help on 25 Gibbs

24 May 2004, 15:57

Deano

help on 25 Gibbs

I'm trying to push the envelope on a 25 gibbs, does anybody have any good hot loads. I know I'll have to start low and work up. It's a Rem.700, 30 inch fluted hart barrel.
Trying to get 3500 fps.
thanks,
Deano

25 May 2004, 04:29

growler

What weight of bullet? I have a 25 Gibbs with a 28" barrel and 100gr MKs go out at 3650 and 115 VLDs at 3450. I have found H4831 and RL22 to be the best for velocity. Work up from 60grs of either and 100gr bullets with 115gr start from 56grs.

25 May 2004, 15:52

Deano

thanks growler,
I was trying for a 120, but I don't think I can get it. 59 Grns. of n160 shows some pressure & gets 3425.I believe thats about tops for that bullet.
Deano

26 May 2004, 00:56

<eldeguello>

I agree! If you are getting over 3400 with a 120 grain bullet, I think you have gone about as far as you can go with current powders in the .25 Gibbs.

But 3400 is pretty good!

26 May 2004, 05:12

ramrod340

MY software says that 59 grs should be showing more than a little pressure.

26 May 2004, 15:24

Deano

Ramrod,
I am above what the books say in all my guns, I am very careful about working up my loads. I am shooting with a commercial reloader that has a cache of guns that alot of people only read about. I have been his test dummy for about a year now and have worked up some pretty wild loads.
Deano

30 May 2004, 04:16

<eldeguello>

Based upon their proven capabilities, the Gibbs cartridges deserve a lot more popularity than they enjoy. Rocky was accused of inflating his results, loading to dangerous pressures, and all sorts of other crap when he was alive. The truth is that he made a pressure gun, and knew that his loads were safe, and hjad his ammo chronograpohed at the Speer plant as he was developing his designs. Most of the charges made against him and his cartridges was pure B.S., a lot of which originated with competitors! Unfortunately, most of his detractors were a lot more vocal than Rocky, so the truth about his cartridges is hard to find these days. I think the most complete source of information about these rounds is contained in GIBBS' CARTRIDGES and Front Ignition Loading Technique put together by Roger Stowers and published by Wolfe Publishing Company in 1991. Stowers seems to have tested each Gibbs round from .240 up to .338, and gives loading data for each. Considering the relatively small powder charges Gibbs cartridges use, the results of Stowers' tests are pretty impressive.

30 May 2004, 04:30

ramrod340

One of the biggest issues was how Rocky measured his barrel. In my reference material he measured the barrel from the front of the bullet not the bolt face. So his barrels were 2.5-3" longer than what others were using. Giving an apples to oranges comparison. I have my own wildcat with basically the same volume as the Gibbs. Accounting for barrel length I find his claims right on. You can't get much more from an 06 case.

31 May 2004, 02:03

<eldeguello>

Quote:

One of the biggest issues was how Rocky measured his barrel. In my reference material he measured the barrel from the front of the bullet not the bolt face. So his barrels were 2.5-3" longer than what others were using. Giving an apples to oranges comparison. I have my own wildcat with basically the same volume as the Gibbs. Accounting for barrel length I find his claims right on. You can't get much more from an 06 case.

I don't recall ever having seen Rocky's personal claims, unless the data in the Ackley books is direct from Rocky (I have a paperback Ackley Handbook that has all Gibbs cartridge data in it, UNLIKE the two hardback volumes!!).

However, the Roger Stowers data was all obtained in McGowan '26" barrels'. I assume these were measured the standard way, from the face of the breechblock to the muzzle, but don't know this for sure either!!

31 May 2004, 04:10

ramrod340

Source data I have other than from Roger Stowers just references the barrel length.

In Roger's work he makes this comments: "To measure velocity for his cartridges Gibbs would load to 53,500 CUP (~63,800 psi) on his own equipemnt, then go to Speer and use their Potter chronograph. His avertised velocities are questioned to this day. Many believe the velocities Gibbs advertised are unattainable. Many of his velocities were corrected from instrumental to true muzzle velocity. This added a few FPS. He considered barrel length as the distance the bullet traveled down the bore, not the distance from the bolt face to the muzzle. That in effect added two more inches of barrel length and another 100 fps or so. Instead of taking the average velocity of 10 shots Gibbs recorded the highest speed achieved."

I have nothing where Gibbs stated these facts but, assume that Roger did his homework. Using my wildcat with basically the same capacity I can dupe Rogers velocities and by adding 2" I can calculate speeds published directly from Gibbs.

06 June 2004, 05:23

Atkinson

Use Gibbs original loads, he was about 20,000 PSI passed max....

07 June 2004, 13:02

Deano

Just got home from the range: I've got good news. I got 3592 fps. average with very little pressure. I worked up a load with N165 and it shoots great.
Thanks for all your help,
Deano

08 June 2004, 04:20

ramrod340

You might be only showing a little pressure. In my opinion if you are getting that velocity you have way to much pressure.

09 June 2004, 22:12

Eagleye

I own a 30 Gibbs with a 26ï¿½" barrel, and I find it to be a fairly efficient cartridge, giving good velocities without burning a huge amount of powder. A 180 Partition with 61.5 grains of Norma MRP [this is NOT a hot load!]yields over 2900 FPS. I also found my Gibbs to be very accurate, but of course, that may have little to do with the case design and more to do with quality barrels and smithing. Regards, Eagleye.