Thread: Incremental load test anomalies

I do ladder, seating and any other tests in the hope that everything will go as expected,incremental and predictable results so that maybe some conclusions can be drawn.often there will be.some random variable that I can't explain ,well outside of what was expected.Replaced my old chrony with labradar and now at least trust my velocities,so there is one less question mark.
Had one of those rare days recently,walked away believing I had.finally cracked it with a 308 load,had some acceptable results in the past but this was more consistent than anything before.
Almost afraid to go back to the range in case I blow it.

Originally Posted by Rated M for Magnum

Sometimes brass can be the culprit, weight sorting can help as often the heavier cases can have a lower internal capacity creating higher pressure.

It's been found that differences in the average mass the mass of the case often comes down to the extraction groove cut on a rimless case which has no effect whatsoever, you'd need to be measuring H20 capacity on each case to be sure, and...

Originally Posted by Waimauku

finally cracked it with a 308 load,had some acceptable results in the past but this was more consistent than anything before.
Almost afraid to go back to the range in case I blow it.

If a .308 does not shoot a 175 SMK seated to 2.8" COAL with 40 odd grains of Varget or similar, it's time to sell the rifle

Originally Posted by shooternz

It is the neck of the case there is only so much gas can flow through the neck of the case when the maximum flow rate is exceeded there is a bottle neck and the gas flow
can't flow fast enough and starts to swirl slowing down the gas and drops the velocity, I did some tests years ago and found as the powder charge went up the velocity
started to go backwards as much as 10fps for 0.5 grain increase .

Thats very interesting, thks!

Originally Posted by Jhon

Thats very interesting, thks!

Greetings @Jhon, @shooternz,
I had read about velocity decreasing with increasing powder charge before but it is nice to hear from someone who has actually tested it. From what I remember pressure still increased with the charge so you seem to to have found your load @Jhon. Generally I load up to a max velocity rather than a max charge so for me my 35P chronograph is essential. I use a 4 foot screen spacing which improves accuracy and the proof channel (a separate reading using a second stop screen) alerts me to the very occaisional dud reading. This system is very useful for loading for older cartridges where load data is varied to say the least. No need to go doawn any rabbit holes for this one. As far as the longer range stuff you need to verify your longer range POI by actually shooting at that range. Preferably zero at 200 metres as well.
Regards Grandpamac.

Originally Posted by dannyb

I started typing up a post with all this and other variables but didn't want to bamboozle the O.P there are so many many things....every time i think i have my system down to a point I'm happy with my process something else crops up
My latest battle is trimming and getting consistent and even chamfering

Yes in hindsight I could've left the first paragraph out

What I was getting at is there is a list of culprits so long it's not even funny and trying to nail it down can you make you tear your hair out. Especially when there is a chroni involved ay @micky_Duck ?

My method I pressure test with a ladder, load some to shoot groups at the high end of pressure, pick the load with the best grouping (fluke) load up some more and validate at range. Plenty good for shooting animals at 300.

As for trimming and chamfering, I keep having to decide if I'd rather jump off a bridge or trim and chamfer brass.

Originally Posted by caberslash

It's been found that differences in the average mass the mass of the case often comes down to the extraction groove cut on a rimless case which has no effect whatsoever, you'd need to be measuring H20 capacity on each case to be sure, and...

Attachment 198713



If a .308 does not shoot a 175 SMK seated to 2.8" COAL with 40 odd grains of Varget or similar, it's time to sell the rifle

Couldn't agree more