Load Development Not Necessary but Interesting

[lclund1946]

I have been shooting gophers with my 527 Kevlar, 20 EXTREME LB with Kreiger 11" twist barrel, along side my original 527 Kevlar with the 11"twist Pac Nor Barrel. I found that I have about 10 loads that I can use interchangeably between the two. The Kreiger barrel has a 0.199" bore which runs my loads about 0.030" closer to the lands. The only load that I had to adjust a bit was the 40 V-Max as it was jamming into the lands about 0.005". Here is the first group I shot from the 20 EXTREME LB with my 39 BK load after two shoot and clean and before final sighting.
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A couple of weeks ago I did ladder tests with the 40 V-Max to 22.2 F grains 8208 in the Win brass and 22.6 F in Lake City REF brass. Neither Case showed any sign of over-pressure and both showed potential to group with my 39 BK load. My standard load with the 40 V-Max, in Win brass, has been 21.2 grains of IMR 8208. I have gotten Chrony reading of 3500 to over 3700 fps with this load with one at 3648 fps. I have been telling people that I am getting 3500-3550 fps with this very low pressure load.

Last Saturday I was out at the range and got a Tikka 250 to help test a new load in my 20 EXTREME LB. He shot a group with the 22.2 grain load, in Win brass, with 4 shots going into 0.24". The first shot from the clean/cold bore was likely the flier that made the 5 shot group 0.7".
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He went out to 400 meters with 4.75 MOA from a 100 M ZERO. This puts the 40 V-Max at 3775-3825 fps depending on how I input data into my ballistics program. The brass expansion mirrored what I got in my ladder test in that the base, at the datum, stretched 0.0009" leaving 0.0014" spring back from the chamber. When I sized the brass the base returned to within 0.0001" of its new diameter. The only pressure sign is primer flowing around the firing pin about 0.0025" and case trim length increasing by about 0.0035". Brass life will shortened, if one chooses to run these velocities, but they are totally safe.

I believe that I can now safely say that my 40 V-Max load with 21.2 grains of 8208 is doing the 3648 fps that the Crony showed on one occasion. Extrapolating up to 22.6 grains in the LC brass should put me near 3900 fps. This also confirms my suspicions that the 20 EXTREME can run very near the 204R and 20 Tac with the 40 grain bullets using 6 to 8 grains less powder. As well it's efficient design and case capacity allows the use of all available 20 cal. with bullets many different powders.

When I showed Lonnie Hummel, Hornady's lead tech, this 95% capacity load from a 12" twist barrel he said "I would stop right there".
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It liked the 32 V-max as well.
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That was over 5 years ago and only the beginning. I have many targets showing sub 1/2 MOA, and even a few sub 1/4 MOA, from about 50 different loads. These loads seem to shoot sub 1/2 MOA or better in CZ, Sako, Remington, and Ruger rifles whether chambered in 9", 11" or 12" twist Pac Nor, Shillen, Kreiger and even re-chambered factory barrels.

[duceman]

first off, thank you for bringing something intelligent to the forum; long overdue!
do you have any targets from 300m out? i know what the ballistic charts say in regard to drop and drift; curious to see real world wind bucking capabilities.
4-3/4" moa drop @ 400 m is impressive! a mid load with a 70gr sierra in my 6br sporter needed 5-1/4 moa at 300m, and my f-gun load with 105's need 5 moa at 300m with 100 m zero's, lee

[tchardy1972]

That's great. I can't wait to put mine together. Soon, real soon.

[spentround]

Thanks....enjoy the writeup and the shootin...cheers!!

[lclund1946]

Originally Posted by duceman

first off, thank you for bringing something intelligent to the forum; long overdue!
do you have any targets from 300m out? i know what the ballistic charts say in regard to drop and drift; curious to see real world wind bucking capabilities.
4-3/4" moa drop @ 400 m is impressive! a mid load with a 70gr sierra in my 6br sporter needed 5-1/4 moa at 300m, and my f-gun load with 105's need 5 moa at 300m with 100 m zero's, lee

Hi Lee,

I did most of my load workup and testing for groups at the Spruce Grove range which only went to 300yds. I know that I got much less wind age than similar loads in the 223. Here are some of the 300 yard targets I shot.
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Tikka 250 did go out to 500 and 600 M on the gongs with that load but didn't record the elevation necessary to get there. He had a 5-10 km/hr wind blowing from behind and had no wind age problem to 500 M but did have to adjust for the 600 M. I have difficulty setting up targets but will load up a few more rounds and see if someone will set up some 400-600 M targets for me. I originally designed the 20 EXTREME to run low pressure loads between 3500 and 3650 fps with the 39/40 grain bullets. Here is how I had it set up for the 40 V-Max at 3650 fps along with how it staked up against other varmint cartridges at 500 yards.
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[duceman]

impressive indeed. if you ever cound yourself with too much time on your hands and the urge to go for a drive, i would like to spend some time on the bench with you. we can shoot to 550 at my place. good spot to play in the wind too, lee

[lclund1946]

Originally Posted by duceman

impressive indeed. if you ever cound yourself with too much time on your hands and the urge to go for a drive, i would like to spend some time on the bench with you. we can shoot to 550 at my place. good spot to play in the wind too, lee

I usually have a lot of time on my hands. However I find it very difficult to travel very far from home. It's not the driving so much as the pain from not having my wheelchair, lift chair and very supportive bed to sleep in. I will surely keep your kind offer in mind.

If you can make it to Consort we could spend some time at the Nose Hill Gun Range. They have gongs and silhouettes out to 1450 to test your long range capabilities in the wind. I have a membership and guests shoot for free.There is room to camp at the range or nearby lakes. I have a spare bed on a first come basis. Laverne

[duceman]

just may have to head that way. supposed to hook up with will to help get f-class butts in at nose hill. will keep you posted, lee

[lclund1946]

Originally Posted by duceman

first off, thank you for bringing something intelligent to the forum; long overdue!
do you have any targets from 300m out? i know what the ballistic charts say in regard to drop and drift; curious to see real world wind bucking capabilities.
4-3/4" moa drop @ 400 m is impressive! a mid load with a 70gr sierra in my 6br sporter needed 5-1/4 moa at 300m, and my f-gun load with 105's need 5 moa at 300m with 100 m zero's, lee

Last evening tikka 250 got a chance to put the 40 V-max, with 22.2 grains of 8208, on pater at 400 and 500 M. Strangely there was no wind at Nose Hill so wind age was not a factor. From a 100 M Zero I will have to come up to 5-5 1/4" MOA to Zero at 400M and at least 8 MOA to Zero at 500 M. In spite of quite a bit of mirage and getting used to the CZ set trigger tikka 250 managed to hold 0.8 MOA to 400M and 0.85MOA to 500M

Did a Ladder test with the 39 BK and RL 10X starting at 20.5 grains and working up to a near Full case at 21.7 grains. Still getting a 0.0007" spring-back from the chamber, at the datum, but primer flow of 0.006" tells me that this is near max for a safe load. Tikka 250 gave up trying to keep track of the individual shots.
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[tchardy1972]

Looks like you needed to back up a touch. Any idea od what kind of speeds you hit?

[lclund1946]

Originally Posted by tchardy1972

Looks like you needed to back up a touch. Any idea od what kind of speeds you hit?

I would normally run this load at 20.5 grains of RL10X as the chart below will show that the pressure is low enough that the shoulder is not fully fire-forming to the chamber. In my 20 EXTREME Chamber the base datum would not expand as much as the 0.0010" larger LB chamber. I believe that this load is running about 3600-3650fps.

You will note that the shoulder is just fire-forming at the datum at 21.5 grains and that the pressure begins rising rapidly at 21.7grains as indicated by the increase in base diameter and decrease in spring-back from the chamber. Although the 20.7 grain is safe at around 3850 fps I believe 21.5 grains would be my best load at about 3775.

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[Elkhunt]

Thanks. Learned something. Please keep posting.

[lclund1946]

Originally Posted by Elkhunt

Thanks. Learned something. Please keep posting.

I prepared this table showing the pressure ladder that I did with the 40 V-max and IMR 8208 which is the best powder suited for this combination of components in the 20 EXTREME. The 22.2 grain load has proven to be awesome and the Nosler 40 BT and Sierra 39 BK loads that I added appear to be compatible although we have only tested them at 100 yards.

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I see I have a couple of typos to correct on the chart. The formed brass would have been 1.2830" to the datum not 1.2803".

[lclund1946]

Originally Posted by tchardy1972

Looks like you needed to back up a touch. Any idea od what kind of speeds you hit?

Looks like you were right. The pressure ladder that tikka 250 did with the 39 BK showed that pressures were beginning to spike at 21.7 grains of RL 10X but showed no other pressure signs except excessive primer flow around firing pin. I had estimated that the velocity was about 3850 fps and appeared safe. I loaded up 10 rounds at 21.5 which I thought would be safe as the ladder test showed 0.0009" spring back from the chamber and brass was not fully fire formed at the shoulder. Tikka 250 did the ladder test on a similarly hot day but run the ladder test from a cold barrel in the shade. I managed to get the Chrony set up so decided to shoot 4, 5 shot, groups with other loads so that I would be shooting the RL 10X groups from a warm barrel. It has been my experience that RL powders are much more temperature sensitive than the EXTREME powders so wanted to try to duplicate a day in the gopher patch.

Even though I expected higher pressures from the RL 10X, in a warm chamber with ammo sitting in the sun, I was surprised at the results. Even the first shot was a bit stiff on extraction and the primer was as flat as I have seen from this cartridge. The next four shots were up and down in pressure, likely depending on how long they were in the chamber, and the sixth shot showed signs of gas leaking around the primer. The seventh shot blew the primer but extracted with a bit of effort on the bolt handle.

When I got home I measured the bases and found spring back from the chamber varying from 0.0007" to ZERO on the brass with the blown primer. This is the first time I have experienced any measurable web stretch with the Winchester brass. Web stretch varied from 0.0003" to 0.0072" on the brass with the blown primer. This is a classic example of a load that is too hot to be safe under all conditions, largely due to temperature sensitive powder, although it appeared safe. Sadly this happens all too often, even in some Factory ammo, with the 17 Hornady Hornet a prime example.

For the record the 21.5 grain load of RL 10X pushed the 39 BK to an average of 3845 fps, at the muzzle, for 7 rounds. I think 20.7 grains should safely push the 39 BK to 3700 fps if I feel the need for speed. Ramshot X-Terminator is a better choice for velocities up to 3700 fps. However I think that I will stick to IMR 8208 that gives me safe accurate loads to about 3587 with a full case and about 3500 fps with my gopher loads.