I would appreciate any advice you experts can offer on this puzzling question. I have a Winchester model 70 which has been rebarreled and chambered for the 338-06 Ackley Improved. It has a short throat. In fact, its throat is so short that I am forced to seat the bullet so that the cartridge overall length is a full 1/10" (0.100") shorter than the "standard" 3.340" OAL. (An OAL of 3.240" leaves the bullet just about 0.010" short of the lands.) However, with any given load this short OAL is no doubt generating higher peak pressure -- maybe MUCH higher pressure -- than in cartridges made with the standard 3.340" OAL. I can tell that pressures are in fact higher, just as one would expect, because the primers on fired rounds are always pretty flat several grains below the charge that the published data lists as maximum. (The published data almost always assumes a 3.340" OAL.) Naturally, this means that I should not assume that the maximum loads shown in the published data will necessarily be safe in my rifle. However, here is my problem: how can I tell what loads are safe in this rifle, when I am working up loads? I can't use the published data as a guide, because the published data was generated using a 3.340" OAL. I can watch carefully for the traditional pressure signs; but I am constantly reading that the traditional pressure signs are not reliable because it is difficult to interpret some of them (e.g., flattened primers), and because by the time the other ones appear you are already way above safe pressure levels. Many writers on the subject also say that measuring case head expansion is unreliable because it is not possible to measure case head expansion accurately enough in a repeatable fashion, and because some types of cases do not expand measurably until pressures are far above safe levels. Faced with these difficulties, most reloaders no doubt just fall back on the published data; but I do not have that option, because the published data does not apply to my rifle.

Do you have any ideas about what I should do, in order to know where I am while I am working up loads? (Other than have the rifle rechambered.)

You don't need a rechamber, just have your local gunsmith re-cut the throat a little deeper. They make a throating reamer just for this job.

I think Tailgunner's suggestion is a good one... just touch up the machine work so that you can use conventional data. If you don't want to do that:

Different bullets will allow different COL with the same rifle. I kinda "squinch" a fired case until a bullet will just roughly slide in and out. Then I put a dab of "crazy glue" inside the neck (NOT on the bullet!!), chamber the combination, and wait a minute. Using this method, I've found that in one rifle, I can make Speer loads .100" longer than Hornady. It's just the difference in the bullet shape. So you might pick up some operating room that way.

The smaller case capacity will tend to give you more pressure for the same amount of powder. So one way to look at it is that you can usually get practically the same MV for a little less powder. Use a chronograph to see if you're approaching max MV. If you're getting the "book" MV, or even 50-75 fps less, you're at max pressure.

Finally, you can buy a strain gauge system. They are about the same price as a mid-quality scope. I mount my gauges under the forestock, out of sight, so they do not disfigure the gun at all.

You're right about conventional pressure signs being unreliable. Based on some work Ackley did, I estimate that if you run your charge up until primers fall out, then back down a grain or two, you're probably running at about 74,000 to 76,000 PSI. I'm not nearly that brave.