Quick Load for bullets heavier than 300 grain

[Siringo]

I have been revisiting using heavy bullets in the 450B. Specifically a resized Remington 405 grain 0.458 bullet. I do have a new barrel with a mid-length gas system and my original loads with Lil Gun do not work well with the mid-length system. This bullet/powder combination originally was used in a carbine length gas system. But in the new mid-length the port pressure is to low for reliable functioning. So I moved to slower powders that would boost the port pressure. Currently I am using 10X, as it was a powder I had on hand that fit the criteria.

Using QuickLoad, I settled on a few charge weights that would keep the chamber pressure for the combination between 30K and 36K psi.I shot them a few days ago and ended up with a charge of 36 grains that gave very good accuracy at 100 yards. In fact the accuracy of the new barrel (1/16 twist) versus original barrel (1/24 twist) is greatly improved. Original groups were in the neighborhood of 2 1/2 inches and the new barrel was 1 inch. Also, the mid-length gas system is much easier on the brass.

So getting to my problem, QuickLoad predicts the velocity at 1595 fps. Actual velocity is 1450 fps. Frankly, this is where I want to be with that bullet weight anyway. But it is apparent that after 300 grains in bullet weight, QuickLoad does not predict well. So if the velocity is off, what about the pressure? Any thoughts?

[Hoot]

With almost no regard to bullet weight, I've found that QL's achilles heel is predicting the powder's behavior. I'll give you an example. Using Win 296 with any reasonable bullet weight in my 450b uppers (both 1:24), QL over-predicts the velocity by as much as 300fps. Switch to Lil Gun and it comes within 20fps right out of the starting gate. It also over-predicts chamber pressure leading to those erroneous velocity predictions. I have yet to witness QL under-predict any 450b bullet/powder combination. I suspect the author is afraid that users won't work up like they're supposed to, so he builds it in whether they want it or not. QL is not a panacea for cold predicting performance except in some more mainstream rifle calibers with long track records already established. That's why I try to dedicate my first time out with a new recipe, to establishing a correction factor to take back to the program and apply for future workups. Using 1680, my experience has been that QL does well predicting the behavior of 300gr and beyond bullets.

I can definitely see where your 1:16 would do a better job with the heavyweights. That's to be expected. There are always going to be contradictions. My 1:24 did surprisingly well with .458 325gr FTX sized down to .452 over top of 1680. Go figure...

Here's a secret that was passed along to me from a reliable source. With the 450b's so-so neck tension, set your shot start pressure to zero for both, all lead and lead core, jacketed bullets. It'll get the result a lot closer to the predicted velocity. In the case of your 10X recipe, it would have predicted about 60fps lower velocity.

Hoot

[Siringo]

Hoot - Thanks for the tip. My old LG load was 27.5 grains and the velocity was 1450ish too. Applying the "0" initiation pressure brings the velocity to pretty much what the chrono said. Close enough anyway. Although the pressure is way off. Originally in the carbine barrel with the 1/24 twist I was bending case rims. Being the bullet is slower, the action was trying to open when the bullet was still in the barrel. Because of that, I had to change buffers, carrier weights, ect. That does not happen with the mid-length. I can run just a 3 oz carbine buffer.

Getting back to the issue, it seems that they program just doesn't take into consideration other powders outside the LG burn rate or the parameters for the cartridge are based on 250/300 grain bullets.

Thanks for the input!

[Siringo]

Another thought ----- using the "0" initiation shot pressure setting and changing the weighting factor to "5" puts the velocity were it should be. HUMMMMM!

[Hoot]

Another thought ----- using the "0" initiation shot pressure setting and changing the weighting factor to "5" puts the velocity were it should be. HUMMMMM!

Be mindful of what you tinker with. I only mess with the Ba (Burning Rate Factor) parameter to get my real word velocity to match the predicted one, regardless of caliber. The "Shot Start Pressure" of zero is a 450b thing. It may also apply to other straight wall calibers that headspace off the mouth, but I've never tried it other than with the 450b.

Hoot