Here's some shot strings:

3247, 3229, 3234, 3171
last one is 1.5" low from the rest

3316, 3296, 3263
last one is well out from the other two

I'm seeing this pattern of a single, slower shot breaking up otherwise decent (never stellar, but sub 1.25") groups and opening them to over 2.5". It happens probably every 2nd or 3rd group. I can call flinches/fliers, and these aren't flinches.

-I weigh each powder charge.
-I am currently seating in contact with the lands
-The brass is of uniform age and lot
-The bullets, primers, and powder are coming form the same box/jug.

WTF...??? The ONLY thing I can come up with is that for some reason I'm not into the lands on the low velocity shots...but the bolt still feels like I'm hitting...resistance to closing is still there IIRC.

Factory stock Ruger M77MKII, 280 Rem, H414, WLR, 100gr sierra JHP...yes I can reach the lands in my rifle with this bullet!

cdh

If it was me I would try some loads with a different primer. Maybe one of the magnums. H 414 is not one of the easiest powders to light. I'd guess you are loading about 55 to 60 grains of powder. That, a regular primer and a light bullet could mean erratic ignition. Just a guess on my part. Good Luck.

Ray

If it were me, I would definitely would not go to a magnum primer. If you aren't already using a match grade primer, you might try the FED210M. I would also try diff loads with the bullet seated a few thousandths off the lands.

Your slowest shots don't really deviate that much from the average and would not cause your groups to open up that much. While the standard deviation of this load is somewhat higher than you might expect from this caliber, it is still not your problem. Also, contrary to intuition, significantly slower shots with the same bullet typically hit higher on the target due to longer barrel time, thus slightly more muzzle rise. However, this is only a rule of thumb, and shots that significantly deviate in velocity can vary in any direction from zero, but rarely do they simply go lower.

The combination of a light-for-caliber bullet with a powder that is somewhat on the slow side for so light a bullet is probably creating not only your velocity devitions, but more importantly is not conducive to accuracy in other ways. The average velocity readings would indicate pressures in the low 40's, which will be kinda squirrely with a ball powder.

My suggestion would be to try a heavier bullet as about a 120 grainer is the lightest typically used in the 7mm bore. I would also suggest selecting a load that provides more pressure. The relatively low pressures that your H-414 load must be generating are not conducive to consistent results in a high-intensity cartridge.

I would say that you need to have a larger sample size. Statistically the difference with only three readings is immeasurable. Shoot ten or more with each load and see how they graph out.

You are cramming your bullets into the lands, it's not a good idea IMHO; Personally I would stay a little back; furthermore, I bet you are not seating your bullet enough, therefore probably there isn't enough neck tension. Remember that you should have at least 0.25-0.27 inches of seated bullet.

quote:

Originally posted by Fjold:
I would say that you need to have a larger sample size. Statistically the difference with only three readings is immeasurable. Shoot ten or more with each load and see how they graph out.

I'm glad you said it, Fjold, so I didn't have to. I feel like a nagging wife when I scold people for trying to evaluate velocity variation with only 3 or even 5 shots.

Thanks for posting the data, CDH. The question of what to do about velocity variation seems to show up about once a week on this forum -- maybe we should have a sticky or a faq? Anyway, I'll add my 2 cents worth.

-- as Fjold pointed out, please use 10 shots (or if you are shooting 3-shot groups, then 9 shots is close enough) to calculate SD. The 10 shot SD should be less than 1% (32 fps in your case) and 1/2% is a realistic goal. If you can get 1/2%, then pat yourself on the back. Your chrony is only accurate to 1/2% so no point in chasing it any further.

-- I haven't tried H414 but they tell me it may be the same as WW760, which I have a fair amount of experience with, and I get lower standard deviation with a magnum primer, either federal or CCI. I haven't tried the WLR's lately.

-- Seating into the lands .... I'm not opposed to it, but it can sometimes be difficult to maintain a consistent degree of engagement. What I mean is, you are fitting a gentle taper (the ogive) into another gentle taper (the throat). A taper-inside-a-taper is not necessarily a stable fit. The fit tends to be either loose or tight with no middle ground. Anyway, to make a long story short, you might try setting the ogive just a hair shy of the lands and see if that makes any difference.

My 2 cents isn't needed here! Very well covered gentelmen.

First...number of shots....I love this forum and the helpfulness guys show, but sometimes guys jump to conclusions without reading too closely. My quote:

quote:

It happens probably every 2nd or 3rd group.

I posted some examples. It's consistent...looking back over my notes it seems to happen with the light bullets. That means every second or third group (6 to 9 shots) I get one significantly below the SD.

I had thoughts of ignition problems but discounted them...it's a medium case after all. Maybe I discounted it too soon...I was in the lands because it was a slow powder, that would help ignition.

The bottom line is that I have a flier problem and it seems to correlate with a low velocity reading...I assume they are related!

I have a hunting load with 140 and 160 grainers...and I wanted a coyote load for the same rifle. Hence it's 100 grainers...not to mention it's a nice plinking/easy shooting load. The hard pad on the Ruger will wear you out with 160 grainers and IMR7828!

cdh

Going back to my response - I don't think the problem is the light bullets. They should work fine. But light bullets in combination with a hard to light powder could very well lead to erratic ignition. In addition to trying a hotter primer you might want to try a tubular powder also.

And BTW, a couple of points raised by others deserve mention.

1) Molar said not to try a magnum primer. Why, I don't know. When I use ball powders it's one of the things I do. There's no danger in it if you back off a grain or two to start but I'd bet that unless you use the Federal 215 magnums you won't have to reduce your load at all. Also, match primers are no hotter or colder than regular primers. They just go through an additional inspection.

2) wildboar and popenmann argued against seating into the lands. Again, I don't understand why. That is an old Benchrest trick that ensures uniform seating, not the other way around. It's impossible for the lands to seat a bullet beyond a certain point. You won't find one seated different than another. And the old-wives tale of raising pressures to dangerous levels is just that, an old-wives tale. If you are operating on the ragged edge it MIGHT make a difference but if you're on that edge you have more important things to worry about.

JMHO and 2 cents worth.

Ray

Cheechako, I'm not a benchrest shooter, but I know that they use special reloading tools and techniques, like turned collets, where the tension is almost nil. CDH is talking about hunting cartridges, he says: "...but the bolt still feels like I'm hitting...resistance to closing is still there IIRC". According to his words I can argue that he is forcing the bullet into the lands rather than seating into the lands, so I keep my objection, for what it's worth of course.

Hi
Gotta agree with Cheechako here.. The light bullet with a ball powder would cause this.
H-414 likes heavier bullets and a hot primer.

If I were working up a 100gr load in a .280 I would start with some IMR4064 of maybe IMR4350 or equivalent. I've had very good results with Fed210 primers in cases of this size.
And experiment with seating depth.

Anyway I would definitely try some different components. I believe you will see those velocity variations go away.

I agree that the bullet is too light for the powder and the twist rate of the .280. I have to ask if the bullet is used just for target or for varmint hunting also? The .280 is tough on deer and even the 139 gr will explode in them. I would NEVER shoot a deer with the 100 or 120 gr bullets from the .280.
The magnum primer might correct some of the fliers, just work loads back up. In my experience, fliers are mostly caused by the gun not liking a bullet.
Stick the chrony in a drawer, it will not tell you what is happening. Some of the most accurate loads would show a LOT more variation then you are getting.
I have an MOA pistol in 7BR that I used for silhouette. Since I no longer do that, I wanted it for deer. I tried the 120 gr SSP bullet (Good for deer with the velocity.) but it would spray the paper at 50 yd's. I have shot 175 gr bullets into 3/8" groups at 100 yd's with this gun and have hit tiny targets at 300 to 500 meters with it. The twist is wrong for the light bullet and I about gave it up. I had some Varget and called Hodgden. They said it would NOT work. I tried it anyway and it makes the 120 gr shoot an inch at 50 yd's and the velocity is up where I want it also. So even the factory was wrong.
So, even if a gun has trouble with a bullet, a powder change can really help.
Work up an accurate load with no fliers, then get out the chrony. I think you will be surprised at how bad the SD and ES is.

quote:

Originally posted by CDH:
...I had thoughts of ignition problems but discounted them...it's a medium case after all. Maybe I discounted it too soon...

Hey CDH, "Maybe" you figured it out.

Or..., "maybe" it is an inconsistent Strain Gauge fiasco not holding the barrel tight enough to keep the Pressure UP.

Another way to get large variations is with a worn throat. A friends rifle (which has visible corrosion damage in the throat) will occasially blow primers (with resulting high vel.). This is in an '06 with No. 4350.

Change the powder.......Would suggest Hodgdon's 4895, with that lightweight-for-caliber bullet. Seat the bullet well. I see no need to jam the bullet into the lands on hunting loads. Too easy to stick a bullet into the lands, and dump a bunch of powder down into the action. Bet your groups become nice, uniform, clusters. Good luck..........Grant.

CDH,

can we assume that all your cases have been trimmed to length before reloading?