Load development

[Kipper]

I normally runs my tests through a hired chrono on a pipe range.. however I haven't had chance to travel to work up a new load.

My club now had electronic targets with velocity measured at poi..

Wondering of this would be acceptable instead off measuring at muzzle to find the ocw?? 

 

Thoughts 

[No i deer]

From what I've read on accurate shooter at long range no...

At 100yds you'd think it would be better

[Catch-22]

OCW is best done at 100m because it’s easier to spot the group sizes with different charge weights. Remember, OCW is all about finding the best group within the middle of a suitable series of groups, where the series of groups all show little dispersion...particularly low vertical. I’m not overly concerned either by chasing low ES/SD. It’s nice when they are in single digits but it’s not essential. Stable group size is!

Muzzle velocity really comes later as it’s important for your ballistic calculator. So I don’t see measuring MV really that important in the initial phases of OCW testing. And actually, I prefer NOT to use the Magnetospeed during initial OCW as strapping it to the barrel will affect harmonics and this group size.

I therefore run my OCW to find the best group, then run a second test on the same group (same bullet and powder charge) but with different seating depths to fine tune (if needed). Lastly I’ll stick a Magneto on the end to record MV which I store in my Kestrel. Done!

With regards to measuring MV using electronic targets, I couldn’t say. It’s likely all down to the system being used and how accurate it is. I would hazard a guess and suggest it’s not going to be quite as accurate as a LabRadar or Magnetospeed, but it might give you a ball park from which to work your Kestrel.
 

 

[Kipper]

I normally travel about 2hrs to a indoor range and run 15 rounds through the chrono to find the ocw ... was thinking it could save alot off travel ..

[KABOOM]

I use an Oheler 35P when doing work ups, always measured at muzzle at the distance my wires are. The range I use is 15 mins from home and when conditions are right ( no wind or zero value)I hop into my jeep and go test.

[Kipper]

Lucky bugger Kaboom..

 

I have to drive 2hrs to a range sadly, cancelled yesterday to find out later there still open . Try again this Saturday 

[KABOOM]

12 hours ago, Kipper said:

Lucky bugger Kaboom..

 

I have to drive 2hrs to a range sadly, cancelled yesterday to find out later there still open . Try again this Saturday 

Indeed I am, now if the mud dries up I may get some good shooting in, right now springish in Wyoming USA the weather is rather variable.

[VarmLR]

Depends on range to be shot.  I use OCW and am concerned about SD/ES for the simple reason that just because group sizes show as consistent at short range, the same may not be true further out when velocity drops off.  That's why low SD/ES figures matter for longer distances.  You may get low vertical dispersion on a one off group at 100yds showing mediocre or high ES but extrapolated to even 600 yds and that dispersion will likely be higher than the larger group at 100yds with lower ES.  The purpose of OCW is twofold:  First to find an economical and repeatable (reliable) solution to discovering your barrel's node points for any given bullet/.powder combo and secondly to be able to fine tune to identify where those same nodes show lowest ES/SD.   I have to admit that over several years trial and error, there is generally some correlation between the sweet spot for at least two nodes for any given load development and reasonably tight ES/SD, but that really does depend on care with case prep and load consistency.  Without being quite careful, you may still end up with similar node points but slightly looser ES/SD and that's generally fine for getting into a ballpark and then refining the load more, or for closer distances, especially where you have no access to a chrony.

What some do, including myself, is to select those node points and then load a further three or so groups of 5 at each to prove a statistically relevant group size can be had.  If it cannot, then back to the drawing board!

[Popsbengo]

 If I've got a good tight group due to having found a 'node' then I find that a wide ES will result in a looser group (if we discount operator error) - it's physics; if the angle of departure is the same and the velocity is different the POI will be different.  We need a harmonic node and bullets doing as close to the same speed out of the muzzle - ie SD/ES.

Consistent loading of quality components, utilising quality equipment, done with skill is what's needed.  Fire some 5 shot groups and find the best.  Simples.

[VarmLR]

Trouble is though Pops that it's not necessarily always the case at 100 yds as differences in velocity of 30 or 40 fps make very little difference and can easily fall within an MOA group at that distance given a reasonably swift enough MV. Arguably though, we're looking more towards quarter moa depending on barrel/load/shooter capabilities, so then I'd probably agree with you in principle.   It's only once out beyond 300yds that BC and stability really starts showing up more in terms of group size.  I've shot some groups with the 223 which were all sub moa at 100 yds, but the same loads at 300yds (flat base G1 profile bullets) were miles apart.  Groups rarely tell the whole story but finding a node where harmonics promote better group consistency is key.  OCW, find the nodes, tune the node (if needed) after trying a few 5 shot groups and crack on. 

[One on top of two]

12 minutes ago, VarmLR said:

Trouble is though Pops that it's not necessarily always the case at 100 yds as differences in velocity of 30 or 40 fps make very little difference and can easily fall within an MOA group at that distance given a reasonably swift enough MV. Arguably though, we're looking more towards quarter moa depending on barrel/load/shooter capabilities, so then I'd probably agree with you in principle.   It's only once out beyond 300yds that BC and stability really starts showing up more in terms of group size.  I've shot some groups with the 223 which were all sub moa at 100 yds, but the same loads at 300yds (flat base G1 profile bullets) were miles apart.  Groups rarely tell the whole story but finding a node where harmonics promote better group consistency is key.  OCW, find the nodes, tune the node (if needed) after trying a few 5 shot groups and crack on. 

👆this 

[Catch-22]

I still think there’s far too much over emphasis on chasing extremely low SD/ES numbers. There’s a huge fixation on getting to the 2-3fps numbers when it’s simply not necessary...even at extreme distances.

Of course, It is entirely necessary to make good consistent ammunition (good hand-loading practice) and find a stable group (validated over successive strings) that demonstrates ‘good’ SD/ES. But I would ask, what is ‘good’ SD/ES to everyone? What number would you deem to be ‘good’ or ‘good enough’? What magic number are you chasing?

An excellent article using Litz’s work, looks at this and calculates that chasing a reduction in SD from 10fps to 3fps yields only a 1% hit improvement rate at 1000yrds on a 20” plate.

https://precisionrifleblog.com/2015/04/18/how-much-does-sd-matter/

Ive personally always been very happy under 10fps but really even that, I’m not overly concerned. If it’s 1% or even 5%, the reason why I’ll miss is overwhelmingly going to be environmental factors (misreading the wind) or poor technique (inconsistent trigger squeeze or poor cheekweld etc)....so is it really worth all the procrastination and effort of chasing super low SD/ES?

[VarmLR]

Yes, I'd agree with that.  I try and aim for 10 on ES as a reasonable target.  Any less would be nice but tbh, environmental factors, changes in wind, poor reading of conditions and slight inconsistencies of technique count for more error and inconsistency.   At 30fps though I'd not be happy and work on it until it's closer to just into double figures.  I'll qualify that and say that's what I'd personally aim for, for my vermin control rounds and target rounds.   For shooting deer under 100yds it doesn't make a scrap of difference whether 10 or 50 provided you have a reasonable group and the right bullet for the job at the right MV.

[No i deer]

I've tried shooting groups with the V3 magnetospeed on and the load that shot the best without the magnetospeed on shot the same with it on..

I just happened to be chronying the load that shot superbly and rather than just bang off 5 shots into the backstop I fired 1 shot at the target..  I adjusted the elevation up then aimed at the bullet hole and shots nearly all went in the same hole. The shot that stepped out the group a fraction was probaly driver error

[Popsbengo]

14 hours ago, VarmLR said:

Trouble is though Pops that it's not necessarily always the case at 100 yds as differences in velocity of 30 or 40 fps make very little difference and can easily fall within an MOA group at that distance given a reasonably swift enough MV. Arguably though, we're looking more towards quarter moa depending on barrel/load/shooter capabilities, so then I'd probably agree with you in principle.   It's only once out beyond 300yds that BC and stability really starts showing up more in terms of group size.  I've shot some groups with the 223 which were all sub moa at 100 yds, but the same loads at 300yds (flat base G1 profile bullets) were miles apart.  Groups rarely tell the whole story but finding a node where harmonics promote better group consistency is key.  OCW, find the nodes, tune the node (if needed) after trying a few 5 shot groups and crack on. 

OK, it was a 'given' to me we were talking about sub 0.5moa groups at 100yds.  I agree that if one is shooting around 1moa at 100yds the rounds will likely be 'all over the place' at distance

[No i deer]

Group photo with the V3 magnetospeed on...

[Brillo]

On 3/15/2020 at 3:11 PM, Catch-22 said:

OCW is best done at 100m because it’s easier to spot the group sizes with different charge weights. Remember, OCW is all about finding the best group within the middle of a suitable series of groups, where the series of groups all show little dispersion...particularly low vertical. I’m not overly concerned either by chasing low ES/SD. It’s nice when they are in single digits but it’s not essential. Stable group size is!

Muzzle velocity really comes later as it’s important for your ballistic calculator. So I don’t see measuring MV really that important in the initial phases of OCW testing. And actually, I prefer NOT to use the Magnetospeed during initial OCW as strapping it to the barrel will affect harmonics and this group size.

I therefore run my OCW to find the best group, then run a second test on the same group (same bullet and powder charge) but with different seating depths to fine tune (if needed). Lastly I’ll stick a Magneto on the end to record MV which I store in my Kestrel. Done!

With regards to measuring MV using electronic targets, I couldn’t say. It’s likely all down to the system being used and how accurate it is. I would hazard a guess and suggest it’s not going to be quite as accurate as a LabRadar or Magnetospeed, but it might give you a ball park from which to work your Kestrel.
 

 

Absolutely spot on. 

Just a note about SD. Many shooters chase an elusive single digit SD and it is totally unnecessary. Because SD is a measurement of a population dispersion from a group mean, it is meaningless for low population counts. Statistically the acceptable minimum population is over 30 data points.

[VarmLR]

47 minutes ago, Brillo said:

Absolutely spot on. 

Just a note about SD. Many shooters chase an elusive single digit SD and it is totally unnecessary. Because SD is a measurement of a population dispersion from a group mean, it is meaningless for low population counts. Statistically the acceptable minimum population is over 30 data points.

That''s a very valid point Mark and one which doesn't seem to be widely recognised.  I must admit that it's ES I work on and usually pay little store on Sd from low count groups especially.  It's still worth noting though (and pretty inescapable) that smallest groups, unless consistent/repeatable, are not always a reliable indicator of low ES.   Low vertical dispersion can be a better indicator but at 100 yds I still use ES together with group size because I've seen too many large ES groups still fall into similar group sizes as low ones on a one off OCW test.  By "large" I mean too large if considering optimal charge weight for long distance (I try for ES10 but for my vermin shooting where longest range tends to be inside 400yds, 15 to 20 is acceptable).  Anything over 20 and I look for a different bullet or primer if I can't optimise on charge/seating distance.

[Catch-22]

I remember a previous rifle I had in 6.5x47.

I was doing everything right and the rifle shot well to 600m, but I was bugged by ES that was in the 50s and 60s.

A simple switch in primers, from CCI450 to Murom KVB-223m, with no other changes at all instantly reduced my ES to around 9fps. Surprisingly group size didn’t change at all, around 0.35MOA at 100m and still low vertical at 600m.

Personally I don’t change bullet or powder, but will change primer and seating depth to really tune a load from Ho-Hum to Yum-Yum. 😆

[n8ess]

Catch-22

off topic slightly but may ask what bullets and loads you were using? I have been using vit140 with some success but my groups could be tighter.

 

[VarmLR]

1 hour ago, Catch-22 said:

I remember a previous rifle I had in 6.5x47.

I was doing everything right and the rifle shot well to 600m, but I was bugged by ES that was in the 50s and 60s.

A simple switch in primers, from CCI450 to Murom KVB-223m, with no other changes at all instantly reduced my ES to around 9fps. Surprisingly group size didn’t change at all, around 0.35MOA at 100m and still low vertical at 600m.

Personally I don’t change bullet or powder, but will change primer and seating depth to really tune a load from Ho-Hum to Yum-Yum. 😆

I use the Muron KVB 223M for both the 223 and 6.5 SR primer brass.  I haven't yet tried the 450's but have a batch of them here so might try them and see whether I get a similar result.

[Catch-22]

Nice - worth a go. Initially I didn’t think it would be the primer, especially as the CCI450 is probably used by most people in the 6.5x47. But for whatever reason, the KVB-223m was better. After seeing that, I went and bought around 15,000 of the buggers!

[No i deer]

The BR4's will give you a low ES in my experience. Saying that I've never used any other sr primer 🤪.

I have got some sr muroms to try that Brillo gave me to test but I've not got around too it yet.

Eric Cortina filmed himself shooting at 1000yds with his 284 f class rig and shot a 1.3 inch group and his first 4 shots were in I think 0.4 inches and his 5th shot open it up too 1.3 inches..

His best ever group and over the labradar he had an ES of 18fps over 4 shots as one of the shots didn't read..

[Catch-22]

12 hours ago, n8ess said:

Catch-22

off topic slightly but may ask what bullets and loads you were using? I have been using vit140 with some success but my groups could be tighter.

 

Hi n8ess,

I still shoot the same load but now in a different 6.5x47.

In my previous rifle (Tikka with 24” Bergara barrel) the load I used was; 123gn Scenar, 38.4gn N140, Murom KVB-223m primer. Gave around 2930fps. No pressure signs (in my rifle) until I hit 38.7gn.

My current rifle (custom Defiance tubegun with 26” Bartlein barrel) and the load I now use; 123gn Scenar, 38.8gn N140**, Murom KVB-223m primer. Gives 2925fps. Zero pressure at all. I could & have tried a higher charge, but the accuracy wasn’t there

NOTE** I coat my bullets and barrel in this rifle with HbN, so it permits me to go at least a full grain more than bare bullets. Do not use either load without working up fully. I’m aware that they’re both way over book max but I worked up safely and know they’re safe for me.

[Re-Pete]

I get the same MV with the same load, but using RS 50 powder in my 6.5x47.

Around 2900-2950 fps seems comfortable for the 6.5x47 and it's certainly accurate.

Pete