My 338 Sherman / Ruger M77 Build

RedSnake

RedSnake

Active Member
Joined
Aug 11, 2017
Messages
38
Location
Dallas, Texas
I breathed some new life into a 1980s tang safety Ruger M77 originally chambered in .270 Win. and had it rebarrelled to a 338 Sherman.

7a75888e-d8b5-49dc-a683-0ec6e0f02b38.jpeg


One of the drawbacks of the ruger action is the limitations it puts on OAL due to the short (3.40") mag well. To allow a longer OAL to feed, I lengthened my action posteriorly with a Wyatt's cut (which included milling away the center floor plate screw). I fabricated an extended mag box from two factory boxes spliced/welded together. The bolt stop was moved posteriorly about 0.25" by tapping/drilling a new retaining screw hole and the window for the stop was enlarged. I am now able to feed rounds up to 3.600.

0b93ded5-e180-413f-8df1-6fb10a648e07.jpeg


Build Specifics
  • Action: Ruger M77 tang safety
  • Caliber: 338 Sherman (LA)
  • Original wood stock (refinished)
  • Pillar and full length bedded
  • Benchmark light palma 1:9.4 finished at 24"
  • APA Little Bastard brake
  • Factory trigger reworked
  • Cerakote midnight blue
  • Leupold 34mm rings
  • NF ATACR 4-16
Accuracy from fire forming loads was surprising accurate using mid range 338-06 loads and Hornady 250 hpbts over Varget.

b08c538d-9378-434c-aef1-470f88085504.jpeg


I plan on loading Rocky Mountain 250gr ULDs. Wanting a more temp stable powder I thought I'd try R-16 and Varget. Prelim load dev using RL-16 had disappointing mv (mid 2600s) — couldn't pressure out before case capacity was at max even with a drop tube.

Switched to Varget and got mv of 2760 before signs of excess pressure with ejector swipe and sticky bolt lift.
* Rocky Mountain 250 gr
* Norma Brass formed from 338-06 A2
* Fed GM215M
* OAL of 3.530" (.005 jump)

91dd8d20-c2a4-4e63-9628-562e2333b78b.jpeg


Hoping to get back to range to finalize loads in next couple of weeks.
 
I really like the older Ruger 77'S. I never thought about rebarrling one. Longer I am on this site.....the longer my wish list gets. Not that's a bad thing.....
 
GREAT build! I especially like your approach to dealing with the factory magazine constraints. Being able to mag feed everything you load sweetens the build by quite a lot.

I also like that you will be testing the Rocky Mountain ULD. I have been very curious about the Rocky Mountain bullets for some time. Looking forward to your results!

It was also interesting to note your use of fire formed Norma 338-06 brass. I would expect it to come out a good bit short (and stated as much to another forum member a few days ago). Looks like it is working well for you. What is the overall case length after fireforming? Also curious to know what kind of case capacity your are seeing.

Glad to see another 338 Sherman long action build, especially on a Ruger action!

RedSnake said:
I breathed some new life into a 1980s tang safety Ruger M77 originally chambered in .270 Win. and had it rebarrelled to a 338 Sherman.

7a75888e-d8b5-49dc-a683-0ec6e0f02b38.jpeg


One of the drawbacks of the ruger action is the limitations it puts on OAL due to the short (3.40") mag well. To allow a longer OAL to feed, I lengthened my action posteriorly with a Wyatt's cut (which included milling away the center floor plate screw). I fabricated an extended mag box from two factory boxes spliced/welded together. The bolt stop was moved posteriorly about 0.25" by tapping/drilling a new retaining screw hole and the window for the stop was enlarged. I am now able to feed rounds up to 3.600.

0b93ded5-e180-413f-8df1-6fb10a648e07.jpeg


Build Specifics
  • Action: Ruger M77 tang safety
  • Caliber: 338 Sherman (LA)
  • Original wood stock (refinished)
  • Pillar and full length bedded
  • Benchmark light palma 1:9.4 finished at 24"
  • APA Little Bastard brake
  • Factory trigger reworked
  • Cerakote midnight blue
  • Leupold 34mm rings
  • NF ATACR 4-16
Accuracy from fire forming loads was surprising accurate using mid range 338-06 loads and Hornady 250 hpbts over Varget.

b08c538d-9378-434c-aef1-470f88085504.jpeg


I plan on loading Rocky Mountain 250gr ULDs. Wanting a more temp stable powder I thought I'd try R-16 and Varget. Prelim load dev using RL-16 had disappointing mv (mid 2600s) — couldn't pressure out before case capacity was at max even with a drop tube.

Switched to Varget and got mv of 2760 before signs of excess pressure with ejector swipe and sticky bolt lift.
* Rocky Mountain 250 gr
* Norma Brass formed from 338-06 A2
* Fed GM215M
* OAL of 3.530" (.005 jump)

91dd8d20-c2a4-4e63-9628-562e2333b78b.jpeg


Hoping to get back to range to finalize loads in next couple of weeks.
Click to expand...
 
benchracer said:
GREAT build! I especially like your approach to dealing with the factory magazine constraints. Being able to mag feed everything you load sweetens the build by quite a lot.

I also like that you will be testing the Rocky Mountain ULD. I have been very curious about the Rocky Mountain bullets for some time. Looking forward to your results!

It was also interesting to note your use of fire formed Norma 338-06 brass. I would expect it to come out a good bit short (and stated as much to another forum member a few days ago). Looks like it is working well for you. What is the overall case length after fireforming? Also curious to know what kind of case capacity your are seeing.

Glad to see another 338 Sherman long action build, especially on a Ruger action!
Click to expand...

Thx benchracer. For the 338-06 brass the neck is shorter than ideal, although accuracy doesn't seem to have been affected at least with fire forming loads which were 1/3 to 1/2 moa so I'm hopeful this will hold true when I shoot for groups to determine best load with a modified OCW method.

Norma 338-06 brass
Initial length 2.485
Fire Formed 2.470
H20 capacity 77.0 gr

I also necked up Hornady Outfitter 270 brass with a Sinclair expander die with .30 and .338 mandrel to see how they did
Initial length 2.495
Fire Formed 2.485 to 2.490
H20 capacity 77.5 gr

7a7485cb-94b9-4a24-9bda-d0779719a1dc.jpeg


b9e77e39-e0e5-42a6-846b-1848fce9fc5c.jpeg

Mv for the Hornady brass was 10-25 FPS slower per charge — I'm guessing due to less pressure from greater case capacity.

s for the RM bullets, I am excited to see how they do as well. Stated G1 per their site is 0.842 but at a mv of 3500. I'm not that optimistic but Nathan at www.ballisticstudies.com has done field testing and says their bc's hold true — good read here... https://www.ballisticstudies.com/Knowledgebase/Rocky+Mountain+Bullet+Test+Fire.html
 
Last edited:
Great stuff guys! I look k forward to seeing more results in the field. H100v at up to 65 grains would run very accurately in my 24" barrel at 2810' and its not too temp sensitive.
 
if you can get to pressure 4955 is quite stable in 06/270 case sizes I'm getting fantasic results in a 65.06ai but it is a bit slower fps than Rl 26.
 
RedSnake said:
Thx benchracer. For the 338-06 brass the neck is shorter than ideal, although accuracy doesn't seem to have been affected at least with fire forming loads which were 1/3 to 1/2 moa so I'm hopeful this will hold true when I shoot for groups to determine best load with a modified OCW method.

Norma 338-06 brass
Initial length 2.485
Fire Formed 2.470
H20 capacity 77.0 gr

I also necked up Hornady Outfitter 270 brass with a Sinclair expander die with .30 and .338 mandrel to see how they did
Initial length 2.495
Fire Formed 2.485 to 2.490
H20 capacity 77.5 gr

Mv for the Hornady brass was 10-25 FPS slower per charge — I'm guessing due to less pressure from greater case capacity.

ade0d184-b274-4249-b817-71ef562fa560.jpeg

As for the RM bullets, I am excited to see how they do as well. Stated G1 per their site is 0.842 but at a mv of 3500. I'm not that optimistic but Nathan at www.ballisticstudies.com has done field testing and says their bc's hold true — good read here... https://www.ballisticstudies.com/Knowledgebase/Rocky+Mountain+Bullet+Test+Fire.html
Click to expand...
I would go with the 2.485" brass. Jumping over a . 025" gap in the neck chamber will likely cause carbon deposits over time and could affect accuracy if it isnt already, to some degree.
The Sherman chamber is 2.495"
Norma 270 brass is usually available too if you cant find RWS.
 
elkaholic said:
I would go with the 2.485" brass. Jumping over a . 025" gap in the neck chamber will likely cause carbon deposits over time and could affect accuracy if it isnt already, to some degree.
The Sherman chamber is 2.495"
Norma 270 brass is usually available too if you cant find RWS.
Click to expand...

Interesting point Rich. I hadn't thought about that.

I'm still hoping that RCC brass is going to make me some 338 S CNC machined brass with custom headstamp.
 
RedSnake said:
Interesting point Rich. I hadn't thought about that.

I'm still hoping that RCC brass is going to make me some 338 S CNC machined brass with custom headstamp.
Click to expand...
oooooh!!! You'll be stylin' 50 or those would last q lifetime
I usually only trim my brass .005" to keep that bullet transition from the neck to the lead nice and smooth.
 

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