How to measure chamber and slug bore of Ross M10?

Kirk1701

Kirk1701

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Can anyone provide me with a step-by-step technique by which you determine chamber size, bore diameter, and therefore bullet size for my new Ross M-10?

Before I begin reloading for it, I want to know the precise numbers for my particular rifle. Experimentation can get expensive. And I want to do right by the rifle.
 
Hi. Ross' don't have the Lee-Enfield barrel issue. Nor do you need to bother with chamber sizes. However, hammer a cast .30 cal bullet or suitably sized lead fishing sinker through the barrel from the breech end with as 1/4" brass rod and plastic mallet and measure with a micrometer. Only a chamber cast will do that.
 
Bore diameter does not determine bullet size. groove diameter does.

Before loading you need to buy bullets. 303 bullets are 311, 312 or 313. When any of those get hit in the ass with 50,000 psi, they will fit the barrel.

A flat base bullet will probably work best. I suggest you start with 180 gr. I would buy a box of round nose and a box of spitzers. I would load 34 to 38 gr of 4895. One of those should shoot well.

If you want to slug the barrel, get a unsized cast bullet. This will be 313 to 315. Clean the barrel well and leave a light oil in it. I start the bullet at the muzzle, where I can start it with a hammer. Once it is in the barrel, the engraving is done. You can either then use a cleaning rod to tap it all the way through to the chamber, or just tap it back out. measure across the bullet to get groove diameter.

If you can locate a suitable size soft lead ball, that would be easier to push through the barrel than a hard lead bullet.

personally, when I want to slug a barrel i load an unsized lead bullet over 6 gr of RedDot and shoot it into some water.
 
Excellent! I figured the Ross would be point and shoot. I'm glad I chose it. I had thought certain Rosses had their chambers enlarged, but I suppose that must not affect accuracy too much?

I bought some Winchester Super X, 180gr soft point ammo just to get a feel for the .303. I've never shot it before.

I already have a couple pounds of Unique for my .38/.357. I should be able to start with that right?
 
Unique would be usefull for lightly loaded, low vel. cast bullets. Think small game/plinking.
Not appropriate for jacketed bullets or higher speeds, IMO.

For full power, something in the Varget to 4350 burning speed will do well.
 
It may affect case life somewhat, if the chamber has been reamed out (though even supposedly large ones can be rather tighter than an L-E). Only a Cerrosafe or Woods metal casting will tell for sure.
 
Welcome to the wonderful world of the Ross rifle.

If you want your cases to last forever (I'm up to 14 or 15 firings on one lot) use the o ring trick on the first firing and then neck size after that. The lee collet neck sizing die is the best bang for the buck!

For jacketed loads I'm loading 35-38 grains of IMR4895 with a hornaday 174gr round nose bullet. I've also used 150gr SP's with good success.

For cast loads I'm using 13 grains of red dot with a 180 grain gas checked lee bullet. I shoot them at 200 yards all of the time with MOA to sub MOA accuracy.

Cast bullets can be more accurate then jacketed, it just takes lots of fine tuning.

Steve
 
I have a full-wood Ross here which does absolute wonders if you feed it what it wants.

It likes 35 grains of IMR-4895 with a 180 Sierra Pro-Hunter, which is a flatbase, seated to the OAL of a Mark VII Ball round (3.05").

This gets about 2250 ft/sec from the Ross, recoil is very mild and accuracy is quite spectacular.

Good luck with your Toy..... and Welcome to the Wonderful World of Ross Rifles!
 
smellie said:
I have a full-wood Ross here which does absolute wonders if you feed it what it wants.

It likes 35 grains of IMR-4895 with a 180 Sierra Pro-Hunter, which is a flatbase, seated to the OAL of a Mark VII Ball round (3.05").

This gets about 2250 ft/sec from the Ross, recoil is very mild and accuracy is quite spectacular.

Good luck with your Toy..... and Welcome to the Wonderful World of Ross Rifles!
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Sounds like I'll have to get some 4895. I was hoping to get by with Unique, but a pound of the 4895 should last forever, I suppose. And I believe my local Crappy Tire carries Sierra bullets. So win-win.

Here's another dumb question: what size of o-ring should I buy?
 
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Theoretically, you can partially resize the case with an FL die. Practically, you may run into issues trying this with a Ross, as there is no way to easily tell if you've sized the case properly. (ie the bolt will close on the resized round, but the rifle will not fire.) Ask me how I know this....
 
cosmic said:
Theoretically, you can partially resize the case with an FL die. Practically, you may run into issues trying this with a Ross, as there is no way to easily tell if you've sized the case properly. (ie the bolt will close on the resized round, but the rifle will not fire.) Ask me how I know this....
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My brother experienced the same problem a few times with his MkIII Ross. The bolt closes 95% of the way but he'd get light primer strikes. I guess he set the sizing die up so that it wasn't bumping the shoulder back enough.

I use the lee collet die myself. One thing though, all you need to do is set your die up so it just barely bumps the shoulder, this way the gun will fire but you're not FL sizing all the way.

I've had my best FL sizing results with my Ross. I did 8 FL resizes on my original brass before I started to have head separations.

Keep your loads light and you'll get reasonable case life even if you FL size yor brass every time.
 
Tinman204 said:
My brother experienced the same problem a few times with his MkIII Ross. The bolt closes 95% of the way but he'd get light primer strikes. I guess he set the sizing die up so that it wasn't bumping the shoulder back enough.

I use the lee collet die myself. One thing though, all you need to do is set your die up so it just barely bumps the shoulder, this way the gun will fire but you're not FL sizing all the way.

I've had my best FL sizing results with my Ross. I did 8 FL resizes on my original brass before I started to have head separations.

Keep your loads light and you'll get reasonable case life even if you FL size yor brass every time.
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Would I still employ the o-ring trick?
 
Kirk1701 said:
Would I still employ the o-ring trick?
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If you are going to try partially sizing your brass then yes use the o-ring trick. Try screwing your die in til it touches the shellholder. Then size like that, instead of giving it an extra 1/4 turn like you would FL sizing. I used that trick with good success before I got my necksizing die. If you are going to FL size then I'd say skip the o-ring trick.

I find that even with the "E" stamped enlarged chambers a Ross still has a tighter chamber then any of my 3 lee enfields.

The best thing about the Ross rifle is if you have a full length barrel you can load lighter rounds and still get all of the power of a heavier loaded round. My loads are usually a grain or 2 below published starting loads. I also find that most if not all .303 chambered rifles prefer light load. My Ross consistently shoots sub MOA with nice light loads of 4895.

Mine really likes 35.5 grains of IMR4895 with a RNFB 174gr .312 hornaday bullet, primer choice seems not to matter. That load in a typical lee enfield shows signs of low pressure. My lee enfields usually need a full 2.5 grains more to achieve the same results as my Ross.

Might I add that light loads are great for the rifle and my shoulder!!
 
Tinman204 said:
If you are going to try partially sizing your brass then yes use the o-ring trick. Try screwing your die in til it touches the shellholder. Then size like that, instead of giving it an extra 1/4 turn like you would FL sizing. I used that trick with good success before I got my necksizing die. If you are going to FL size then I'd say skip the o-ring trick.

I find that even with the "E" stamped enlarged chambers a Ross still has a tighter chamber then any of my 3 lee enfields.

The best thing about the Ross rifle is if you have a full length barrel you can load lighter rounds and still get all of the power of a heavier loaded round. My loads are usually a grain or 2 below published starting loads. I also find that most if not all .303 chambered rifles prefer light load. My Ross consistently shoots sub MOA with nice light loads of 4895.

Mine really likes 35.5 grains of IMR4895 with a RNFB 174gr .312 hornaday bullet, primer choice seems not to matter. That load in a typical lee enfield shows signs of low pressure. My lee enfields usually need a full 2.5 grains more to achieve the same results as my Ross.

Might I add that light loads are great for the rifle and my shoulder!!
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Is the E stamped into the lip of the stock? If you consult the attached photo, there's one with a clear proof mark and a visible E. Is that the enlarged chamber stamp? I would've thought it would be on the barrel.

 
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