"high" standard deviation... why?

[bgood1130]

I have been loading for a while now, but I am just getting into long range, so I wasn't too concerned about velocity variation before now. My rifle isn't anything special, it is a m77 vt in 25-06, with a SS 10x42 scope. It has been about 100 rounds since I have done any cleaning, I am just learning about the whole fouling equilibrium stuff, so I don't know if that is too much that it could be causing my problems. I get 1/2 moa 3 shot groups at 100 meters, but 5 shots go to 3\4 or 7\8 moa. That could also just be the result of poor shooting on my part.


I haven't been able to get my sd's under 19. I am using Nosler brass that is prepped, federal large rifle primers, swift scirocco 100 gn bullets, and 52 gns of imr 4350 which gives me velocities a little over 3100 fps. Should I be switching to a gold medal or cci br2 primer?

I am also wondering about my scale, I have been using just a Lee balance beam. Is that scale repeatable enough for the kind of shooting we want to do?

Any help would be appreciated

Thanks

 

[kansas]

Actually 19 is a pretty good SD for using a Lee scale. Nothing wrong with that scale for starts but i prefer the better electronic scales for accuracy. Federal primers should be fine. I've had trouble with higher SDs with Winchester so I went with BR2. Also I don't know how close to max load you are but my SDs creep up with higher charges. Good luck.

 

[918v]

Charge weight consistency, while desirable, does not guarantee a low SD. There is a lot of voodoo associated with reloading. Some powder/primer/case/bullet/firearm combinations are not as good as others.

 

[40xs]

weigh and separate your bullets. If you want lower SD get a better scale and if using a balance beam, after trickling up to your "0" pick up the pan and set it back down... you will probably notice a heavier charge. When I trickle I stop just under the balance point and pick up the pan and set it back down again. trickling usually throws heavier because of friction needed to raise the beam. My experience anyway!!

 

[Steel head]

Consistent neck lengths and thickness, cleaned up flash holes and brushing inside of case necks have shown positive results for me in getting decent SD/ES #'s.

As was mentioned above some Voodoo is involved also.

I've also found god like ES#'s and accuracy don't go hand in hand either.

 

[Jrb572]

I stopped using my chargemaster and went with a tuned scale from Scott Parker. That lowered my ES & SD. In no way am I saying do not use a chargemaster. Many people here use them with great success. I do not know what I am doing wrong with my chargemaster.

 

[CharlieNC]

Earlier this year I replaced my Savage factory barrel with a nice custom, and had to switch to slower powder. After exhausting the work with brass, bullets, technique, etc that was the fix in this case.

 

[dauntedfuture]

I suggest you look at ES and SD, 9 x rounds at 3000 fps and 1 rd at 3100 will give some impressive SD, 10 fps I think but that 1 round is what you are attempting to eliminate. With the small sample sizes that we are testing, usually 10 at most, ES can provide some statistically unreliable information. I consider evaluating ES as a better measure as were working with small sample sizes. With that said, I look for SD and ES when evaluating 10 round groups. If I see that 8 of ten rounds are within 10 FPS of each other and 2 rounds have a much higher then average velocity, its an indication that I need to look hard for a possible cause of the spike in velocity and if I have weighed powder, bullets etc. and CANT get the ES down then I might try another combination. In short, if I evaluate a load and it has a very low SD with a ES over 50 fps, then I know its not going to hold up well in a .308 at 1K.

 

[FN in MT]

YMMV...but for me getting my gem pro electronic scale is what got my ES basically cut in half.

May have been a bad bam scale.....who knows.

I also saw a drop in ES and better accuracy when I went to a set of REDDING neck bushing dies using .002" grip.

LOTS of voodoo for sure...... all the way from the components and tools used to the barrel.

 

[bgood1130]

the 19 SD is a perfect representation of my ES, which was 38, I guess I should have also mentioned that

 

[former naval person]

Chronograph accuracy factored in?

 

[bgood1130]

Chronograph accuracy factored in?

it is a beta chrony, sooo... ?

 

[zipollini]

You haven't mentioned at what distances you will be shooting at or what kind of precision specs. you are striving for. If you are shooting most shorter distances (100-300) then maybe an SD of 19 will be perfectly acceptable. However - if you are looking to shoot out to 1K yds and beyond then things get a whooooole lot more difficult and more expensive. Let's assume for the moment you are looking at distances of 1K. You will most definitely want to get both your SD and ES in to the single digits.

I've been fighting this battle for the past 4 months and this is what finally got me into the low single digit SD and ES. I just followed the bench rest guys.

Equipment - Gun - T2K chambered in 6XC - Norma brass - Lapua Scenar L 105gr and DTAC 115gr BN coated - 39.5 gr H4350 powder - Wolf lg rifle primers

Brass prep for pre fired and prepped brass

1. deprime
2. tumble brass in Thumler's Tumbler with stainless steel media with 1 liter H2O, 1 tsp LemiShine and 1 tsp cream of tarter for 3 hrs - this does a great job on primer pockets
3. separate media and brass and rinse in filtered or distilled H2O
4. dry in oven at 200deg. F for 2 hrs
5. anneal after EACH FIRING with Benchsource annealing machine - http://www.youtube.com/watch?v=OaXzARG5Qz0
6. spray lube cases and inside of case necks with One Shot spray lube - make sure you don't spray inside of case body - just the necks
7. measure neck thickness of each case and sort by .0005 to .001 inch groups - I use the Sinclair neck thickness gauge - http://www.sinclairintl.com/reloadi...inclair-case-neck-sorting-tool-prod36959.aspx

8. full length size with Redding S type FL sizing die and proper size neck bushing to yield .0015 to .002 neck tension - I use a .269 bushing size. I use a RCPS single stage Rock Chucker Supreme press. Nothing fancy.

9. Expand neck using Sinclair expander - http://www.sinclairintl.com/reloadi...ir-generation-ii-expander-dies-prod38807.aspx - Note : if the cases are new and haven't been inside chamfered yet I do that step before I expand the necks. I also sort brass in this step. If I feel the expander inserts into the case either too easily or too hard I pull the case out of the batch.

10. trim brass to length using Sinclair/Wilson trimmer - control length to .001 inch - http://www.sinclairintl.com/reloadi...air-stainless-ultimate-trimmer-prod39292.aspx

11. chamfer inside of neck with K & M adjustable chamfer tool - this is really important !! - keeps chamfer depth consistent - K&M Shooting - Controlled Depth Tapered Reamer, Large 6mm - .338

12. chamfer outside of neck with standard tool
13. uniform primer pocket with standard tool - mine is motorized
14. chamfer, deburr and uniform inside of flash hole with K & M tool - pretty important - K&M Shooting - Flash Hole Uniformer, Professional - Standard 0.080

15. wash cases in warm soapy water
16. while washing brush inside of case necks with nylon brush to remove brass chips and case lube
17. while still wet, wet sand outside neck chamfer with 2000 grit sand paper. Make sure you do not thin the neck. Just smooth out any burrs on the outside chamfer

18. final H2O rinse in filtered or distilled H2O.
19. dry in oven at 200 deg. F for 2 hours

Finished brass sorting

1. weigh each case and separate into groups of .10 grain groups. Heavier cases will generally yeald faster MV while lighter cases will generally yield lower MV.

Priming

1. I use Wolf primers that are fairly hard and need to be carefully seated deep and to the same depth every time. I use the 21st Century adjustable primer seater. It's a work of art. Great piece of equipment - S.S. Priming Tool

Charging

1. Throw charge on a Chargemaster to 1 grain under my final desired weight

2. trickle up to final weight with an Omega II trickler - Ammo Reloading | Reloading Equipment | Omega Powder Trickler | Dandy Reloading Tools

3. I use a Sartorius Entris 64-1S analytical balance that weighs to one kernel or .001 grain easily. I switched from a Chargemaster to this scale and my SD and ES were cut in half immediately. Not cheap but worth every penny in time saving and accuracy. - Lab analytical balance Sartorius Entris64-1S

Here is a great video or the scale and the Omega II in action - https://www.youtube.com/watch?v=jr1Wso6P9ZI

Bullet sorting

1. With the DTAC 115 bullets I sort by bullet weight into groups to .10 grain. I use the Sartorius analytical balance for this. Very fast.
2. With the DTACs I also have to sort by bearing surface length using the Sinclair bearing surface gauge - http://www.sinclairintl.com/reloadi.../sinclair-bullet-sorting-stand-prod38769.aspx

3. With the Lapua Scenar L 105 grain bullets the QC is so incredibly good that I do not have to sort by weight or bearing surface.

Bullet seating

1. I use a Forster competition micrometer seater and seat both the DTACS and the Scenars .040 long and then just close the bolt gently on them to seat them in the lands. This way my seating depth is always the same. For me it yields great accuracy also.

2. I never check for bullet run out as I have checked it many times with my Hornady runnout gauge and it has never been more than .001 inch. I suppose I should probably be checking cases for neck concentricity but have not found it necessary so far. Maybe in the future.

That's about it. A lot of prep time and a lot of expensive equipment.

Note : I have recently been experimenting with a different method of sorting brass. Instead of sorting by weight I sort by MV when running over a crony. I record the MV of each test shot and then later group the cases by MV. This seems to yield better SD and ES than sorting by weight. I will also be experimenting with water weighing the cases as soon as I get the 21st Century tool - http://www.21stcenturyshooting.com/Primer_Pocket_Plugs.php - More pain in the ass and record keeping though.

Good Luck

 

[bgood1130]

Currently I have access to 500 yds, but once I have things like this figured out and I have done more 500 yd shooting there is a 1k range a couple hours away that I would join to be able to shoot 1k

 

[Beiruty]

Some math for 300 WM with Hornady 208 gr A-max.
Assume SD is 20fps out of 3000fps, confidence range from 2980fps to 3020fps.
1) At 2980 at 1K yrds, drop is -246.9" or -23.6 MOA
2) At 3020 at 1K yrds, drop is -239.1" or -22.8 MOA
3) Delta: 7.8" or 0.8 MOA, +- 0.4MOA at 1K yrd
4) If your rifle/load is Sub MOA at 100, it would be 1MOA due the powder, and factor the user error at 1kyrd. So if your target is 24" or so. MV SD variation is not that a factor. Human error is more important.

 

[bgood1130]

Right, having a low SD just "makes the target bigger"

 

[MCSO1357]

JFC, zipollini !!! That's a process! I get single digit SD with Fed GMM brass uniformed flasholes, primer pocket, case length with CCI 200 primers and 175 gr SMK over Varget thrown by Chargemaster. Rifle is GAP Rem 700 in 308.


Sent from my iPhone using Tapatalk

 

[dave300]

tag

 

[LawnMM]

Have you chrono'd different charge weights? Ladder test?

 

[Mad_Charlie]

One thing for sure, Mr. Zipollini is willing to spend the time and money to get his ammo as consistent as possible.

 

[zipollini]

I've changed a couple of things from my last post. When I tumble my brass in my Thumler's tumbler with stainless steel media I now use 1 liter of softened H2O, 1 tsp of LemiShine, and now 1 tsp of cream of tarter. The cream of tarter really makes the brass shine like it is new. Makes a real difference. Can find it in the spice section at any grocery store.

I am also now sorting all my brass by water weighing instead of just weighing the dry cases. This tightened some things up nicely. One would think that a heavier dry case would automatically yield a heavier water weight but it sometimes doesn't. Was pretty enlightening comparing the different weighing results side by side. This is what ya need to water weigh the cases.

Primer Pocket Plugs

 

[Mad_Charlie]

I have always checked h20 capacity by using a case that was fired in my rifle before resizing, but if you are sorting new brass, those plugs are what you need.

 

[Rprecision]

1 tsp cream of tarter for 3 hrs

I'm sorry that just flat made me laugh........I can picture a fight breaking out in the kitchen over a recipe.

All joking aside, Brother how do you find time to shoot with all that reloading ?

OP, reasonable component segregation, choice of primers and good powder choice has proven the most effective for me. When it comes to segregation, if you buy good bullets then save your time and worry about the cases.

I have only met a handful of people in my life that could shoot the differences in a match bullet lot, most however will see the difference of 7 grains case to case(generally).

If you found a good powder charge, slowly start tweaking things.

One thing to not forget is bore condition. Towards the end of a barrels life things get interesting, I guess that can be true for us as well !

 

[TacticalBoltKnob]

Start annealing and making sure neck tension is consistent. Weighing and sorting cases and bullets helps a bit, too.

It's my opinion that it's rarely powder charge or quality of primers. Those things are USUALLY up to par.

 

[zipollini]

I'm sorry that just flat made me laugh........I can picture a fight breaking out in the kitchen over a recipe.

All joking aside, Brother how do you find time to shoot with all that reloading ?

I have to store the "cream of tarter" on my reloading bench so the wife won't try it. Neither of us had ever heard of it before. It makes a huge difference on the cases. Really cleans them up and makes them shine. I would hate to see what it would do on my stomach. As for reloading time, having the right equipment really makes things go faster and cuts down on waste both in time and materials.

 

[AndrewS]

Great thread! I will be coming back to this one.

 

[308220]

You haven't mentioned at what distances you will be shooting at or what kind of precision specs. you are striving for. If you are shooting most shorter distances (100-300) then maybe an SD of 19 will be perfectly acceptable. However - if you are looking to shoot out to 1K yds and beyond then things get a whooooole lot more difficult and more expensive. Let's assume for the moment you are looking at distances of 1K. You will most definitely want to get both your SD and ES in to the single digits.

I've been fighting this battle for the past 4 months and this is what finally got me into the low single digit SD and ES. I just followed the bench rest guys.

Equipment - Gun - T2K chambered in 6XC - Norma brass - Lapua Scenar L 105gr and DTAC 115gr BN coated - 39.5 gr H4350 powder - Wolf lg rifle primers

Brass prep for pre fired and prepped brass

1. deprime
2. tumble brass in Thumler's Tumbler with stainless steel media with 1 liter H2O, 1 tsp LemiShine and 1 tsp cream of tarter for 3 hrs - this does a great job on primer pockets
3. separate media and brass and rinse in filtered or distilled H2O
4. dry in oven at 200deg. F for 2 hrs
5. anneal after EACH FIRING with Benchsource annealing machine - Bench-Source Case Neck Annealing Machine - YouTube
6. spray lube cases and inside of case necks with One Shot spray lube - make sure you don't spray inside of case body - just the necks
7. measure neck thickness of each case and sort by .0005 to .001 inch groups - I use the Sinclair neck thickness gauge - http://www.sinclairintl.com/reloadi...inclair-case-neck-sorting-tool-prod36959.aspx

8. full length size with Redding S type FL sizing die and proper size neck bushing to yield .0015 to .002 neck tension - I use a .269 bushing size. I use a RCPS single stage Rock Chucker Supreme press. Nothing fancy.

9. Expand neck using Sinclair expander - http://www.sinclairintl.com/reloadi...ir-generation-ii-expander-dies-prod38807.aspx - Note : if the cases are new and haven't been inside chamfered yet I do that step before I expand the necks. I also sort brass in this step. If I feel the expander inserts into the case either too easily or too hard I pull the case out of the batch.

10. trim brass to length using Sinclair/Wilson trimmer - control length to .001 inch - http://www.sinclairintl.com/reloadi...air-stainless-ultimate-trimmer-prod39292.aspx

11. chamfer inside of neck with K & M adjustable chamfer tool - this is really important !! - keeps chamfer depth consistent - K&M Shooting - Controlled Depth Tapered Reamer, Large 6mm - .338

12. chamfer outside of neck with standard tool
13. uniform primer pocket with standard tool - mine is motorized
14. chamfer, deburr and uniform inside of flash hole with K & M tool - pretty important - K&M Shooting - Flash Hole Uniformer, Professional - Standard 0.080

15. wash cases in warm soapy water
16. while washing brush inside of case necks with nylon brush to remove brass chips and case lube
17. while still wet, wet sand outside neck chamfer with 2000 grit sand paper. Make sure you do not thin the neck. Just smooth out any burrs on the outside chamfer

18. final H2O rinse in filtered or distilled H2O.
19. dry in oven at 200 deg. F for 2 hours

Finished brass sorting

1. weigh each case and separate into groups of .10 grain groups. Heavier cases will generally yeald faster MV while lighter cases will generally yield lower MV.

Priming

1. I use Wolf primers that are fairly hard and need to be carefully seated deep and to the same depth every time. I use the 21st Century adjustable primer seater. It's a work of art. Great piece of equipment - S.S. Priming Tool

Charging

1. Throw charge on a Chargemaster to 1 grain under my final desired weight

2. trickle up to final weight with an Omega II trickler - Ammo Reloading | Reloading Equipment | Omega Powder Trickler | Dandy Reloading Tools

3. I use a Sartorius Entris 64-1S analytical balance that weighs to one kernel or .001 grain easily. I switched from a Chargemaster to this scale and my SD and ES were cut in half immediately. Not cheap but worth every penny in time saving and accuracy. - Lab analytical balance Sartorius Entris64-1S

Here is a great video or the scale and the Omega II in action - https://www.youtube.com/watch?v=jr1Wso6P9ZI

Bullet sorting

1. With the DTAC 115 bullets I sort by bullet weight into groups to .10 grain. I use the Sartorius analytical balance for this. Very fast.
2. With the DTACs I also have to sort by bearing surface length using the Sinclair bearing surface gauge - http://www.sinclairintl.com/reloadi.../sinclair-bullet-sorting-stand-prod38769.aspx

3. With the Lapua Scenar L 105 grain bullets the QC is so incredibly good that I do not have to sort by weight or bearing surface.

Bullet seating

1. I use a Forster competition micrometer seater and seat both the DTACS and the Scenars .040 long and then just close the bolt gently on them to seat them in the lands. This way my seating depth is always the same. For me it yields great accuracy also.

2. I never check for bullet run out as I have checked it many times with my Hornady runnout gauge and it has never been more than .001 inch. I suppose I should probably be checking cases for neck concentricity but have not found it necessary so far. Maybe in the future.

That's about it. A lot of prep time and a lot of expensive equipment.

Note : I have recently been experimenting with a different method of sorting brass. Instead of sorting by weight I sort by MV when running over a crony. I record the MV of each test shot and then later group the cases by MV. This seems to yield better SD and ES than sorting by weight. I will also be experimenting with water weighing the cases as soon as I get the 21st Century tool - Primer Pocket Plugs - More pain in the ass and record keeping though.

Good Luck

Fuck dude. Your prep looks more like a job than a fun hobby. If I had to do all that, id quit reloading and buy factory ammo. Takes all the fun out of it. I try to spend more time on the trigger than on the press. But thats just me. Different strokes for different folks for sure.

 

[zipollini]

Fuck dude. Your prep looks more like a job than a fun hobby. If I had to do all that, id quit reloading and buy factory ammo. Takes all the fun out of it. I try to spend more time on the trigger than on the press. But thats just me. Different strokes for different folks for sure.

I get plenty of trigger time. I'm an RSO and instructor at an upscale pistol and rifle range. We even have an indoor 100 yd rifle range which I can use in the winter. Get to shoot both pistol and rifle 6-7 days a week