Question on bullet seating.

Alaskaman11

Alaskaman11

Gunny Sergeant
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Jan 21, 2009
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#1
Question guys.
Does bullet seating effect std dev?
The issue I’m getting, with my dasher and 308, I get a std dev in the single digits, my 223 bolt gun is getting around 25 to 30 std Div. My process is the same on all, but the difference is I use LW Wilson seating die for the dasher and the 308 and a standard rcbs for the 223. It’s the only difference I can find. Thoughts?
 
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#4
Lots of threads and at least as many opinions...

First will be the faux statisticians...how many rounds are you evaluating and that is not enough unless you shoot 6000 rounds...not 100% incorrect but missing much.

I support the theory that the smaller the case volume, the more influence vary small variations contribute to things such as velocity...and, by extension, SD of that velocity.
 
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#6
Alaskaman11 said:
Question guys.
Does bullet seating effect std dev?
The issue I’m getting, with my dasher and 308, I get a std dev in the single digits, my 223 bolt gun is getting around 25 to 30 std Div. My process is the same on all, but the difference is I use LW Wilson seating die for the dasher and the 308 and a standard rcbs for the 223. It’s the only difference I can find. Thoughts?
Click to expand...

OK : Take #5 closest matched cases in .223 ,that have been fired from YOUR weapon . Clean and prep identically . Then reload as near as accurately and identical as you can including OAL . Take those #5 test group to the Range ,with a CLEAN bore fire #2-3 any old rounds for fouling .
Now fire the #5 test group for accuracy as well as Measurement within 1 minute . Post YOUR results .

This is from Ballistics POV :

Statisticians have determined that values no greater than plus or minus 2 SD represent measurements that are are closer to the true value than those that fall in the area greater than ± 2SD. Thus, most QC programs require that corrective action be initiated for data points routinely outside of the ±2SD range.

I've been pulling the handle closer to 60 years now and I've NEVER gotten 2 SD !.

I have on #3 occasions placed two 7.62X51mm and four 5.56X45mm into the same hole at 100 yd. and 200 yd.
I'm NOT talking about a ragged hole group but the exact .308" and .224" hole diameter . Had there been No backer change ,I'd not have been credited with the hits .

Fyi : One of MY personal best groupings of #15 shots averaged 87 SD and a Dime covered the entire group with change at 200 yd. . So go figure and that Rifle is MY 1990's 20" ES2 A2 AR 15 Bushmaster bone stock ,with MY handloads (y)
 
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#7
Ex E6 said:
OK : Take #5 closest matched cases in .223 ,that have been fired from YOUR weapon . Clean and prep identically . Then reload as near as accurately and identical as you can including OAL . Take those #5 test group to the Range ,with a CLEAN bore fire #2-3 any old rounds for fouling .
Now fire the #5 test group for accuracy as well as Measurement within 1 minute . Post YOUR results .

This is from Ballistics POV :

Statisticians have determined that values no greater than plus or minus 2 SD represent measurements that are are closer to the true value than those that fall in the area greater than ± 2SD. Thus, most QC programs require that corrective action be initiated for data points routinely outside of the ±2SD range.

I've been pulling the handle closer to 60 years now and I've NEVER gotten 2 SD !.

I have on #3 occasions placed two 7.62X51mm and four 5.56X45mm into the same hole at 100 yd. and 200 yd.
I'm NOT talking about a ragged hole group but the exact .308" and .224" hole diameter . Had there been No backer change ,I'd not have been credited with the hits .

Fyi : One of MY personal best groupings of #15 shots averaged 87 SD and a Dime covered the entire group with change at 200 yd. . So go figure (y)
Click to expand...
I’ll do this. As for your last point on the FYI, all 5 groups were a ragged hole. Maybe I should just stop worrying about it
 
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#9
Alaskaman11 said:
I’ll do this. As for your last point on the FYI, all 5 groups were a ragged hole. Maybe I should just stop worrying about it
Click to expand...


I did this off the dirt NO mat at a LEO BBQ/Picnic Accuracy demonstration one afternoon ,so as to demonstrate the benefit of loading your own . With BLC-2 Bulk bullets with cannelure no less and 1990 LC cases . Note the classic Paper BBQ plate target ;)
Back then MY Bushmaster wore a Simmon AETEC 2.8X10 44mm scope ,not exactly a precision piece of glass but did well enough on 6 power at 200 yd. .
 

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#11
Neck tension can cause irregular pressure ,thus effecting velocity .

There are SET variables which NONE of us can account for or compensate . Powder same lot same canister can vary 3 +% ,Primers 2 +%

Those two factors alone make 2% SD ; IMPOSSIBLE .
 
#13
Ex E6 said:
OK : Take #5 closest matched cases in .223 ,that have been fired from YOUR weapon . Clean and prep identically . Then reload as near as accurately and identical as you can including OAL . Take those #5 test group to the Range ,with a CLEAN bore fire #2-3 any old rounds for fouling .
Now fire the #5 test group for accuracy as well as Measurement within 1 minute . Post YOUR results .

This is from Ballistics POV :

Statisticians have determined that values no greater than plus or minus 2 SD represent measurements that are are closer to the true value than those that fall in the area greater than ± 2SD. Thus, most QC programs require that corrective action be initiated for data points routinely outside of the ±2SD range.

I've been pulling the handle closer to 60 years now and I've NEVER gotten 2 SD !.

I have on #3 occasions placed two 7.62X51mm and four 5.56X45mm into the same hole at 100 yd. and 200 yd.
I'm NOT talking about a ragged hole group but the exact .308" and .224" hole diameter . Had there been No backer change ,I'd not have been credited with the hits .

Fyi : One of MY personal best groupings of #15 shots averaged 87 SD and a Dime covered the entire group with change at 200 yd. . So go figure and that Rifle is MY 1990's 20" ES2 A2 AR 15 Bushmaster bone stock ,with MY handloads (y)
Click to expand...
Hmmm??? "NEVER gotten 2 SD" in that time :eek:
Having been precision reloading for ~ 9 years now, my .308 has given me several SD's of 2 or less (all 5 shots or less). One 3 shot with an SD of 1.0 . And only once I got a 1.7 SD with 5 shots out of my 6.5 PRC. ;) LOL, yeah . . . I know, that statistical thing, and that 1.0 SD group I got wasn't particularly good and didn't go with that load because of the poor mean radius number. In fact, I've had a 5 shot SD of 2.0 and the group size was over 1 MOA. But, most of my low SD's I've recorded have had very good groupings. For sure, a low SD just does not guarantee a small group. 😵‍💫
Alaskaman11 said:
I’ll do this. As for your last point on the FYI, all 5 groups were a ragged hole. Maybe I should just stop worrying about it
Click to expand...
Low single digit SD's are a good thing to strive for, but what count's is what you get on target. I simply look at SD's as measure of how well I'm putting together my cartridges. . . . consistency with all the elements matters! :giggle:
 
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#15
Alaskaman11 said:
Question guys.
Does bullet seating effect std dev?
The issue I’m getting, with my dasher and 308, I get a std dev in the single digits, my 223 bolt gun is getting around 25 to 30 std Div. My process is the same on all, but the difference is I use LW Wilson seating die for the dasher and the 308 and a standard rcbs for the 223. It’s the only difference I can find. Thoughts?
Click to expand...
To answer you're question, IMHO, yes. . .but to the extent of how much variation there is in the seating. You need substantial variation to see it in the SD's. Probably the biggest factor here is, the difference in cartridge selection, which often is THE major factor. For example, a Dasher is one of the cartridges that's much easier to get good performance on paper and in terms of consistency. A 223 is much tougher to get the kind of performance one can get out of a Dasher or a .308.

Don't know if you saw this in another thread, but the graph produced by Little Crow Gunworks should give you some idea as to the relationship of things that effect things like SD's and precision the most:

1746380322937.jpeg
 
#16
Are you using 223 components that are of equivalent quality as the dasher brass?
The answer will 95% be “no.”

Crap components, that much of 223 is, won’t ever shoot well. Get lapua brass, anneal it, mandrel it, develop a good load and you should be able to get it below 10. An sd below 10 on a 223 is pretty dang good.

“Bullet seating” alone won’t affect crap. You need to get more specific with your queries to get good answers.
 
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