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 240 Gibbs data
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jighead45
Average Member

USA
193 Posts

Posted - Feb 11 2007 :  11:47:53  Show Profile Send jighead45 a Private Message  Reply with Quote
Looking for data and source of cases for 240 Gibbs and any other general information you may have.

Thanks.

AC

Your reputation far exceeds your skill level.

ranger335v
Advanced Member

1633 Posts

Posted - Feb 12 2007 :  09:29:53  Show Profile Send ranger335v a Private Message  Reply with Quote
I no longer have any data and it can be hard to find, hopefully someone else can help you with that.

The case is a blown-out and neck shortened 30-06 so the volume is slightly larger than a .240 Weatherby. You could use the Weatherby data as a starting point and ease up as pressure conditions permit. As a wildcat, there are no SAMMI type spec.s for pressure or velocity.

The 240 Gibbs works best with slow powders, at least in the 4350/4831 or slower range, and with 100 to 105 gr. bullets.

Bullets lighter than 100 gr. won't allow the Gibbs to develop its best performance.

At the time of its introduction, many people hoped to use it as a really fast varmit cartridge with light bullets but the smaller .243/.244 cases are better for that. It never was a successful wildcat because most canister powders were too fast.

For cases, you will have to size down -06 brass and fireform them to properly fit your chamber. Be careful, get info if you're not experienced with fireforming and blowing shoulders out.

Loaded correctly, the .240 Gibbs is a truly flat-shooting cartridge.
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jighead45
Average Member

USA
193 Posts

Posted - Feb 12 2007 :  09:34:51  Show Profile Send jighead45 a Private Message  Reply with Quote
Thanks, that's a good place to start.

I have no experience with fireforming cases, so any suggestions are welcome.

AC

Your reputation far exceeds your skill level.
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skyline
Advanced Member

Canada
2807 Posts

Posted - Feb 12 2007 :  10:33:36  Show Profile Send skyline a Private Message  Reply with Quote
Might think about using .25-06 cases as it is less of a downsize. That is what is recommended in the manual of cartridge conversions.

************************
The gene pool could use a little chlorine.
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Jim1 AB
Senior Member



Canada
428 Posts

Posted - Feb 13 2007 :  15:34:15  Show Profile Send Jim1 AB a Private Message  Reply with Quote
I have a booklet here published by Wolf " Gibbs' Cartridges and Front Ignition Loading Technique".
Loading data from a 24" barrel 1 in 12 inch twist. CCI 250 primers and R-P cases.
Highest velocitys
75gr RL-22/63.0 3665ft/sec
85gr RL-22/61.0 3469ft/sec
105gr IMR-4831/57.0 3224ft/sec

Have fun, Had one of these made, 25 Gibbs, by Huntington and with out any aparent reason would have pressure spikes. To the tune of three times having to go to a gunsmith. My neighbor built a 270 and had no problems.

Jim
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skyline
Advanced Member

Canada
2807 Posts

Posted - Feb 13 2007 :  19:34:35  Show Profile Send skyline a Private Message  Reply with Quote
One of the most common methods used is:

Prime your cases with pistol primers to keep pressures reasonable. Do not use rifle primers.

Use a small charge of Bullseye or similarly fast burning pistol powder. The late George Nonte wrote, "Ten grains of Bullseye will do a good job of forming the .219 Zipper Improved cases. Sixteen grains of the same powder does an equally good job in blowing out standard .30-06 cases to size and shape for the .35 Whelen Improved ... start with a small charge of Bullseye that will fill about ten percent of the volume of the unformed case. Work up from this until a charge is reached that gives a cleanly formed case. Watch the primers closely for any signs of excessive pressures. It is entirely possible to develop a dangerous pressure with this type of load. Half grain increases are plenty until adequate expansion is achieved."

A charge of 10 % for a start load is frequently recommended and can be determined by completely filling an empty, unformed case with a spent primer in place with Bullseye powder. Pour out the powder onto a powder scale, weigh it and divide this weight by 10.

Take a quarter of a sheet of toilet paper, wad it up, and gently tamp it onto the powder. Then fill the case up to the mouth with a granular, non-abrasive filler, such as Cream of Wheat or cornmeal. (Don't use anything so fine that it can form a hard block, such as flour........make sure it is granular). To keep the filler from spilling out, press a small blob of bullet lubricant over the mouth of the case or a wax plug.


Make sure you go to an area where the discharge noise won't cause calls to 911. Even though this method is quite safe, you should obviously point it in a safe direction to fire the rounds when fireforming.

Check the first case you fire and determine if the starting load is too weak to fire-form the case all the way out against the chamber wall......and if it is load another case with a slightly larger powder charge - no more than 0.5 grain increase - and try it, but ONLY if the starter load gave no signs of dangerously high pressures."

Another method desribes the use of a cartridge trim die and a home made stricker to fire the cases in. This method is detailed in Donnelly's Handloaders Manual of Cartridge Conversions. This has the advantage of not requiring you to fire the fireforming loads in your rifle and sending that concoction down the bore.

This stuff will cause a mess and you should check your bore after each firing and run a rod down it every few rounds to keep anything from building up in the bore.


************************
The gene pool could use a little chlorine.
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POP
Junior Member



USA
63 Posts

Posted - Nov 19 2011 :  22:33:16  Show Profile Send POP a Private Message  Reply with Quote
http://archives.gunsandammo.com/content/240-gibbs

"We are what we repeatedly do. Excellence, then, is not an act, but a habit." - Aristotle

fotis416@yahoo.com
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eric2381
Advanced Member



Canada
2028 Posts

Posted - Nov 24 2011 :  17:24:10  Show Profile Send eric2381 a Private Message  Reply with Quote
I have a 30 Gibbs, and I love it. Well worth the small hassle of forming brass. I have a 338 Gibbs that I've been working on for years, and I'll be shooting it this coming summer. I have dies for 6.5 Gibbs, and can't wait to make a rifle in that chambering.

The 240 Gibbs looks like a real hotrod.

I've never saw a hearse with a luggage rack....
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