308 Nosler Ballistic Tip Change of Powder From H4895 - N140

[LesC]

Hi Folks, new to the forum so apologies if not the correct place to post.

As you all are aware Hodgson Powders are nigh on impossible to get, for longer than I can remember I have been using a Blaser Pro Success, 22" 1:11? Twist 308W Lapua Cases, Load was Nosler 150Gr Ballistic Tip Spitzer (P/N 30150) with H4895, 45.4 Gr, 2.800OAL, MV is in the region of 2860fps and accurate enough for my needs.

Unfortunately Im down to my last few grains of H4895 but do have lots of N140 left over from other loads, Im hoping to make use of the N140 and Im ready to start working through some loads.

Im planning on starting at 44.5gr in 0.2gr increments upto a max of 46.3 was wondering if this is worth trying and if anyone has run this combination of bullet and powder through the QL software?

The Vihtavuori software doesnt list the Ballistic Tip Bullet?

https://www.vihtavuori.com/reloading-data-tool-rifle-handgun-cowboy-action-shooting/#/imperials/1/30/Nosler/AccuBond/150

Any advice appreciated, TIA 

Les

[banus02]

WARNING, may not affect your load or your rifle BUT my rpr shows pressure signs at 44.3 grs,stiff bolt, case head marks. be very careful with n140 . start low and work up

[Laurie]

The standard advice from powder companies when your particular bullet isn't listed is to use data for another same weight and same type bullet. By 'same type', that means only use cup and core bullet data with another cup and core construction bullet; monolithic copper with similar and so on. (I'd also add, same basic shape as long bearing surface flat base bullets can create more friction / higher pressures in the barrel than same weight FMJBTs, BTSPs, and HPBTs with shorter parallel bearing sections.) Then treat very cautiously ...... ie take the data with the lowest charge weights, start low and work up in smallish steps (1% of maximum so no more than 0.4gn steps here, 0.3gn better as you get up to half way between the two charge levels). The advice for selecting the lowest charges alternatives is very apt in this case given a 3gn + range of maximum charges for Viht's N140 data for 150gn cup & core bullets. Case make can also affect top loads, but you're loading Lapua as does Viht. (Many US cases, especially Winchester, have thin walls / greater internal capacity which reduces pressures so you need to drop listed 308 Win max loads by a grain or 1.5gn using heavier RWS, Norma, and Lapua brass.)

As it happens Nosler's #9 reloading manual has your combination covering all Nosler 150 and 155gn models. Nosler case, Fed 210M match primer, 2.800-inch COAL for the 150 BT. Start: 42.5gn / Max 46.5gn N140 (2,887 fps from a 24-inch Lilja SAAMI spec barrel.) 42.5gn N140 is also highlighted as the 'Most Accurate' combination in the cartridge with this group of bullets.

The Nosler case may or may not require some charge reductions, but in any event this company's loads tend to err on the 'hot side' IME, so I'd be very leery of that 46.5gn maximum charge. You'll also find the case fill-ratio is high with N140 and the 2.8-inch COAL. Nosler lists the starting 42.5gn charge as 100% (of available space under the seated bullet) and the 46.5gn max as 109% in its brass. If these values are correct, the top load is quite heavily compressed.

[snakeman]

14 minutes ago, Laurie said:

the top load is quite heavily compressed.

And I would also say at 65,000psi is over-pressure

ATB

[LesC]

Thanks guys, I will start lower probably around 42.2gr and work up until I find the most accurate at as close as possible to my aspirational 2800fps.

 

[Laurie]

2 hours ago, snakeman said:

And I would also say at 65,000psi is over-pressure

ATB

 

Where did you get 65,000 psi from? Presumably QuickLOAD or GRT both of which are useful models, but not real life.

Wary as I am of some of Nosler's max loads, I'm 100% convinced that its manuals' data are obtained by competent people in a proper pressure barrel made to SAAMI bore/groove specs and likewise with a SAAMI compliant chamber and in that particular set of kit and components, the published loads are within SAAMI MAP (Maximimum Average Pressure) specs, in this case below 62,000 psi as determined using SAAMI approved measurement kit and methods.

Where manufacturers such as Hodgdon quote the recorded pressure for their loads, what is noticeable is that the margin below SAAMI MAP for max loads has reduced noticeably in recent years, so that recent additions are now often a few hundred psi below allowed pressures instead of a 'safety net' of a couple of thousand as would have been the case. I assume that's because of their customers' obsession with getting ultimate MVs, often achieved at the expense of everything else.

[snakeman]

8 hours ago, Laurie said:

the published loads are within SAAMI MAP (Maximimum Average Pressure) specs, in this case below 62,000 psi as determined using SAAMI approved measurement kit and methods.

Yes, Laurie ..my version shows 65,318psi ... which to me determines QL ('model' or not) as unreliable, if somewhat precarious software that someone could quite easily read as fact, and if used quintessentially as the 'be-and-end-all' could cause serious injury to themselves and/or others

Very interesting though to see the discrepency from published data to (purchasable) software

ATB

 

 

 

[LesC]

Guys

Thanks very much for taking the time to give me such clear explanations and guidance, it's very much appreciated.

I think you have ignited my thirst to look into the science behind all of this now, I will look at obtaining some software to look at load characteristics, what do you recommend?

Would be helpful if there were some online (ewetube) videos available to get me started?

[banus02]

enter p-max ballistics in your search bar ,very useful information.