338 RCM

[Seabeeken]

That is awesome!! The RCM's are the father of the 6.5 PRC. The more i worked with it, the more I liked it. It is a sleeper that is maligned and overlooked. If I had to go into an alder thicket after a mad beast, this would be my choice out of the rifles i have. Short barrel, short action heavy hitter. I can rack the bolt without taking my eye off the scope and swing it easier in the thicket. It always goes with me. Light and quick. Well thought out rifle and cartridge IMO. Powders that work in the 308 work well in the RCM, IME

 

[Seabeeken]

It is an extremely efficient cartridge indeed. I just worked up a new load for mine today. It is a Ruger 77 Hawkeye that was originally chambered for the 338 RCM from the factory but I didn't like the thin barrel so I had my gunsmith re-barrel it with a #4 Bartlein 22" (should've went with a 3B contour either 22" or 24" if I was to do it again) and man does it shoot for a traditional style hunting rifle like most of us grew up learning to use. The new load I worked up today is 62.0 grains of RL-17 with 230 grain ELD-X bullets. They're 2.852" cartridge overall length, CBTO measuremet is 2.102". Muzzle velocity with that load average is 2,790 FPS with single digit ES numbers. With the 230 grain ELD-X's having a G7 BC of .310 I had no problems shooting my 1,000 yard target with it today and consistently shooting under half MOA groups. I'm usually a big bore speed demon when it comes to cartridge selection but I really do like this short fierce little hammer of a cartridge! Below is my sight in shot today on my 1,000 yard target.

I ran your load in GRT because it sounded like the speed was high for that bullet. It showed that you are almost 78,000 psi. Be careful. Surprised you arent getting stiff bolt and ejector flow

 

[PapaSmurff]

I ran your load in GRT because it sounded like the speed was high for that bullet. It showed that you are almost 78,000 psi. Be careful. Surprised you arent getting stiff bolt and ejector flow

Yes I ran it myself too on Quickloads. I matched the speed with the bullet at that cartridge overall length to get my pressures and I think it said it came out to 69,000 PSI which I am very surprised because it doesn't seem like it at all while shooting it; especially still getting that kind of accuracy. No pressure signs whatsoever. The primers are still slightly rounded on the sides, etc. This is one of the few instances where I don't think quickloads is correct because when I chrony factory 225 grain SST ammo through it, the chrony says 2,750 FPS. So I'm only 40 fps faster than factory ammo with these handloads with a top choice powder and no pressure signs at all on primers or cases. I'm gonna run some other published loading data in Hornady's book into quickloads for this caliber and I'll update about the pressures this afternoon.

 

[Seabeeken]

I got that pressure after calibrating the powder model to your velocity

 

[Calvin45]

I got that pressure after calibrating the powder model to your velocity

If it truly is at that kind of pressure, and I don't believe it is…can't we dare say that it's okay?

I would go that far. The brass is the weak link, not any modern well made bolt action.

 

[PapaSmurff]

Here is the Quickloads data for the load combination that I'm using. There is no pressure signs whatsoever on the brass, the primers are still rounded on the edges, and bolt lift is still normal. The load shoots great. When all the correct parameters are typed in, it gives me a psi of 69,228. That is around 4-5,000 psi over what I would usually want to load a cartridge up to. However it shoots so good (all the way out to 1,000 yards) and with no visible pressure signs at all I will most likely be staying with this load for the foreseeable future. I had to go up to 62.3 grains charge weight on quickloads to match my real velocity of around 2,790 fps. But my load is 62; .3 grains lower than that. My barrel could be 10-15 fps faster could be the difference here. All in all, fairly close predictions charge weight of 62.3 equalling 69,288 psi. Posting a picture of my quickloads screen for reference. I don't advise anyone use this load however; it is only deemed safe by me in my firearm.

P.S. if I lowered the charge weight to match 2,750 fps with psi about 65,000 there was only a difference of 2.0 grains of charge weight. So it appears that it is slightly over pressured but there certainly aren't any visible signs of that in my particular rifle.

 

[PapaSmurff]

A picture of my re-barreled semi custom Ruger 338 RCM. Leupold VX-5, 3-15x44 scope.

 

[Seabeeken]

Here is the Quickloads data for the load combination that I'm using. There is no pressure signs whatsoever on the brass, the primers are still rounded on the edges, and bolt lift is still normal. The load shoots great. When all the correct parameters are typed in, it gives me a psi of 69,228. That is around 4-5,000 psi over what I would usually want to load a cartridge up to. However it shoots so good (all the way out to 1,000 yards) and with no visible pressure signs at all I will most likely be staying with this load for the foreseeable future. I had to go up to 62.3 grains charge weight on quickloads to match my real velocity of around 2,790 fps. But my load is 62; .3 grains lower than that. My barrel could be 10-15 fps faster could be the difference here. All in all, fairly close predictions charge weight of 62.3 equalling 69,288 psi. Posting a picture of my quickloads screen for reference. I don't advise anyone use this load however; it is only deemed safe by me in my firearm.

P.S. if I lowered the charge weight to match 2,750 fps with psi about 65,000 there was only a difference of 2.0 grains of charge weight. So it appears that it is slightly over pressured but there certainly aren't any visible signs of that in my particular rifle.

Ive never been able to seat a bullet on a 108% case fill. Max for me is usually 105% and sometimes that is difficult. Did you measure the water capacity of the case? 71 gr is the default capacity. My recent update to quickload seems to have different results. Did I miss a setting?

 

[Seabeeken]

Here is a GRT simulation with the powder model calibrated to your velocity. Not all that different from QL. IME, brass flow happens around 74,000 psi depending on brass hardness. Just because you dont see brass flow doesnt mean you arent over pressure. You shoot what ever you like. @Calvin45 you can dare say anything you want to. I for one dont want to touch off 75-80,000 psi inches from my face based on a computer simulation and pray the brass and primer holds. A few degrees in temp variation could cause severe injury or death since reloder 17 is not that temp stable to begin with. I've done my due diligence and I hope I'm wrong. God Bless

 

[sable tireur]

Bear in mind that both softwares are 'predictive' which means they are not absolutes when calculating data. Take into consideration the changes in lot batches of smokeless gunpowder, the difference in the brisance of primers, the alloys used in the manufacturing of the brass for the cartridge cases. All of these few variables can have a significant effect on the solution that the software provides. None of the answers are fixed in stone as being an absolute.

Condescension and condemnation don't add to the solution. Careful evaluation of the process and the variables can lead to a better understanding of the load in particular. Tuning the software variables will refine the solutions provided.

I think most of us here are adults and as such are capable of making sound decisions given our level of knowledge and experience. If we questions something then we should examine the reasons for the questions and work towards a solution.

Enjoy the process!

 

[PapaSmurff]

Ive never been able to seat a bullet on a 108% case fill. Max for me is usually 105% and sometimes that is difficult. Did you measure the water capacity of the case? 71 gr is the default capacity. My recent update to quickload seems to have different results. Did I miss a setting?

Somehow your quickloads results did come out differently than mine. Yours is showing a velocity of 2,843 fps whereas mine is coming out to a true velocity of 2,785-2,790 fps (which is what my rifle is getting). Like I said in a previous post: The 225 grain Hornady factory ammo is going 2,750-2,760 fps, a difference of only 30-40 fps so I feel fine about my load pressures in this particular rifle. I would never be comfortable shooting 75-80,000 psi and I wouldn't do it either.. This rifle is not putting out that much pressure. I know what pressure signs look like and I know what it feels like when rifles are firing in higher pressures. It simply is not that high; I can believe 69,000 psi possibly, but it doesn't even seem that much. I can barely tell any difference between my loads and factory ammunition when firing each. On Quickloads you always want to match 3 main criteria: the cartridge length, the actual H2O capacity of your fired cases, and the velocity you're actually achieving. Don't always go by the powder charge weight because often times that number seems to be wrong to some degree. The bullet velocity with all the other correct parameters installed (no matter whatever the powder charge weight says) will denote the correct psi.

 

[PapaSmurff]

Bear in mind that both softwares are 'predictive' which means they are not absolutes when calculating data. Take into consideration the changes in lot batches of smokeless gunpowder, the difference in the brisance of primers, the alloys used in the manufacturing of the brass for the cartridge cases. All of these few variables can have a significant effect on the solution that the software provides. None of the answers are fixed in stone as being an absolute.

Condescension and condemnation don't add to the solution. Careful evaluation of the process and the variables can lead to a better understanding of the load in particular. Tuning the software variables will refine the solutions provided.

I think most of us here are adults and as such are capable of making sound decisions given our level of knowledge and experience. If we questions something then we should examine the reasons for the questions and work towards a solution.

Enjoy the process!

Well said Sable, they are predictive programs not perfected to absolution. And I do always use mine when working up a new load for a new caliber. They are wonderful tools, but not absolutes.

 

[Calvin45]

It seems some folks believe what the computer program says more than what the chronograph and pressure signs are saying

 

[RCMSTER]

Hey All, new here and soaking up as much info as possible. The 338 RCM seems like a highly underrated caliber and I'm on the band wagon. I want to build one.
The factory ammunition numbers I've found appear to not be repeatable because they used a proprietary powder that's not available. I understand it's been designed for short barrels. A 22" to 24" barrel looks to be the sweet spot, and a brake sounds like a requirement. From the guys who have built 338 RCMs, anything you wish you would have done differently? Thinking 225 grain pills with H1000 would be some bad medicine for elk.

Here's a typical shot group outta my 338 RCM. I did have a Timney trigger put on it, and I pillar bedded and glass bedded, and then floated the barrel, but otherwise, it's a stock rifle. I was gonna have it recrowned, but the gunsmith checked it, and said was about perfect. Didn't need it. According to Western data, I'm .2 grains over max, but if I drop the charge even .5 grains, the accuracy goes south, so I'll keep running it as is.