Yeah Baby !! 204 Slingshot time

[Shotafterdark]

We can definitely load that little fifty five and maintain four thousand feet per second without any pressure signs

Will those little burgers hold up?That's the question

 

[urbanrifleman]

We can definitely load that little fifty five and maintain four thousand feet per second without any pressure signs

Will those little burgers hold up?That's the question

I don't mean to second guess, but, why a 7 twist?

Terminal spin for an 8 twist is 3500 fps. 4000 is way over terminal spin in an 8 twist. Terminal spin is 3000 fps in a 7 twist. So, you'll be 1000 over terminal. The bullet will be deforming on the way to the target.

 

[7315br]

We can definitely load that little fifty five and maintain four thousand feet per second without any pressure signs

Will those little burgers hold up?That's the question

The answer is...probably not. Years ago I tried what you are trying to do now. I even did a .20-.223WSSM... "a really stupid move". I recall it took another 12 grs of powder to go another 190 fps faster than a .20 BR with the 55 gr Berger! I was trying to get to a 1000 yds + with a .20 cal. for Praire Dogs. I never made it with the .20-.223WSSM. It was a Royal PIA to make brass! I finally cut the barrel back at about 50 rds and made a .20 PPC. Much better...lol!

I did make the 1000yds + on PD's with the .20/.250...but it proved not worth the effort. I did manage to smack a number of PD's (I recall 1135 yds as the furthest kill)...but the 55 gr Berger started to pencil on hits beyond 800 yds. One had to break bone or a headshot beyond the 800 yd distance. All of my barrels were 9 or 10 twist bbls. Folks back then were complaining of the 55gr Berger having failures after 300 rds or so with even 8-twist bbls (much less a 7-twist) on this forum.

I then went to the .22/.243 Improved. Problem solved!!

I spent a ton of money to find all this out. You will too...lol! Best of luck in your endeavor.

 

[L.Sherm]

My money is as soon as you get couple hundred rounds on it those 55's will go poof, there's guys who have done it in 8's.
Its why the vast majority of us run 9tw with 55's

 

[AckleymanII]

OP, did you order a die reamer(S) for full length sizing Ger'r done!

 

[STS]

I don't mean to second guess, but, why a 7 twist?

Terminal spin for an 8 twist is 3500 fps. 4000 is way over terminal spin in an 8 twist. Terminal spin is 3000 fps in a 7 twist. So, you'll be 1000 over terminal. The bullet will be deforming on the way to the target.

What happens if you exceed “terminal spin?”

 

[L.Sherm]

What happens if you exceed “terminal spin?”

POOF!!

 

[Shotafterdark]

OP, did you order a die reamer(S) for full length sizing Ger'r done!

I did NOT ,,I Have already made a custom die and dropped a Redding bushing die on top of it at the neck juncture and the top of the shoulder..
I will do this for the 250 as well

I'm not worried about the shoulder set back
when that time comes and the bolt starts to close a lil tight
I already have a shell holder with a few thousand ground off

see how easy that was to remedy ?? lol
I'm not spending another $250 when it's not needed.

See that surface grinder in the back room ? he has 3 of them ...
cylindrical grinder as well.... We have a full tool room to play in.

 

[Shotafterdark]

I don't mean to second guess, but, why a 7 twist?

Terminal spin for an 8 twist is 3500 fps. 4000 is way over terminal spin in an 8 twist. Terminal spin is 3000 fps in a 7 twist. So, you'll be 1000 over terminal. The bullet will be deforming on the way to the target.

Hey Brad always a pleasure to have you around I have decided to just use the 55's in the 20 sploder you sent me in my Tikka ,


I've already played with that and I can keep it at 3500 no problem

I Have decided to take an exit ramp and avoid any problems Just got off the phone with Don and he is going to supply me with some 62 and heavier, that he says people are using daily at 3900 feet per second without any incidents going out to 1000 yards.

He said "they are hitting coyotes with them and doing a devastating job" on them
his words,

He has some 60 grainers I believe on hand right now that I'm going to get sent ASAP
And we will move forward with this project without worry

 

[Shotafterdark]

The answer is...probably not. Years ago I tried what you are trying to do now. I even did a .20-.223WSSM... "a really stupid move". I recall it took another 12 grs of powder to go another 190 fps faster than a .20 BR with the 55 gr Berger! I was trying to get to a 1000 yds + with a .20 cal. for Praire Dogs. I never made it with the .20-.223WSSM. It was a Royal PIA to make brass! I finally cut the barrel back at about 50 rds and made a .20 PPC. Much better...lol!

I did make the 1000yds + on PD's with the .20/.250...but it proved not worth the effort. I did manage to smack a number of PD's (I recall 1135 yds as the furthest kill)...but the 55 gr Berger started to pencil on hits beyond 800 yds. One had to break bone or a headshot beyond the 800 yd distance. All of my barrels were 9 or 10 twist bbls. Folks back then were complaining of the 55gr Berger having failures after 300 rds or so with even 8-twist bbls (much less a 7-twist) on this forum.

I then went to the .22/.243 Improved. Problem solved!!

I spent a ton of money to find all this out. You will too...lol! Best of luck in your endeavor.

LOL !! Spent a ton of money pursuing an endeavor that you set out on ...
Nothing wrong with that ,,,,at least you had the drive to do it...

I think that is commendable in itself

 

[Shotafterdark]

All right I just got off the phone with Don I gotta tell you he is an American treasure

I honestly don't think Boots Obermeyer had anything over on Don
After talking to him about his custom reamers he has made to match the ojive to his barrels and his bullets
He also has a step at the datum line on the shoulder he calls a dual radius

And we talked in detail about that He is certainly a wealth of knowledge
I'm gonna have him make me up about 4 barrel blanks after the first of the year right after he makes me a batch of 500 63 grainers

I have 200 63 GR VLD on the way
100 57 VLD
200 55 VLD


He said 63 is as heavy as he can go in a 20
And that's quite alright with me That little thing is over an inch long


If anybody decides they want some of these bullets as well That's the best way to get a hold of him and his landline is still available he says he will always have that maintained.

 

[AckleymanII]

Web dimension is what I worry over, the shoulder bumps you have covered. You could cut the bottom off a std FL sizing die and use it as a ring die.

 

[Shotafterdark]

We will cross that bridge when we get to it no worries

After all, how hard is it to do a quick calculation of the coefficient of thermal expansion?
With the carbon steel composition of a p t g blank, for example,

quickly cut the chamber with the reamer at three hundred 23 hundred and fifty degrees

then let it cool

i'll bet you a bottle of your favorite wine that that thing's going to be 3 to 4 thousand smaller across the board.

Heating the die blank
it won't be hard

Please excuse the typos.I am talking to text while I am driving

 

[Shotafterdark]

Come to think about it, I probably won't be buying p.T g d die blanks anymore, cause it's easier just to make our own from some cold roll

 

[urbanrifleman]

All right I just got off the phone with Don I gotta tell you he is an American treasure

I honestly don't think Boots Obermeyer had anything over on Don
After talking to him about his custom reamers he has made to match the ojive to his barrels and his bullets
He also has a step at the datum line on the shoulder he calls a dual radius

And we talked in detail about that He is certainly a wealth of knowledge
I'm gonna have him make me up about 4 barrel blanks after the first of the year right after he makes me a batch of 500 63 grainers

I have 200 63 GR VLD on the way
100 57 VLD
200 55 VLD


He said 63 is as heavy as he can go in a 20
And that's quite alright with me That little thing is over an inch long


If anybody decides they want some of these bullets as well That's the best way to get a hold of him and his landline is still available he says he will always have that maintained.

I SEE!!!

I wonder what the BC is on those.

 

[Bodhisafa]

will 9 twist stabilize those heavy 20 cals?

 

[Shotafterdark]

will 9 twist stabilize those heavy 20 cals?

Not sure but if you can push em fast enough ..possibly

only one way to find out ....

 

[Shotafterdark]

I SEE!!!

I wonder what the BC is on those.

Ill find out the G7 on all these ...he knows
Ill give him a call tomorrow..
Im gonna get another 1000 made after the 1st of the year
hes jammed up on a 46 barrel order for bench rest crowd
he has to complete....

 

[Shotafterdark]

I have no inspections scheduled for tomorrow
That means I get the whole day to play

So in that spirit I decided to load up some more 55's
and fire form some brass as I wait for Don's bibs to arrive

25 Fressshhhh Starline 6.5 Grendel worked down to my
chamber with 32 grains or 2000 MR ...oooh I can't wait .

 

[Shotafterdark]

I was able to fill an unfired case to 30Grains of RL15 max it gave 3650 FPS
No signs of pressure and it was a compressed load.

I then filled a fire formed case to thirty two grains

The chrony, unfortunately, did not give me a read, which is crazy
And the bolt was hard to open, and I had the same signs of high pressure.So we will not be doing that again, either

I'm sure it was probably a little faster than the two thousand m.R over pressure