Home Forums Hunting & Shooting Ask The Gunwriters measuring facotry ammo expansion

It has been awhile, but I used to fire off three factory rounds and then measure the case with a micrometer. Then when I fired my hand loads I would see how much they expanded. That combined with chronograph velocities, load data and case life would eventually lead me to believe I had a safe load.

On case life I always figured loading the same round eight times and shooting it in the same rifle with out issues was good enough.

When the gun smith has my rifle done I will be loading for a .348 Ackley Improved with Winchester and Starline brass.

My question is, how can I measure case expansion on the .348 Improved? I never thought to fire a factory round off in the rifle before I took it in. Maybe I am stuck using load data and a chronograph. Crap.

That's probably the most accurate way to use CHE, but in my experience (which includes pressure-lab experience) it's far less useful than a chronograph for "estimating" safe pressures. Since affordable, accurate chronographs have been around for a while now, I haven't bothered measuring CHE for years.

CHE produces about a 50/50 mix of information and random noise. You can average down the noise by taking a very large sample, but most shooters aren't willing to expend ~150 rounds to extract a useful measurement.

A chronograph is a much better tool for estimating pressure.

Yep.

I played with CHE just enough to realize it was pretty worthless.

Personally, I look to see where the Chronograph, manuals and Quickload more or less line up.

Thanks for the info gents, much of my out of date pressure info was gleamed from books by Bob Hagel, makes me feel old. After all the years of putting ammo together I feel more ignorant then ever, but I must be erring on the side of caution, as I have long case life and no ruined guns.

I just wonder how accurate my pact Chrony is, maybe I need an Ohler 35P.

The editor of a magazine Bob Hagel worked for once told me that Hagel's handloaded ruined more than one rifle.

Agreed; I started reading Bob Hagel material in the '60s and have always thought he was one of the very best gunwriters, except for his load data. Some of those loads appeared to be way too warm, probably to the point of being dangerous in some guns.

I'll also agree that chronographing is likely the best method available to most handloaders for determining a safe load. However, with regard to measuring case head expansion, here's what I tried a number of years ago in working up data for a New Ultra Light Arms rifle chambered in 7x61 Sharpe & Hart, purely from a curiosity standpoint...

I had one box of Norma factory ammo, something not real easy to come by. I fired several rounds and measured CHE. I then broke down several of the factory cartridges and used my own load with my own primer in the new cases and measured CHE again, comparing the two measurements of the factory loaded brass and my own handload in the same factory brass. Granted, a few case head measurements don't really provide you with much in the way of usable information, but since it's all brass from the same box, the information obtained might be slightly more valid than comparing measurements from different brass brands or lots. Of course, lots more shooting would tell a lot more, but that wasn't possible. I'm not recommending this procedure and I'll stick to using chronograph numbers.

MD: Not a Dave Scovill fan but he is absolutely correct about Hagel's data. I used the .243 load data in GAME LOADS and PRACTICAL BALLISTICS" for a rear locking Remington 788. Bolt locked up so tight the soldered on bolt handle broke off. Despite Hagel's nuclear load data, I learned an awful lot about hunting, exterior ballistics, handguns, etc. from his books, articles and column in Wolfe publications. Your 4 to 1 rule and a chronograph is by far the best guidance for cartridges without pressure tested data. Do you know why so few powder manufacturers no longer provide pressure data with their reloading data? IMR is an example. I can see why an author does not provide it due to the cost of laboratory testing or strain gauge equipment but manufacturers with a ballistic lab sure have access.

I read Hagel's stuff and soon learned there is one handloading rule that should have been named the Hagel Rule - start 10% below listed max.

Sorry if this is off topic, but I have a question. Have worked up a load in a M70 FWT 257 Roberts. 120gr Speer Deep Curls and H4831sc. The load is very accurate ans shows none of the "typical" signs of excess pressure, but it is above max in the reloading manuals {and we all know that the Bob is notorious for being underloaded).

The velocity, measured several times on different dates is right at 2900fps. So since velocity is the best way to estimate pressures, can I assume that the pressure in this load is "acceptable". Thanks in advance...

SAAMI specs the 257 Roberts +P with 117 grain bullets at 2920 FPS, so I think you're probably OK, assuming your barrel is the same length as the one SAAMI uses.

There is one thing to watch when estimating pressure from MV: Sometimes, as you increase charge, MV will stop increasing. Just make sure that MV moves up fairly smoothly with increasing charge, so you know that hasn't happened with your load. As long as MV moves up smoothly, it is highly correlated with pressure and is a good indicator.

Excellent point!

Same here.

Ok. Seeking counsel from the brain trust,. Loaded some new-to-me 117gr SSTs in my 257 Bob M70 FWT. Using H4831sc, which I know is considered fairly slow for this cartridge. But it has worked well with 120s, so I thought I'd start with it.

Loaded 8 rounds, 1 each, starting with 43grains, ending with 50gr:

43gr-2656fps
44: no reading
45: 2750
46:2827
47: 2892
48: 2922
49: 2982
50: 3007

Looks to me like 48gr might be a reasonable place to max out. What are your thoughts? thanks

I would also consider the ES and SD with the velocity when evaluating the data.
YMMV
David

He only loaded one each.

CasualShooter,

Aside from what mathman pointed out, most handloaders do not fire enough rounds in a chroographing string to arrive at meaningful statistical data. Even if they fire 5-shot strings (most do 3-shot), that's worthless for meaningful standard deviation numbers.

But a lot of today's handloaders firmly believe in the SD numbers from 3-5 shot strings. Why? Because their chronograph provides them, and it sounds nifty.

ES is even more meaningless.

I have never been askeered of Hagel's loads as used common sense. Reduce and work up.

Hagel himself was apparently not quite as sensible. Again, I got that directly from one of his magazine editors, who said Hagel ruined several rifles.

One of the problems was that Hagel assumed chilling or heating ammo, then firing it in a 70-degree rifle, would result in the same pressures/velocities as testing with everything (including the rifle) at the same ambient temperature.