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Starting over

04 Jun 2020
@ 12:25 pm (GMT)

Paul Leverman

Not really a problem, maybe. I've been working on a 30 cal and got it to where I was pretty happy. But, I ran out of bullets. I bought the same kind from the same manufacturer, same part number, same weight, etc. But the length is way different from the original. Not talking, one or two thou, or even five thou. What I consider a substantial difference of twenty thou. To me, this signals that the form factor may be significantly different from the original, which would change the BC, but not really concerned about that as this will be an intermediate long range load, say out to 500 yards. What I am more concerned about is how much this will change the harmonics/accuracy.

I have loaded three rounds so far, set to length by the ogive. This is where the discrepancy showed up. Even though the new loads are set to 8 -10 thou off the lands, the overall length is short by about 16 - 18 thou.

I even went as far as making a new "dummy" case to check my jam length. Sure enough, 19 - 20 thou short.

So what was supposed to be a final test/confirmation/sighting in day at the range, is now taking six rounds and seeing what happens. Frustrating to say the least.

Replies

07 Jun 2020
@ 05:32 am (GMT)

Paul Leverman

Re: Starting over
The difference is definitely in the length from the base of the bullet to the datum line on the ogive. Using the Sinclair comparator, the difference between the bullets is .020". Somewhere along the line, manufacturer decided to change the form. Weights are all the same between lots (as close as I could measure). Maybe it doesn't change anything accuracy or pressure wise. Guess I'll find out after the range.
08 Jun 2020
@ 09:14 am (GMT)

Paul Leverman

Re: Starting over
At the range today, and results were exactly what I anticipated. Not horrible, but not acceptable, either. I did, however, get two good starting groups that were next to each other in load charges, so it wasn't all that disappointing. It gives me a good reason (as if we need one) to do more shooting.

Totally unrelated to this, but many thanks to Nathan, as technique has definitely improved. To the point where I think I can safely say it's not me, it is the rifle. Proof positive that even old people can change for the better.
 

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