What distance to the lands are you using? (12BVSS)

[lonestardiver]

You need to look at Dan Newberry’s OCW (Optimal Charge Weight). It also ties into this but is more powder charge related prior to fine tuning with seating depth.

[Ted_Feasel]

You need to look at Dan Newberry’s OCW (Optimal Charge Weight). It also ties into this but is more powder charge related prior to fine tuning with seating depth.I'll look it up for sure

Sent from my SM-N975U using Tapatalk

[6mmBR_Shooter]

My BVSS 308 liked the 168gr AMAXs at .020 off. Varget was the best powder through that barrel.

[Ted_Feasel]

My BVSS 308 liked the 168gr AMAXs at .020 off. Varget was the best powder through that barrel.Varget is really good, I got lucky and picked 4 x8 lb jugs same lot and I've found the magic load for .308

Sent from my SM-N975U using Tapatalk

[Ted_Feasel]

I'm not exactly sure what you mean by 'exit node'.

If you're referring to exit time tuning, then I can provide some information.

The bullet exit time is the time it takes for a bullet to proceed down the barrel and exit the rifling.
It is both powder charge and barrel length dependent because those two factors along with bullet weight determine how far and fast the bullet moves down the barrel.

When the round fires, there is a shock wave that tries to expand the barrel and it proceeds down the barrel towards the muzzle and then reflects back to the chamber. It does that again and again until the bullet exits.
The concept is that barrel steel has a reflection speed that is far faster than a bullet can progress down the barrel and leave the muzzle.
The reflection speed is dependent on barrel length too, but it is also dependent on the amount of carbon in the steel.
Old barrel steel, pre-WWII vintage barrel usually had a reflection speed of 18,916 fps.
Savage barrels use 3% carbon steel and have a reflection speed of 19,107 fps.
4140 and 4150 stainless have a speed of 19,969 fps.
416R stainless steel has a reflection speed of 20,014 fps.

To do anything with the theory, you need to know what your barrel length from breech to muzzle and the type of barrel steel.
It doesn't matter what caliber because the reflection travels in the steel not the hole in the barrel.

I find that for most calibers 6.5mm and larger, with barrel lengths of 24-inches, the bullet exits somewhere around 1.15 to 1.3 msec. depending upon what charge you use.

For a Savage 24 inch barrel, the reflection speed is about 0.104 msec. to go from chamber to muzzle.
It takes another 0.104 msec. to get back to the chamber. (the 2nd reflection).
That means that you have to set your load to get the 10th or 12th reflection, depending on how close you are getting to Pmax.
At the 12th reflection in a 24-inch Savage barrel, the exit time would be 1.256 msec.
If you set up your load to get your bullet to exit the muzzle at that exit time, that reflected shock wave is at the chamber and the vibrations at the muzzle are minimum and the crown is the tightest.
The theory is that it should yield the best accuracy.

A 26-inch Savage barrel has a 12th reflection time of 1.361 msec.
A 22 inch Savage barrel has a 12the reflection time of 1.154 msec.
It you use a muzzle brake, a flash hider or a suppressor you need to include that length because the reflection travels all the way to the end before it reflects.
The complication is that the steel in those devices has to be considered because it most likely isn't the same as the steel in the barrel.
Most of mine are 4150 steel. (Colt AR flash hiders also use 4150 steel)

I have tested this effect for about 3 years now and, after minimizing my shooter induced variations and taking temperature into consideration, I have found that my 7 most accurate rifles actually do shoot the best when I load for exit time and get it within 0.002 msec.
I have one rifle (maybe because the steel batch was slightly different or my barrel measurement was a bit off) that likes to be 0.005 faster than I calculated.
QuickLOAD gives you exit time for loads that seems to be accurate enough for my testing.
There is a difference of about 0.060 to 0.090 in average group accuracy between having the exit time with the reflection at the chamber or the reflection at the muzzle.

I have found that with a new rifle, and I have used the approach on three new rifles, I get great results right from the first groups.
Then all I have to do is find out what bullets, powders, bullet weights, and jump the rifle likes the best. They all seem to be different but I don't have to hunt for nodes.So if I am understanding this, you should be able to find multiple loads that are equally accurate, only difference would be the range that they maintain accuracy and also if applied properly you should be able to find a load that works well on barrels of different lengths, it would just be a matter of finding a load where the plots intersect in relation to barrel lengths? Or am I completely of target here? (Pun intended [emoji4])

Sent from my SM-N975U using Tapatalk

[Ted_Feasel]

Here is a link to the Long family's V4 report.
I don't think that is the original article, but it might help.

http://www.the-long-family.com/shock%20wave%20theory%20summary%20explanation.pdfT hank you for the link:)

Sent from my SM-N975U using Tapatalk

[charlie b]

You are correct. The pressure wave travels back and forth many times before a bullet exits. You can use any one of the nodes by changing velocity of the load.

That's why if you do a longer ladder test you may see two loads that are accurate with several in between that are less accurate.

[Ted_Feasel]

You are correct. The pressure wave travels back and forth many times before a bullet exits. You can use any one of the nodes by changing velocity of the load.

That's why if you do a longer ladder test you may see two loads that are accurate with several in between that are less accurate.That's pretty cool, now if I can afford a copy of quick load lol.. if it can really narrow down the possible loads it may pay for its self on the saving of reload components costs

Sent from my SM-N975U using Tapatalk

[charlie b]

But where is the fun in that? :)

I have considered it as well for the same reasons.

[lonestardiver]

I have a .25-06 sporter barrel I was trying to find ammo for years back and nothing really jumped out as good enough. So I took a few boxes and reset the ogive to 0.018 off the lands and then I was able to get moa to sub moa at 200 yards with factory ammo. I recall somewhere that many of the savages like around .02 off the lands. I don’t have enough empirical data to support or refute that statement.

[Ted_Feasel]

I have a .25-06 sporter barrel I was trying to find ammo for years back and nothing really jumped out as good enough. So I took a few boxes and reset the ogive to 0.018 off the lands and then I was able to get moa to sub moa at 200 yards with factory ammo. I recall somewhere that many of the savages like around .02 off the lands. I don’t have enough empirical data to support or refute that statement.I would recon there are alot of factors the determine a rifles sensitivity to jump. Bullets themselves are jump sensitive compared to others. I've read secant compared to tangent is a big factor in a bullets sensitivity to jump but like you I have never built any any imperical data to prove or disprove. I guess my point is I imagine one savage may be and another not.. probably depends alot on components used.

Sent from my SM-N975U using Tapatalk

[CFJunkie]

Ted

You are absolutely right on same weight bullet types (manufacturer variations) with different ogive shapes resulting in sensitivity to jump.

I have measured many bullets of different manufacturers of the same weight and found that they most often exhibit different brass base to ogive lengths in a particular rifle's chamber so the jumps would be different.
I have also found that a few 'clones' (like Nosler CC and Sierra SMKs in 168 grain .30 gal bullets) that have almost identical bullet base to ogive measurements and apparently the same shapes.
I haven't done enough concentrated testing of those two bullets with exactly the same loads and jumps to determine if the performance at a particular jump would be the same.
However, I do have data on my .308 rifles and several of my range buddies .308 rifles and there are definite preferences among about 6 rifles for one or the other of those 'clones'.
The results can only be considered to be indicative of the probability of particular rifle preferences (even among clones) and individual shooter induced variations may be skewing the data also.

Unfortunately, my testing with .308s has concentrated on 150 SMKs, 155 TMKs, 168 SMKs and 168 TMKs with one rifle and 175 SMKs and 175 TMKs, 190 SMKs, 195 TMKs, and 200 SMKs with the other.
I have shot 150s, 155s, 168s and 175s with both rifles but didn't pursue extensive testing with bullets weights that particular rifles didn't shoot as well.
The larger group sizes with bullets that don't shoot as well made it difficult to track exit time impact on accuracy because the contribution to exit time is on the order of several hundredths of an inch so you need to be at optimum performance to compare the improvements when you are attempting to measure the effect of varying exit times.

My testing emphasis in the .223 and 6.5mm Creedmoor calibers concentrated on exit time has used different bullets, weights, and manufacturers and they all are all different enough to have different jumps.
I have never identified 'clones' in either caliber.
All the manufacturers seem to make very different bullets in similar weights. Some bullet weights are unique - 142, 143 & 147 grains for 6.5mm.
A good example would be the 140 grain SMK, ELD-M, and the Berger Match, Long Range and Hybrid variations or the 130 grain TMK, TGK and ELD-Ms all in 6.5mm.
Of all of these examples, the 130 TMK and TGK are the closest in shape, but the difference in jacket depth seems to demonstrate the effect of spin on the POI, even at 100 yards.
The TGKs impact about 1/4 inch further right compared to the TMKs but at the same relative height.

[Ted_Feasel]

Ted

You are absolutely right on same weight bullet types (manufacturer variations) with different ogive shapes resulting in sensitivity to jump.

I have measured many bullets of different manufacturers of the same weight and found that they most often exhibit different brass base to ogive lengths in a particular rifle's chamber so the jumps would be different.
I have also found that a few 'clones' (like Nosler CC and Sierra SMKs in 168 grain .30 gal bullets) that have almost identical bullet base to ogive measurements and apparently the same shapes.
I haven't done enough concentrated testing of those two bullets with exactly the same loads and jumps to determine if the performance at a particular jump would be the same.
However, I do have data on my .308 rifles and several of my range buddies .308 rifles and there are definite preferences among about 6 rifles for one or the other of those 'clones'.
The results can only be considered to be indicative of the probability of particular rifle preferences (even among clones) and individual shooter induced variations may be skewing the data also.

Unfortunately, my testing with .308s has concentrated on 150 SMKs, 155 TMKs, 168 SMKs and 168 TMKs with one rifle and 175 SMKs and 175 TMKs, 190 SMKs, 195 TMKs, and 200 SMKs with the other.
I have shot 150s, 155s, 168s and 175s with both rifles but didn't pursue extensive testing with bullets weights that particular rifles didn't shoot as well.
The larger group sizes with bullets that don't shoot as well made it difficult to track exit time impact on accuracy because the contribution to exit time is on the order of several hundredths of an inch so you need to be at optimum performance to compare the improvements when you are attempting to measure the effect of varying exit times.

My testing emphasis in the .223 and 6.5mm Creedmoor calibers concentrated on exit time has used different bullets, weights, and manufacturers and they all are all different enough to have different jumps.
I have never identified 'clones' in either caliber.
All the manufacturers seem to make very different bullets in similar weights. Some bullet weights are unique - 142, 143 & 147 grains for 6.5mm.
A good example would be the 140 grain SMK, ELD-M, and the Berger Match, Long Range and Hybrid variations or the 130 grain TMK, TGK and ELD-Ms all in 6.5mm.
Of all of these examples, the 130 TMK and TGK are the closest in shape, but the difference in jacket depth seems to demonstrate the effect of spin on the POI, even at 100 yards.
The TGKs impact about 1/4 inch further right compared to the TMKs but at the same relative height.Good info to have, thank you:) I am getting ready to start from scratch on my ar10 6.5 creedmoor barreled with criterion and my 308 bolt barreld 28" shilen. I'm using 3 different pills on each one. On the creedmoor I'll be using 143gr ELD X, 142gr SMK, and 140gr berger. The 308 will get 175 gr berger, 175gr SMK and 178gr ELD match. Along with just finding accuracy load for all the above I am going to play with jump and make detailed documentation of the results.. I will definitely post the data for everyone. This probably wont start happening till next month and will likely take a few months because my range is a 1hr drive and only 1 of my days off they are open

Sent from my SM-N975U using Tapatalk

[hardnosestreetcop]

Hi

I recently bought a 12BVSS (2004) in 308Win and was wondering what distance / jump to the lands (or COAL for 175gn bullets) most folk are finding that this make / model tends to like?

Thanks in advance
Oly

Oly since every rifle is different, my recommendation to you get the Hornady OAL gauge which will give you a reference to YOUR lands with the Sierra 175 Gr BTHPMK. Also with the different comparator inserts, you can measure your Headspace.

[Ted_Feasel]

Oly since every rifle is different, my recommendation to you get the Hornady OAL gauge which will give you a reference to YOUR lands with the Sierra 175 Gr BTHPMK. Also with the different comparator inserts, you can measure your Headspace.I have one, I do all my seating on precision rounds by base to ogive measurements once I find the "magic" number.. it is a PITA to do that on a 100 or even 50 rounds but I've found if you pre measure all your pills and sort them by pill base to ogive (shocking the inconsistency in even the best pills) that you can do it with minimal adjustments on your seating dies [emoji4]

Sent from my SM-N975U using Tapatalk

[darkker]

Not trying to talk you out of QuickLoad, just don't expect it to give you a solid answer on OBT. QL makes a lot of assumptions and in terms of pressures for many powders; needs a lot of "tweeking" to make pressures and burning curves match reality. It's a calculator, not a measurer.

Cheers

[charlie b]

No but it will narrow down the possibilities. Instead of 20 loads I would be testing maybe 5 per bullet. I already have a chronograph so I would be checking velocity as I shot.

[Ted_Feasel]

Not trying to talk you out of QuickLoad, just don't expect it to give you a solid answer on OBT. QL makes a lot of assumptions and in terms of pressures for many powders; needs a lot of "tweeking" to make pressures and burning curves match reality. It's a calculator, not a measurer.

CheersI found another article in a method this guy uses, sounds interesting or at least worth trying

http://www.65guys.com/10-round-load-development-ladder-test/

Sent from my SM-N975U using Tapatalk

[CFJunkie]

Ted and charlie-b,

To answer your assumption that multiple reflections will yield equivalent results:
Theoretically, there are multiple reflections that would create nodes that would provide better accuracy.
But practically, we're loading with powders that have pressure limits, both low and high, so there will always be restrictions on the range of reflections that will fit within those limits.
I find that two even reflections (at the chamber) are usually the only candidates for a reflection time target for any barrel, primarily because of minimum and maximum charge limits for the powders that are appropriate for specific calibers.

In my .308 with a 24-inch barrel, with an reflection target time of 1.256 msec., using powders that are traditionally used for .308, only the 12th reflection falls between Pmax and Pmin, eliminating alternate reflection choices.
In my second .308, with a muzzle brake that extends the reflection target at the 12th reflection to 1.359 msec. The 14th reflection is too light a load to stay within Pmin and trying to push the load to hit the 10th reflection at 1.135 msec. exceeds Pmax pressure.
There may be powder choices that would allow two reflections but based upon experience with other calibers, the faster reflection would be very close to Pmax.

In my two 6.5mm CMs with 26-inch barrels which shoot best with slower powders but also can use traditional .308 powders, the 12th and 14th reflection are within the limits of the slower powders but the 14th reflection doesn't perform quite as well. With the faster .308 powders, the two reflections are a bit more restricting and the best accuracies are not as impressive as with the slower powders. With the slower powders, the accuracy at the 14th reflection is a 'node' but the node is not quite as accurate as the 12th reflection. It took a lot of groups to get a sample large enough to be sure there was a difference, it was so small. Small sample sizes might show that there is no apparent difference.

In my 6.5mm CM with a 24-inch barrel, the 12th reflection works nicely but it is 0.105 faster than the 26-inch barrel reflection target. That limits using the next faster reflection because of Pmax concerns. I tried the 14th reflection but it didn't show any improvement and was also slightly less accurate.

The .223s, with traditional powders and 69 and 77 grain bullets, generally have two reflection options but one is usually close to Pmax.
The lighter bullets provide more chance to fit easily within two reflection options but the faster powders work best.

In my .223 12 FV with a 1:9 twist, I can manage two reflections, the 10th and the 12th with bullets up to 69 grains if I use the right powder. But at the 10th reflection with the 69 grain bullets, the load is pretty close to Pmax and it shows in primer pocket wear. I use the 12th reflection with 77 grain bullets. The 69 and 77 grain bullets shoot more accurately than the lighter bullets in the 12 FV.

In my .223 Les Baer Super Varmint with an 18-inch 416R barrel with a 1:8 twist, the reflection that works best is the 14th reflection becaise the barrel is so short and the reflection 416R stainless is so fast that the 14th reflection time is only 1.047 msec. At the 12th reflection (0.897 msec.) with 77 grain bullets the load is over Pmax. With 69 grain bullets, there are two options but with 69s the 12th reflection is close to Pmax but does not exceed it. I tried the 12th reflection with both 69 and 77 grain bullets but I paid the price with primer pocket wear. Fortunately, it turns out it is just as accurate at the 12th reflection - a least I couldn't see a significant difference in the large sample average.

[Ted_Feasel]

Ted and charlie-b,

To answer your assumption that multiple reflections will yield equivalent results:
Theoretically, there are multiple reflections that would create nodes that would provide better accuracy.
But practically, we're loading with powders that have pressure limits, both low and high, so there will always be restrictions on the range of reflections that will fit within those limits.
I find that two even reflections (at the chamber) are usually the only candidates for a reflection time target for any barrel, primarily because of minimum and maximum charge limits for the powders that are appropriate for specific calibers.

In my .308 with a 24-inch barrel, with an reflection target time of 1.256 msec., using powders that are traditionally used for .308, only the 12th reflection falls between Pmax and Pmin, eliminating alternate reflection choices.
In my second .308, with a muzzle brake that extends the reflection target at the 12th reflection to 1.359 msec. The 14th reflection is too light a load to stay within Pmin and trying to push the load to hit the 10th reflection at 1.135 msec. exceeds Pmax pressure.
There may be powder choices that would allow two reflections but based upon experience with other calibers, the faster reflection would be very close to Pmax.

In my two 6.5mm CMs with 26-inch barrels which shoot best with slower powders but also can use traditional .308 powders, the 12th and 14th reflection are within the limits of the slower powders but the 14th reflection doesn't perform quite as well. With the faster .308 powders, the two reflections are a bit more restricting and the best accuracies are not as impressive as with the slower powders. With the slower powders, the accuracy at the 14th reflection is a 'node' but the node is not quite as accurate as the 12th reflection. It took a lot of groups to get a sample large enough to be sure there was a difference, it was so small. Small sample sizes might show that there is no apparent difference.

In my 6.5mm CM with a 24-inch barrel, the 12th reflection works nicely but it is 0.105 faster than the 26-inch barrel reflection target. That limits using the next faster reflection because of Pmax concerns. I tried the 14th reflection but it didn't show any improvement and was also slightly less accurate.

The .223s, with traditional powders and 69 and 77 grain bullets, generally have two reflection options but one is usually close to Pmax.
The lighter bullets provide more chance to fit easily within two reflection options but the faster powders work best.

In my .223 12 FV with a 1:9 twist, I can manage two reflections, the 10th and the 12th with bullets up to 69 grains if I use the right powder. But at the 10th reflection with the 69 grain bullets, the load is pretty close to Pmax and it shows in primer pocket wear. I use the 12th reflection with 77 grain bullets. The 69 and 77 grain bullets shoot more accurately than the lighter bullets in the 12 FV.

In my .223 Les Baer Super Varmint with an 18-inch 416R barrel with a 1:8 twist, the reflection that works best is the 14th reflection becaise the barrel is so short and the reflection 416R stainless is so fast that the 14th reflection time is only 1.047 msec. At the 12th reflection (0.897 msec.) with 77 grain bullets the load is over Pmax. With 69 grain bullets, there are two options but with 69s the 12th reflection is close to Pmax but does not exceed it. I tried the 12th reflection with both 69 and 77 grain bullets but I paid the price with primer pocket wear. Fortunately, it turns out it is just as accurate at the 12th reflection - a least I couldn't see a significant difference in the large sample average.Reading about it,it seems you could do this without QL just using paper and a calculator. All my match barrels ,.criterion and shilen are 416R.
When you are talking about measuring barrel, are you measuring from where the bolt face locks to the muzzle?

Sent from my SM-N975U using Tapatalk