Federal 215M primer and a 200 Nosler AB. Maybe I'm looking for the holy grail but I'm trying to get my ES down to at least single digits. Am I dreaming. I'm getting a bit over 1/2" groups and am trying to get them down to 1/4" if possible but its going to take a single digit ES to do it. Is Retumbo the wrong powder to use or would differant primers do the trick. I sure would like to get this thing dialed in before the barrels gone. [img]/ubbthreads/images/graemlins/crazy.gif[/img]
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  #2  
Old 04-23-2007, 06:25 PM
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Location: Blackfoot, Idaho
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Re: Extreme spread

I was in the same boat as you except with a 338 RUM.

I tried all of the combinations of bullets and typical powders for the cartridge.

Just for fun or desperation or just plain bull hardheadedness I tried US869 w/300 SMKs. WaaLaa. Five shots: 2732/2732/2731/2732/3731.

A possibility would be some 869 and some 240 gr bullets. If the load gets the ES/SD down the extra BC would more than compensate for the lower velocity.

Also I'd consider setting the target at at least 300 yds to let that long bullet go to sleep somewhere along the line. Plus you'd be more apt to see the vertical spread do to the velocity differences.

Just a thought.....
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  #3  
Old 04-23-2007, 06:43 PM
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Location: Fredericksburg VA
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Re: Extreme spread

Couple things not clear here.

1. How accurate are the charge weights? Are they each weighed and on what?

2. Accuracy of the chrony? What type chrono or are we talking chrony chrono?

3. Try different primer first for 5 shots to see if ES comes down. I would start with a F210, then CCI. Many times it will even though not a mag primer.

4. Different powder next. I have not used the U869 but it might be the ticket. If you can find some MRP2 (Graf and Sons and Black Hills are stocking it), I know a standard primer will normally beat the mag in that and it is equivalent to RL25.

You must have uniform charge weights for uniform MV and your chrono has to be accurate within its own range. The chrony chronos are touch and go when comparted to an Oehler, so you might have problems in eithe one of those areas.

BH
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Old 04-23-2007, 06:48 PM
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Re: Extreme spread


work up the charge a bit. The first 2 shots gave you a large enough extreme spread. 5 shot test if the first 2 are close would be enough to know if further development is an option......
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  #5  
Old 04-23-2007, 11:08 PM
 
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Re: Extreme spread

Thats what I was thinking (Moving up the charge and changing primers) This barrel is FAST. Kind of suprised me that it was getting that kind of volocity average. I was getting approx .50" groups with both loads tried so far and for the initial lower load I tried working my way up but everything shoots great so I bought the crony cronograph to try and see is was easier to pick up the accuracy node by watching the extreme spread and then working with primers and COL to adjust from there. If 96 grains of Retumbo is max I'm not sure what kind of volocity this thing will get once I get there. Might hit a peak and go back down before I get there. I started loading it at the lower end hoping to find accuracy and maybe get a bit longer barrel life. [img]/ubbthreads/images/graemlins/crazy.gif[/img]
Thanks for the info guys. Will try the heavier load and maybe some Remington primers next.

Also yes the loads are all weighed on a beam scale. A Pacific and its adjusted to zero correctly. All my cases were weighed and picked to be all within 1 grain. Flash holes debured. Neck thickness checked and made uniform with a RCBS neck thickness turner.
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  #6  
Old 04-24-2007, 06:58 AM
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Location: Fredericksburg VA
Posts: 4,137
Re: Extreme spread

BillR

Not sure that you can ID node by watching extreme spread, just never heard of that and not sure how that works. Maybe you hit in the middle and maybe you hit at one end.

Normally a node can be ID'd by a ladder with sequential incremental charges fired and normally 3-4 rounds will have very close MV while the rounds before and after will take dramatic jumps again. If the charges are say .2-.3gr apart that will show you the node start and end. Start tuning in the middle.

Would recommend you change one thing at a time and work powder first. Ie stick with increasing charges of Retumbo if 96 is a safe level and leave primers for last IF you need to go there.

Your weighing etc looks to be good, so no issues there. The chrony might be questionable. I would say at some point in the future set up your chrono and a someone elses and check them together, particularily if the other is an Oehler. That way you can have some degree of confidence in it and comparison. I had an older PACT that was very uniform in its readings but just a little slower than my Oehler, but at least I knew it was consistent and that is the key.

BH
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  #7  
Old 04-24-2007, 07:12 AM
 
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Re: Extreme spread

I checked it against an Oehler and its right there with it. I was having a bit of problem that day due to wind. Also the reason I didn't post a target. Wind kept blowing everything over so I just went to trying to narrow ES. I had a total of 3 false readings due to clouds and wind conditions. Even locked down the wind would spin my Chrony around. [img]/ubbthreads/images/graemlins/ooo.gif[/img] I don't think the wind ever quits out here. If it did everyone would fall over. [img]/ubbthreads/images/graemlins/crazy.gif[/img]
I have another day later in the week and IF it quits blowing long enough I'm going to try a ladder.
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