[jsmyers]

I loaded up 10 rounds last night. I'll report back after I get to the range.

I just noticed something even odder:

The 11 ed Hornady manual lists more power (H380) for a 174 grain than for a 150 grain...and not by a small amount (2+ grains). Color me skeptical that the 150 grain load is actually a max.

 

[Darkker]

Given the essentially obsolete cartridge, I wouldn't be terribly surprised if some of the data is simply an old re-print.
You can email/call and ask for last tested dates of the various loads.

Cheers

 

[jsmyers]

Given the essentially obsolete cartridge, I wouldn't be terribly surprised if some of the data is simply an old re-print.
You can email/call and ask for last tested dates of the various loads.

Before I saw your reply, I'd called them. The response was to point out that the 150 grain has a larger bearing surface than either of the 174 grain bullets. I notice that many but not all of the listed loads are heavier for their 174 grain bullets than the 150 grain.

I didn't think to ask for test dates.

 

[unclenick]

If it's the bearing surface, why is their 150-grain load of IMR4350 2.2 grains heavier than their 174-grain bullet load of that same powder? Both loads claim 2600 fps, and there's just no way to get the 174 to the same velocity as a 150 at the same pressure. Also, with 47 grains of H380, Hodgdon only got a 150-grain bullet to 2461 fps, and that was with a 1/2" longer barrel than Hornady's. It could still be explained by gun differences. Neither were the tight chambered pressure and velocity test barrels. But it makes me suspicious of the tests done by Hornady. It's very hard to explain. Dates might help, as there was a time when powder burn rate control was poor compared to now.

I don't know which bullet weight you are loading, so I can't offer a procedure with any detail. I would suggest you have a chronograph with you and start with Hodgdon's starting loads and watch for extreme velocity mismatch and not try to exceed Hodgdon's velocities.

 

[jsmyers]

I don't know which bullet weight you are loading, so I can't offer a procedure with any detail. I would suggest you have a chronograph with you and start with Hodgdon's starting loads and watch for extreme velocity mismatch and not try to exceed Hodgdon's velocities.

Right now, I'm loading 150 speers. I have some loaded up at 43-43.4 grains (below the Hodgdon minimum load--a few each at 3 steps). I haven't gotten to the range. I might bump that up a bit depending on my results.

A few years ago I bought 2 boxes of a low-power load by XCaliber Ammunition (site now redirects to Premium Rifle & Handgun Ammo - Steinel Ammuntion Co. (XCaliber)). My goal is to duplicate this load. These are loaded with a 150 speer and were advertised as achieving ~2310 fps. The point of impact within 100 yards has closely matched some norma 180 grain soft points I have.

I also have some 180 grains from Hawk Bullets: The World's Premier Custom Bullet Manufacturer | Hawk Incorporated that I intend to load for hunting, but I haven't started on that project yet. When I do, I'll need to push closer to the pressure limits.

If I believe Hodgdon's data and believe the Hawk bullet is like a 180 grain seirra, then the H380 max is 45 grains and a 26" barrel will result in ~2257 fps.
If I believe Hornady's data (11 ed) and believe the Hawk bullet is like a 174 gr hornady interlock, then the H380 max is 46.9 grains and a 25.5" barrel will result in ~2600 fps.

🤷‍♂️

The Hornady data lists a lot of powders that will achieve that velocity range with a 174 grain.

 

[MikeG]

I think, at this point, there's enough confusion around some of the published data that you'd be best served working up your loads with a chronograph, if you have a certain velocity goal. I really doubt anyone has gone to the trouble of testing with anything but CUP for such an old/uncommon cartridge, and some of your data might go back decades (as was already pointed out).

So starting from scratch, basically. Best of luck......

 

[unclenick]

CAUTION: This post discusses experimental load suggestions that either are not published anywhere or have not been properly tested for safety and may exceed published pressure maximums for the cartridge(s) mentioned. Neither the writer, The Shooter's Forum, nor the staff of The Shooter's Forum assumes any liability for damage or injury resulting from using this information. DO NOT ATTEMPT TO DUPLICATE THE DESCRIBED LOADS without first working them up while watching for pressure signs. If you don't know how to do that, don't try.

I would add that because the rifle design itself is known to be exceptionally strong, there really is no reason other than weak brass to suppose it wouldn't handle loads in the 60,000-67,000 psi range just fine, as other bolt gun designs routinely do. Assuming that is the case, pressure signs, which have very poor accuracy for making pressure estimates, do just fine in telling how your brass is holding up. For a close measurement of absolute pressures, you would need to invest in a Pressure Trace.

A workaround, if you have a good chronograph, is to load the Hodgdon starting load and see how your rifle's velocity compares to it after compensating for any difference in barrel length. If your velocity is higher, your pressure is higher, and you should reduce the load. If your velocity is lower, your pressure is lower, and you can increase the load. These things are not directly proportional because, as you increase powder charge, the peak pressure goes up faster than the muzzle pressure does, preventing velocity alone from being a measure of peak pressure. But, as long as you need an increased charge weight (higher than theirs) to match their velocity, your peak pressure will not exceed theirs. This is because the larger gas quantity made by the larger charge mass raises muzzle pressure. That would mean a larger percentage of the bullet speed gain is occurring after the peak pressure is falling than was the case for Hodgdon. They got less acceleration near the muzzle, so more of their bullet's velocity was provided by their peak pressure being higher.

 

[Carpe Diem]

While the Type 99 design is one if the strongest of all military rifles, individual rifle quality can depend on the date of manufacture. Late-war rifles were not of the quality of earlier production (I’m not talking about the cast iron parade rifles), so some knowledge of the individual rifle’s history is a good-to-know. Nine different armories built Type 99s, so there were inevitable build variations. Bore dimensions also varied widely, from .310” to .317”. These are reasons for the low-pressure loading data.

Chances are that the OP’s rifle is plenty strong, but has he checked the headspace? Done a chamber cast? Slugged the bore? Run a bore scope through it?



.

 

[unclenick]

More information never hurts but can prevent someone from getting hurt, so I'm all for that.

 

[jsmyers]

While the Type 99 design is one if the strongest of all military rifles, individual rifle quality can depend on the date of manufacture. Late-war rifles were not of the quality of earlier production (I’m not talking about the cast iron parade rifles), so some knowledge of the individual rifle’s history is a good-to-know. Nine different armories built Type 99s, so there were inevitable build variations. Bore dimensions also varied widely, from .310” to .317”. These are reasons for the low-pressure loading data.

Chances are that the OP’s rifle is plenty strong, but has he checked the headspace? Done a chamber cast? Slugged the bore? Run a bore scope through it?

Not yet on the bore slugging. The chamber is pretty generous in dimensions based on the size of fired brass. I haven't checked headspace. I suspect my grandfather had. It was one of his favorite projects until he gave it to me around 2002. I believe Tom gave it to him immediately after the war.

I believe it is a pretty early model. I often wonder about the action it saw.