Surprising Chronograph Numbers

[jgh4445]

Some of you may have read my earlier thread on the 130 gr Game King for the .260. I had worked up a very accurate load with H4350 and another with RL 19. Always one to try to do just a little better, I wanted to bump my loads up just a notch to see if I could get a bit faster and still have a tiny group. I checked pressure signs very carefully and these loads showed no issues in my Sako 85 Bavarian Carbine. Warning...disclaimer...whatever you want to call it... do not start with these loads in your rifle!!!!

I thought from muzzle blast and felt recoil that the RL 19 load was a faster load. Boy, was I surprised. I never would have thought the H4350 loads would be almost 400 fps faster. But, although this chronograph talks, I don't think it lied. Its a CED Millenium II. Pardon the crude record keeping but the chronograph doesn't have a printer. It does have a computer cable but I didn't hook it up.

Another thing I noticed was that the loads with RL19 ALL shot to the POA. The H4350 load shot almost 2 inches above POA. I think I'm gonna stop here and go with the H4350. The RL19 load is a max load at 45.5 and according to the manual I was using the H4350 load is a half a grain over max. Again, DON'T TRY THIS IN YOUR RIFLE!

So now we know that at least in this case, H4350 produces more velocity than the RL19 does. I don't think there would be any way to safely get over 300 fps more with the 19.

 

[amlevin]

What did the cases look like after firing the loads with H-4350?

If you have no pressure signs like heavy bolt lift, difficult extraction, or super flat primers (with more cratering at the firing pin mark than normal) I'd say you have a good load.

You might want to shoot more than just three rounds so you can see some good, meaningful stat's on the loads. Which shows the lower ES/SD numbers will play a role as well--------------as long as you aren't over-pressure.

 

[spitballer]

May have to do with barrel length. Using certain powders to take advantage of a longer barrel may result in a remarkable increase in velocity without a corresponding increase in pressure. I ran into this phenomenon while searching for a combination a 30" bbl. However accuracy should be goal, not velocity.

 

[snuffy]

You have a corvette for a chrony, but you're feeding it regular unleaded and driving it in second gear! While the numbers are better than nothing, you should definitely get it hooked up to your computer so you can analyze the numbers.

I just got my CED M-2, I've used it just once. Today was supposed to be #2 but it's blowing like a gale force wind out there.

The info that chronograph gives you is priceless. The added benefit is you can carry it home to put the readings in a file that you can access at any time. Or take a tablet or laptop with you to the range to feed it right away.

As for your readings, I don't know what to tell you, there's not enough info from your crude notes. reminds me of my Pact chrony, I'd forget my spiral notebook, have to write the readings on a target or scrap of paper.

 

[jmr40]

I think you just have a "slow" barrel. Some barrels just shoot slower with the same loads than others. According to my loading manuals the RL19 loads are about 100-150 fps slower than I'd expect with that powder charge. I've seen identical rifles shoot that much different with loads from the same box of ammo.

My manuals show 42.7 gr as a max load of H4350, but with almost identical speeds as you are getting with almost 2 gr more powder.

When approaching max loads the chronograph is a better indicator than pressure signs. If a max load of a particular powder is supposed to be 2800 fps, then when you hit 2800 fps you are at the max load in your rifle. That could happen when you are still 2 gr below the published max, or in cases like yours at 2 gr above published max.

I don't like to load much above the max published powder charges even if I'm not getting the speeds I want. The load you have may well be perfectly safe in your rifle, but in a different rifle could be 150 fps faster and a dangerous load.

If it were my rifle I'd back off to the published max powder charge, or very close and see what I get. I'm betting that 42.5- 43 gr wouldn't be all that much slower and I'd feel better about shooting it.

 

[spitballer]

The info that chronograph gives you is priceless...

very well stated

 

[jgh4445]

The cases looked fine, no cratered primers, no heavy bolt. The extra .05 gr with the 4350 opened up the group a tad so I'll go back to the 45 gr load. Yeah, I've got to hook up to the computer and get out of second gear.