30 Super Belted Rimless H&H, 02-05-15

Pmax = 3650 bar

Cartridge overall length = 3.60"

Case body length to beginning of shoulder = 2.100"

Case length including the shoulder = 2.475"

Overall case length = 2.85"

Thickness (length) of the belt = 0.2189"

Barrel bore/grooves = 7.61mm/7.82mm

300 H&H Magnum aka 300 H&H Belted Rimless N.E (sometimes improperly referred to as 30 Super Belted Rimless H&H), 11-05-25

Pmax = 4300 bar

Cartridge overall length = 3.60"

Case body length to beginning of shoulder = 2.105"

Case length including the shoulder = 2.479"

Overall case length = 2.85"

Thickness (length) of the belt = 0.2201"

Barrel bore/grooves = 7.62mm/7.82mm

Neither should be confused with the rimmed version:

30 Super Flanged H&H aka 300 FL. N.E., 11-05-25, Pmax = 3200 bar

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quote:

300 H&H Belted Rimless N.E (sometimes improperly referred to as 30 Super Belted Rimless H&H)

Generally regarded as one and the same cartridge or at least interchangeable in most chambers.

Early Kynoch ammo boxes were labelled 300 H&H (30 Super H&H) so I don't think there was anything "improper" about it and I'm sure most users of the 300 H&H Magnum in those days didn't care too much what it was called.

Still always good to recognise these historical facts.

I always viewed them as the same caliber, both of which weren't anything great until you handloaded them, then the 300 H&H will walk on water pass my 300 Win. and bite the heels of the 300 Wby..What a great caliber.

quote:

Originally posted by eagle27:

quote:

300 H&H Belted Rimless N.E (sometimes improperly referred to as 30 Super Belted Rimless H&H)

Generally regarded as one and the same cartridge or at least interchangeable in most chambers.

Early Kynoch ammo boxes were labelled 300 H&H (30 Super H&H) so I don't think there was anything "improper" about it and I'm sure most users of the 300 H&H Magnum in those days didn't care too much what it was called.

Still always good to recognise these historical facts.

I don't think the dimensional differences are significant unless you consider a head spacing difference of 0.0012" to be so, but I'm not a gunsmith.

What is significant is the difference in maximum operating pressure, 3650 bar vs 4300 bar, or about 53,000 psi vs 64,000 psi. The former approximates modern .30-06 performance and the latter modern .300 magnum performance. If Kynoch boxes were labeled "300 H&H (30 Super H&H)" surely they were loaded to the lower pressure level.

The biggest criticism the .300 H&H has suffered stems from ammunition loaded to original 30 Super Belted Rimless velocities. Thankfully, most major ammunition manufacturers have finally gotten it right. My favorite factory loads are the Federal 180 grain Trophy Bonded Tip and 180 grain Nosler Partition, both with a cataloged velocity of 2880 fps. Sadly, some ammunition manufacturers are still loading 180 grain bullets to 2700 fps or less.

One criticism of the belted magnums has always been the variation found in the belts and in most cases belted factory ammo is a sloppy (but safe) for in the chamber. The difference in belt dimensions between the 300 H&H and the 30 Super H&H is just the manufacturing tolerances.

As for the difference in maximum operating pressures, again just a manufacturing nuance. Same dimensioned belted cases and used in the same rifle, the difference in pressures was not going to mean anything in terms of action strength etc.

As Ray has pointed out, the 300 H&H was anemic anyway with early factory ammunition and could be handloaded right up with the best of the magnums.

The difference between the 30 Super and the 300 H&H lies in the historical development of the cartridge and CIP discerns between the two because of their mandate as a safety regulator.

CIP regulates Proof and therefore have to based on the pressure allowance as well a minimum and maximum dimensions for chamber and cartridge separate the two as separate entities.

If chambers are cut to the minimum allowed a 30 Super will chamber in a 300 H&H chamber and not the other way around. The most important factor is the max pressure allowance for the original vs the more modern 300 H&H.

Consideration should also be given to the fact that old British proofing was done with a copper crusher mounted against the base of the case and pressures measured in this manner are different to that of a measurement taken with the CIP method and different to pressure measured in the SAAMI method.

The loading of the 30 super had much to do with the fact that historically doubles have been consider only for very low pressure..However Jack Belk has a different opinion..Jack feels the double rifle is as strong as a bolt gun..Most of us have never attempted to blow one up. but I have seen single shot break open rifles in 270 and 30-06 that took hot handloads loaded for the owners bolt gun..???????

Ive always been curious and wanted to do that testing but doubles are too damned expensive to test..There is so much old wives tales on double rifles that just pure made up BS, such as 4831 blowing them up, monolithic bullets blowing them up, have to be shot front trigger then back trigger as that's how they were regulated and on and on!!

The pressure issues in break open guns have zero to do with them blowing up. What is an issue, much more so in times past with poorer powders and brass, is extraction. Early in the Nitro era the Brits noticed how cordite would have significantly higher pressures in the heat. Higher pressures lead to stuck cases. My own .30 super flanged is loaded to factory original velocity of 2650 fps with a 180 grain pill. The Farquharson action was a black powder design and is well known to stick cases. My gun pops open on the shot if run too hot and extraction is hard. The other issue with high pressure in doubles is the beating the locking system takes. Lower pressure rounds stay tight and on face. No mysteries here, just common sense really. If you want to hot rod things go with a bolt gun, they were designed to digest high pressure cartridges from the beginning and do so splendidly.
Steve

skb



The 30 Super flanged was apparently designed as a solution for H&H's 276 "problem"

SKB,
Would that apply to all break open single shots?

The only single shots Ive had any personal experience is a break open Savage that was originally a 30-30 but was Imp. at some point then later punched out to a 30/40 Krag and IMP...I shot it a few times with factory ammo as a 30-40, and the ejector was so strong Im quite sure it would pull a case in half were it stuck..The other was a Ruger no. 1 in a 300 H&H and there is no stronger action and not a break open..The other part of the post was just passing on info second hand. I realize that many SS, doubles, and even bolt guns of some makes are inferior..

The 300 Super was to be the follow up to H&H's failed 275.
The 275 was loaded to a pressure of 19 tonnes using 40gr of ? modite (MDT) giving 2700 fps on a 160 gr bullet.

Because of the sticking case problem Eley dipped the cartridge in wax.

There were apparently only 5 rifles built in this caliber on Holland's Patent single shot action and all shot "loose" over time. The same happened to doubles in this caliber.

The 300 super flanged was introduced as solution to the failed 275 in 1925 and no examples exist of this cartridge on a Holland's patent single shot. They did however use other actions.

The 300 Fl was loaded with modern smokeless. the pressure was dropped to 17.5 tonnes and it ran a 180 gr bullet @ 2700 fps.

Alf, so that's in the vicinity of 35,000 to 38,000 PSI, correct? Basically the 300 of yesteryear wasn't any more than a 30-06 or so Ive been told and at these pressure that seems to be the case..sticking cases at these pressures certainly give one the impression the guns of the day were very weak indeed, although some very distinguished experts claim otherwise.

Ray:
Yes but there is a important point that needs to be brought up in this.

The British tested their ammo using a copper crusher cage mounted against the base of the case, thus actually measuring bolt thrust.

this gives a different reading to when pressure is measured by conformal gauge mounted in the breech a inch from the base (SAAMI) and different from a gauge mounted in the breech with the gauge exposed to the gas in the case ie a hole drilled in the case as per the CIP system

The Frankford Arsenal actually tested the 275 H&H and they obtained a pressure of 50,000 plus psi. Sticking cases was a big issue


It is true that the 300 Super flanged is actually under gunned when compared to a 30-06

quote:

Originally posted by Atkinson:
SKB,
Would that apply to all break open single shots?

The only single shots Ive had any personal experience is a break open Savage that was originally a 30-30 but was Imp. at some point then later punched out to a 30/40 Krag and IMP...I shot it a few times with factory ammo as a 30-40, and the ejector was so strong Im quite sure it would pull a case in half were it stuck..The other was a Ruger no. 1 in a 300 H&H and there is no stronger action and not a break open..The other part of the post was just passing on info second hand. I realize that many SS, doubles, and even bolt guns of some makes are inferior..

It seems to apply to those that have spring loaded ejectors similar to double rifles such as the New England Handi-Rifle. I have one in .243 that will eject cases only from very mild loads, anything the least bit hot sticks and fails to extract and eject.

Well Alf, that makes since to me and I would have over looked that, duh!!

As to the H&H, that has the so called hated belt, therefore its hard on brass, but that's nothing more than ignorance on the shooter/reloaders part, but it certainly exist in that some folks resize case to the belts that are not all alike...

Whereas the knowledgable handloader uses the shoulder to resize 300 H&H and 375 H&H cases to fit the individuals personal gun, just like one should do with any non belted case. I do this by blackening the neck and shoulder with a match, then set the die to resize only a about fourth or less of the neck using the blackening as a guide, continue to resize the neck until the case goes into the chamber with only a very very light pressure to close the bolt, then I may take another quarter of a turn on my die..that ends the streatching of the case, and the 300 H&H belted brass lasts as long as any brass...I would tend to do likewise with a 30 Super, a 30-06 or any case..