308 loads too high velocity

[rockys]

Hi guys,

First time poster.
I was doing my first time ever load development for my savage fcp-10. 308 24" 1-10 barrel. I am using ssa cases resized , federal primers, barnes 175 gr match burners, AA-2495. Seated to 2.169" base to ogive. Gives about a .058" jump if I did the chamber measurement right. Temp was around 80.

I couldn't find any data on the match burners so I used the sierra 175 match king data from accurate's manual.
I loaded up 39.5, 40.3 and 41.1 for sighters. And had 4 of ea from 41.1 to 43.1 in .4 gr increments to ocw test. I felt a slight powder crunch on seating but can still hear powder shake so I don't think they are compressed.

I had the chrono set up about 10' away and shot some 168 gr rogue river defense reloads I bought through it and the we're 2625-2675ish fps. So I don't think the chrono is reading way too fast.

The first 2 sighter errored then the 41.1 sighter had 2795!
I fired the 41.1 and 41.5 loads and they both errored. Then the 41.9 came up 2730 and had stiff bolt lift.
Primers look a little flat but I don't see hard ejector marks.
Well I stopped there and didn't go any further.


I was figuring 43 to be a max load but now I am questioning it.
Might be the brass is closer to mil spec brass.
Is this way too hot of a load?
Should I back off 2 maybe 3 grains and start over?

Thanks for any help.

 

[Twoboxer]

If your chrono is accurate/reliable, your 41.9gr load was significantly slower than your 41.1gr load. That would indicate charge weight/user error.

If your chrono is inaccurate/not reliable (that day), the fps readings don't matter much if at all.

Do you always have that many chrono "errors"?

If your OAL is significantly different than 2.800", the increase in velocity could be attributed to that. I guess if I were using OCW, I do the recommended - seat normally (~2.800), find the node, THEN play with seating depth. That would also give you more info regarding the velocity "anomaly".

 

[rockys]

It's a caldwell chrono and was my first time using it so I don't know it's accuracy. It was a sunny day and I had the sunshades on.

I don't think I can seat to 2.800" overall as the bullets are quite a bit longer than 175 sierra match kings. 1.329" vs 1.245".
Right now they are around 2.830 oal.

Would compressing them more raise the pressure?

Does leaving them out more raise velocity?

I don't think I am jamming them into the lands as I measured the chamber with the hornandy tool like 50 times and came up with 2.227 base to ogive which I seated to 2.169 to give room for error.

I could be off on powder charges as well I was throwing then tricking them up to weight on an rcbs 505 as best I could.

Maybe I will toss the match burners as there is no data avail be on them and start over with some sierras.

 

[agbm]

velocity should be okay. I'm running out of a 26 inch barrel, bore is moly coated
175 gr SMK
LC brass
CCI BR2
IMR 4895 45 grains
ogive 2.225
coal 2.807
2831 FPS

 

[mtrmn]

color your bullets with a black magic marker and maybe some of those errors will go away.

 

[Rem7targetactical]

Hmmm.... So if your bullets are longer than a Matchking, leaving them out may be too close to your lands causing a pressure spike? (just thinking out loud) If you accidentally measured your chamber wrong.... and pushing them into the case would also cause a pressure problem. I would back the powder down to 37-38 and work up from there using a OAL of 2.800

 

[Twoboxer]

Most times (some would say always) seating longer increases pressure. Personally, I think it depends lol - at least in one of my rifles.

So trying to think what *I* would do next - with no published data and no access to Quickload. I'd accept that the data I gathered was reasonably accurate.

And so I would leave the OAL where it is at 2.830, consider 41.5 my "max", back off 10% from that and re-do the OCW. If following the instructions strictly, the loads would be: 37.4, 38.1, 38.9 and then 39.6, 40.0, 40.3, 40.6, 40.9, 41.2, 41.6. That last charge may or may not also be hot.

Good luck!

 

[Thump_rrr]

Bring the chrono out further if possible to eliminate the effect of the muzzle blast.

 

[rockys]

Thanks for all the help guys.

I will try setting up the chrono a little further and backing the loads off.

I will post up the results when I can get back to the range.