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.300 PRC

15 Apr 2020
@ 01:12 pm (GMT)

Aaron Greiner

I really like what Hornady is doing with their newer cartridge designs. The.375 Ruger is a great parent case. This design offers a long neck to help hold bullets which I would think aid in cartridge concentricity? Doing away with the unnecessary belt of the .300WM. More freebore for the newer heavier longer bullets. But I already have a .300WM. This looks like a great cartridge to neck down to 7mm for that 7mm I have always wanted due to the high BC of the 7mm, without the kick of a .30. Anyone know if a 7mm PRC is in the works? In the long range game the 7mm seems to be the sweet spot? Any thoughts on this Nathan? By the way Nathan thank you very much for putting together all this information for us hunters to make more efficient kills on the game we hunt! It is greatly appreciated. I’ve already learned a great deal from your website and YouTube videos. I have plans to modify the shortcomings in my current hunting bullet selections due to things I have learned from you. Looking forward to your book set to learn more.


16 Apr 2020
@ 10:34 am (GMT)

Nathan Foster

Re: .300 PRC
Hi Aaron, there are several complexities to your questions that are difficult to answer in one post sorry. I will try to at least answer some of this.

The .375 Ruger was necked down to 7mm by wildcatters almost immediately after its introduction.

Another tactical whateverthefkyouwannacallit crowd made their own proprietary version of this and called it the 7mm LRM soon after.

Nosler introduced similar designs thereafter including the .28 (7mm) and .30 Nosler.

Tests performed by my peers (same batch barrels / dimensions etc) proved what I had already written about in the 7mm Practical article, that the case volume of the .300 Win Mag was about as far as the 7mm could be pushed for velocity. Any further attempt at gains via the above 7mm cartridges could lead to other problems.

The .300 PRC is problematic in that the throat was designed long in order to generate full power. The max OAL is listed at 94mm / 3.7" but this is not the same as the actual / true max OAL with the bullet on the lands. If you want the bullet on or near the lands, you will need a Wyatt mag box in an M700 or clones, or utilize either a Weatherby MkV or CZ 550M action. But take note, if you do try to seat close to the lands, some bullets will end up sitting out too far in the case neck. Most shooters will be forced to seat to mag length, put up with the jump and put up with whatever accuracy they get.

Current .30 Nosler rifles are also exhibiting similar COAL problems.

I have learned a great deal more about throat design in these recent years, all thanks to teachings from Dave Manson. The subject is complex, a change of .0001" or simply a lack of ratification in exact datum points can lead to major changes within a throat which may effect the max OAL by up to .100" or more. What we start out with and what we end up with from manufacturers can be quite unexpected. I believe that the Creedmoor also went through ratifications on the fly.

Fortunately, Manson reamers are at the cutting edge of throat geometry. We have also been combining our research with regards the FMR reamer designs. But none of this has any bearing on what others may be doing at any given time. I am also now asked on a weekly basis, whether I can design a shorter version of such and such whizz pop cartridge so that it will better fit some plastic piece of shit the client is using. Readers must understand that many cartridges are heavily reliant on a good measure of freebore in order to obtain high speeds. If we (myself and Manson) change the design significantly, the cartridge may lose a lot of power - up to 50fps per 1mm / .040" of free bore removed depending on case to bore ratio. The .260, 6.5x55, 7mm-08 and .308 all fall into this category. In other instances the reader / client simply fails to understand that its the plastic gun (cheap / insufficient action length / materials) is to blame for the cramped cartridge, not the cartridge design which was optimized some 50 to 70 years before Mickey Fking Duck got involved with his 'innovative' (cheap) chuck a BMW logo on it gun manufacturing.

All I would suggest to you, is that the case size (or design re belted vs non belted) is only part of the picture and that it is imperative that actions (mag box lengths) are taken into careful consideration. If a factory cartridge is rated at A.BCD" OAL (eg, the Nosler reloading pages online), add a good .120" to the OAL to get a more realistic max figure (includes the PRC) and up to .400" for other 'hot' magnums (WBY / Nosler), then allow another .040" for smooth feeding from a magazine. This is an extremely rough guide but it will get you closer to the truth without having to spend a buck.

Those are the very basics but there are several contradictions. Like I said, its a complex subject, especially with such radical differences in current projectile lengths.

Not sure if that helps any Aaron. Food for thought perhaps.


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