Should I chase best group or SD's during load development.

[Kermit_88]

I've recently gotten into hand loading. So far I've been loading 6.5 creed and 6.5 Grendel. With the Grendel when testing I often find that my best groups often have highest SD's and lowest SD's aren't the greatest groups. For example I've been loading some 100gr ELD-VT with IMR8208XBR. I've narrowed it down to 28.2gr or 28.8gr so I loaded up 10 of each. With 28.2gr I got 2555fps out of a 20" barrel. SD of 19.3 and group of 1.35". With 28.8gr I got 2605fps SD of 11.8 and group of 1.52". Initial 5 shot groups I was able to get 0.26" out of the 28.2gr and 0.80" out of the 28.8gr. With final load development would you recommend chasing the best group size or best SD? I'll be using this round mostly for mid/long range out to around 1,000yrds and Coyote hunting.

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[NeoBlackdog]

Groups. As I understand 'accuracy' in firearms it means the ability to put as many bullets as possible in as small a circle as possible. Doesn't matter how fast they're going, just matters that you poke lots of holes as close together as possible.

 

[roseburger]

I've had really good luck with factory loads honestly.

 

[DizzyJ]

If long range, both.

 

[Kermit_88]

I've had really good luck with factory loads honestly.

My barrel (Ballistic Advantage 20" DMR) is extremely picky with factory ammo. For example factory Hornady 123gr SST shoot very poorly at around 2.3". With hand loading I can pull that into just over 1". My barrel has a very loose chamber so just bumping the shoulder back 5-8 thousands on once fired brass makes a significant improvement in accuracy. I'm planning on swapping out the barrel at some point but for now I'm working with what I got. I also just enjoy load development. I've gotten my Tikka T3X CTR 6.5 creed down under 0.5" groups. Factory ammo hasn't been able to consistently do that for me.

 

[Kermit_88]

If long range, both.

I'm working on seating depth testing at 28.8gr to see if I can improve group sizes and still have good SD. Not sure if it will help yet.

 

[roseburger]

My barrel (Ballistic Advantage 20" DMR) is extremely picky with factory ammo. For example factory Hornady 123gr SST shoot very poorly at around 2.3". With hand loading I can pull that into just over 1". My barrel has a very loose chamber so just bumping the shoulder back 5-8 thousands on once fired brass makes a significant improvement in accuracy. I'm planning on swapping out the barrel at some point but for now I'm working with what I got. I also just enjoy load development. I've gotten my Tikka T3X CTR 6.5 creed down under 0.5" groups. Factory ammo hasn't been able to consistently do that for me.

Hornady 178gr for the 308 win after cleaning as my two fouling shots before hunting at 100 yards on a bench with a bipod and a rear bag. She didn't like the 165 gr Hornady.

 

[NeoBlackdog]

Hornady 178gr for the 308 win after cleaning as my two fouling shots before hunting at 100 yards on a bench with a bipod and a rear bag. She didn't like the 165 gr Hornady.

View attachment 2183297

That is... acceptable.
Just barely, but it'll do. I think you can tighten that up a bit more though if you work at it.

 

[Koda]

With the Grendel when testing I often find that my best groups often have highest SD's and lowest SD's aren't the greatest groups.

If you have a low SD but big groups, adjust your seating depth.
If you have high SD but tight groups, bad combustion adjust your powder charge, primers or other components. If you want to shoot past 500yds you need low SD/ES.

View: https://www.youtube.com/watch?v=6VEMZJYovMA

 

[Kermit_88]

If you have a low SD but big groups, adjust your seating depth.
If you have high SD but tight groups, bad combustion adjust your powder charge, primers or other components. If you want to shoot past 500yds you need low SD/ES.

View: https://www.youtube.com/watch?v=6VEMZJYovMA

That's kinda what I was thinking. I loaded to 2.245" CBTO of 1.591". I'll try bumping OAL incrementally to 2.260. Seems like no matter what loading for precision just takes up a lot of materials during development.

 

[Koda]

Seems like no matter what loading for precision just takes up a lot of materials during development.

I am new to precision reloading and have had my own frustrations. Following Litz and Cortina has really uncovered a few tips... I've read to deburr your flash holes (if needed) and uniform your bullet meplats can really reduce SD/ES.

170K views · 2.9K reactions | MV SD Threshold ⚡ #AppliedBallistics #thescienceofaccuracy | Bryan Litz Ballistics

MV SD Threshold ⚡ #AppliedBallistics #thescienceofaccuracy

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[Kermit_88]

I am new to precision reloading and have had my own frustrations. Following Litz and Cortina has really uncovered a few tips... I've read to deburr your flash holes (if needed) and uniform your bullet meplats can really reduce SD/ES.

170K views · 2.9K reactions | MV SD Threshold ⚡ #AppliedBallistics #thescienceofaccuracy | Bryan Litz Ballistics

MV SD Threshold ⚡ #AppliedBallistics #thescienceofaccuracy

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I haven't tried either of those techniques yet. Started trimming cases closer to max OAL and that has seemed to help a little with SD. With a gas gun I'm happy to get SD's in the low teens. My Tikka 6.5 creed I've gotten them into the single digits. That rifle has in incredibly long throat so I'm seating way over max OAL but rounds fit in the mag and feed just fine.

 

[orygun]

Inconsistent neck tension can play havoc with SD.
I don't shoot long range. Probably wouldn't take a shot at an animal at 400 yards unless the conditions are perfect.
But I like nice, tidy groups and I'm mostly concerned that the first shot lands exactly where I want/expect it to.

 

[Steel Head]

I shoot a lot of long range so ES is very important
Inside of 400 yards going for good groups is fine.