338 Mega

[codyadams]

I have lurked and never posted, but Rich suggested I share all my data for the 338 Mega. I'm including all my powder tested, charges, and velocitiese. I'll also include a chart that might be close to accurate for energy and velocities, etc. My final loads for the 250 Berger OTM and the 250 SBD2 are at the end. FYI, I am on my 18th firing for my first 16 pieces of brass. This is exceptional brass life given the performance I'm getting out of my final loads. Hope this helps.

338 Sherman Mega
ADG Sherman 300 Mega Brass CCI 250 Primer
Case Length after Necking up=2.147 Case Length after Fire Forming-2.137
Fire Formed with 64 gr. RL19 (2540 FPS) with Spear 225 gr. Bullet jammed at .020"

Final Neck tension is .004 (364 bushing)


Pressure Testing
250 Berger OTM (.010" off lands) RL26

75 gr.	2886
75.5	2892
76	2917
76.5	2955
77	2918
77.5	2928-No pressure but load feels compressed but not pushing the bullet out.

250 Super Bulldozer 2 H4350

65	2707​
65.5	2708​
66	2738​
66.5	2753​
67	2770​
67.5	2772​
68	2789​
68.5	2794​
69	2820​
69.5	2854​
70	2861​
70.5	2864​
71	2909​

250 Super Bulldozer 2 N550

68	2892
68.5	2914
69	2918
69.5	2939
70	2943
70.5	2963
71	3003-Pressure Signs

338 Sherman Mega 1000 Yard Data (250 Super Bulldozer 2)

Muzzle Vel	1K Vel	1K Energy	1K MOA	Supersonic (roughly)
2770	1869	1939	24.6	1900
2800	1891	1986	24.0	1900
2850	1931	2072	23.0	1950
2900	1973	2159	22.1	2000
2950	2013	2249	21.3	2050
3000	2053	2341	20.5	2100

Here are my final loads, but at least the info above can let you see the ballpark velocities for a few different powders with two different bullets.
338 Sherman Mega (250 Berger OTM)
250 Berger OTM
ADG Brass
Case Length=2.139"
Shoulder set at 1.767" with E-420 Gauge
Ogive=2.265" (.110" Off Lands)
CCI 250 Primer
68.5 gr. N550 @ 2940 fps


338 Sherman Mega (250 SBD2)
250 Super Bulldozer 2
ADG Brass
Case Length=2.139"
Shoulder set at 1.767" with E-420 Gauge
Ogive=2.283" (.090" Off Lands)
CCI 250 Primer
67.8 gr. N550 @ 2860 fps

Barrel length?

 

[cmcshooter]

Barrel length?

26"

 

[PapaSmurff]

Picked up my Bergara 338 Mega build today while up in Idaho. It has a 24" Bartlein 3B barrel and an extended 3.1" magazine. The rifle started as a Bergara Highlander 6.5 PRC. I will be breaking in the barrel and starting some load development when I get back down to my Colorado ranch next week. I will post pictures and updates throughout the load development process.

 

[Idaho Trecker]

Who did your build in idaho?

Your other build seems to be doing great also.

 

[PapaSmurff]

My gunsmith up here is named Chris Brown. His business name is Long Range Customs. He does most of my builds these days, and he's friends with Rich who also lives close by.

 

[Idaho Trecker]

Yup. I know who he is. I wish I hadn't ran out of time today or I would have stopped to see Rich when I was up there. I've been watching your data which is nice to see more built since I did the original.

 

[HandgunHTR]

Got an email from Preferred that my barrel has entered production. Shouldn't be long now. Now I just need my stock and for Mountain Tactical to send me my Raptor mount that has been on backorder since March.

 

[PapaSmurff]

Back at the Colorado Ranch as of this afternoon. Cleaning the barrel on the new Bergara Highlander 338 Mega build, measuring cartridge maximum overall lengths, and getting ready to fire the first shots through her tomorrow. It looks like with the medium length reamer and my magazine box length of 3.100" that the Barnes 250 LRX, the Hornady 230 ELD-X, the Barnes 225 TTSX, 210 TTSX, 185 TTSX, and 160 TTSX, Nosler 200 and 180 grain Accubonds, and also the Berger 250 Elite Hunters will all fit comfortably in the magazine (the Berger 250 EH's will have to jump about .115" though to fit and feed reliably). Looking forward to firing some pressure testing shots and starting initial load development tomorrow!

 

[jsmitt6]

I just wanted to throw in my pressure test findings in my 338 Mega. I am going to load up some 250 Bergers over H100v with CCI 200s to see if I get the same findings as @PapaSmurff. Would be cool to grab 50+ more FPS.

Using the long reamer on a Tikka action. 21" barrel from X-Caliber

Fireform Load - 200gr Hornady SST over 58gr of Varget. COAL 3.232" CCI 200

270 ELDX (COAL 3.317")-

H4350 (CCI 250)
67- 2599 fps
68- 2656 fps (stiff bolt)

H100V (CCI 250)
66- 2602
67- 2668
68- 2696
69- 2730 (stiff bolt)

H4831sc (CCI 250)
66- 2408
67- 2441
68- 2478
69- 2525
70- 2568 (stiff bolt)

250 Berger EH (COAL 3.310")

H100v (CCI250)
67.5- 2720
68.5- 2752
69.5- 2820
70.5- 2824
71.5- 2884 (stiff bolt)

 

[elkaholic]

I just wanted to throw in my pressure test findings in my 338 Mega. I am going to load up some 250 Bergers over H100v with CCI 200s to see if I get the same findings as @PapaSmurff. Would be cool to grab 50+ more FPS.

Using the long reamer on a Tikka action. 21" barrel from X-Caliber

Fireform Load - 200gr Hornady SST over 58gr of Varget. COAL 3.232" CCI 200

270 ELDX (COAL 3.317")-

H4350 (CCI 250)
67- 2599 fps
68- 2656 fps (stiff bolt)

H100V (CCI 250)
66- 2602
67- 2668
68- 2696
69- 2730 (stiff bolt)

H4831sc (CCI 250)
66- 2408
67- 2441
68- 2478
69- 2525
70- 2568 (stiff bolt)

250 Berger EH (COAL 3.310")

H100v (CCI250)
67.5- 2720
68.5- 2752
69.5- 2820
70.5- 2824
71.5- 2884 (stiff bolt)

N550 is your Huckleberry! 2884 isn't too bad for a 21" barrel though

 

[PapaSmurff]

I've decided that the long throated reamer and action length of at least 3.340" or longer is the way to go. My Bergara build on a short action with its 24" barrel feels and points like a dream but I just can't seat the bullets far enough out to do much good with anything heavier than a 225-230 grain since my magazine will only allow 3.100" length or shorter. I'm thinking I'm gonna dedicate this one to 180, 185, 200 grain pills for a whitetail deer thumper. A medium length or long action with Rich's long throated reamer is the way to go I've decided after having 2 rifles built now on the medium length reamer.

 

[jsmitt6]

N550 is your Huckleberry! 2884 isn't too bad for a 21" barrel though

My local store has a stupid amount of N550.. Might have to pick up a pound or two to try out. But I do have 6 pounds of H100v on hand and am not mad at a 2825 load!

 

[jsmitt6]

Update with the CCI 200 instead of the 250...

Berger 250 EH 3.310" COAL

H110v (CCI200) -
71- 2858
72- 2877 (Ejector mark/swipe)
73- 2916 (Stiff bolt)
74- DNS

So I am getting about 30 FPS faster with the same pressure signs. I am going to do an accuracy test with the CCI 250 and 70 grains of H100v and the CCI 200 and 72 grains of H100v. See what kind of accuracy I can wring out of this sucker before hunting season. I am at 125 rounds through this barrel, 100 of which were fireforming loads. I havent even shot at paper yet to see what to expect.

 

[PapaSmurff]

Update with the CCI 200 instead of the 250...

Berger 250 EH 3.310" COAL

H110v (CCI200) -
71- 2858
72- 2877 (Ejector mark/swipe)
73- 2916 (Stiff bolt)
74- DNS

So I am getting about 30 FPS faster with the same pressure signs. I am going to do an accuracy test with the CCI 250 and 70 grains of H100v and the CCI 200 and 72 grains of H100v. See what kind of accuracy I can wring out of this sucker before hunting season. I am at 125 rounds through this barrel, 100 of which were fireforming loads. I havent even shot at paper yet to see what to expect.

Don't know all the specifications of your build, but If you can keep your bullets seated out pretty long then I would give Reloder 26 a try. It seems to be the fastest powder option for either of the 338 Mega's I've worked with as long as you seat the bullets out far enough that you can squeeze enough of it in the case. With 250 Bergers you could probably run them up as high as 74-77 grains with a long seated 250 Berger, just an educated guess.