Has anyone got experience with .35-303 or .375-303?

[W.R.Buchanan]

Looking for information on .35-303 or .375-303. Thinking about boring a Lee Enfield Barrel to a larger caliber..

Like to hear any experience with either of these two rounds.

Also looking for outfits that can bore, rifle, and chamber a barrel.

Also looking at .348 Winchester as an alternative. So far no one will do that one.

Randy

[Frank46]

There is a cartridge based on the 303 case necked up to .375. It's called the 37 rimmed and is made by necking up the 303 case to .375 and that is about it. Still leaves a tiny shoulder even after necking up. Just for the heck of it I made up a .375 expander out of some threaded rod I had and with some die wax worked easily. Don't have any loading data for either cast or jacketed bullets so maybe at this time would use 38-55 loads as a starting point and go from there. I have a copy of the print but me and computers don't work well together. PM me your address and if you want a copy let me know. I have a semi turned .375 bbl blank with a 1x12 twist that may go on a longbranch sporter Frank

[303Guy]

We have the 38 Hawkins here in NZ. It's a 303 with the neck opened out to remove the shoulder. The forming die removes the thickness irregularity of the shoulder. JeffinNZ can tell you more. He has one! He sent me a case former which I still have. I made a former which didn't smooth out the shoulder area. No residual shoulder in the 38 Hawkins (375/303). It looks a bit like a 375 Winchester.

I would look at the depth of the holes in SMLE barrels. I thought they were too deep for boring out to more than 35 cal. No.4's would your oyster. I did know a man who bored 303's to 410 shotgun. I just assumed he did MLE's which have a heavier barrel.

goodsteel has built a 358 Malcolm which is his own 303 wildcat. It has a sharp shoulder and less body taper. I think it is a cartridge to be reckoned with. It would be licking at the heels of the 357 Winchester if not equalling it (it has a larger case capacity).

I was interested in a 375/303 because I wanted a 'large' bore with a parallel case interior in the boolit seating region so I could use a wad. I also wanted it to feed from the 303 Magazine and not be too large with a 300gr boolit with fair sectional density and reasonable velocity. Well, I never got there. I was planning to bore out a MLE barrel and rifle it. The chamber was to have been done on a lathe. I got the rifle but made no further progress. I now plan to make that rifle shoot as it is with it's rust damaged bore which I did fire-lap.

[MBTcustom]

It's the 358 Malcolm. Fun cartridge. I made it specifically for shooting paper patch boolits and had a lot of fun with it summer 2011.
It's a 35/303 improved with a tight neck, and I made a Lee loader to reload it. The brass should last forever because the neck sizing die only bumps the neck diameter down .002 from its fired diameter.
Took a bit of filing and dremel tool to get the darn thing to feed without beating the cartridges back to their original shape. The SMLE is a different take on CRF IMHO. I also had to modify the follower and the feed lips on the magazine.
If I could do it all over again, I would not make a straightwall improved cartridge design. My thought at the time was to reduce bolt thrust so I could ramp it up a little more with the 250gr cast lead (which I succeeded in doing) but at this point, I realize that for knocking over most any north american game, the 35 caliber rifle doesn't need all that sauce, and in retrospect, I would have made things easier on myself in the feeding department and just played it straight with a simple, necked up 303 British. You change the body angle and shoulder diameter of a cartridge, you pretty much commit to changing everything that interacts with it below the bolt to match.

[Bullshop]

I did have but no longer have a Siamese Mauser action chambered for the 375 Kraig. That would be very close the the 375 Britt.
With that rifle I was able to get to within 100 fps of published ballistic performance for the 375 H&H cartridge.
Published data for the H&H cartridge is no where near what the full potential of the cartridge is but then it has proven for over a century that it does not need to be loaded to its full potential.
At any rate I was very impressed with the performance I got from that combination of cartridge and action.
Now I don't consider the Lee Enfield action quite the equivalent of the Siamese Mauser as to absolute strength so you may not be able to get thye same performance I did. On the other hand the Lee action has been chambered to to 308 win which is no slouch in the pressure department.
If though I was to use an Enfield to base a rifle of this type on it would not be the Lee action it would be the 1917 action. 1917 actions in 303 are not too hard to find. With that action and perhaps an Ackley Improved type chamber I believe you would be able to equal published performance of the 375 H&H. I say equal published performance but not saying you could equal full potential performance. The reason is pressure, the H&H round is not loaded to full potential pressure so by exceeding the pressure the H&H is loaded to you can equal the performance but still stay within safe pressures for the action.

[Love Life]

There just so happens to be 1917 in 375 H&H listed on Gunbroker with a very fine stock for $1,300.00. I have been eyeballing it myself for the last 2 months.

Moving along.

Randy- My opinion on it is (we all know how opinions go!!) is that a rebore just isn't worth it to me. By the time you send it out to be rebored and get it back you are nipping on the heels of the cost of a premium barrel made of modern steel and usually stress relieved. With the tools and skills you have, you could probably cut, chamber, and mount it yourself and "Save" (in quotes because your time is worth something) the cost of a gunsmith and major down time.

Just my humble opinion, but I will be watching with interest to see where you go with this one!!

[Multigunner]

1917 actions in 303 are not too hard to find.

Those are the P-14 rifle, the rifle the M1917 was based on.
For a time you could order stripped M1917 or P14 actions with choice of bolts intended for either. So long as the barrel breech is of the type intended for one or the other the bolts of one will work in the other receivers. The breech end of the barrels are made differently to avoid putting the wrong bolt in.

I would look at the depth of the holes in SMLE barrels. I thought they were too deep for boring out to more than 35 cal. No.4's would your oyster. I did know a man who bored 303's to 410 shotgun. I just assumed he did MLE's which have a heavier barrel.

Good points. I've found SMLE barrels with rear sight cross pin holes that almost cut into the bore.
A No.4 barrel can be fitted to a No.1 action. The thread starting points are not quite the same and it may not be a really close fit.

Having a barrel made from a blank would probably be less costly in the long run than reboring a barrel and cutting new rifling.

[Bullshop]

There are a couple 1914/1917 rifles in 303 Britt on GB priced in the $400.00 range

[Multigunner]

Unless you just have to have a cartridge based on the .303 case, through having a mountain of boxer primed .303 cases to play with, the M1917/P-14 action is better suited to longer cartridges, which is why so many have been rebarreled or rechambered to belted magnum cartridges.
The parent action of the P-14 was the P-13 which was chambered for a long rimless high velocity 7mm cartridge. Development of the P-13 stalled due to cordite and other available double base powders being unsuitable for the intended performance envelope. Barrels burned out quickly, the report was awesome, and the muzzle blast was visible for a mile or so.
When production of the SMLE lagged early in WW1 the British had the rifle design altered to handle the standard .303 cartridge and contracted manufacture to Remington and Winchester in the USA.

The SMLE and No.4 actions are slick and fast to operate, qualities valuable for a woods rifle which is the best use I could see for a medium case capacity .375 cartridge. BSA marketed their sporting version of the LE in similar chamberings. I'd look at those first to get an idea of how the project should go.

While the No.4 has been converted to 7.62 NATO in the past the British NRA doesn't consider the converted No.4 entirely suited to all mdern 7.62/.308 loading especially the most recent long range match cartridges.
The L42 and similar converted No.4 rifles were designed around the 144 gr standardized ball cartridge with maximum pressures of 48,000 CUP. Some modern long range loads exceed that figure by 10K CUP. To use the modern cartridges in competition the converted rifles must be reproofed. So if building a No.4 in .375/303 it might be best to keep chamber pressures below 50,000 CUP. Theres little to be gained by over amping the action.
The SMLE has historically not held up to conversion to .308 and some have been damaged by the .303 Mk8z mg cartridge which is in the same pressure class as the 7.62 NATO Ball , the Indian 2A rifle in 7.62 is as strong as the standard No.4 so if you like the classic looks of the SMLE action a 2A action might be the better choice with greater margin of safety.

[Dan Cash]

.375 x 2 1/2 inch flanged is essentially what you are talking about with your wildcat. 270 grain bullet at 2100 is nothing to sneeze about. Barnes Cartridge of the World says that it was not a very popular cartridge but as I have a Styer rifle in that caliber, I can attest that it is a thumper and very accurate considering my very crude cartridge forming and reloading.

[W.R.Buchanan]

Guys Thanks for all the info. What I will have as of this Sunday is a Sporterized, barrel cut, #4 Mk1* The reason why I am looking at doing a rebore is because the rifling appears to be weak and the throat also appears to be weak as well. Prime candidate for a Rebore job.

Also I am doing this one with real live sporter wood and it is going to look similar to some of the purpose built BSA Sporting Rifles from back in the day. Also similar to what Von Gruff did with his #1's

I was originally looking at .348 Winchester, but saw problems with feeding rearing their ugly head, so after talking to JES Reboring I "Pivoted," (You gotta love that term direct from POTUS) to one of the common .303 wildcats. after looking at the SAMMI drawing for .303 British it appears that either .35 or .375 will work just fine as the case diameter at the shoulder is .401. I'm leaning towards the big one.

As far as power goes,,, I expect either of the above calibers to be more than suitable for anything in the NA with any loading.. I see no need to push either one to pressures even above 30K psi. .45-70's at 28K psi will knock over pretty much anything, and 405 gr boolits at Trapdoor Pressures have already knocked over everything.

I see a 300 gr .375 bullet at 1800fps being a devastating round and more than enough for me and no real stress on the action. Obviously the potential is there for more power should someone want it down the road.

My bro in law got a lesson in big bore riflery today.

We were shooting at a 8" dia 1/2" thick steel plate hung from two cables at 100yards. He was shooting his AR's at the plate off a rest, and hitting it made the plate dance around a little..

I hit it with a 250 gr LBT WFN boolit from my .44 Mag. 1894CB rifle (with newly installed Lyman 66LA) on the first shot,,, offhand, and the impact almost knocked the whole target stand over! The LBT Boolits were making dents 3/8" in dia and .030 deep in the AR500 target and they were only running about 1600 fps! The .223 was making dents 1/8" in dia and .010 deep.

Point being,,, a bullet 5 times bigger hits a lot harder than a piddley little 55 gr pill buzzing along at nearly twice the velocity.

I also killed a "rock" which was laying on the range about 35-40 yards in front of the line. It started out about 40 lbs and ended up as gravel with about 10 shots hitting the various pieces.

He had never shot anything bigger than a .308 and had no idea of the power big bore rifles have. And this one was only a pistol round! He understands a little more about the power of the big hole now and He wants to shoot my .45-70 Marlin next.

My whole point with this story is that big boolits just don't need to be pushed that hard to be able to do Devastating Damage.

The other caliber I was toying with for this project was .45-70. However the feeding problems with that would have been a big PITA and it also would require a different barrel which would cost me more in the end than just reboring mine.

The .375-303 should be a plug and play conversion, as JES bores, rifles, and chambers the barreled action in one sitting. Less than one week turn around too.

We'll see how this project goes I can tell you it will be something different.

Randy

[Bullshop]

Not trying to sway you or pivot you but just FYI I did a Lee Enfield in 45/90 once. The mag has to be converted to single stack but when done right they feed just fine. There is plenty of room in that long mag for the 45/90 too. It started as a 45/70 but the shorter case just looked so small in that long mag I decided to re chamber to the longer case. Shot good too but when loaded to near top end pressures for the action recoil was nose bleed fierce.
There was a long ago article in Rifle magazine on converting the Lee and how to convert the mag to single stack.

[W.R.Buchanan]

Bullshop: I would be interested in seeing some info of converting the magazine to feed those rounds. Nothing is set in stone on this project yet, other than I will not be inducing a Nose Bleed! Mid Range be good enough for me, as I am a fragile sort. IN fact if I go .375-303 the gun will be at about 9lbs when done.

I really don't like to start a project when there are major questions about what is going to be done. This usually brings in issues which if not coped with in their needed order tend to either stall the project or require a do over. I hate do overs on guns.

I have a bunch of stalled gun projects that are on hold for the arrival of one or more skills or more properly the knowledge to complete them properly. I hate ending up with less than what I envisioned.

I have a Jeep project that I have been working on for the last 8 years coming to fruition slowly but surely. I already know pretty much everything I need to know to complete that project and believe me, There is a lot of different skills involved in building a car from scratch. That project has just come down to chipping away at it until done.

Guns are a different story. Every move you make on a gun has to be thought out ahead of time. Right down to just picking it up and not dinging the stocks or the metal by running it into a file laying on the bench or something else. I just finished another #4 Enfield and whereas it was hardly a Masterpiece, it turned out really well, especially for an Amateur, and definite improvement was made.

I knew how to do every single part of that build simply because I had done everything before on different projects. Even so I want to add a little knowledge to each project and build more skills. This last one was about matching colors on different types of wood, and whereas there was improvement I still didn't get exactly what I wanted.

But,,, last week on "How's its Made" there was a segment on Turnbull Restorations redoing a 1886 rifle. I picked up a bunch of techniques from that program on both metal and woodworking. That part about matching the color on two pieces of wood goes much better if they are cut off the same blank! So now I know how they do it and I can do it too since I already know how to stain wood! They gave away just enough of their precious secrets to help me advance just a little further. I taped that show and have watched it 6-8 times so far. I get just a little more each time I watch it.

I am hoping for something a little better this time. I guess we'll see.

Randy

[Bullshop]

That rifle article was more than 25 years ago to be sure. The way they did the mag was to fasten some type of hard plastic to each side of the mag box on the inside so it would only allow single stack. They also had to make a follower to fit the narrow slot.
If you have ever seen the Gibbs conversions what they did to the mag is stamp the sides in to create the same effect. I ended up using a Gibbs mag but they may be awfully hard to come by now.

[W.R.Buchanan]

I get the idea of the plastic liners That is what Ruger did to the AI .308 magazine to choke it down to take the .223 rounds for the new .223 Scout which is nothing more than a regular .308 Scout with a smaller hole in the barrel, different bolt face, and modified magazine.

What did they do with the feed lips on the front of the mag? It would almost seem like they would have to remove them altogether and just rely on the ones gripping the rim in the rear. The follower is no problem and I can already see what that would need to look like.

Weren't those Gibbs Mags only 3 rounds ? Thought I heard or read that somewhere. Also were they Hourglass shaped?

Randy

[303Guy]

One could chamber the Lee Enfield to 444 Marlin too. I would personally want to use the 303 Brit case.

I have a 25/303 on an SMLE action with a long slim barrel. Now that is a worthy cartridge.

Anyway, my leaning would be to a 40 bore. I made a case forming die just to see how it would work. I sized a case up to 40 then back down to 303 then back up a few times to see how well the brass would stand up to it. All that happened was the case mouth became a bit irregular.

Green Mountain I think it was, were selling 40 cal barrel blanks for a good price at one stage but I would not have been able get one shipped to my parts.

A No.4 barrel can be fitted to a No.1 action. The thread starting points are not quite the same and it may not be a really close fit.

I have such a gun. It's a LE I. The gunsmith faced the breach faces to align the extractor slot. He did need to put a reamer into it to get it to take standard cartridges. It has a tight chamber and just that much less throat free space. An accurate rifle with free floated barrel. I had the same 'smith fit a No4 barrel to my Dad's Lee Speed action and that one required no reaming but new cases were firm on locking the bolt. It wasn't quite as accurate as mine with the same bullets but pretty impressive just the same.

[W.R.Buchanan]

2 days until I get the gun. I am still undecided on the caliber conversion, but leaning towards the .35-303 as I don't really see needing more and the bullet choices in that size for both Pistols and Rifles are extensive. I can go from 100 gr to 280 gr with nice readily available moulds and Gas Checks or not. Also a large selection of Jacketed bullets as well. Not so much for the .375's, although in reality there are probably more than enough for them as well.

Using 100 gr Wadcutters to pop birds for dinner when on your Bear Hunt of a lifetime seems like a good way to go. Or 280 gr RN Bore Riders for the bigger stuff, or 250 gr Jacketed bullets as the big hunting load.

I see a lot of possibilities with the .35-303 here. The problem I see with the .375's and .400's is no further need for the .400 Whelan Springfield I would like to build down the road a little.

Will make a decision after the gun is in my hands and I take it apart and see exactly what I have to work with.

Randy

[Idaho Mule]

I got drawn into this, being a fan of the 303. The other day curiosity got the best of me while at the loading bench and I dug out a well worn 303 case. I then dug out my .35 cal neck expanding die and opened her up. The case looks pretty cool stretched out to .35 cal. Then I grabbed an RCBS 200 FN and seated to the crimp groove, and then just took the bell off the case with my 356 Win. crimp die. This is an awesome looking round to me and I can see myself needing one. I just happen to have a spare SMLE standing in the corner. Hmmm... JW

[W.R.Buchanan]

IM: See what happens? Could you post a pic of the Round as you made it?

The growing enthusiasm for these guns here and on other Websites is great. Many of these guns were modified and have no collectors value. however they can be made into downright gorgeous Sporters if the "Sporterizer" has any bit of good taste when it comes to gun design.

Here is two good examples of what I am speaking about. Both done by front line custom Gunsmiths.

One in .45-70 on a #4 action (on the Buffalo) and the other #1 action in .348 Winchester . Note: The Excellent Lines on both of these guns, and the attention to detail with the checkering and Shadow Line Cheek Pieces, and the one really classic point of the Winchester Red Rubber Butt Pad on both guns.

Both of these guys understood perfectly how to make these Sows Ears into Classic Sporting Rifles. These are my inspiration for my build and whereas I don't possess skills that this level,,, I can get close. And so can many others who possess the ability to work carefully on a project. These guns didn't come about in a few days it took months to complete either one.

I quick look at Von Gruff's Thread in Special Projects will give a more complete idea of the time it takes to produce a first rate gun.

Randy

[Idaho Mule]

Here are pics for you.