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358wcf it's a 03A3 Remington 4,000,xxx range no worry there. I thought before I started leaning on it I would use fireformed brass, newer commercial variety at that. Right now I'm just shooting it and fireforming some mil brass I have, but If I had a hunt tomorrow I sure would be confident with it for as far as one would care to shoot at a game animal with a K4 weaver.
3584elk, while I just retired the last 35 years I've worked in the geo technical and civil engineering fields. In engineering the first thing they teach you is the word "assume" means ASS U ME. So out of habit I never assume very many things. I certainly did not assume that you knew the things I mentioned or that you would be offended that I would courteously bring them up. So I will in the future not reply to any of your posts. MB


" Cheapest velocity in the world comes from a long barrel and I sure do like them. MB "
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I had an 8mm Gibbs built for Dad about 20 years ago, using his first ever deer rifle(98 Mauser) for a donor(needed a new barrel anyway). It's been a lot of fun, it's that rifle that got me started reloading.

That being said, I don't load it much past full house Euro 8x57 anymore. Some of the "published" loads for Gibbs rounds are blasted HOT!!!. The 30 Gibbs comfortably fills the gap between the 300 Win Mag and the 30/06. If you enjoy it for what it is, a neat retro oddity(probably a design ahead of it's time), go for it.


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I don't always shoot Mausers, but when I do...I prefer VZ-24s.

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Originally Posted by 358WCF
MedRiver, I think you're short changing yourself with a 22" barrel, but your results will be interesting.


Too short of a barrel is the story of my life wink

I like the feel and balance of 20-22” barrels for my all-purpose hunting rifles. I am not worried about maxing velocity of the case...more interested in real world improvement in the same barrel at a finished length that I want to pack around.

Dropped it with my ‘Smith today and rented a reamer. Could be shooting a Gibbs next week!

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Originally Posted by 358WCF
Greydog... Equal pressure & valid comparisons? SAAMI for 30-06 & 280 is 60K. It's 65K for the 280 Ackley & the 270. The sharper shoulder in itself does not make brass withstand higher pressures. Brass is brass & is still the weak link in the chain. If you can find a copy of Ackley's book you can read his test results for yourself, but you might read something you dont want to hear. Paraphrasing from memory he says that the improved case, upon firing, grips the chamber walls better than a tapered case, thus reducing the bolt thrust. If I remember right there are a few tests to destruction of various actions in both standard & improved cartridges. I think there was a lever action chambered to 30-30 Improved tested with no locking mechanism, but am too lazy too dig out the books this morning. The day's a wastin' & the grass needs cuttin'.

MedRiver, I think you're short changing yourself with a 22" barrel, but your results will be interesting.

Enjoy your Ackley Bob. Dont be afraid to push the envelope a bit with care & within reason. Hoping you got a high # 03. IMR 4350 was the powder when I did most of the development. The 4831s filled the case well before before pressuring out. RL 19 & 22 were showing promise with 150s & 180s respectively. The new (plastic) jug of IMR4350 I got doesn't develop anywhere near the same speeds as the old (metal) can. Very disappointing. With the newer powders, RL17 has given good results with 150s. The biggest gains were realized with 150s & 165s so far, but with the plethora of newer slow burners, who knows? I will be trying some RL23 soon with 150s & 165s & may try RL26 with 180s.


I have a copy of Ackley's book which I got as a Christmas gift 56 years ago, when I was fifteen. I am very familiar with his theory on reduced bolt thrust and believed it until I was 16. It was then that I separated a case with a hot load in my Lee Enfield. At this point my thought process was like this; if the case separated, the forward portion of the case must have been gripping the chamber wall sufficiently to remain in place while the base moved back. If this was the case, why would gripping the chamber wall even more tightly reduce bolt thrust? If the 303 british case (plenty-o-taper) could hold on tightly enough to not move back, what difference would the improved case make? At the time, I decided the difference might have been in Ackleys use of the 30/30 in his tests. Maybe 30/30 brass behaved differently.
It was a few years later that I started gunsmithing myself and was able to try testing some of these things on my own. I am convinced, practically speaking, case taper makes no difference in bolt thrust though it may have some effect within a very narrow range of pressure; with this depending on brass thickness and hardness. At high pressures, ALL cartridges grip the camber walls sufficiently well to allow the head of the case to blow off if not adequately supported. In addition, the amount of deflection of the bolt at a given pressure most certainly comes into play. A strong, front-locking, bolt action will deflect very little at 70,000 PSI. So little that brass stretch is largely meaningless. If the bolt face deflects by .001", the amount of pressure required to stretch the brass that much is insignificant.
If unsupported, brass can only do so much. Primer pockets expand at the same pressures regardless of shoulder angle or case taper. Rimmed cases which are fully enclosed in the chamber, as in most single shot designs, may be able to withstand higher pressures than rimless designs but I'm not convinced enough to say it is so. GD

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Originally Posted by colodog
I remember an article in Shooting Times where Rick Jamison (if I spelled his name correctly) shot his rifle and then re-chambered it to the next cartridge.
It showed that the velocity gain was modest from the 30-06 to the 30-06AI and then the 30Gibbs, When loaded to the same pressure!

I'm no expert, I just read the magazine several times as it had an article on 22-250 1-8 twist.




Just a question, does the Gibbs actually clean up the shoulder of an Ackley ?

The examples of Gibbs cartridges I’ve seen have diameters closer to the Standard .441”, just pushed forward some. I’ve also seen some which were actually botched Ackley rechamberings, with .455” shoulder diameter.
Created without being properly set back and then reamed forwards deeper,
to create an Ackley/Gibbs chamber. Usually involving similarily bubba’d dies


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A Roger Stowers drawing lists the shoulder at .455", so it should clean up an Ackley chamber.
I guess it all depends on the final chamber dimension, like the old saying...cut with a fresh reamer or a well worn reamer.

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Thanks for the info, I quickly googled to confirm that shoulder dimension.
Trust but Verify.

A 35 degree shoulder angle is pretty trendy. Maybe the short neck is the off putting part.
Surely it isn’t the case forming steps. 🥴


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I had one built on a Savage 110 back in the 90's. It was my first experience with a wildcat.

I'd have to look for my data on it but, but I seem to recall 3050 FPS with a 165 grain NBT and RL22 gave me good case life, this was out of a 22 inch barrel. I finally figured out it was easier to just get a 300 Win Mag.

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WHY?

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Got mine back from the gunsmith last week. Got some cases formed and some rounds loaded for velocity testing. The fireforming loads I made with 150 Hornady Spire points seems to shoot really well so I may take them antelope hunting this weekend. Did some with Bullseye and cornmeal last night also. I have good data from the original factory 22" barrel that I tested a couple weeks ago with the 165 Hdy BTSP, 180 NBT, and 200 NAB, all with RL 22. Planning to reshoot the same bullet in the same barrel (now with a Gibbs chamber) to see what I actually gained. I will post the results. I may start a new thread that goes through the whole process and testing.

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Originally Posted by Switch
WHY?


Is the question why a Gibbs?

I can't answer for others but for me it is simple...I found dies cheap, .30-06 guns and brass are everywhere (and cheap), I can probably approach .300 wsm velocities with four in the magazine, the chambering work is not crazy expensive, I like dinking around with this stuff.

No more, no less.

I already have an accurate .30-06 and .300 Win Mag so it really won't do anything for me that I couldn't do with the others but it has been a fun project and a little nostalgia makes hunt prep more enjoyable for me.

I think Patches O’houlihan summed it up best...

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