Help me interpret results ... OCW load development

calgarycanada said:
Every gun is different, minor flattening is ok, I go by flattened primer where head of primer is just as big as its diameter, ejector swipe and heavy bolt. Here's a video that shows some excessive pressure signs

https://m.youtube.com/watch?v=orJdUR_X67M
Click to expand...

OK! That video is a waste, OK! Being able to produce a you tube video doesn't make an expert! OK!
Excessive high pressure should be avoided, not corrected after a come-apart. When load testing bring a quality caliper and/or a micrometer, note book, and a crayon. Measure cartridge diameter above extraction groove, across the web, (the area that sizing dies cannot reach) and measure the recess of extraction groove. Record both measurements and compare after firing. Web expansion of .002" would be the max acceptable expansion. Any expansion of extractor groove, is unacceptable, reduce powder charge at least 5%. A rebated rim cartridge in a tight chamber with high quality brass might not expand across "the web", but will flow brass back into extraction groove, this may or may not produce any excessive pressure signs on primer.
Lapua Palma brass (also 6mm BR, 6.5X47) with small rifle primers will expand across web and extractor groove long before primers indicate a problem.
 
This all sounds rather nit-picky just to bump up the velocity. Would I really see that big of a difference if I pushed the envelope on pressure?
 
Head/tail wind usually doesn't affect vertical POI, unless there are local range geographical features that cause the effect (sloping land or gulleys along the range). At Springfield range, which is flat and enclosed, I have not see vertical shifts due to wind (however even though it is sheltered, fairly modest winds there can randomly open up groups a bit, which can really frustrate your ammo testing!)

If you're able to fire your ammo over a chrono, that would be another nice crosscheck to see where you are on the load spectrum. I *think* people who shoot 185s (I don't have personal experience so this is hearsay) are using 44 or 44 point something grains of Varget, as a nice hot near-max load for target shooting. So 40 and 41 H4895 seem like perfectly reasonable points, and I would be tempted to explore 42 and up to 42.5 grains.

Why would you want to load a hotter load? Because oftentimes max or near-max loads burn more consistently. So it's not that you are after higher velocity per se (though that is a plus, provided you do not give up on accuracy or safety), rather, you are looking for very consistent muzzle velocities. In order to shoot tight elevation spreads at long range, you need to have tight velocity spreads. So long as your barrel isn't doing some sort of perverse whipping thing, a nice hot load that shoots tight groups at 100 and has tight chrono spreads, has an excellent chance of shooting well at 900m or 1000m.

Note that since you have easy access to a 1000m range, shooting groups at 900m or 1000m is a perfectly valid substitute for chrono'ing your ammo. If you shoot tight elevation spreads at long range, you have a good load.

Today looks like a nice shooting day, then we have four cold wet days forecast, hmmm I think I want to get to the range this evening.... ;-)
 
Got to the range again yesterday and the wind picked up as I was shooting, again with a tail wind that felt pretty strong. I have no Kestrel but with Weather Channel app said winds in the area would be around 20km/hr.

I fired the following groups:

41/41.1/41.2/41.3/41.4 next range trip will be 41.8/42/42.2/42/4

95BD8C90_zpsef550990.jpg


41 made a nice tiny group at 100m but I'm not sure why 41.1 and 41.2 started stringing vertically. Any ideas? The same thing seems to have happened at 300m with loads above 41. 41.4 seems to settle down a bit and that's why I'm going to go higher and see what happens.
 
Perhaps your barrel got hot. Maybe fouled. I've noticed that with my .308. After around 50 shots, groups open up. When I clean the bore when I get home, lots of blue and black.

Just say'n.
 
I've never been one to really clean my barrels. The TRG has max 100 rounds through with the shots on the target pictured above. I think I may have even cleaned the barrel prior to shooting those, if not, there were maybe 20 rounds of fowling shots before I went to the range and shot the target I just posted.
 
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