12fv build w/ pics

[scootergisme]

Please post the mathematical equation. Please and thank you!

[Dave Hoback]

There is a reason I eluded to it Dug. Being a custom Knifemaker for a number of years(and one of the ONLY one armed knife makers in the known world), you learn a thing or three about carbon/stainless & allow steels, among other metals. Inevitably, such information is learned to an extent.

I think your barrel choice will work wonderfully Dug. Again, I am planning to go with 27 on next swap(and all others in the future), as I believe it delivers the best/highest velocity to harmonics ratio. But that is not to say that choosing a 26” is wrong. It’s what I am using now...26” Varmint contour. And I am very happy with it thus far.

[wbm]

Please post the mathematical equation. Please and thank you!

Here ya go. http://www.ocwreloading.com/. Can also read some of Chris Long's research on Optimal Barrel Time.

[DesertDug]

I will give my limited take on it.

Explosion on shock wave travels in the material explosion takes place. In a material like steel, the shockwave travels at the same speed. Independent of overall lenght or thickness. Knowing this speed and with a program like quick load you can time out bullet exit with the closest even number refraction of the explosion wave.

For barrel steel, like the barrel existing on this build, the refraction time is 18,916 fps or 0.1104 msec.

with known lenght of barrel one can calculate exit time prediction with known refraction speed, in a load worked up in quick load program.

Disclamer, I do not have quick loads but have been trying to get an understanding of the theory.

[CFJunkie]

Here is a link to Chris Long's original article - copyright 2004
http://www.the-long-family.com/shock%20wave%20theory%20summary%20explanation.pdf

I discovered it in 2015 and wasn't convinced by the data - partially because I didn't think it was statistically significant.
I tested it for about 2 years and discovered that even if it had merit, I was unable to prove it because my shooting technique was not consistent enough and because I had not accounted for the effect of temperature on temperature sensitive powders.
After a lot of effort improving the consistency of my shooting technique and reloading technique, I finally was able to see the benefits.
I now have well over 1,000 groups measured and recorded and am convinced that Chris was right.

Note, in the article Chris was also using QuickLOAD.

Now back to DesertDug's concern.

In my opinion, anything over 24 inches will work and we know that 26 inches also works.
There is no reason why 27 inches won't also work beautifully.
A 27-inch barrel would be perfect for bench shooting, but I'm not sure you will want the extra barrel weight when hunting.
That decision is purely up to you and your understanding of the use you intend.

[DesertDug]

Here is a link to Chris Long's original article - copyright 2004
http://www.the-long-family.com/shock%20wave%20theory%20summary%20explanation

In my opinion, anything over 24 inches will work and we know that 26 inches also works.
There is no reason why 27 inches won't also work beautifully.
A 27-inch barrel would be perfect for bench shooting, but I'm not sure you will want the extra barrel weight when hunting.
That decision is purely up to you and your understanding of the use you intend.


What i I just realized was I am trying to get the best of both worlds in one when I have the best of both worlds but I need two. On for each world. This is a savage after all. Surprised no one else smacked me in the head with this one...

[Dave Hoback]

Ah, yes I forgot you are looking for a hunting rifle. But you did say “long range” didn’t you? So that is to be considered. I left the hunting world years ago, so I rarely give it thought. But I do remember still that when lugging a rifle on my shoulder, there was indeed a significant difference, in weight between a 24” & 26/27” stick. I like your 2 gun idea though. I have a friend that spent a bit turning his Model 70 into a long range Hunting/target rig chambered in 6.5-06. He is now building another rifle starting with a Titanium action. WEIGHT became a bigger issue than turning 1/4moa groups.

[DesertDug]

Placed order.

started to prep cases to keep busy. Set up the worlds finest triger and used it for the first time.
If you are unfamiliar with this trimmer, I have a thread about it here:
http://www.the-long-family.com/shock%20wave%20theory%20summary%20explanation.pdf

it was not any more precise then my hornady hand trimmer.
https://i.postimg.cc/mhWbRSSf/IMG-1817.jpg (https://postimg.cc/ZvjkxpgV)

[DesertDug]

Cases chamfered and flashholes debured.

[CFJunkie]

Are all the brass in the picture trimmed, or just the 1.898 and 1.899 brass.
Was there a difference in 0.011 between the 1.899 and the 1.910 due to trimming.
I suspect that
the 1.910 brass had not been trimmed (since it is right on the SAAMI recommended trim length and wouldn't need trimming anyway)?

I think the difference of 0.001 between 1.898 and 1.899 trimmed brass is really good, although I think at 1.899 the brass is 0.005 shorter than I would prefer unless I was going to neck size my brass.
It actually could have been much worse.

Remember, a bit of extra pressure or a little less pressure on the caliper can change a reading by 0.001 in the blink of an eye.
A bit of extra pressure on the trimmer and remove a few extra thousandths pretty quickly, only once the brass is trimmed, there are no 'do overs'.

[DesertDug]

Dyslexia and reloading do not go...,tape should read 1.900 and 1.901

[CFJunkie]

Having the vast majority of your brass within 0.001 is really good.
Your trimmer is consistent.
But the trim length is 0.010 short of SAAMI recommended trim length and is just at the minimum. That would decrease your velocity by about 4 fps and decrease the pressure slightly by about 171 fps with all other things being equal. Letting the brass grow out to 1.920 would increase the velocity by 3+ fps and increase the pressure by about 171 fps.

Trimming short like that is a good idea if you are finding the cartridge length is increasing with sizing.
When that happens I adjust my seating depth to compensate and keep the net muzzle velocity the same (more correctly to keep the bullet exit time the same) until the length gets to 0.010 longer than the SAAMI recommendation for the cartridge.

Being short by 0.010 isn't a big issue, because the brass will grow as you reload, especially if your sizing dies are moving the shoulder back.

When I used to neck size, I was seeing quite a lot of neck growth - enough to force me to trim some brass about every 4-5 sizings. That, and a .308 that doesn't like to shoot more than one resizing with neck sizing convinced me to full size everything.
Recently I have been careful with not moving the shoulder during full sizing with my 6.5mm CMs and have been surprised with very little trim length creep.
Distribution after 4 reloads was still right around 1.910 as a median for 55% of 100 Lapua 65.mm brass with a +/- 0.002 range for the remaining 45% of the brass in almost a perfect normal distribution.
The new Lapua brass all started out of the box at exactly 1.910.

[DesertDug]

Was just looking things over again and realized my mess up. I was shooting for 1.910. Case we're starting around 1.914 once fired factory loads. I set the trimmer up,for 1.900". I will not scrap brass just yet as CFJ has stated ,mit will grow.

[CFJunkie]

You're not the first reloader to trim shorter than you wanted to and you surely won't be the last.

Think of it as just gaining more resizings without having to trim again.
With some of my rifles, I purposely trim 0.005 short to minimize having to trim brass. I just let the brass grow to 0.010 longer than SAAMI recommended trim length and then trim the brass.

Like I said, a bit of judicious seating depth adjustment and you will still be right on your velocity goals or you can just increase the load by about 0.1 grian of powder charge to compensate for the short brass unless you were planning to load right up to PMax.

Message me when you get ready to load and I'll send you a few loading sheets that let you decide the best options to adjust.

[Dave Hoback]

I use the same trimmer. I agree it’s not any more “precise”. But it’s quicker/easier in my opinion. As I’ve said, it’s great for someone like me who currently loads only one caliber. But for those with several calibers, would far out cost a standard trimmer.

[DesertDug]

It sure was nice and quick and easy on the wrists. No more cranking the cutter around. I am trying to keep the 6.5cm trimming done on it so I can keep the Hornady trimmer set up for my .270

[DesertDug]

Got 10 prepped. Once fired brass tried to 1.910".
https://i.postimg.cc/BZM2tG7v/IMG-1818.jpg (https://postimg.cc/14V8YbQx)

I reset the trimmer by setting it right to a piece that was 1.919 afer full lenght resize. With the slightest of touch and all by fell I bumped the setting. Luck, who knows, but with just the right touch and pressure you can get it dang accurate. All with pressure and touch.

So ok. In my quest.

[DesertDug]

Got home and loaded up 10.
143 eld-x, 4831sc, 42.8, 2.821 oal, cases 1.910, bullet exit 1.361ms at 2688fps.

First off this is the best powder I have on hand at the moment, and can I say wow on the lenght of these bullet, and how much lenght goes into the case. I was surprised that the bullet base is at or, so close, to the start of the shoulder. Definitely more then the width of caliber, as the standard I have learned. I know, I am late to the game and fan fair of the 6.5cm.

Here is a pic of the final total weight distribution.
https://i.postimg.cc/W3rC4sLY/IMG-1819.jpg (https://postimg.cc/zbz0tZfT)gas stations that sell e85 gas near me (https://gasstation-nearme.com/e85)

Just seems like I should be able to get the final weight within 1 gn. Or is this not even a concern. I did not start with sorted cases, just some first fired factory load brass I had. I do have some factory formed unfired brass to use when I start to dial her in.

https://i.postimg.cc/HkgwGHBs/IMG-1820.jpg (https://postimg.cc/1fvn6kkL)

[CFJunkie]

I love shape of the 143 ELD-X and all the 6.5mm Creedmoor bullets.
How can you complain about a ballistic coefficient of 0.623 for the 143 ELD-X unless you compare it to the 140 grain ELD-M with a BC of 0.646 and the 147 ELD-M with a BC of 0.692.

Did the factory brass all have the same headstamps?
If not, that was probably the biggest variable.
I see you said you didn't weigh the brass before you charged them with powder so you don't know what variation is due to the brass.
My suspicion is that the brass is probably the biggest contributor to the variation in weight in your result.
You'll find out what the impact is when you shoot the rounds for the first time, but I don't think it will be as big as you think.
Besides, you're going to be using these rounds to get used to this rifle stock anyway so you really shouldn't expect perfection from this set of rounds.

Just a suggestion though,
If you really are going to go to the trouble of loading for a rifle with a custom, high cost barrel, a very expensive stock and are taking the time to measure everything - a very wise approach I might add - you really need to start with 100 cases of some really good brass, all from the same lot. It will eliminate most of the variations that you can't control.

I use Lapua because I get more reloads with Lapua than any other brass before the primer pockets wear out, more reloads than with Norma that costs more but is equally good in quality.

Factory brass never seems to manage more than 8 reloads - usually fewer. Norma brass manages 16.
Lapua gets me more than 20 reloads - 23 to 25 with the 6.5mm Creedmoor - that's 2,300 to 2,500 rounds with the same 100 brass.
Some might say that would be enough to wear out a 6.5mm barrel.

The Lapua brass comes out of the box with exactly the same trim length, all annealed perfectly with drilled primer holes that don't need chamfering, with primer pockets that are just about perfect.
I just reloaded my 4th reload with new Lapua brass that I bought especially for my new 12 FV 6.5mm rifle, full sizing every time I reload.
The results of measuring the 100 brass after 5 firings and 4 re-sizings without ever trimming are as follows:
Length
1.912 - 9
1.911 - 15
1.910 - 38
1.909 - 24
1.908 - 7
1.907 - 7

That is a slightly skewed normal distribution with no trimming or any need to trim.

38% of the brass in this lot is still at the SAAMI recommended trim length and 77% is still within +/- 0.001 of the recommended trim length.
At this rate, with none of the brass close to approaching the 1.920 SAAMI limit for trim length, I may not have to trim any of the brass until the primer pockets wear out, as long as I adjust for any growth in trim length when I load the rounds.
As you are aware, I adjust the seating depth to accommodate the variation in trim length for each load of 25, but all the brass in each load is normally within +/- 0.001 across the 25 rounds in the load, so that takes variation out of the equation for each load.
Since I generally use a different bullet and bullet weight for each load, I have to recalculate the seating depth anyway for each load.

[Dave Hoback]

Great info CFJunkie! These are great times for the lot of us 6.5 fanatics. Our choices in bullets are vast. The ELD’s are certainly a top performer. But I am old school...still prefer my SMK’s-140 & 142gr pills with their “lowly” sub-shy 600BC..LOL! Love your info on the Lapua brass.