Bradley Walker
Why is the 20BR better than the 22BR? I mean the 22 bullets are so plentiful and cheap...
20BR Report!!!!!!
- Thread starter xswanted
- Start date
Bradley Walker
I wish I had the money to build guns out of novelty...
NorCalMikie mentioned something in passing that got my attention... pressure sneaking up on us with these small high pressure cartridges. i have , until recently been a "jumper" and am now testing a lot with "jammed" bullets. NorCalMikie notes pressure problems when jumping not being there with bullet into lands? this may be an expression of pressure spikes variations that occur from primer ignition thru propellant sublimation. when jumping, the primer produces enough pressure to move the bullet. the pressure drops as the bullet engages the lands and then the pressure goes way up with propellant sublimation and bullet goes down the barrel. of course, all this happens in fractions of a milisecond and i've read there might be as many as 3 or 4 such spikes and with each, bullet movement variations. a jammed bullet can't move much with primer ignition, so propellant ignites more immediately and more efficiently, producing a smoother pressure curve(no spikes) with a more uniform bullet movement and probably better accuracy. i could be all wet, but understand pressure spikes explains why a very under charged case can result in a "detonation" with really bad outcome.
NorCalMikie
Gold $$ Contributor
It "does" have something to do with pressure spikes. Don't know all the in's and out's on the subject but I first noticed it when I built my 6BR. I start "everything" at a jam then work back to a jump if I want to start changing things. It may not work that way for anybopdy else but that's what works best for me.
And I make sure I get barrels chamberd with a "short throat" so I end up with lots of bullet contact in the case neck and still be able to jam into the lands. As the throat wears, I can go to heavier (longer) bullets and still jam.
And I make sure I get barrels chamberd with a "short throat" so I end up with lots of bullet contact in the case neck and still be able to jam into the lands. As the throat wears, I can go to heavier (longer) bullets and still jam.
xswanted
Gold $$ Contributor
Okay...more testing data for this little bugger!
I decided to give the 55 Bergers a try so I ordered a batch and started looking for loads.
I started at 27 grains of Varget, and kept going up until I was getting pressure signs. 32 grains of Varget showed extractor marks on the case and a sticky bolt. The velocity was unreal for this little case. 3777 was what my chrono read on the sticky bolt shot!
I decided to back a off a couple tenths and try again as 31.5 had no pressure signs so I settled on 31.8 grains as my load to try.
Went back to my range and shot two three shot groups, one just under a half inch the other put two shots into one "keyhole" and the guy running the gun yanked the third high....still managed a half inch group.
Velocity readings came up with 3730-3745. Chrono was out in front of the muzzle about 15 feet so averaging it out and correcting I'm figuring a 3750 muzzle velocity.
This is absolutely unreal velocity in my eyes, I never would have imagined I could get this. Gun is a 9 twist Douglas with a 24" barrel. 4 taper, pretty lightweight setup, it only weighs about 7.5 pounds with scope and bipod!
I decided to give the 55 Bergers a try so I ordered a batch and started looking for loads.
I started at 27 grains of Varget, and kept going up until I was getting pressure signs. 32 grains of Varget showed extractor marks on the case and a sticky bolt. The velocity was unreal for this little case. 3777 was what my chrono read on the sticky bolt shot!
I decided to back a off a couple tenths and try again as 31.5 had no pressure signs so I settled on 31.8 grains as my load to try.
Went back to my range and shot two three shot groups, one just under a half inch the other put two shots into one "keyhole" and the guy running the gun yanked the third high....still managed a half inch group.
Velocity readings came up with 3730-3745. Chrono was out in front of the muzzle about 15 feet so averaging it out and correcting I'm figuring a 3750 muzzle velocity.
This is absolutely unreal velocity in my eyes, I never would have imagined I could get this. Gun is a 9 twist Douglas with a 24" barrel. 4 taper, pretty lightweight setup, it only weighs about 7.5 pounds with scope and bipod!
NorCalMikie
Gold $$ Contributor
At 31.8 grains, you're running on the ragged edge and not leaving yourself any wiggle room. What if you get a temperature shift?
If it was me, I'd be back down around 28.5 or 29.0, working my way up "a little at a time" while looking for bug holes. And your brass will last longer. You don't have to be fast to be accurate.
If it was me, I'd be back down around 28.5 or 29.0, working my way up "a little at a time" while looking for bug holes. And your brass will last longer. You don't have to be fast to be accurate.
xswanted
Gold $$ Contributor
NorCalMikie said:
Most likely a good idea. I would like to hang right around 3600-3650, that was my speed I had in mind when working up loads for this guy with these bullets. I had 3650 with the 50s and thought it was impressive. Tomorrow will have some more shooting involved!
xswanted
Gold $$ Contributor
The only thing is, today was as hot as I'll most likely ever shoot this load.
It was 52 degrees while I was shooting, and since this will be my coyote rifle, I'll be using it primarily in temps well under 30 degrees.
It shot great, however I goofed the one shot up! I'm going to shoot it at 300 yards tomorrow and see what I get.
It was 52 degrees while I was shooting, and since this will be my coyote rifle, I'll be using it primarily in temps well under 30 degrees.
It shot great, however I goofed the one shot up! I'm going to shoot it at 300 yards tomorrow and see what I get.
NorCalMikie
Gold $$ Contributor
It's your rifle and your loads so shoot whatever you feel comfortable with. Just remember to CYA. 
Nothing worse that have a temp switch (95* and you loaded at 55*)
and start having problems with pressure. When it takes two men and a boy to get the bolt open. you'll remember.
Sounds like you've got things pretty much covered. Good job! 8)
Nothing worse that have a temp switch (95* and you loaded at 55*)
and start having problems with pressure. When it takes two men and a boy to get the bolt open. you'll remember.
Sounds like you've got things pretty much covered. Good job! 8)
xswanted
Gold $$ Contributor
NorCalMikie said:It's your rifle and your loads so shoot whatever you feel comfortable with. Just remember to CYA.
Nothing worse that have a temp switch (95* and you loaded at 55*)
and start having problems with pressure. When it takes two men and a boy to get the bolt open. you'll remember.
Sounds like you've got things pretty much covered. Good job! 8)
Hahaha! No doubt....its a wicked hot load you are WAAAY correct on that one. I actually blew a primer shooting at 300 yards today. Sooooo.....we're gonna step away from that load!
And I was actually disappointed in the results in a few different charges that I tried at 300 and 400 yards. The 55's just didn't group as good as the 50s....I'm not really sure why.
So for now, I think I'll stick to my original load of 50s....they shoot the "bugholes" at 100 you speak, most of the time! At 300 it hung around 1.5" and just under 2" at 400 so nothing wrong with that I guess!
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