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338 Remington Ultra Mag load data desired

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Unread 08-13-2001, 12:32 PM
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Re: 338 Remington Ultra Mag load data desired


Like you said, the 300 RUM and 375 RUM cases are longer than the 338 RUM, by .1 inch I believe. (I believe this was to accomodate the 338 bullets in production with cannelures.)

I'll check the water capacity of a case this evening.
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Unread 08-13-2001, 01:34 PM
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Location: San Antonio, Texas
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Re: 338 Remington Ultra Mag load data desired

Presonaly I think it was a mistake not to have all the RUM cartridges the same dimentions. To hell with the damn cannelures!
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Unread 08-14-2001, 07:47 PM
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Re: 338 Remington Ultra Mag load data desired

Another load test tonight in the 338 RUM.

Temp 80
Humidity 80%

I tried 90 grains of RL25 over the Fed 215M primers and the big 300 grain Sierra MatchKing. (Load Density 100%)
OAL 3.650 (magazine limited)

Four rounds over the Crony:
2712 fps
2709 fps
2729 fps
2735 fps

Avg: 2721
ES: 26
SD: 12

No pressure signs on any case, first round was cold bore.

I tried the 300 Sierra MatchKing on a crop damage deer at 200 yards, pretty devastating.... it was a bang-flop proposition.

BTW, water capacity for once fired cases, 111.3 grains (water to top of case, primer in backward)
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Unread 08-15-2001, 09:33 AM
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Location: NC
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Re: 338 Remington Ultra Mag load data desired

seeinng how you've got the first venison of the season we can all come to your place for steaks right?

Thanks for the info on the water volume. that 111.3gr H20 is just about the same as a standard 338 Lapua Mag volume. I've measured both Norma and Lapua, 338 Lapua brass, right out of the box and it measures roughly 112gr gr H2O before fireforming to my imporved case. I guess R25 is working good for you with those numbers. keep it up.

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Unread 08-15-2001, 02:41 PM
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Re: 338 Remington Ultra Mag load data desired


Yeah... it's the first venison... but we'll be having hamburger and not steaks!

Thanks for the info on the Lapua 338, I didn't check any I have here.

You might find it interesting to mote that I use my 338 Lapua dies to neck size and seat the bullets in the 338 RUM. I reset the sizing die to neck only and the seater I didn't need to change for the 250's, but I needed to run the seater in 1 5/8ths turns to seat the 300s to 3.650.
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Unread 08-27-2001, 02:58 PM
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Re: 338 Remington Ultra Mag load data desired


I received a 338 Rem Ultra as a gift from my wife a few weeks ago. It was very nice of her to hear me say that I was interested in getting one, then to go out and get it for me. Anyway, I mounted a scope on it, worked the trigger down to 2 1/2 pounds and then reloaded a few rounds for it. I had some H870 sitting around to start with and one hundred 300 grain Matchkings.

Here is the data;
Remington 700 Stainless Sendero 26" bbl
Tasco 20x42 Sniper Scope (need a better scope!)
ProChrono@15 feet

300 Sierra MKHP
COL - 3.775" (.010 off the lands)
New re-sized/trimmed Remington Cases
Fed 215GM
Hodgdon H870
100 yds.
Altitude 8800 feet/Temp; 70F - 85F/slight breeze from any direction (mountains)

88.0 gns 2233 fps (cleaned barrel)
89.0 gns 2365 fps " "
90.0 gns 2420 fps " "
91.0 gns 2465 fps " "
92.0 gns 2495 fps (cleaned barrel)
93.0 gns 2485 fps
94.0 gns 2565 fps
95.0 gns 2610 fps

88 to 92 gns went into 2.8"@100 yds. (I would expect from being cleaned after every round fired)

93 to 95 gns went in to .550"@100 yds (without being cleaned after every shot)

No pressure signs were visible on the cases. I cleaned the barrel after each of the first five rounds then after each three shot group.

98.0 gns - 2575 fps
- 2611 fps
- 2594 fps
Av - 2593 fps S/D - 54
group size .880"@100yds.

99.0 gns - 2649 fps (slight ejector mark)
- 2597 fps (slight ejector mark)
- 2674 fps (slight ejector mark)

Av- 2640 fps S/D - 42
group size 1.250"@100 yds

100.0 gns - 2674 fps (ejector mark)
- 2611 fps " "
- 2549 fps " "
Av- 2611 fps S/D - 38
group size 1.760"@100 yds.

99 and 100 gns is over max as the velocity fell off but the pressure increased. Accuracy went away pretty fast also. Looking at the data I would expect 93 to 95 gns to be the sweet spot. This rifle has no brake on it and it recoils very heavy. In fact it was very hard not to flinch as the charge and velocity increased. I may have to put a brake on it to survive the recoil. It kicks much harder than my 340 Weatherby in a Win Mod 70 Sporter.

I'm not sure I trust the Standard Deviation that the chrono was giving me.

I will be trying Reloader 25 and 22 this weekend with both the 250 Gameking and the 300 MKHP. I'll post the data if you are interested.

Sorry for the long post.

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Unread 11-10-2001, 05:50 PM
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Re: 338 Remington Ultra Mag load data desired

Move this to the top for a new members' use
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