Tolerance in Bullet Weight

This is the fourth of a five part series on tolerances in ammunition reloading.

In this part we look at bullet weight tolerance and, in particular, what is common practice among Bullseye shooters for this most critical item.

In this area, you may hear considerable discussion of what precision is needed. I will have to plead ignorance and inexperience. I’m learning — and that’s where I will be writing from, my ignorance flavored with a tiny amount of (recent) “learning experience.”

You may have read earlier blogs here on this topic. I will quickly summarize them before going on.

Specifically, I bought a cheap batch of bullets and, after reloading a couple of hundred, I discovered that they would not group any tighter than 10″ at 50 yards. After considerable head scratching, I discovered that the 200 grain bullets weighed out individually between 195 and 204 grains. And while that’s only a ±2.5% variation, as far as performance was concerned, that was way too much!

Checking weight variation in some high quality bullets (that group to 2″ at 50 yards), I found a variation of less than one grain. That’s less than 0.5% — and they flew to the target almost exactly the same way from each round.

Good bullets: 0.5% weight variation or, for the very best performance, to 0.05%. For more details on the “best” end of this range, I’ll refer you to Tony Brong, a much better Bullseye shooter than myself. His article, “Loading the .32 S&W Long” (click to read) is excellent on this issue (and many others).

Bad bullets: 2.5% variation. I know because that’s what I loaded, tested, and saw in the erratic results in the targets.

Some reloaders including Tony (see above) say they weigh even “the good stuff” into 0.1 grain groups and then reload and box those groups separately. That’s a tolerance of ±0.05%. Wow!

Right now I’m experimenting with a much broader range, 1.0 grain batches (tolerance is, therefore, ±0.5 grains), but the jury is still out.

Suffice to say, however, bullet weight is a very critical parameter, and is probably the single most important “tolerance” to monitor.

In the next and final part, we look at brass. And while it is true that the reloader of handgun ammunition does very little to modify it, there are some critical issues in what our guns will and won’t “tolerate”.


(Click here for part five.)

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