Hubris

[brewer12345]

I found a load my rifle liked with the classic rcbs 35 rem boolits. Recently I got a noe copy of the same mold. Same weight, lube, alloy, gas check and size, so I figured the same load would work. Apparently not as I found out at the range. Just a reminder, when you switch molds, work the load up again.

[sigep1764]

What went awry?

[brewer12345]

Poor accuracy. The rifle has a speed limit above which I go from small groups to a shotgun pattern. It is also possible that the load I developed at 40 degrees is above the limit at 70.

[725]

I had the same thing happen when I used one T/C type maxi-ball vs the original maxi-ball mold. Go figure.

[Smoke4320]

It is also possible that the load I developed at 40 degrees is above the limit at 70.

vey possible ..

[Char-Gar]

I would look to other factors, such as alloy diff, lube diff etc. etc.. Not likely a change to a mold of the same design would result in such dramatic difference.

[brewer12345]

I have no worries about pressure because I am was, way below max. I will back off on the charge to where accuracy first got good and try a couple loads this summer. If a cool weather load also works in the heat I will have a winner.

[JonB_in_Glencoe]

I suspect the issue could be that the RCBS boolit fits your Rifle's throat better than your NOE copy. You may or may not get the NOE to shoot as good as the RCBS in your rifle.

Boolit molds can have slight variance from mold to mold, even from the same manufacturer, let alone from one manufacturer to another. NOE does a great job when he copys a mold design, but sometimes those copies are altered during the initial group buy discussion (like widening or deepening a lube groove)...also there are tolerances built into drawings, one manufacturer may machine it toward one extreme, and the other could be toward the other...all within tolerances, but end up being different enough to not work the same in the same Rifle.

Here is a good thread on boolit throat fit.
http://castboolits.gunloads.com/showthread.php?44765-Throat-fit

[brewer12345]

You may be right, in which case I will go back to the rcbs. Want to try the backed off loads first.

[Black Jaque Janaviac]

I had something similar happen to me. I started with a Lee 358-158-RF in 2-cavity. I really liked how it did, and realized that it was difficult to cast enough to keep my '92 Rossi fed so I got a 6-cavity mold. I just went right to castin' and threw the new boolits in the same jar as the leftovers from the 2-cavity molds.

When I got to loading them I noticed the OALs were very different, and that box of ammo shot horribly. Once the old boolits were purged and sent down range, happiness was restored as accuracy came back. The flat point of the 2-cavity mold has a noticeably smaller meplat. This affects how the seating die engages the nose and is what causes the seating depth variation.