Charge weight vs. bullet type

[LRH]

I would like to reload two different 125 gr 30 caliber bullets for use in a variety of 308 rifles, one bullet a Sierra Match King in 125 gr (product 2121) and the other a Nosler Ballistic Tip 125 gr (product 30125).

Here is my situation: Nosler advertises in the enclosed load card with the Ballistic Tips that 47.5 grains of 748, what Nosler says is the accuracy powder for that particular bullet, Nosler says that 47.5 grains is the opening load on their load card, though I don't know if that is the lowest charge weight.

When I examine The Sierra Loading manual (I don't have Nosler's), they list the opening load for 748 and a 125 grain soft point at 42.8 grains in 308 caliber.

Can I load both bullets at 42.8 grains if I would like a lighter recoiling cartridge?

 

[Ned Ludd]

FWIW - the Speer reloading manual lists 46.0 to 50.0 gr of 748 as the charge window for 125 gr flat base bullets, with the 50.0 gr listed as being a compressed load. The Berger manual lists 45.5 to 50.6 gr of 748 for a 125 gr flat base bullet. The Hodgdon Reloading Center webpage lists 52.0 gr of 748 as a max load, but provide no data at all for a minimum/starting load (i.e. "null"). The predicted velocities for the Speer 46.0 gr starting load is 2726 fps, and the Berger starting load of 45.5 gr lists 2911 fps as the predicted velocity (24" test barrel). You can see immediately that there is quite a difference in the velocities predicted by the two different manuals. The real question is whether 42.8 gr would behave as too low a charge weight, with the brass issues that can sometimes accompany excessively low charge weights/pressures? This may be one you simply have to test yourself, watching carefully for dented/pushed-in shoulders, etc., in the brass.

Given the starting charge weight velocities listed in the two manuals, I'm not sure 42.8 gr of 748 will be a sufficient charge weight for a 125 gr bullet, with a very crude estimate being in the 2500-2700 fps range based on the two starting load values in the manuals. Nonetheless, testing charge weights between 42.8 gr and the starting values listed among the various other reloading manuals (around 45.5 - 46.0 gr) shouldn't be too difficult. I rather doubt you're going to notice a major difference in recoil with such a light bullet and only 2 to 3 gr more powder, but again, it's not too difficult to test for yourself to answer the question unambiguously.

The two different 125 gr bullets typically wouldn't be expected to provide markedly different results in terms of pressure/velocity, but stranger things have happened. Because you're interested in starting charge weight [low] end of the test range to minimize recoil, you should be safe in terms of loading up the two bullets for comparison. How velocities with the two different bullets might compare with the exact same charge weight will provide a starting point for load development (i.e. the velocities are very close to one another, or differ by some measurable amount). With that information in hand, it shouldn't be to difficult to tune the two bullets in at the same time.

 

[LRH]

FWIW - the Speer reloading manual lists 46.0 to 50.0 gr of 748 as the charge window for 125 gr flat base bullets, with the 50.0 gr listed as being a compressed load. The Berger manual lists 45.5 to 50.6 gr of 748 for a 125 gr flat base bullet. The Hodgdon Reloading Center webpage lists 52.0 gr of 748 as a max load, but provide no data at all for a minimum/starting load (i.e. "null"). The predicted velocities for the Speer 46.0 gr starting load is 2726 fps, and the Berger starting load of 45.5 gr lists 2911 fps as the predicted velocity (24" test barrel). You can see immediately that there is quite a difference in the velocities predicted by the two different manuals. The real question is whether 42.8 gr would behave as too low a charge weight, with the brass issues that can sometimes accompany excessively low charge weights/pressures? This may be one you simply have to test yourself, watching carefully for dented/pushed-in shoulders, etc., in the brass.

I in fact contacted Nosler by email Thursday night but have not heard back from them on that very question and did see that Hodgdon lists "null" as the opening charge weight. Thank you for the other data from the Speer manual and Berger's manual.

 

[358WCF]

Nosler #9 lists 47.5 to 51.5 with W748 in Nosler brass. Sierra used Winchester brass. The internal capacties of different makes of brass can have profound contrasts in pressure.

 

[3Sigma]

https://www.nosler.com/308-winchester

 

[Nick Caprinolo]

Each bullet manufacture develops a load for their brand of bullet. Bullets are made in different shapes and require a specific formula for accuracy. Look at the Hornady loading manual. In many cases, they list different loading data for several bullets of the same weight.

 

[RegionRat]

The CMP games use the old wooden guns at 200 yards. Downloading with light 30 caliber bullets in those 30-06 guns is popular for getting the recoil down for better performance in rapid stages.

The use of H4895 and IMR4895 in downloading works well for those 125 weight bullets in the 30-06 and is probably worth a look in 308 for the same reason.

With certain powders, you can start lower then typical yet still work up, and H4895 tends to be one of the better ones at this.

ETA: Trail Boss link added.

https://hodgdon.com/wp-content/uploads/2016/11/h4895-reduced-rifle-loads.pdf

https://hodgdon.com/wp-content/uploads/2018/12/trail-boss-reduced-loads-2018.pdf

 

[LRH]

I was just able to get through to both Sierra and Nosler. Sierra says you can load the 2121 or SMK 125 grain flat base down to the same level as the soft point at 42.8 grains of 748 while Nosler said since they've only tested the charge weight at 47.5 on the 125 grain Ballistic Tip (30125) that is all they could recommend. I think the exact quote is "not unless you have data that says otherwise."

Now my other question was then is the load date for Sierra Match Kings 155 grain similar to Lapua Scenar 155's using American made powders such as IMR and Winchester powdesr. Lapua load data, to my knowledge lists primarily Vihtavouri powders.

The tech at Sierra suggested they would be similar and the load ranges would be as well. If anyone knows any load data on the 155 Scenars using any of the following powders, IMR 3031, IMR 4064, Varget, or Winchester 748, that would be handy.

 

[LRH]

Here is what Capstone, Lapua's US servicing agent sent to me. They suggest that Lapua Scenars and Berger VLD and hybrid bullets can utilize similar charge weights and ranges.