30-06/ 30-06 ackley / 30 Gibbs

[fps plus]

Project of testing these cartridges on the same barrel is well on its way. Have some data for the 30-06 and have now got that barrel reamed to 30-06 ackley

Test rifle is a Ruger M-77 factory with 22 inch barrel

[Coiloil37]

I was just thinking about this project today. It’s been a few months since you first brought it up so I’m glad you’ve got some testing done and are moving ahead with it.

Let’s see some data...

[Pioneer2]

As a G+A issue a couple years back..........they tested all three.

[260 Rem]

Looking forward seeing the differences.

[sikwhiskey]

Po akleys books are cheaper lol.

[Pioneer2]

With a 24" barrel but use what you have available.Unlikely Ackley used a chronograph as a lot of his data was rather optimistic and or warm.

[fps plus]

This will be using the same barrel for the comparison

[Pathfinder76]

How will chamber pressure be determined?

[bat119]

Originally Posted by Pioneer2

With a 24" barrel but use what you have available.Unlikely Ackley used a chronograph as a lot of his data was rather optimistic and or warm.

Ackley used a pendulum chronograph as described in his book, not sure how accurate it was the formula used was way beyond my math skills.

Ackley's pendulum used pendulum arms of exactly 66.25 inches (168.3 cm) in length, from bearing surface to bearing surface, and used turnbuckles located in the middle of the arms to provide a means of setting the arm length precisely. Ackley recommends masses for the body of the pendulum for various calibers as well; 50 pounds (22.7 kg) for rimfire up through the .22 Hornet, 90 pounds (40.9 kg) for .222 Remington through .35 Whelen, and 150 pounds (68.2 kg) for magnum rifle calibers. The pendulum is made of heavy metal pipe, welded shut at one end, and packed with paper and sand to stop the bullet. The open end of the pendulum was covered in a sheet of rubber, to allow the bullet to enter and prevent material from leaking out.[9]
To use the pendulum, it is set up with a device to measure the horizontal distance of the pendulum swing, such as a light rod that would be pushed backwards by the rear of the pendulum as it moved. The shooter is seated at least 15 feet (5 m) back from the pendulum (reducing the effects of muzzle blast on the pendulum) and a bullet is fired into the pendulum. To calculate the velocity of the bullet given the horizontal swing, the following formula is used:[9]
V = M p M b 0.2018 D {\displaystyle V={\frac {Mp}{Mb}}0.2018D}
where:
V {\displaystyle V}
is the velocity of the bullet, in feet per second
M p {\displaystyle Mp}
is the mass of the pendulum, in grains
M b {\displaystyle Mb}
is the mass of the bullet, in grains
D {\displaystyle D}
is the horizontal travel of the pendulum, in inches
For more accurate calculations, a number of changes are made, both to the construction and the use of the pendulum. The construction changes involve the addition of a small box on top of the pendulum. Before weighing the pendulum, the box is filled with a number of bullets of the type being measured. For each shot made, a bullet can be removed from the box, thus keeping the mass of the pendulum constant. The measurement change involves measuring the period of the pendulum. The pendulum is swung, and the number of complete oscillations is measured over a long period of time, five to ten minutes. The time is divided by the number of oscillations to obtain the period. Once this is done, the formula
C = p i T 12 {\displaystyle C={\frac {pi}{T12}}}
generates a more precise constant to replace the value 0.2018 in the above equation. Just like above, the velocity of the bullet is calculated using the formula:[9]
V = M p M b C D {\displaystyle V={\frac {Mp}{Mb}}CD}

https://en.wikipedia.org/wiki/Ballistic_pendulum

[ROA]

Nosler manual has pressure tested data for the 30-06 Ai. A quick call to them would tell you what pressure they took it to compared to the regular 30-06 data. There are no secrets here any more but it could be a fun project.

[fps plus]

Originally Posted by chuck

How will chamber pressure be determined?

Unfortunately I don't have pressure testing equipment . For the ackley Nosler has some data. The Gibbs I will have to measure the web of the cartridge as well as primer indicators.

Yes I know it's not a perfect scientific experiment but it's my ball and I get to play by my rules haha.

[fps plus]

Already some interesting results firing std 30-06 in Ackley improved chamber

[260 Rem]

How much more powder does the Improved chamber take?

[fps plus]

I'm guessing approx 5% more capacity in the ackley

[fps plus]

Getting closer
Have results for 30-06 and 30-06 ackley in process of reaming to 30 gibbs

[bat119]

The 30 Gibbs should be an impressive difference I went through a Gibb phase 30 years ago and was very pleased with the results.

[fps plus]

It will be interesting to see the results of the Gibbs.

[eric2381]

My 30 Gibbs shoots 155gr SMK at 3400fps with zero issues. 26” 1:14” twist rate

[fps plus]

Originally Posted by eric2381

My 30 Gibbs shoots 155gr SMK at 3400fps with zero issues. 26” 1:14” twist rate

Wow that's smokn

[eric2381]

I have a 270 Gibbs, 30 Gibbs, and 338 Gibbs. Bought the 30 Gibbs used as a cheap experiment, and it shoots amazing.

[bat119]

I had an 8 Gibbs 200 gr, partitions @2850 fps my buddy has a 25 Gibbs firing 100 grs @ 3500 fps, 75 grs, at 3900 fps The Gibbs conversion is a winner.

[Don_Parsons]

The fellow on the USA army forum is pretty much matched with the 300 Winchester Magnum.

180gr @ 2987 ft-per seconds,,, RL-22 if I recall. Still a bit shy.

I got my long throated 06 to this mark, but it was to much powder crush, so I backed it down to 2780 with the Hornady 178gr ELD-X for game Harvesting.

It's sitting at 2700 ft-per seconds flat for the target season now.

Just closing in on the 5000 round count.

Don

[Pathfinder76]

Can someone explain to me the physics behind these results?

[rembo]

Hang on guys.....I was poking around in my tooling stash today and came across the answer to this thread. Sorry I didn't find this earlier. I could have saved you guys a lot of typing time.

[bat119]

Originally Posted by rembo

Hang on guys.....I was poking around in my tooling stash today and came across the answer to this thread. Sorry I didn't find this earlier. I could have saved you guys a lot of typing time.

I can buy one of those at Canadian Tire where's the fun in that?

[fps plus]

Originally Posted by chuck

Can someone explain to me the physics behind these results?

Some of it is pushing the pressure threshold .Some is the less taper on the improved creates less bolt thrust and sticky bolt lift is a less prevalent pressure sign .Some may be due to how powder burns in a sharp shoulder but that's pure speculation on my part . I would guess the guys with extreme high velocities are pushing pressure thresholds ,maybe fast barrel? Possibly 2-3 reloads before primer pockets are unusable anymore ? Maybe those guys could let us know how many times they can use a brass. I had a previous Ruger 30-06 Ackley 22in bbl that would achieve 2950 fps with 180 but on the 3rd loading the pockets were getting loose..

Some times guys get fast barrels and sometimes slow barrels ,nobody likes to talk about their slow barrels .

Any ways I have a bit of info compiled and need to complete the Gibbs chamber to compare.

[bat119]

As I remember my 8 Gibbs was not hard on brass, I formed them from 35 Whelan first down to .338 than to .323 forming a good shoulder for a fire forming load, after trimming I outside neck turned the brass.
I started with 98 a Mauser commercial action 24" barrel in 8x57 I originally wanted to rechamber to 8-06 my gunsmith suggested the Gibbs.

https://www.loaddata.com/Cartridge/8...ding-Data/2711

I used 150 gr. on deer around 3200 fps and 200 partition @ 2850 on moose. The Gibbs was one of the few cartridges I could substitute a cheaper 200 gr. Speer with the same velocity and POI.

[Beeman3]

The Sherman design is similar to the Gibbs, but has a longer neck. My 6.5 Sherman drives a 140 Berger out of a 28" Hart at 3339 fps. Very impressive for a 270 parent cartridge. Rich now has The Sherman line from 6.5 all the way up to 338 caliber.

[fps plus]

The ackley is now a Gibbs. I will have to form some brass now. Think I will load trailboss with bullet jammed into the land s

[fps plus]

Brass is formed . Used 180 bullets seated into lands with trail Boss powder , All formed with no spitting ,I'm becoming a fan of Trail Boss powder