Sako 6.5 Grendel

[A1Vixen]

At the moment I have some issues with my new Grendel bolt action.
I tried the 108/123g Scenar and the 123SMK without any good results. The 123g Nosler Competitioun were ok, but could be much better.

I am still at the beginning, so no need to worry, but could it be possible that the Grendel doesn't like beeing near the lands?

All I tried was about 0.012" off the lands. This is the distance my Creedmoor prefers and is shooting awesome groups around 0.3inch.

Alexander Arms is using 1:9 barrels as I do, so it can't be a twist problem.

I am trying now to load some rounds around 53kpsi and only changing the distances to the lands. There must be a way that this barrel starts to perform!?

[grayfox]

Hi A1,
I've been reading along on your posts from time to time, and am not an expert in long range, so some caveats up front.
But I've done some extensive studying on optimal barrel timing, which is related to optimal charge weights (OCW). Dan Newberry developed an approach to defining and finding muzzle velocity nodes for a barrel given only the barrel length. Have you tried using any of these OBT/OCW concepts for your new shooter? An OBT approach might help you find the nodes, and consequently the MV, for your bullets. Then look for powders that can deliver that for you and test loads in the vicinity of the predicted node. Then play with overall lengths for best groups
Do you have a chronometer?
As to bullet jump, I do not like using bullets that need to be close to the lands - that's just my preference. The Nosler's that I've used (129-130) have done pretty well for me but I am more hunter than accuracy-shooter... As example, my 129 ABLR Nosler for the 6.5 Grendel I load in my bolt-action at 2.305", but I was limiting myself to mag length not to the lands (my Howa mag allows 2.320" max lengths) - actual jump is longer. And my 130 Accubond is at 2.300". Best 100 yd groups I've been able to do are in the 0.3"-0.4" range but more likely I get about 0.7-0.9" on my typical day, shooting with bipod off of a bench/ rear bag indoors 100 yd range.

Anyway maybe this will give you some ideas even though they are Nosler's. I have some formulas I use to guide me in my OBT node searches.

[A1Vixen]

Yes I have a Shooting Chrony and a Magnetospeed. I checked the Homepage of Dan Newberry, but I prefer my ladders.
There are a lot of theories out there, like only choosing the right load with the Chrony speed...
I know a lot of very accurate shooters. They all do ladders with the try and fail system.
For my next ladders I will try different distances to the lands down to the CIP/SAAMI max OAL.
Best group till now was a 0.78" @100m which is not really good!

But I will continue and I'm sure I will arrive to get lot better groups.

[grayfox]

Ok, no problem. Actual shooting is indeed the final judge. Theories only get you started.
Keep us posted on your work, I for one will certainly learn something!

[A1Vixen]

I forgot to write that the barrel contour I planed first is far away from the contour I got for my old Sako.
The only barrel I could get in 1:9 twist was a Lilja in Standard contour Nr. 3.

And that's probably the accuracy problem. It is a 26" barrel but really thin contour.

I'm still not happy with the groups out of my Sako. I also have a new Alexander Arms Modell 20" Entry Rifle AR15 which shoots better groups than my bolt action! This is for me a sign that I have a serious problem with my Sako!

Now I consider to cut the barrel back to 20". It is not what I planed first, but if it is the only possibility to get better groups. Than it will still be a fun rifle to shoot with silencer and I can use it for hunting too.

[BjornF16]

I placed my order.

I ordered my custom reamer based on a Grendel II but with .290 neck.

A1, I hate to rain on your parade, but I suspect I've highlighted your issue above. Unlike the SAAMI Grendel compound throat which has proven to be very accurate with a wide variety of bullets, the "Grendel II" is a bit more picky on what it will shoot well. Keep searching for a bullet it likes.

[VASCAR2]

Try 120 grain Sierra Match King with Grendel II chamber.

[A1Vixen]

I will send my barrel back to the gun smith. So he can cut it down to 20" and I want to have the throat beeing 1,5mm longer to the lands.
As I use the rifle only as single loader there should be no disadvantage.

At the moment I have doubt that there is a chance to get this long extreme thin barrel grouping. The best results I got was with the 120g Partizan HP BT, but even those groups were ok, but not good enough.
For me, just SUB-MOA is not what I am searching for with this setup.
Half MOA should be possible.

[A1Vixen]

Thanks BjornF16 for sharing your concerns about the throat. We will see how this will work after the barrel is 20" and my gun smith will recut the throat.
I've prepared a dummy with a 123g Scenar at the OAL I want to use, so he can adjust the throat length.

I have tested the 120g Partizan, 123g SMK, 123g Nosler, 108g Scenar and 123g Scenar. The reason I want to have my barrel shortened because it is that thin and long, you'll notice that with less than 10 shots the barrel is hot and groups opens up. That's not funny. Better having a shorter barrel with less V0 and less problems with the barrel oscillation.

[A1Vixen]

Here now a pic after the barrel is now shortened to 20"
31606589_1699364780177901_8347930025437167616_n.jpg

The throat depth is now perfect for the Lapua 108 and 123, as I wanted to have.
At the moment I'm too busy to et to the range, but as soon as I have some loads tested I will report.

I will also buy now a suppressor, so I can use this rifle also for hunting.

EDIT: My new OAL with the 123g Scenar
31743469_1699940170120362_3828684489337339904_n.jpg

[A1Vixen]

Finally I had time go to the range to test the modified barrel.

Now I also have Lapua Grendel Cases, neck turned and these are some results of the first shots with the new cases.

33869801_1727071934073852_7485035228398878720_n.jpg
extra long seated 108g Scenar 6.5 Grendel vs 6,5 Creedmoor.

33617080_1727070470740665_5551804817074028544_n.jpg
My best group yesterday. Under half MOA @ 100m.

33657808_1727070500740662_6010918756383981568_n.jpg
I need to train with this rifle, it isn't that easy to get good groups because you have to led the rifle more than my other rifles.
My opinion is, this is because it is a light weight barrel.

But I'm really happy with the result. After forming the new cases I will now shoot some load ladders. Under 10mm should be possible.
All V0 were higher than Quickload calculated and there were no pressure signs, even with the 108g Scenar and 30.5g TAC. V0 was 830-840m/s!
Best group yesterday was 108g Scenar / 28.5g TAC with avg. 781m/s.

[Sticks]

...

But I'm really happy with the result. After forming the new cases I will now shoot some load ladders. Under 10mm should be possible.
All V0 were higher than Quickload calculated and there were no pressure signs, even with the 108g Scenar and 30.5g TAC. V0 was 830-840m/s!
2720+ for the metrically challenged
Best group yesterday was 108g Scenar / 28.5g TAC with avg. 781m/s. 2562fps

I had to convert to SAE, thought I would share.

I have found with my Howa and the Grendel, you have a lot more room to push velocity than in an AR15 chamber. I've pushed some 123 ELDs out into the low 2700fps (822ms) with no pressure signs or sticky bolt. I may explore that further.