Hi folks.

My recent thread was on forming a Rimmed Roberts from 444 Marlin cases. (A recent trip to the gun shop revealed an absence of 444 cases). This one is about chambering that No.4 to a 'Rimmed 220 Swift'. This is because I have the barrel but it is not a full 26 inch, that I would think I need.

So, will a shorter 23 inch barrel make such a project a waste of time?

Secondly, will loading a Swift to starting loads or even less make the project a non-starter?

Then thirdly, will blowing out the 303 case to almost straight walled, make up the difference in performance i.e. allow me to get near Swift velocities at 303 pressures.
(I believe I would be able to load up to 47,000 CUP in the No.4 but at some pressure limit the flex in the action may cause accuracy problems. Anyway, I want to keep to 45,000 CUP as a max - as best I could).

If I stay with the 257 Rimmed Roberts idea, I would have to buy the barrel blank for a few hundred dollars and then pay someone to chamber it. The rest of the machining I will do myself. If I go '220 Rimmed Swift Improved' I would do the chambering myself using a method discussed in my previous thread and the whole thing will cost me no more than my time. Lots of it - but that is a good thing!

The ballistic calculators have shown me that the 220 Swift, even at lower end velocities will shoot as flat with the same wind drift as the 257 Roberts, using bullets that are common versus bullets that seem harder to find for the 257.

303Guy,
Say again? What are you trying to achieve? The old 303/22Improved was a definite 220Swift equaller but from P14's, not a No4 where its probably more of a 22/250 equaller.

I'm just about to start putting a 303/35 together on a No4 ... then I keep wondering whether to take the barrel of the P14 in 303/25 to rebuild an 'old World' varminter in 303/22. Cost of custom dies is the killer though.
Cheers...
Con

Con, just to equal a 22-250 would be fine but I suspect it won't even do that. Not in a short barrel anyway. At least, that's what I think. I have the barrel and I am a machinist so I could put the barrel onto the No.4 for the cost of my time. I am wanting/needing a long range varminter to complete my 'array' of rifles. That being a 303 sporter, a 22 hornet and a 22lr. I'm just not covered for those longer shots.

I think the 303/35 is a great idea! Ideal for the No.4. You could select a case design that allows the use of a combination of standard dies for forming and load with a neck sizer only. The 220 Swift case is so similar to the 303 that I wonder whether those dies would work. What would you do with your 303/25 barrel?

P.S. Is there a difference between the 25/303 and the 303/25? A mate has a 303/25 and the case body is shorter than the standard 303 (by about a millimeter).

It seems I have found the answer to my barrel length question. I will lose some 75 fps over a 26" barrel with my 23" barrel. A smaller case would give a smaller loss. So, the most I could reasonably expect to get would be 3500 fps with a 55gr bullet. A bit short of the 3800 I am aiming for!

#1). Mr. Parker Ackely, US gunsmith, did a 2 volume set of books that are still available in paperback, I think, on thousands of cartridges, factory, Improved, and wildcat. Eabco.com had the paperbacks. You see them on ebay now and again but you have to ignore the stuff by "Ackley" the nurse. He retired in 1985 or so. No PPC to speak of. But prior to that, he about covers it.

Mr. Brown at eabco.com has worked much with rimmed cartridges, more the .219 Don Wasp. Great accuracy. Somewhat less velocity.

#2). You mention case availability. A military nut friend told me, I believe, that there was quite a run of #4 SMLE's in 308, excuse me, 7.62x51mm NATO, for competition use. This gun would get you "rimless" and a rimless magazine and a common "brass"... There is a .22/243 that should about equal the Swift at slightly lower pressures for the MK IV. .243 is being loaded with light bullets at barrel burning velocitys.

#2). There is a long list of "rimmed" cases. 6.5 Jap was "semi-rimmed." .220 Swift is from the 6mm LEE Navy. Semi rimmed. (Mr. Ackley seemed to think the Swift case was perfect for 6mm.) Never heard anything about using these "rims" in a SMLE but with all the Mausers in US, no surprise. I previously mentioned the "sameness" of the .303 and .30/40 Krag US case. And the work of many making wildcats for single shot rifles. And the reference to Mr. Epps, Canada; .303british.com. In the books by Ackley. The .22/.303 would be in the .22/250 range. .22/303 Improved might approach the Swift.

From there it is "where do you want to go" and "what can you afford." Mike at Bellmtcs.com has cartridges on both the .444 case and the .307 WCF case. You could take either to .22/250 size or .22/250 Improved.

Mr. Ackley says for the .22/250 Improved, "use standard Swift loading data." Mausers, not Mk IV's.

"If I stay with the 257 Rimmed Roberts idea, I would have to buy the barrel blank for a few hundred dollars and then pay someone to chamber it." No. Here, anyway, you can buy barrels chambered for that kind of money. You would have to do magazine work. One option is the slightly deep chamber that is finished by "facing off" the end of the barrel to correct headspace. Top US barrel makers, most, advertise on benchrest.com.

Reading Jack O'Connor, I was a .25 fan too. But I have to acknowledge, in US anyway, that the number/variety of 6mm bullets vastly exceeds the number of .25 bullets available. It is better than a few years past, but still no comparison.

.22, without getting into the fast twist barrels (that wear more quickly), does not offer the bullet weight/wind resistance that larger calibers do. 6mm or .25 (or 6.5 in some uses). Calculators have their uses and limits.

Enjoy your project. It is pleasant pass of time. And when you decide. !! Until then, LUCK.

Thanks a heap iiranger.
Chambered barrels, of course! I am not so sure about in my part of the world but I can make enquiries. We do have a barrel maker here but those are premium barrels and chambering is extra. Besides, I want the fun of doing the whole thing myself (At least then, if it does not shoot straight, I will know whos fault it is - and I can do it again at no extra cost). Interesting just how similar the Lee Navy and the 303 Brit cases are - both having being designed by the same man!

303Guy,
Regarding the 303/25 ... yes they're shorter than 303British which is where many get in trouble thinking its just a necked down 303Brit. But ... there probably is a full length version out there somewhere as they were all wildcats except for the version (slighty shortened) that Riverbrand and Super sold as commercial cartridges.
Many years ago, a mate had a No4 in 303/22 which with the Super ammunition chronographed right on hot 223Rem velocities with a 50gr pill. That ammunition would have been made with SMLE's in mind, so there may be a bit more to be gained in the stronger action. My 303/25 on a P14 will run with a 257Roberts +P if given its head.
Sprinter in Sth Australia can cut you any 303 wildct you like including improved versions and supply the barrel, as his father was one of the ones doing the original wildcats. I've discussed the 303/35 with him and he confirmed he can cut 'standard' and 'improved' versions with the reamers he has on hand. Given that your 'handy' just keep in mind that Lee dies can be bored out relatively easily, my 303/35 dies will be honed out Lee RGB 303British dies.
A few other rimmed cases that may be of use ... 30/40Krag and 7.62x54R. Both should be able to be made to feed through a No4 with little trouble. I necked the 7.62x54R up to 35cal and its case capacity is greater than a 358Win and closer to a 35Whelen which is a pretty handy place to be!
Cheers...
Con

Thanks for that Con.
The penny has just dropped! The slightly shorter version 303/25 would be a logical one to commercialize as it will fit all 303-25 wildcat chambers!

My suspician with the 22/303's is that they will not perform much better than a 223 because these 'overbore' calibers need a bit of pressure to get their full potential.

I will look up Sprinter - thanks!

(In the meantime, I have mounted the scope rails - would you believe alloy bicycle cranks make excellent scope rails? - so I will concentrate on seeing what I can get out of the two groove 303 barrel. Just for fun, I plan to try 308 bullets, cast bullets of my own design - therefore customized to suite the throat - and maybe, just maybe, 8mm bullets - if they will enter the throat. I little swaging may be necessary but... I might have to lap the bore but is otherwise pretty good).

I don't know if I am being responsible calling this to your attention, but what the heck...

The "belted magnum" case is the same "rim" diameter as the .303 case. "Rim" but not "body diameter. Opening up P14s to take the .300 H&H case was "no sweat." I think this was the test bed for Mr. Weatherby, more the M17s, but almost the same gun...

Now the SMLE is not up to the length of those cases full length or the pressures of these hotrods, but I have no idea what your case availability is and this might be another avenue. I hate to think of the magazine work to get, say, a 6.5 Remington Magnum case to feed, but it is your project. luck.

I was looking at those belted magnum cases! Not a bad idea at all. And since I would be the only one loading for it, I would be in controll of the pressure levels. The case base area is bigger so that would require reducing pressure proportionately to compensate. I'm not sure how one would know. But, the case walls of those belted cases is thicker than than the 303 case so that would reduce the base area a bit. The same applies to the 6.5 Swede case. But if someone else got hold of this creation, they might be tempted to load to belted magnum pressure and break something! Mmmmm........