I am thinking of having a .240 Gibbs or something like that in .243 caliber made up has anyone out there also made something like that or has used one. It must be based on the 3006 case,(long action std action).Any info will be appreciated.
Happy Hunting
Posts: 182 | Location: Okotoks, Alberta | Registered: 23 September 2001
I've got one about half finished, I still need a stock for it, built on a Mauser action. When I get it done I'll post the results. I kind of fell into it when I came across the reloading dies cheap. Just out of curiosity, anyone else put rifles together because of a deal on dies or components? - Dan
Posts: 5285 | Location: Alberta | Registered: 05 October 2001
The .240 Gibbs is based on the 30/06 case (trim to length of 2.494), necked down to .243. The case is blown out to a minimal taper and the shoulder is pushed forward and to a 35 deg angle. The neck is quite short (approx .250).
With the .240 Gibbs you should be able to get 3600 fps with a 75 grain bullet, 3500 from an 85gr bullet and 3200 from a 105 grain bullet.
I have a 6.5 Gibbs and love it. If you have any other questions, feel free to e-mail me.
Another poster here (358Mark) has the whole line of Gibbs cartridges and I am sure he'd be more than happy to share load info.
Canuck
Posts: 7123 | Location: The Rock (southern V.I.) | Registered: 27 February 2001
Gonzolas, I have a 240 Gibbs that is built on a Mauser. Its a hot rod for sure. This rifle likes the 100 g bullets best and will throw them out at 3400 with HOT loads. Back it off to about 3300 and its just fine.
The thing that I noticed when developing loads for this case was that there is a very small thin line between loads that are just right and WHOA thats way too much. So when I start seeing the beginnings of the preasure signs I increase in 1/10 grain increments.
All the cases must be fireformed and I use 30-06 LC Match brass necked in increments till I get to 6mm leaving it long for a tight headspace. Using Unique and Cream of Wheat gives a good form.
My chamber has a neck diameter large enough that I can neck down that 30-06 to 6mm and use it as is with out neck turning. Call it a cheap semi-fitted neck. works.
Fun wildcat for sure. Ballistics like a bolt of lightning...... Ray
[This message has been edited by Jn316 (edited 12-27-2001).]
The 6mm-284 has the same case volume as a standard 30-06 case although the case design of the 6-284 is more efficient. Where the 240 Gibbs starts with a 06 case, blows it out to a minimum taper and relocates the shoulder (35 d) forward leaving about a 1 caliber neck length.
The loads and performance numbers that Rocky Gibbs published in his book and articles of the time are definately hot. I cannot duplicate those numbers without definate pressure signs. I read somewhere that Rocky measured his barrels from the start of rifling to crown. That would may account for his published loads being on the high side.
Gonzolas If you must have a hot 6mm I would suggest you try the 243 super rockchucker. (std 06 case with sharper shoulder). Case prep would be a lot easier than the Gibbs and I doubt there is any difference in ballistics. Another possibility is the 240 WBY. Cases are expensive but you can form them from 25-06 with a forming die. At least this is a factory round and you have a chance of selling it should you decide you no longer want it. What do you figure any of these will do that the 25-06 can't??
Thats as good a reason as any. I got my 6.5 Gibbs just for fun and to own something different, and I have learned a lot about case forming and reloading because of it. I think everyone should try something like it at least once.
Canuck
Posts: 7123 | Location: The Rock (southern V.I.) | Registered: 27 February 2001
Hey, I have some Gibbs rifles.If you build a .240 Gibbs.Use 25-06 brass to form your brass,it puts less stress on the necks.It is easier than going from30-06 to .240. 1geejay www.shooting-hunting.com
Canuck