Home Forums Hunting & Shooting Ask The Gunwriters Partitions and A-Frames Pressure w/ 338wm, 250gr

I'm starting below max's 5%, and working up loads. I know bullets, chambers, throats, elevation, temp, all have effects on pressure. But I've not worked with A-Frames that much, and was wondering if the mantel and construction of them are that much different and pressure increasing than the Partition? Any discussion is appreciated.
stevek

A-Frames result in noticeably more pressure with the same powder charges. It's not so much the interior construction but the softer copper and lead of the jacket and core.

That's interesting. It might explain why I get the same noticeable pressures with 196gr Woodleighs and 180gr Hawk .318 bullets, given the same moderate powder charges of 45gr of IMR 4064 or 45gr of R15. I'm comparing bullet to bullet with a given powder.

Given then the differences in pressure due to bullets, the guide would still be velocities given as starting and max for stopping, but also consider barrel length, most books show 26" barrels, mine is 24, should loose a little off max velocity.

Not necessarily. With "soft" bullets the maximum velocity possible tends to be less than with less-grabby bullets.

One illustration of this is Hodgdon's and Western Powder's load data. Often they'll include loads with the same powder for different bullets of the same weight. The listed pressures indicate how much extra pressure some bullets tend to create.

Along with A-Frames, among the highest-pressure bullets are other copper-jacketed, soft-core bullets like Woodleighs. The heavier Nosler E-Tips also create a lot of pressure for their weight, just like the pre-TSX Barnes bullets did.

Among the lowest pressure bullets for their weight are Hornady Interlocks and Barnes TSX's, especially in lighter weights for their caliber, because they have less bearing surface.

John, I still say that an article on various bullets and their "degree of grabbiness/pressue" would be both valuable and well-received.

Agree with all's said here, but confused some with the Barnes TSX's. I thought also with their rings they had less drag and bearing surface, but their manual #4 lists a max of 65gr of H4831sc, with other manuals at 5 to 6 grains hotter. Regarding MD's comment on velocity, I was referring to each manual's max velocity. Sure wish Nosler would make more of the Partitions at 250,I've more experience with them and the TSX's, and the Hornady's as general purpose ungulate shooting. I need to tweek some bullets prior to going to the range today.

carp,

Comparing the data from different manuals isn't nearly as helpful as comparing data from the same source, because the test barrels and the means of measuring pressure vary. Plus, the general skill of the lab can even play a considerable role, so some sources of data can be more reliable than others. I know of one lab that tested one relatively small .22 caliber centerfire and got velocities as high as a much larger .22 cartridge, at the same pressure levels, which is a physical impossibility.

Thanks for the reply John, appreciate your efforts working with the Philistines. I understand that the variables are increased with the different manuals, that makes sense. I went back to some of my older books, PO Ackley vol II 1980, it lists 4831, no designation IMR or H, at 71 to 75 grains for 250 gr bullets. Not that I'm going that high with my H4831. With this going on I did find and purchase a couple of boxes of 250gr Partitions, so I'm working with these, 250 Spire Points and 250 A-Frames, working up from 69-72 grains, we'll see how it goes. Thanks again to you and other replys.

You do know that Swift has a reloading manual?

Yeah, and it lists H4831 to 72.5 max, for 2610 or there abouts, Nosler's says about 71.5 for 2700something and Hornady says 73 something for some other speed. The troubling one is Barnes, they say 65 max, that threw me.

Ok,didn't know if you had the Swift manual.

Could be that Barnes is a longer bullet,could be,maybe.

It's a LOT longer, which is no doubt the reason for the lower maximum charge weight. The velocity listed is only a little over 2500 fps, indicating the powder charged maxed out due to the space inside the case, not pressure.

Thanks MD.

Elkhntr and MD, Yes the Barnes is longer, they don't discuss compression or load densities in their manual, Speer, Nosler, Hornady, and Swift all mention this. And while I'm finishing up a pound of H4831sc on Friday, I go buy a couple more and notice, it's not short cut anymore, just straight 4831. With the chunkier bullets I'm already packing it a little bit using the SC style. Back to trickling and shaking it down I guess.

I bought a box of 210 gr. Swift Sciroccos to try in my 338 RUM as soon as Swift came out with them, and before they had done any load testing.

I had shot some 210 gr. Ballistic tips and found they shot well at Nosler's maximum load data. So..... since the weight and shape were the same, I loaded the Swifts at Nosler's recommended STARTING load.

I had to drive the bolt open with a 2X4.

I called Bill at Swift and told him about it. He apologized for not having developed data for the bullet before placing them for sale.

I got similar velocities in my 7 RUM using the same powder loading for 150 gr. Scirrocos and 150 gr. Ballistic tips, but it sure didn't work for the 338.

Back from the range yesterday, with A-Frames 250gr at 71 grs H4831sc, vel 2441-2448, 72 grs and vel 2503-2517. The Swift book has max load at 72.5 grs of H4831. The Noslers 250 Part at 71 grs of H4831sc, vel 2451-2468 and 72 grs gave vel 2512-2533. The Nosler Manual has max at 71.5grs of H4831. Velocity was taken at 14 feet from muzzle with a CED Melenium crono. The Hornady 250 SpPts were right there with the first two. There were no visual signs(primers flat or powder residue, or case signs) of pressure, and bolt lifts were normal. Will stick with 72 grs of the 4831 just to see if the velocity stays consistent. I know this is contrary to the discussions above regarding the A-Frames and Noslers, but this is what I'm seeing in this rifle so far.

The rifle is an early 90's Ruger 77, push feed tang safety model, that is new to me. Was hoping to do better than 35 Whelen speeds, but I'll continue. The rifling and groups show promise if I keep off the coffee while shooting. I wanted 250's for this rifle as I have a 300 H&H that shoots 180's and 200's nicely.

I might give Reloader 22, 19, and that new 23 a whirl also.

My observations on least to most with a few premiums are: TSX/TTSX, Partition/Accubond/North Fork, and A-Frame.

Made it back to the range yesterday, but had problems with the crony, no readings and kept moving closer to the screens and got a few readings, that actually approached normal velocities expected. With RL19, 250 gr Hornadys, at 72 grains got 2650 to 2670, then I got too close, dead center and 1/4 inch into the crony. I never liked it anyhow. The good thing is the rifle is more normal, and worth working with. Now to find another crony. carp

I've shot two chronographs,welcome to the club.