Help Choosing OCW (.308 Tikka CTR)

[Nature Boy]

What's the purpose for the 3 "sighter" rounds? Loading some up now and not planning on making these

 

[Andrew Leigh]

They essentially foul and warm your barrel and give you an idea of the initial charge and whether it is safe to proceed.

 

[Dave P]

"will the same charge weight for different lots of the same make/type of powder be best for accuracy for all other components of the load not being from the same lot?"

Well, it all depends. I never felt I had to repeat the tests when I opened a new box of primers, for example. A better shooter, with a more accurate rifle might want to re-test.
My tests were normally 308's. And my ladder tests let me find great groups while shooting 10 rounds of the ladder. To me a great group is 5 rounds at <.75 MOA (or so).

 

[Bart B.]

"will the same charge weight for different lots of the same make/type of powder be best for accuracy for all other components of the load not being from the same lot?"

Close enough in my opinion. Unless you want to wear out a barrel trying to prove otherwise. I've never done any load work up changing component lots nor barrels. The new load may shoot the bullet out 60 fps faster or slower than the previous one; easily corrected for by adjusting the sights.

Sierra Bullets uses the same recipie for all bullets of the same type even when changing component lots and test barrels.

 

[Andrew Leigh]

"will the same charge weight for different lots of the same make/type of powder be best for accuracy for all other components of the load not being from the same lot?"

Close enough in my opinion. Unless you want to wear out a barrel trying to prove otherwise. I've never done any load work up changing component lots nor barrels. The new load may shoot the bullet out 60 fps faster or slower than the previous one; easily corrected for by adjusting the sights.

I share a different experience. 60fps is more than sufficient to take one off any accuracy node. I do agree however that 60fps represents a reasonably marginal change in vertical displacement. Take a .308 with a 165gr Sierra GK, zeroed at 200yds @ 2 600fps. The difference in vertical displacement at 100yds with an increase in velocity of 60fps is 0.13". I would argue however that the group will have opened up / changed in shape.

Sierra Bullets uses the same recipie for all bullets of the same type even when changing component lots and test barrels.

Indeed but they use SAAMI specifications as a base to work from. My experience is that from manufacturer to manufacturer internal case volumes change, enough to make a difference. Not are all bullets created equal and a 165gr. from two different manufacturers can alter chamber pressures more than one would think. Lets look at two bullets I am familiar with and results I can attest to.

165gr Sierra GK = 2401fps = 38 175fps
165gr Accubond = 2463fps

Now with a change in internal case capacity of -2gr. H2O

165gr Sierra GK = 2445fps
165gr Accubond = 2512fps = 47 010psi

So a move in brass of -2gr. H2O and a change in bullet for a given load in this case could result in a circa 9 000psi change in pressure.

For this reason my experience has taught me to develop an new load for any change in component or COL.

 

[Nature Boy]

OK, yesterday I shot the 168 AMAX with Varget in my FN SPR. Used Hornady published data as my max of 44g and worked off of that. I loaded the powder by hand and used my Dillon 650 to seat primers and bullets. I used LC cases, Federal 210 match primers to an OAL of 2.892 (to the lands)


I fired 8, 3 shot groups shot in round robin fashion per the instructions. Here are the results, which frankly I'm having a had time interpreting.



I realize we're looking for distance from point of impact to point of aim and not group size so maybe its my paradigm that needs to adjust. Having said that, after shooting this test I felt I need to check to make sure my rifle (and me) were still able to produce a tight group so I shot 5 of my pet load of H4895 and 180g Nosler BTTs.


The things I can make from this are:

1. Varget may not be the best powder for this rifle, or maybe it is and the nodes are outside the range I tested (41.8-43.9)
2. of the groups tested, group 1, group 4 and group 6 were closest, so maybe working up some loads there and trying them would be in order
3. I need a manual powder dispenser if I'm going to do a lot of this. dipping and trickling onto a pan is tedious.
4. The concept is intriguing and I'm learning from it. Nothing wasted there and I want to try more combos.

What do you guys think?

 

[Andrew Leigh]

Do you possess a chrony?

What is your barrel length?

43.3gr. looks like the number.

Without the speed and more specific chamber data it is difficult by I will assume standard everything and see what QuickLoad spits out as a first pass.

 

[Nature Boy]

Andrew, here's the data you need except FPS, I didn't chrono these

Bullet type Hornady AMAX
Bullet Mass 168 gr.
Bullet length 1.275 in
Bullet treatment none
Cartride (not calibre) .308 WIN
COL planned of loaded round - 2.892 in
COL of Rifle, bullet seated on the lands - 2.892 in
Jump 0.000 in
Trimmed case length 2.005 in
Barrel Length 24 in
Case capacity 54 gr. H2O
Powder Type Varget
Primer Type Fed 210 Match

 

[Andrew Leigh]

Given the absence of any velocities and the lack of a measured barrel length (they are often different from the data sheet) I have the following observations.

- You are running around 2 688fps and at 60 300psi.
- The closest node would be 1.102ms and you are at circa 1.141ms.
- To speed up to get to 1.102ms you will exceed pressure limits and therefore would need to drop to 1.228ms, the next available node.
- At 1.228ms you will need to load about 40.4gr.

When you do another load development exercise then chrony the speeds of the different groups and give me the exact measured barrel length.

On your pet load, assuming the same brass and that you are also on the lands;

- To get to 1.228ms you would need about 39.2gr to give 2 542fps.
- Pressure is about 55 500psi.

Could you confirm your pet load and speed please.

 

[Nature Boy]

Here's the Nosler load data Andrew

Bullet type Nosler Ballistic Tip
Bullet Mass 180 gr.
Bullet length 1.360 in
Bullet treatment none
Cartride (not calibre) .308 WIN
COL planned of loaded round - 2.810 in
COL of Rifle, bullet seated on the lands - 2.922 in
Jump 0.112 in
Trimmed case length 2.005 in
Barrel Length 24 in (that's spot on, from bolt face to crown)
Case capacity 54 gr. H2O
Powder Type H4895
Load 39.6g
Primer Type Fed 210 Match

Average speed on this load was 2538fps 15 feet from muzzle

Thanks for your help

 

[Gtscotty]

Well, I stretched out my chosen A-max load some, and am quite happy with the results.

5 shots at 300 yds (1.3 mil elevation, .3 mil windage):



Unfortunately I think it may be a bit warm for my rifle. First inklings came when I chrono'd both the 168gr and 178gr loads I worked up. The 168 averaged 2664 fps, and the 178 averaged 2648 fps (despite having .7 gr less powder), both pretty stout out of a 20 inch tube.

Warning: Dumb ideas and bad practices to follow

I had been using some Winchester brass that I got once fired (in a semi-auto) from a buddy years ago to work up my .308 loads, but the primer pockets were somewhat loose on a portion, and I suspected I was getting some primer blowby staining my bolt. I was at the range getting my scope setting with this load yesterday when I was invited to a local informal long range match. I had to load up 50 rounds, and didn't want to run the risk of my old brass allowing blowby to etch my bolt, so I picked up 50 new Hornady brass and loaded it up for the match today ( I know, I know, bad idea). I've read Hornady match .308 brass is similar in capacity to Winchester, and I think it must be close as I was able to score first round hits at 500, 600, and 700 using my Winchester brass dope. On the down side, I think the Hornady brass has confirmed that my load is a bit over, as several of my fired cases show ejector marks. I think I'll pick up some new Winchester brass and try out some loads in the 43.5gr area, which also showed promise on the original OCW workup.

I hope new Winchester brass is the same capacity as older lots... What kind of .308 brass are folks having good luck with these days.

 

[Andrew Leigh]

Nature Boy. PM me you e-mail address please so I can get some QL data stuff through to you.

 

[Nature Boy]

You should have it Andrew, you and I have been corresponding over the weekend