More powder, less velocity?

[rodell]

I was at the range today, testing velocity against a variable charge of RL-33. I suspect some strange pressure curves, or, possibly some neck tension issue. All of these cases were prepped exactly the same way and are new Norma brass. The chrono is a LabRadar, so I believe its numbers.

 Charge (RL33)	V0	Delta
1	86.0	   3252	
2	86.2	   3310	58
3	86.4	   3270	-40
4	86.6	   3285	15
5	86.8	   3326	41
6	87.0	   3343	17
7	87.2	   3312	-31
8	87.4	   3318	6
9	87.6	   3375	57
10	87.8	   No Data	
11	88.0	   3385	10

You will note the idiot on shot 10 forgot to arm the chronograph. With only a 10 fps difference between 87.6 and 88.0, that looks like a possible accuracy node. Possibly another one at 87.3. However, I’m looking at Shots 3 and 7, where the delta is negative – more powder, less velocity.

Seen this before? As an aside, all of the charges together shot in a 2” group at 100 yards, without particular attention to technique. That’s pretty awesome in itself, considering the Es is 133 fps.

Thoughts?

As an aside, I shot 4 of the 87.0. They were 3343, 3336, 3331 and 3331 for an Es of 12 and a Sd of 5.6. I'm not sure what that tells me with respect to the other data. It does indicate no problem with neck tension.

 

[Dwh7271]

You might be pretty close to the middle at 87. I might try a few at 86.8 just for fun.
That ES and SD at 87 is nice though. If it’d group for you and you’re ok with speed then you might be done.

 

[TackDriver284]

You might be pretty close to the middle at 87. I might try a few at 86.8 just for fun.
That ES and SD at 87 is nice though. If it’d group for you and you’re ok with speed then you might be done.

Not to insult your intelligence but curious to know why you picked 87 grains? I see his 4 rounds have a nice ES, but there are two flat spots at 86.5 and 87.3 grains on the ladder test, wouldn't you try those flat spots as well?

 

[jimbires]

neck size your brass and run your test ladder again . I don't like virgin brass .

 

[Dwh7271]

No offense taken.
It just appeared to me that may be shortening the equation a little but from 86.2 or .4 to 87.4 the true variance was only about 8 FPS. Big flat imo. I actually kind of like 86.8 but he was already at 87 with a decent SD and ES.
Guess maybe I simplified it a little.
And ditto Jim’s comment on new brass.

 

[rodell]

I loaded a few extra for this test at 87.0 because FOTIS had good luck at that number, no other reason. It was nothing more than an attempt to cheat.

This is 6.5x300 Weatherby with the 127 LRX.

I will anneal the cases and do it again. I figure my barrel life is 1,000 rounds at best, so I'm trying to keep development rounds at a minimal level.

 

[Dwh7271]

Cool. At 3300 that thing is a laser.

 

[SJB358]

You may not be hitting consistent pressure either to settle RL33 down. It came to life as I got to max in my 7 MSM and 175’s.

 

[rodell]

Well, it looks like the culprit was, as suggested here, the new brass. Back to the range today. I took yesterday's brass, annealed it, sized only the necks, chamfered and loaded.

87.3 grains brought an Es of 8 and a StdDev of 4. A 3 shot group was .994 MOA.

87.8 grains brought an Es of 9 and a StdDev of 4. A 3 shot group was .675 MOA and an ATC of .3 MOA.

I shot the 11 shot ladder again, and, there was still one charge that didn't show an increase. All of the rest behaved. For reference, all of the ladder loads went into a 2 MOA group. The new brass, annealed and resized, behaved like the 1x cases. I use a lot of Norma brass - I won't make that mistake again!

 

[69gto]

Rodell: if you want to achieve full potential from your 6.5-300 I would suggest trying US869 powder, the velocities your are getting are less than a 270 WBY with 130g bullets. I have been using WBY.brass which is Norma for 50 years with great results.

 

[rodell]

Rodell: if you want to achieve full potential from your 6.5-300 I would suggest trying US869 powder, the velocities your are getting are less than a 270 WBY with 130g bullets. I have been using WBY.brass which is Norma for 50 years with great results.

I started with US869 but didn't get great accuracy out of it. Now that I have a more consistent neck tension, I may try it again. Many sources seem to think US869 is THE powder for the 6.5-300. I have 3 pounds of it so all I have to lose is a little barrel life!

In my 257 and 300 Weatherby loads I use only IMR7828SSC. It works very well there but does not seem to suit the 6.5-300.

 

[69gto]

IMR 7828 works great with Wby's from 257-340 but the 6.5-300 needs a slower burner. Nosler uses in in their 26 Nosler. I am using it in my 6.5-300 with 140 acc going 3400fps, my rifle shoots almost the same size group at 350 yds. as it does at 100 yds., under an inch. Good luck with your's.

 

[rodell]

What load are you running? Do you find COAL makes a difference in your rifle?

 

[69gto]

91G US869, F-215 P, new brass, 3.535 oal., 140g acc. I shot this at 350 yds. 2 rounds with new brass and 2 with once fired and 3 shots were in 3/4 inch and shot number 4 made the group 1 1/4 inch. I don't think the length made much difference, the factory loads are 3.50 length. My rifle is bedded at the first 2 inches of barrel and free floated and is an Ultra light weight.