50gr Zmax OFFICIAL Load Thread!!!

[CodySPowell]

Working on some 50gr Zmax
LC brass
CCI# 41 primers
H335

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[sagela]

Recently acquired a Remington very pretty M788 in .22-250; 24" 1:14 twist bbl, plain wood stock. I mounted a Weaver 3-15x50mm Tactical
scope on QD rings and a steel Picatinny base. I had to float the barrel 20 thou to get below 2.5" groups. Someone had skim bedded the action in fiberglass.
Confident in my bullet (50Zs rule!) I ran through several powders giving me 1.5" and narrowed those down to TAC and IMR4166.
TAC gave me 1.2" grps @ 3560'/s. Not sizzling MV and for coyotes I could have lived with the accuracy but....

I re-focused on IMR4166...
On this target I worked up a 4166 load using 0.2gr incremental increases until I got my first sign of pressure...very slight bolt stick on opening. (Pink dot target: 1.1" group overall @ 100yds)
I backed off 0.2gr and fired 5 at the orange dot: All 5 hits are under the dime. LabRadar says 3740'/s, +/- 15. These were the 4th loads through this Hdy brass and the primer pockets are still tight.
(Hdy 3x brass, neck sized and LEE Factory Crimped, 2.355" c.o.a.l., 0.55" group, 3740'/s MV. I'm calling this my std load. It is not compressed.)

My Shooter phone app says I'm an inch high @ 100 for a 300yd zero and only 4" low @ 400yds. Fairly flat.
I've made up 50 rds of this standard load to haul around with me looking for places to prove the trajectory in the field under low wind conditions.

Meanwhile I reviewed the relationship between barrel twist and MV as affects accuracy. My std .223 prairie dog (PD) load is quite accurate from 5 different rifles with 8 and 9 twist barrels at MV ~3200'/s. One site suggests MVx720/twist = bullet RPM. For my PD load that's 3200x720/9 = 256,000RPM. The TAC .22-250 load above looks like this: 3650x720/14 ~ 187,700RPM, considerably lower.
My new std IMR4166 .22-250 load looks like this: 3740x720/14 ~ 192,300RPM. Considering nothing else, this would suggest that 187k RPM is not sufficient to stabilize our 50Z but 192k RPM is.
Given that my .223 PD loads are roughly twice as accurate at 256k RPM I'm almost willing to wish for a 12 twist .22-250 barrel. (3740x720/12 ~ 224,400RPM)

My next project will be to work up loads for my Savage 24" .22-250 bench rifle with 1:12 twist to see if I can duplicate the MV with this bullet - and see if the increased MV results in better accuracy than previous loads from that rifle at lower MV.
Then I'll be looking for .22-250 loads with 68gr bullets.

One final note, our wonderful 50Z bullet does NOT fly apart in mid-air under centrifugal force even at 256k RPM. I wonder whether, with increased heat and friction ripping at its almost 'frangible' jacket, it might come apart at 3740'/s from a 10 twist or, even faster, barrel?

Anybody got field or bench data from such a combination?

[CodySPowell]

Can't get the damned pic to stand upright but "you get the picture."

Recently acquired a Remington very pretty M788 in .22-250, 24" 1:14 twist bbl, plain wood stock. I mounted a Weaver 3-15x50mm Tactical
scope on QD rings and a steel Picatinny base. I had to float the barrel 20 thou to get below 2.5" groups. Someone had skim bedded the action in fiberglass.
Confident in my bullet (50Zs rule!) I ran through several powders giving me 1.5" and narrowed those down to TAC and IMR4166.
TAC gave me 1.2" grps @ 3560'/s. Not sizzling MV and for coyotes I could have lived with the accuracy but....

I re-focused on IMR4166...
On this target I worked up a 4166 load using 0.2gr incremental increases until I got my first sign of pressure...very slight bolt stick on opening. (Pink dot target: 1.1" group overall @ 100yds)
I backed off 0.2gr and fired 5 at the orange dot: Hdy 3x brass, neck sized and LEE Factory Crimped - 2.355" c.o.a.l. 0.55" group, 3740'/s MV. I'm calling this my std load. It is not compressed.
My Shooter app says I'm an inch high @ 100 for a 300yd zero and only 4" low @ 400yds. Fairly flat. I've made up 50 rds of this standard load to haul around with me looking for places to prove
the trajectory in the field under low wind conditions.

Meanwhile I reviewed the relationship between barrel twist and MV as affects accuracy. My std .223 prairie dog (PD) load is quite accurate from 5 different rifles with 8 and 9 twist barrels at MV ~3200'/s. One site suggests MVx720/twist = bullet RPM. For my PD load that's 3200x720/9 = 256,000RPM. The TAC .22-250 load above looks like this: 3650x720/14 ~ 187,700RPM, considerably lower.
My new std IMR4166 .22-250 load looks like this: 3740x720/14 ~ 192,300RPM. Considering nothing else, this would suggest that 187k RPM is not sufficient to stabilize our 50Z but 192k RPM is.
Given that my .223 PD loads are roughly twice as accurate at 256k RPM I'm almost willing to wish for a 12 twist .22-250 barrel. (3740x720/12 ~ 224,400RPM)

My next project will be to work up loads for my Savage 24" .22-250 bench rifle with 1:12 twist to see if I can duplicate the MV with this bullet - and see if the increased MV results in better accuracy than previous loads from that rifle at lower MV.
Then I'll be looking for .22-250 loads with 68gr bullets.

One final note, our wonderful 50Z bullet does NOT fly apart in mid-air under centrifugal force even at 256k RPM. I wonder whether, with increased heat and friction ripping at its almost 'frangible' jacket, it might come apart at 3740'/s from a 10 twist or, even faster, barrel?

Anybody got field or bench data from such a combination?

Wow! Great information, thanks for sharing this! [emoji106]

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[sagela]

You're welcome. Now I have to learn to operate a Dropbox!!!

[Muddydawg75]

Dropbox is awesome, drag and drop just like moving from folder to folder.


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[sagela]

OK, I figured it out and edited the post. Pic is vertical and I reworded some of the findings slightly - hope it's clearer now.

[Sgt Greybeard]

Best group so far testing Benchmark.

Savage 110 223 Varmint. 26" 1:9

I'm going to push the load up just a tad more and see if it tightens up.

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[CodySPowell]

Best group so far testing Benchmark.

Savage 110 223 Varmint. 26" 1:9

I'm going to push the load up just a tad more and see if it tightens up.

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Very nice!

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[mtbert]

Yes very nice indeed. [emoji853]


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[sagela]

"My next project will be to work up loads for my Savage 24" .22-250 bench rifle with 1:12 twist to see if I can duplicate the MV with this bullet - and see if the increased MV results in better accuracy than previous loads from that rifle at lower MV."

Since the IMR4166 powder worked well in the Rem788 .22-250 I used the same powder to work up loads in my Savage 12 hvy bbl (24" 1:12) .22-250.
Neck sized cases from the Rem788 won't chamber in the Savage, indicating its chamber is tighter and with its faster twist it hit 3820'/s with 0.2gr less powder.
3820z720/12=229,200 RPM, a bit higher than I needed to test the theory that RPM correlates with accuracy. (In working up the 4166 charges
all 10 rds went into 1.5".)
I have 20 rds and two sighters/bore foulers made up for an accuracy test with the 3820'/s load. Results later today, I hope.

Savage12 50Z 4166.jpg

Results: 4ea 5 shot groups under 1moa, averaging 3835'/s with our favorite Z-Max bullet. Ready for prairie dogs.

I'll reload these cases and shoot some more groups without the chrono running, take my time and see if I can shrink the groups a bit
but basically, I'm done.