I have a Ruger 77 mkII in.280 Remington. It has been a challenge to get it shooting but finally got a fairly good load going that shot around an inch. 150 Nosler Partitions (I have always found them accurate) over 55.5 grains of RL-22. I finally took it to the range and set up my friend's good Oehler chronograph to see what it was doing. Extrapolating,I was thinking 2850-2900 out of a 22" barrel. Imagine my surprise when five shots averaged 2150 fps!

It wasn't the chrono--the loads I checked out on either side of the .280 corresponded exactly with previous experience. Did I make a mistake measuringing powder? I don't think so, the bullets fell on the target exactly where they did the previous two times I shot that load--still in a good group. I might make a measuring load mistake once but not three times in a row. it wasn't that batch of powder; I had some .257 loads loads from the same container that were going within 15 fps of the last time I chronographed that load.

Anyone have any thoughts?

If you checked that can of powder with other loads and were getting the correct velocity makes me think you may have some undersized bullets. Any chance you loaded some .277 cal bullets on those 280 cases??

Could you have weighed out 45.5 instead of 55.5? Its not hard to bump a counterweight one notch on a scale, and once it moves its in the same wrong spot for all the loads that follow. Do you have any of that ammo left? You could pull it down and check.

I did have this happen. My .270 should have been sending those 130 grain bullets at ~2900 fps, but the chromo registered (if memory serves) 2450 fps.

I use a CED Millennium chronograph, and the sky screens slip onto the ends of a square boom. Turns out one of them was only about halfway on, which increased the distance between the sky screens enough to make the difference.

If I understand what you're saying, this may well not account for what happened to you, but sky screens being separated too much will register significantly slower velocity than you actually are getting.

Not that many are following this but it turns out that high-dollar Oehler chronograph was malfunctioning. Possibly this may have been because of variable sunlight, a given with all the sudden thunderstorms and rain clouds we have been having. It would give an accurate (based on loading manual figures) reading one minute and some very hinky results the next. Will try later on a nice sunny day. In the past with cheaper chronies I have experienced one or two bad readings out of five but never five in a row.

Thanks for the follow-up. I was wondering what ailed your chronograph.

I, for one, would appreciate any further news on this.

Time to call Doctor Oehler! roger

Not quite as dramatic but my go arounds with a Robert's made me wonder,,my last one was a 77 with a 3" mod, I suuffed powder into those cases until the floor was slippery. Never got that bugger evev within 300fps of the expected velocity,, thankfully a local pilot had a 458 that he had no need for and a trade was made. My Norma Mag, 425 Express, and 458 all run close to manual loads though!

A few thought here

That load by itself is a mild load and if 55 gr of Re22 is used with 150 gr bullet, you should get around 2600 fps. Yes I know the Nosler manual says 2900 + but in my experience I can go up to 58 grains before I get to higher velocities and pressures - 10 reloads for a lot of brass and the primers still seat firm.

Re 19 is a better powder for this cartridge along with H 4350 or VV N160.

You probably got the charge wrong - set the scales wrong?? Or an old batch of powder or used 120 gr bullets by mistake - something is not right.

I would suggest rechecking a batch with fresh components.

Great caliber and bullet weight for animals up to elk!

Reloading books are just a guide, and with frivolous law suits they are to some degree worthless or perhaps a starting place..

Every serious handloader should invest in a chronograph and work up his own max loads in his particular gun using the chronograph and the multitude of warning signs. Its a learning process, but well worth the effort.

I have a dozen Reloading books and the grain for about any powder varies as much as 5 grs. in some cases and 2 or 3 in every case.

In your case your well below max.