How much velocity gain in the Ackley version? how much different is the 300WBY? One last question...Can one safely fire 300H&H in a WBY chamber. I should know these answers but my memory fails me. Sorry.

Andy

300 Wby has a .37" long parallel freebore of .3085" diaemter.

The last time of I saw 300 H&H brass being fireformed was several years ago, Winchester brass and was used to make 7mm STW. It had a very high split rate through the shoulder. Had been fired in a 300 Wby chamber the same splits would have occurred.

An 300H&HAI would be close to the 300Wby. Unless you built it with a long freebore you wouldn't be able to reach Wby claimed velocity.

You can fire a h&h case in the wby chamber it will headspace on the belt. However you are going to stretch the shoulder a bunch. Splits would be common and necks would be short. I would look to a different starting brass.

UPDATE I should have looked at my dimensions closer. As F. Guffey stated the H&H case is listed as being .025" longer. Depending on how tight your chamber dimensions are you might have an issue as he stated. In my opinion the bullet would release but pressure might have a huge spike.

It would be a mindless mistake to chamber a 300 H&H into a 300 Weatherby and pull the trigger, the recommended case for forming 300 H&H is 375 H&H because both cases are the same length, that would be .025 longer than the 300 Weatherby case. Chambering a 300 H&H in a 300 Weatherby would not allow the bullet to be released, the person chambering the H&H in the Weatherby should suspect something is going wrong when the bolt closes with extra effort.

When necking a case down the neck gets longer, when necking up a case to form a second shoulder the case gets shorter, when fired the case 'should' fill the the chamber, the case gets shorter when the case fills the chamber, when forming 35 Whelen and 30 Gibbs from 30/06 cases the case shortens as much as .040 thousands, Meaning the neck pulls back when the shoulder and case body if formed when it fills the chamber.

As indicated, expect splits! If the cases are not new. Expect splits if the cases are to be necked up and are nickle plated. Expect splits if the cases have been fired multiple times, in the perfect world of forming new cases are used..

When forming 7 mm STW it is recommended 8 MM Remington Mag cases be used.

1 800 533 5000 RCBS Special Order Catalog for information when locating case forming dies and special order dies,

26665 part # for forming 7 mm Shooting time west from 8mm Rem Mag

I say NO! do not fire a 300 H&H in a 300 Weatherby, I am sure there are those thet claim it is done all the time, I take the time to research first, I start with the special order catalog from RCBS, a group 'A' die is $40.00, a group 'G' die is in the $90.00 range.

F. Guffey

One point not being covered.

If a .300 H&H is being rechambered to the Weatherby version, then the case length worry are not of a concern in fireforming.

Over the years I have fire formed a lot of them for rechambered Mod 70's. Splits were non existant. However, I tried it a couple of years ago to make some weatherby and 7 STW and splits were over 50% with current brass production. I had a lot of H&H and none of the other, so tried it, but what worked 30-50 years ago didn't work. I didn't try annealing the shoulder , that might help. Currently, it looks chaeper to just buy the right brass in this case no days.

Before this gets too out of hand let me state that I do not have a 300 mag of any flavor. I saw one for sale and was curious about the cases and forming processes and the potential velocity gain. I do have componants to build one and am strongly considering an H&H variety. I like the old warhorse just the way it is.

As far as fireforming go shoot a bunch of 300Savage rounds in a 308Win chamber. Totally safe. Leaves a neck just shy of .060!

please dont fireform 300 Savage in a 308. The savage brass is MUCH harder to find and more expensive.

drew, just bought that .300 HH AI over in the classified...my understanding is that it comes close to Weatherby data but not. Parker claimed the round to exceed the factory round by roughly 11% and ranks in his designs at the 7th spot out of 10 best Ackley rounds....optimistic? In any case it surpasses the standard round...some. Some state that it is difficult to get the velocities that Weatherby claims when they reload but is what some wildcatters want outside the standard loads. I reload and it won't bother me a hitch to roll some and fireform. I won't be shooting anything lighter than a 200 grainer so it will be all good. I tend to think I am going to like this caliber. Gonna do some load development soon as I get it in my hands. I won't be using Weatherby brass either...seems to be enough HH brass available.

Africanhunter, the 308 W has been chambered to 30/06, not a good choice, the 308 W chamber can not be cleaned up with the 30/06 reamer because of the larger diameter case, the shoulder is .011 thousands larger on the 308 W than the body of the 30/06 at the same juncture when measured from the head of the cases. Cases fired in the 30/06 chamber will have a ring around the case that is caused by the failure to remove all of the old chamber. A better choice for the 308 W is the 30/06 Ackley Improved or the 30 Gibbs.



The 7mm 57 has been chambered to 280 Remington, the 7mm 57 had/has a larger diameter chamber neck than the 280 R, fired cases when ejected from the 280 chamber will have two different neck diameters.



If someone is thinking about chambering the 300 H&H to A Weatherby some consideration should be given to the possibility the neck diameters may not be the same. Back in the old days holding the case to the rear was the big concern, head spacing was on the rim or belt, the responsibility of the case (ahead of the rim/belt) was to hold all the components together and seal the chamber. In the beginning the long tapper of the case was ideal for manufacturing cases, 303 British, 30/30 W, 375 H&H, 30/40 Krag and later the 300 H&H.

Gets out of hand? On the outside chance others get an ideal about chambering an existing chamber I believe there is no such thing as luck taking the place of planning and research. There is a long list of 'do not(s)' as in do not chamber a 308 W in a 30/06 chamber and then pull the trigger, it has been done and those that have were forgiven, the 308 W head spaces on the large diameter case, meaning the case should not be easy to chamber because part of the case is sized when chambers, when extracted the case will almost have the appearence of a straight wall case with the beginning of what looks like a shoulder.

Not everything mentioned is a mistake, but when finished some have to live with it, or take the time to do it correctly the second time.

F. Guffey

I have a set of RCBS Ackley imp 40% dies if anyone needs them.

I found that annealing the neck and shoulder area prior to fireforming just about totally eliminated case splits while fireforming .257 AI and .30 Gibbs cases.

I've personally fireformed lots of 300 H&H to WBY. Back then I had very few lost cases. Used new Win. brass. No big deal.

It is, however, much easier and cheaper to boot, to just FL size 8mm Rem Mag brass.

Rich

The 300 Mag AI is the 300 Win Mag improved. They both are 2.6" cases and and the Weatherby is a 2.8" case.

With my .300 hh Ai, I am doin some load development and thus far and it is early yet but with Speer 165's I am getting 3128fps avg. with IMR 7828 SSC. I was using the data from Speers .300 WM section of 79 grains...there low powder charge. This beats what Speer's section in the .300 Weatherby has with the same powder. I was not nor am interested in being a "hotrod" but suspect this caliber to be right along with Weatherbies. Looking foward to goin up to 180's then 200's. First I will "wring" out the lil' SPeer 165's for accuracies since I've enough of em and don't use them for anything.

The .300 Ackley is based on the 2.85" case, the same as the Roy. They are very close, so close SOME cartridges from SOME guns will fit in the other chamber. Both were wildcats, so the specs varied. The Roy was based on the .300 PMVF but got standardized when he started producing factory ammo. He had to give SOME number to Norma. The AI will do anything the Roy will, with allowances made for the freebore.
Ackley wanted to build a .30 cal mag to fit in a standard action, Springfield, Mauser, etc. At first, the 'smith had to turn a thread off the barrel before rechambering. The #2 version was longer, so the chamber would clean up. Of course, if you started with a new barrel, you took your pick. The shorter case was 2.5", The longer was 2.6, as was Mashburn's "Super."
Have fun,
Gene