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338 ulta verses 338 kt mag

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Old 09-04-2001, 08:52 PM
Junior Member
Join Date: Jul 2001
Location: pa
Posts: 23
338 ulta verses 338 kt mag

what is the difference between these when using 250 and 225 grain bullets.
elmer keith said th kt delivered a ton or so energy to 600 yds using 26 in barrels.
can i do the same with the 338 ultra?
what king of acc can i expect from a factory ultra in the 338 cal?
gary b
gary brezinski
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Old 09-05-2001, 07:34 AM
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Re: 338 ulta verses 338 kt mag

I just received a new Remington 700 Sendero with a 26" barrel in the 338 Ultra Mag. I have tried three different powders to date Rel 25, H1000 and H870 with the Sierra 300 grain MK. The average high velocities from safe loads have been from 2565 fps with H870 to 2688 fps with both Rl25 and H1000. These are not hot loads in this rifle. All three powders have shot the 300 MK into groups from .458" to .800" at 100 yards. This rifle is very accurate but it does have heavy recoil. This weekend I will work up loads with the 250 Sierra and the 210 Nosler.

My son and I shot accross the canyon out to 910 yards with the 338 Ultra this past Sunday. Ranges were from 620 to 910 yards with the 300 MK. The 338 Ultra hits a whole lot harder than my 300 Win Mag. The 338 Ultra had no problem at these distances using the ballistic data spreadsheet that Peter Crohelm (sp?) and Dave King have developed. This spreadsheet calculates that the 300 MK with a BC of .768 and started at 2650 fps, at an altitude of 8800', has 2408 lbs/ft of energy at 1000 yards.

I am not familiar with the 338 kt so I can't comment on the comparision between the two. I am happy with the 338 Ultra. Hope this helped you a little.
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Old 09-05-2001, 08:20 AM
Platinum Member
Join Date: May 2001
Location: Pennsylvania
Posts: 1,757
Re: 338 ulta verses 338 kt mag

Run the ballistics for the 300 Sierra MK at .800 BC.
It will work out much closer to your drop charts at the speed you are running the bullet.
We are driving the 300 gr much faster from our 37 1/2" to 40" barrels and found that the drop charts were off when using the lower BC.
Oehler reports the 300 gr 338 MK at .800 BC.
A 300 gr will most certanly hit harder then the 30 cal coming from a 300 Win mag.

You have a great place to reach the new 338 out. We go through that part of Colorado on Rt 70 on our way to the Aspen-Glenwood Springs area every year.

Darryl Cassel

[ 09-05-2001: Message edited by: Darryl Cassel ]
Darryl Cassel
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Old 09-05-2001, 10:35 AM
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Re: 338 ulta verses 338 kt mag

Thank you for your input. I had read your previous posts and Dan Lilja's comments concerning the actual BC of the 300 MK. We used .798 to compute our drop chart for the 338 Ultra and it matched the actual shooting data we collected last Sunday. Peter's and Dave's excel spreadsheet is the most accurate cacluator that I have used. The price was right too, thanks again to them.
I do have a question that maybe you could share some insights on. I think the rifle is dumping rounds to the right at longer ranges. We are shooting from bags and we have a scope level. We zeroed the rifle for the 300 MK at 100 yds and checked the velocity of the load (90.0 gns/H1000/Fed 215GM/once fired-neck sized cases for av-2688 fps & S/D of 24). At 620 yds the bullets were impacting 3" right. We had to progressively add more left adjustment into the scope as the ranges increased. The farthest distance that we shot was 1610 yards. With the scope set at 50 1/2 moa up and 0 windage, the bullet impact was right on for elevation but 24" and 36" right for two rounds. It was an absolute calm day with no wind and all ranges fired showed the same horizonal dispersion. What should I check for in the rifle/scope system? And what about the load? Or is this normal behavior from a factory rifle and barrel?
Thanks for the compliments about Colorado. I feel very fortunate to live here with all the outdoor activities that abound, especially elk hunting. You were probably refering to the Loveland ski area on I70 from my signature. We live in Loveland (the town) north of Denver. My wife and I (the kids too...) own land a few miles north of Rocky Mountain Natl Park. This is where my son and I hang out and shoot. Great hunting and fishing and it's our backyard.

Thanks in advance for any thoughts.
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Old 09-05-2001, 09:06 PM
Platinum Member
Join Date: May 2001
Location: Pennsylvania
Posts: 1,757
Re: 338 ulta verses 338 kt mag


Thats normal for the twist rate of the rifle and you should figure it into the scope setting when ready to fire at the extended ranges.

That's another reason we shoot a sighter round either in front 100 yards or behind 100 yards or over the animal to make the correctins of wind and rifle twist variations.
I'll bet your son makes a good spotter on the long shots?

My wife and I are getting the gear ready for the trip out your way at the end of October.

Yake care
Darryl Cassel
Darryl Cassel
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Old 09-05-2001, 11:02 PM
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Join Date: May 2001
Posts: 2,369
Re: 338 ulta verses 338 kt mag


Bullets impacting right... If you're sure of your data and shooting what (theoretically) you may be seeing is Magnus Effect/Force or I believe it's also called 'spin drift' and perhaps some Coriolis. Coriolis could easily be several inches at 1000 yards to a fairly larger value at 1600 yards.

Coriolis can be calculated based on time-of-flight, location on the planet, and direction of projectile travel.

Spin Drift is something I don't know how to calculate.

There are ballistics experts that frequent this site and perhaps they can tell us how to calculate spin drift.

There are huge debates about these effects and it nearly always makes for a lively discussion.
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Old 09-06-2001, 11:16 PM
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Re: 338 ulta verses 338 kt mag

Darryl and Dave,

I will input this info into our "real data" drop chart based upon your thoughts. I am assuming to add the correct windage moa to adjust for the bullet impacting right first, then add to that setting the ammount of moa nesessary to correct for the current wind value. We will re-verify this data on Saturday. If we do try LR hunting this November, we will fire spoter round(s) first. Thank you for sharing your knowledge.

My son is a good spotter AND he shoots much better than I [img]images/icons/confused.gif[/img] . Dang kids.....

Good luck next month.
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