FPS nodes for 6.5mm 139gr scenars ?

[SND]

I've read a few times on here that some bullets like a certain speed range, so I'm wondering what you guys have found to be the best speeds for 6.5mm 139gr scenars. I'm hBN coating and pointing them, and using lapua brass. N160, H4831(gotta get some SC), tried 4350 but seemed too fast and harder on brass(no problem for the 123s got 3040fps with 43.5gr ). 29.6ish " Bartlein barrel, barnard S action. Edit: 1:8 twist, 5R.

Today I finally did my first load tests with a chrony to get and idea of what book data gives for FPS in my rifle with its new mods and such, and to get an idea of what they look like at 200yard.
So far 44.5gr of H4831 (2735fps) gave the best group, only 4 shots but it was .466(worth investigating I think) and then they opened up again when I went to 45 and 45.5gr(2778fps).
Now the brass looks great, measures good, no pressure signs which has me wondering if I should keep pushing for faster to see if it'll get more accurate again?
I plan to also up the dose on N160 as at max by the book(40.6gr) I only get 2600-2625fps and there still a fair bit of room in the case, were as the 4831 was packed pretty full(SC should help with that eh?)
After 83rounds and no cleaning (last 20 or so rounds N160) could hardly see powder in there, maybe hBN helps? (never checked if there was any residue difference with 4831 though but will next time)

About how fast can 139's be pushed by in 260rem and still get decent brass life?

Thanks for the help. I'm hoping to load the next batch closer to optimal performance, and I gotta do more mods on the rifle and rest until then.

 

[BadAsMo]

The accuracy node will depend primarily upon your barrel twist rate. A fast twist will have a low velocity accuracy node and a slow twist will have a faster velocity node. I don't see your twist rate in your post so we are flying blind here without it.

The basic theory behind it is in obtaining the ideal balance between bullet weight (meaning length), velocity and spin rate. Once you have all that dialed in, then that last little bit might be tuned in with a barrel tuner, but I believe that’s getting into the realm of voodoo.

If anyone advises you the “perfect” speed without qualifying that with the above criteria, dismiss the advice.

You can determine your ideal velocity on your own by the basic ladder test.

My ladder test is with powder charges in 0.5 grain increments and any less is a waste of time. I load 2 rounds per powder charge starting light and working up to 0.5 grains past the maximum recommended load USING FIRE FORMED CASES ONLY. I load them with a seating depth that just touches the lands and I never jump them.

When I shoot them (at 100 yards on a very calm day), I start with the lightest rounds and shoot the 2 each with the same powder charge at the same aiming point. I then work my way up in powder charge (each pair on a new target) paying close attention to the force required to open the bolt. At the first sign of stiff bolt lift, I stop shooting. Any leftover rounds are not fired and are disassembled.

Now I just analyze groups looking for groups that were close in the 2 shot pair as well as the adjacent powder load. If lucky, I will have a hard time deciding between them. More than likely the best groups will be at one end of the powder charge range or the other. If the best group is also the hottest load, then I may want to consider a 1 inch faster barrel twist rate for my next barrel and vice versa.

 

[vviking]

Don't have a .260, unfortunately.
Shot from quite a few 1 in 7.9" twist 6.5x55's, the uncoated 139 Scenars have shown a consistently accurate node at 2650-2675fps.
In a 1in 8" twist 6.5/06, that fine bullet worked best at 2850fps for this rifle.

Unlike the 140 Amax which likes to jam, the Scenar seems to work best with 10-30 thou. jump to the lands.

 

[SND]

Thanks for the replies, Twist is 1 in 8".

I did work up in .5grain, I see about a 30-35fps increase per .5grain.
I loaded some at seating depths of .01, .02, .03 off the lands with 39gr N160 but didn't really see any effect on accuracy at this time, it was the first loads I shot early morning, lots of mirrage from the frozen ground turning into 3" mud as well and sun coming from the front/right side was blinding so I couldn't trust those targets at all. (other post coming soon about that sun thing...)

I like the idea of loading up only a couple rounds of each and stopping when the signs show up, I'll give that a try, carefully, with the N160. I'll bring a micrometer to check the cases as they come out for any sign of base getting bigger. Range is an hour away each way so if I can save a trip or 2 in load development it helps.

 

[redshooter]

I wouldn't worry about measuring the case. If the primer fills the pocket completely you've got a wee bit too much pressure. If the case is a little sticky coming out you've a wee bit more than that. If you've got shiney spots on the base, the stamp is smeared or indistinct, or the primer falls out after you got your case unstuck wacking at your bolt you've got waay too much pressure. The only sympton I don't get to excited about is the flattened primer, any one round of a given load that results in the others though the offenders go home to be dissasembled and powder and COL confirmed.

 

[rhs]

My 260AI shoots well at 2850 using 48g 4831SC with 139 Scenars.
This is not a hot load for the AI, but would be for a regular 260. Barrel
is a 26" Shilen 1:8. Jump is almost 60 thou because of the mag. Was going
to have the barrel set back after I went to the AICS stock, but it is shooting
well enough so am not gonna mess with it until the throat goes.

 

[Toolman]

I get 2850 using 43.3gr of H4350 pushing 139 moly coated scenars in a 8 twist 30" Gaillard barrel. Brass life is really good. I'm over 10 reloads on my necked up 243 lapua brass.