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338/375 Ruger or 375 Ruger with high BC bullets?

 
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  #8  
Old 09-12-2013, 02:29 PM
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Re: 338/375 Ruger or 375 Ruger with high BC bullets?

Hi Ross

Apologies in advance for the hijack, but how did the build with the doner action turn out? I have the exact same action, and am really conflicted on how to use it. Am thinking about a 375 RUM using an aftermarket mag/bottom metal, but conflicted as to whether this is the best use of any of the components.

So very interested to hear if you are happy with how your project turned out for you. Did the 7mm build you decided on live up to expectations?
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  #9  
Old 09-12-2013, 03:28 PM
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Re: 338/375 Ruger or 375 Ruger with high BC bullets?

IMO no hijack.

The 30" 7mm Rem mag would still be that chambering but I was mislead into getting a 1 in 7 twist 3 groove. It shot the 180 Berger hunting VLDs excellently with the accuracy velocity of 2975 or so. Got up to 3050 fps but not as consistent. Unfortunately this barrel configuration go to round count 225 or so and began to occasionally throw the VLDs away from POI.

I first discovered the diverging bullets when I went to shoot my coues wt at 400 yds! It wounded the animal instead of the easy hit it should have been. I shot another four with some off by FIVE feet! I grabbed my other rifle my friend was using and finished it off with next shot.

I tried 180 Target VLDs and 75 rounds later THEY also had issues with the worn barrel. Finally used 140 accubonds till I was disenchanted by ho hum wind drift numbers and pulled the barrel.

I sent that #7 SS lilja to Dan Pederson in Prescott and he rebored/rifled the barrel to 338 dia. I gave him my 338 RCM reamer and had him long throat it for the 300 gr Berger hybrid. I shot it for several years.

Just this past spring I FINALLY got around to making a 7mm/375 Ruger on that platform. It is not the LRM version but simply necked down to 7mm. My friend sold me a 7 STW with 400 rounds through it for $200. It was 30" #5 fluted 6 groove lilja 1 in 9 twist. I chopped off the threaded shank and rethreaded for the Mark X action myself. Then chambered it to 7mm/375. It shoots the 180 Berger match target hybrid @ 3200 fps with RL-33.

It has a Near Mfg picatinny rail and a Joel Russo stock. Factory trigger set at 1 lb. It IS unusual to use a Mark X for a F class style rifle but it works, feels great and gets some interesting comments. I'd say put your action to use!

So that platform has two barrels 338 RCM and 7mm/375 and looks like this:

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  #10  
Old 09-12-2013, 04:59 PM
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Re: 338/375 Ruger or 375 Ruger with high BC bullets?

Hi Ross

Thats awesome! Thanks for all the info. That does prompt me with a bunch more questions, so I hope you dont mind (incidentally, nice how you brought the thread back on topic due to the barrel rebore to 338! ;)).

It looks like the barrel profiles you have used are all on the long side, in heavy contours - I take it you do not experience any negative issues hanging this much barrel off the action? Mausers are not renowned either for tack-driving accuracy or stiffness (or have much tenon for that matter), so I was worried the action just may not stand a heavy profile. It doesn't look to have been the case for you, so gives me a bit more confidence for my planned project.

Did you do any other work to the action to true it up prior to the barrel work? All my Zastava (Mark X / Daly) actions are rough out of the factory. I intend to polish up the raceways, but wondered if they would benefit from a full-on blueprint.

What performance/ballistics are you getting from the 338 RCM? I am interested in the mid range 388s, and the 338/375 Ruger seems to have some good potential here as an easy to form, beltless case. I know thats not the same as the DCM, but your findings with the DCM version s still worthwhile data to bear in mind.

Lastly, what die set are you using fr the 7mm/375 Ruger? That cartridge also seems to have a lot of potential, and is something I am seriously considering for another project.
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  #11  
Old 09-12-2013, 07:02 PM
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Re: 338/375 Ruger or 375 Ruger with high BC bullets?

The larger 338 cal barrel is a #7 unfluted lilja profile. It is totally floated. The receiver is bedded in the action. I torque the action screws: rear 35 in/lb, front 40 in/lb.

No work has been done to the action. It is an older Mark X and is quite smooth compared to the newer Mark X/Daly. The trigger was reworked by Joe at Lawson's here in Tucson.

The long throated 338 RCM ( see pic) with 300 gr Berger 57 gr of RL-17 vel 2550 fps. It isn't as bad as it seems. Retains 3000 ft/lb at 550 yds. Wind drift at 500 yds in 10 mph crosswind is 8.8" (4000 ft elevation) The recoil is very tolerable with this 13 lb rifle. Can shoot 8-10 shots before it gets warm. Cleanup is easier with such a slow bullet speed.

Die set for 7mm/375? I have an assortment of dies on hand including a whidden 338 RCM combo FL/bushing die.

Here is how I made the cases with dies I already had: (from my documents file)

Procedure for necking down 375 Ruger

1) Hornady 338 RCM FL die
2) 300 RUM FL die to taper mouth of case
3) 7 RUM seater followed by FL to reduce neck dia
4) Whidden 338 RCM bushing die with .329 bushing
5) Whidden 338 RCM bushing die with .312 bushing
6) Open up with K and N mandrel, neck turn to .013” neck wall thickness
7) Run brass into Whidden 338 RCM bushing die using .310 bushing


I used the 7mm/375 reamer on the body tube of a 7 rem mag Redding comp die for seating.

338 RCM:

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  #12  
Old 09-12-2013, 07:54 PM
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Re: 338/375 Ruger or 375 Ruger with high BC bullets?

Thanks for that. It helps me confirm some of my thinking on this. I am going to go ahead with my 375 Ultra build on this action. I think I have sourced a barrel, and have the action on hand. So I think I am on track for this project.

I am going to have to do some research on the 375 Ruger case. I am swinging back this way for a 7mm, and can see some real benefits for a 338 on this case too.
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  #13  
Old 09-12-2013, 08:15 PM
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Re: 338/375 Ruger or 375 Ruger with high BC bullets?

A 338/375 Ruger would be easy to form. The 338 RCM and 375 Ruger share the same shoulder diameter and angle. You can use a 338 RCM FL die to neck the 375 down and size necks of fired cases. Could also use the 338 RCM seater die. A 375 Ruger FL die can do the shoulder/body sizing.


I forgot to mention I use a 375 Ruger die for my body/shoulder bump die. Even though it doesn't size all of the shoulder of the 7mm/375 I am getting excellent accuracy without bolt closing issues.
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  #14  
Old 09-12-2013, 10:51 PM
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Re: 338/375 Ruger or 375 Ruger with high BC bullets?

Thanks. Right now I am thinking I will use a 338 RCM and 300 RCM for the forming stages.

For day to day loading, I think I will bite the bullet and get John Widden to make me up a set of his dies with a full length bushing die and micrometer seater. Not cheap, but very nice.
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