Thread: Published vs actual load variations.

Originally Posted by PERRISCICABA

In this photo you can see 4 different chronographs that was shifted in positions (excepted the magbetospeed) for velocity comparison, they are 2X ProChrono, one CED thing and the magnetospeed, velocity variation was about 50ft/s if I am correct. @greghud may confirm the results.

Cheers

Mac

Attachment 77506

So was that 50 between chronys or the 'known' speed Mac?

Originally Posted by Gibo

So was that 50 between chronys or the 'known' speed Mac?

Sorry Gibo, In Between chronys!

Originally Posted by PERRISCICABA

Sorry Gibo, In Between chronys!

Yeah all good mate. I hear the magneto are almost spot on anyway so was just curious. Thanks

Originally Posted by PERRISCICABA

In this photo you can see 4 different chronographs that was shifted in positions (excepted the magbetospeed) for velocity comparison, they are 2X ProChrono, one CED thing and the magnetospeed, velocity variation was about 50ft/s if I am correct. @greghud may confirm the results.

Cheers

Mac

Attachment 77506

this guy has got to be ocd. Im running a 7mm rem mag tikka 24 inch barrel. running 162 amax with adi 2225 73.5 grains doing 2960 fps. thats book max.

Originally Posted by Tim Dicko

this guy has got to be ocd. Im running a 7mm rem mag tikka 24 inch barrel. running 162 amax with adi 2225 73.5 grains doing 2960 fps. thats book max.

That is exactly my load and it was precise 3050 from my 22” barrel and 3120 from the 24”, same speed shooting 72.6gr out of a Browning Hells Canyon 26”... @Boaraxa own the Hells Canyon, you can ask him, crhonographed with my magnetospeed with pressure sign been not a word in the process, just the accuracy node.

Good load it is to , accurate & fast mac tried a bunch of different loads but the one above is best in the browning .

Originally Posted by HuntGatherRepeat

So I may have opened Pandora's Box by getting a hold of a chronograph.

I set myself up for an OCW test this morning and went out with loads for my 7mm Rem Mag. Powder is H4831SC and bullet is 162gr ELD-X over CCI mag primers and Norma brass. Rifle is a T3 with 23.5" barrel and T2 brake.

I ran a couple of shots through to ensure I was on target for testing and to get the chrony set up and ensure it was working.

Started with a load at 62gr and went up to 65gr which is 1gr over advertised max load in Hodgdon data. Hodgdon suggests that a similar rifle should be producing 2731FPS with 60gr of powder; I'm getting 2550FPS with 62gr. Moving to the max side, at 64gr Hodgdon reckons I should see around 2870FPS and I'm getting just shy of 2800 with 65gr of powder which is over max recommended load. I see no pressure signs at all on the 65gr cases.

Anyone else see deviations like this? Anything I should be looking for?

The chronograph will be out I had exactly the same problem with it, I used Applied ballistics (with a custom curve) to do a Ballistic Calibration and the speed given from the Chrony was 105fps too slow.
Sorry I forgot to mention that when I dropped it off.