View Full Version : Converting 1903 30-06 to .300 Win. Mag

March 26, 2011, 02:21 AM
I am planning on rebarreling, chamber, and altering my Rock Island 1903 to acept .300 win. Mag. I have the (I think) all the carbide tool bits I need. I plan on opening up the bolt face on a lathe. However I am unsure on the best way to open up the feed ramp to .532:confused:. I just wanted to know if any one has done this before. If so, is there any advice you could give?

March 26, 2011, 06:31 AM
I would very carefully weigh your plan.
Its your rifle,you can do things your way.I'm sure it has been done before,I won't tell you it can't be done.
First,you need to evauate your serial number range.Some Springfields are "low number" rifles,and even shooting them with 30-06 is questionable to unsafe.
While I am not saying the 1903 cannot handle the pressures,SAAMI maxpressure for a 300 win is 64,000 psi vs 62,000 for the 30-06.The larger diameter of the case head translates to a little more bolt thrust.The cone breech leaves more brass unsupported than some other designs,which can be important when case stretch weakens brass .
Is it in original issue trim?If so,the surplus import laws say there won't be any more coming back to the US,there are no more Springfields.If you alter it,you will greatly decrease the value.What may well be a $750 rifle original(conservative estimate) will become a $250 rifle,if you spend at least another$400 or so on it.
You may well have the feed rail issues that concern you,ignoring that,add the price of:
bolt handle job for scope clearance,a new safety,as the original won't work with a scope.Drill and tap for scope mounts.Do you have a chamber reamer and headspace gages?
Unless you go Adams and Bennet or equivalent,barrels start at about $225 and go up to about $350 if you don't get too fancy.
You might want to go to the Winchester web page,I guess they are back up and running,and see what a new M-70 will cost you in 300 Win mag.
I think if you do the figuring,for the same money,you can keep your original 1903 in 30-06,and buy a new M-70.
I have sporterized a number of milsurp actions and built rifles.It is something I have enjoyed,and learned from.I don't tear down rifles,I buy a bare action when I find one.Today,if I had a good 1903 action,I'd get a Kreiger/Criterion original contour 30-06 barrel,one of the new replacement stocks,or I might find my own piece of good american old dense walnut and have an original made on a duplicator.Then I'd scrounge the rest of the furniture to make a mil trim 1903.In 30-06.

March 26, 2011, 08:09 AM
Thank you for the reply. I have a 30 in. .308 Shillen Match Grade barrel blank. At the moment I do not know what contour to turn it down to. I am thinking of turning the whole barrel down to the diameter of the action, so in the future when throat erosion is bad all I have to do is cut the shank off and start anew. I have the apporate and needed tools for the job.

The stock I plan on making and checkering my self. I have a very nice bastogne (I do not know how to spell it) rifle blank. I plan on putting in some cross pins, will regular drill rod do for this?

I did not even think about the safty interfearing with a scope, thank you for that. The bolt however I plan on bending carefully. I have a Timney single stage trigger. I plan on putting it in and setting it for a nice 3 lb. pull. On a side note I am doing all the work.

March 26, 2011, 08:38 AM
You might want to rethink this build, I agree with HiBC. If you have a low number gun don't mess with it (less than 800,000 I believe). Years ago I built a 264 mag on a 03-a3 it was a real pain, the bolt was glass hard, I had to buy carbide bits to drill the scope mount holes, I would suggest that when you start to tap the mount holes use Hi-speed Steel taps for no other reason than that you can chip them out when you bust them off in the holes. If you do a good job of inletting you wont need any cross bolts to me they take away from the look of a nice piece of wood. Getting the darn thing to feed was a real pain too, there was some good information in one of the Gunsmith Kinks books from Brownell's even then it was not one that I would like to do again. If you really want to build a 300 there are lots of nice Mauser 98's out there and they will hold a 300 just fine as long as its in good shape.

Good luck

March 26, 2011, 08:55 AM
I just gave my son his grandfather's Rock Island Springfield to take back to Ft Benning. I had first shot it as an 8-year old back in the early 50's when it was in the original 30-06 chambering, as it was kept through the mid 60's for deer hunting in Texas.

In the late 60's my father rechambered it to 300Win Mag for brown bear, and I inherited it in that configuration in the mid 80's. I continued to shoot it from then until three years ago when I pulled it apart to pillar-bed the old/original stock and rebarrel w/ a 26" Krieger (still 300WM). In this configuration it remains a very light hunting rifle. While not unpleasant, it is not "fun" to shoot continuously off the bench.

All of 5'11/155-lbs, YoungSon sat down weekend before last to fire it for the first time before returning to Benning:


Rangers are tough. :)

On a Tech Note:
Because of the low-numbered Springfield problem, Rock Island began making their receivers out of nickel-steel o/a Serial# 319,921 instead of the Springfield arsenal's original Class-C steel. (Hatcher). While the exact serial# is debated, all such RI receivers have "ns" stamped on the face at the front end. Although covered by the barrel this stamping can be seen when rebarreling. (As it was in my case.)

YMMV (that's the lawyer speaking), but these RI/nickel-steel receivers are as strong as they come.

March 26, 2011, 08:57 AM
I am building off a Rock Island Arsenel 1903. Its ser.no. is 318,668, the recomended cut of is 286,506 for the Rock River Arsenel. Thanks for the tip about Kinks, I am skimming th ones I have now. I do agree about the cross pins. I am planning ahead in the event I screw somthing up on inleting.

I cecked the unalterd feed ramp with .300 win. Mag. dummies ad a dummie shank/chamber. At the moment it almost cycles the same way with 30-06 and the mag. well holds 3. Looks like the feed ramp needs to be moved back a little bit, due to it shaving a bit of the bullet tip.

March 26, 2011, 08:59 AM
You are at the edge.

Check for the required 'ns' stamped in the front receiver ring (see above) before proceeding. Otherwise it is the older steel/but supposedly with the revised heat treatment for carbon/manganese steel receivers

March 26, 2011, 09:16 AM
No "ns" stamp on it. I should probally add that the first owner of this rifel bought it from CMP (paperwork to go wth it).

March 26, 2011, 09:36 AM
See if you can get hold of Hatcher's Notebook Chapter 9 from someone. He provides the whole story and all the specs.

The real bottom line is that the Old Double-Heat Treated method was complex. When done right it was an exquisite combination of hard surface/softer interior -- none better. But both Springfield and Rock Island found it very difficult to maintain a consistant process.

March 26, 2011, 10:07 AM
The barrel on the 1903 at the moment is "toast". With that in mind I ran a about 150
30-06 max loads. The loads were 180 grain bullets with 53 grains of IMR 4831. When I am done I plan on putting 24 test rounds with the .300 win. mag.

March 26, 2011, 10:18 AM
Don't bend the bolt handle, replace it. You will have to rework the feed rails to accept the bigger cartridge. Once you do that there's no going back.

March 26, 2011, 11:21 AM
I'd have to agree if in military form keep it stock.Now if it was a 1917 or a 1914 that someone had already altered I'd go for it.Got a 1914 British that someone altered to 300 back in maybe 1990 with a synthetic stock that shoots great.But they had turned the ears off and re-barreled so collector value was nil.

March 26, 2011, 11:50 AM
Colector value is not a issue.

March 26, 2011, 03:20 PM
Fair enough.My discouraging words were from my practical side.If you have chosen to go for it,cool.I find the Springfield action an elegant beauty.
I do not know what you will find by searching,but look for "Springfield bull guns" Folks of your mind were doing it long ago.Have fun,keep us posted.

March 26, 2011, 05:07 PM
Kind of a crappy pic but here's my 03A3 Smith Corona. Still a 30-06 tho.


March 26, 2011, 08:16 PM
Nice picture. Thanks for the information. One of the reasons for convert is that it would be a 1903 I am able to shoot without fear of damaging any colectors value. I have 6 original 1903s, one is a very rare Remmington 1903, around 75-80% condtion. I dare not shoot any of thoes.

March 27, 2011, 06:55 PM
The Sptingfields have been my favorite for 40 years. I would not even consider modifying or shooting a low numbered one.

It it's original the price is way up there. Sporterized gun are worth about $400 or less around here. One of these could be considered.

I had a 308 Norma mag. that was rechambered. The ballistics are almost the same as the 300 Win. I bought the gun used, and had no preblems with it. It would shoot 1 1/4" 5 shot groups. Maybe better with another shooter. It was common for gunsmiths to rechamber these guns in the early 60s. They had to use 3/8s freebore to keep pressures reasonable.

Good luck with your project. Eagle

March 27, 2011, 09:50 PM
Shipwreck, according to documents from Rock Island, the actions with the Nickel Steel and double heat treated Class C steel started at serial number 319,921, August 1, 1918. Yours is of the old steel that failed far too often with a 50,000 CUP load. You are expecting to go up in pressure and bolt thrust on a highly doubtful action. I' would strongly suggest taking it to a smitty to have the action tested for hardness. Otherwise, I'd suggest a big life insurance policy for your family.

March 29, 2011, 06:29 PM
Thank you for that information. I did further reserch based of that information. I will be building this off a remington 1903.

March 30, 2011, 11:39 AM
50 years ago, when I was a little boy on the playground, another little boy told me that his father had converted a 1903 Springfield from 30-06 to 300 Win Mag.

April 1, 2011, 02:24 AM
Could be worse as I saw a military remington action rifle in 300 win mag once too. It was a US 50-70 that had been converted. The main issue you will have is the feed lips and the folower. Make a dud up and stick that in the action and try to feed it and work on where it binds up. Personly I consider going from 5 30-06 rounds in the mag to 3 .300s a step back though.

April 2, 2011, 07:31 PM
????????????You saw a US Remington in 50-70 that had been converted to 300 Win Mag?
Sounds like a Rolling Block!In a black powder action,no less.I do not think that would work out well.Sounds like an impending fatality.