.300 RCM and Short Barrels

[WoodsQuest]

How much velocity does the 300 RCM lose from a 77 Compact (16.5in bbl)? Is it worth reloading for 300 RCM? Is it dying?

 

[Mobuck]

My understanding of the 300 RCM is the original design was based on a short barrel. With this in mind, the ammo should perform as advertised in a short barrel.

 

[Silent Sam]

It won't lose anything if you don't shoot it in a longer barrel...;-). If you've got brass it's not dying.

 

[WoodsQuest]

I don’t have anything for it. I was looking at picking up a Compact in 300 RCM. I know the RCM was designed for a 20 inch bbl.

 

[Silent Sam]

...and that was based primarily on the case capacity and powder they used to load it. The only way to know what the actual velocity is in any barrel is to shoot it and measure it.

 

[WoodsQuest]

Yea, but you can get an idea based on other people's experiences.

 

[Silent Sam]

Your best bet would be to contact Hornady. They developed the ammo using their (Hodgdon) Superformance powders although other powders will also work. Perhaps a better question would be what bullet weight & velocity do you need for your intended use. Hornady claims 75 to 100 fps difference between 20" & 24" barrels in their 9th edition reloading manual. I would expect you would be in 308/30-06 territory (from a 22" barrel) velocity-wise in a Compact RCM.

 

[gunzo]

I've read several very good barrel cutting articles that were very well done, factory loads, reloads, different bullet weights, etc. Cut 1" chrono, cut another, usually from 24 or 26" to 16.5". There have been a few anomalies, but most cartridges show an average loss of 20-25 fps per inch.
Hodgdon data for a 180 in a 300RCM shows an approx. avg. of 2800 fps for max loads with a 24" barrel. So a 16.5" barrel will theoretically produce 2600-2640 fps.
I'd bet a few bucks on that, but only a test of the individual firearm will be the answer. 8)

 

[WoodsQuest]

That's about what I figured. Seems like a lot of hassle with a proprietary cartridge with little gain over a .308 out of the short tube. I have to assume an rcm is more overbore than the 308 and will experience more velocity loss the shorter you cut the tube.

 

[gunzo]

That's about what I figured. Seems like a lot of hassle with a proprietary cartridge with little gain over a .308 out of the short tube. I have to assume an rcm is more overbore than the 308 and will experience more velocity loss the shorter you cut the tube.

Agreed on all points, your call.
Enjoy 8)

 

[Silent Sam]

I guess it depends if you want that short a barrel or not... The only "hassle" if you reload would be that brass isn't as plentiful and likely more expensive. You definitely will have significantly more velocity with the RCM over a 308 with any given barrel length. Assuming the example given is close to reality, you would need a 24" barrel in 308 to reliably get 2600+ fps with a 180gr bullet.