20” 300 PRC

[DocDoc]

The slow powder in a short barrel can have high pressure on bullet exit of the barrel. I am not sure what that might do for SD and accuracy. At the same time the specialty pistol guys seem to have the short barrel accuracy issue figured out.

 

[SENAL]

Long time lurker of LRH and just joined. Looking for some opinions on a short barreled 300 PRC I want to build.

I'm wanting to build a 20-22" 300 PRC for my go to "western" hunting rig. I have a 6.5 CM with a 22" proof research barrel on a trued R700, laid in a manners EH6-A stock that I use for mule deer and below. This 300PRC would be built off a Big Horn action and am looking at another proof barrel. I plan on this being my mule deer and above gun.

My question is, besides lower velocities, what are the biggest downfalls to a shorter barrel in a big round like the 300 PRC. How much would that shorter barrel effect accuracy out to 700-800 yards? Also, twist rates suggested? One caveat, I plan on running a can on this rifle.

Realistically I want this rifle to be light and compact/packable in the back country and be able to take an elk size animal at 700 yards. What are your thoughts or experience.

I am with a lot of why David Emerson said. Bigger case and short barrels can have some funky curves on them. That is pressure at chamber and down the barrel. I don't think the 300 WM and 300 PRC would have to much trouble if you use RL26.

The OMENs do a good job at managing the pressure and ditching what isn't needed.
We find some insanely high pressures on the faster short actions and have to mitigate that in many ways.

A 300 WM difference with 20" vs 24" barrel and my old loads, Rl26 97% fill, burns it all even in the short barrel. 2945FPS(Caldwell Chrono before LabRadar) and the 24" would chrono 3090 FPS. This is roughly 5k psi under max.

In closing, do you mind that 130 FPS difference. I personally wouldnt.

V/r,

Richie

"Send It, Quietly"

 

[yorke-1]

The slow powder in a short barrel can have high pressure on bullet exit of the barrel. I am not sure what that might do for SD and accuracy. At the same time the specialty pistol guys seem to have the short barrel accuracy issue figured out.

I'm one of those specialty pistol guys and there really isn't any difference when working up loads in short (16-20") barrels when compared rifle barrels. In fact I typically end up with nearly the same loads in a given chambering when used in both short and long barrels; identical loads in a few guns.

 

[David Emerson]

I'm one of those specialty pistol guys and there really isn't any difference when working up loads in short (16-20") barrels when compared rifle barrels. In fact I typically end up with nearly the same loads in a given chambering when used in both short and long barrels; identical loads in a few guns.

Thank you

 

[Elk Hunter 338]

my ES's are very low

 

[David Emerson]

I have gotten into 2 technical discussions here.Along the way I lose someone and they get confused and turned around. Powders are still made from (gun cotton) nitro cellulose.Yes they have made advances but in copper reduction and temperature stability only. No magic powders that can make a short barrel equal a long barrel in speed. Both single base and in double base.Remember the Hornady Super velocity loads?They did it by blending to the perfect burn rate for the application and stuffing the cases as full as they could get them. OK I am gone on this discussion before another pops up that thinks he is the God of rifledom.

 

[David Emerson]

my ES's are very low

I believe that

 

[David Emerson]

I am with a lot of why David Emerson said. Bigger case and short barrels can have some funky curves on them. That is pressure at chamber and down the barrel. I don't think the 300 WM and 300 PRC would have to much trouble if you use RL26.

The OMENs do a good job at managing the pressure and ditching what isn't needed.
We find some insanely high pressures on the faster short actions and have to mitigate that in many ways.

A 300 WM difference with 20" vs 24" barrel and my old loads, Rl26 97% fill, burns it all even in the short barrel. 2945FPS(Caldwell Chrono before LabRadar) and the 24" would chrono 3090 FPS. This is roughly 5k psi under max.

In closing, do you mind that 130 FPS difference. I personally wouldnt.

V/r,

Richie

"Send It, Quietly"

So 145 ft for 4 inches. 35 ft per inch. That is in line with normal. If I remember right it gets down to about 25 or so as you get longer. Being we are having this discussion I am curious about something. Let,s use a 300 weatherby for an example. Why is it a 24 inch gun has so much more blast and fireball than a 26? If all the powder was burned the muzzle pressure should not be much different. Correct? And if all the powder was burned why so much more muzzle flash? The 264 was really bad for that. Cut one shorter and you have a noisy 270 win.

 

[SENAL]

So 145 ft for 4 inches. 35 ft per inch. That is in line with normal. If I remember right it gets down to about 25 or so as you get longer. Being we are having this discussion I am curious about something. Let,s use a 300 weatherby for an example. Why is it a 24 inch gun has so much more blast and fireball than a 26? If all the powder was burned the muzzle pressure should not be much different. Correct? And if all the powder was burned why so much more muzzle flash? The 264 was really bad for that. Cut one shorter and you have a noisy 270 win.

Well this could get deep in the thick of it. Good thinking. I have owned a few weatherbys and see eye to eye with what you mention.

Couple theories -

1. Powder shape/size. We have a few that are fireballs, even through a silencer, that burns all the powder. 338 WSM does that with RL17 and an 18" barrel. The longer powders seem to do that. We use W748 in the 458 WSM. Have never seen a fireball out of that. CFE223 and H110, same thing. I think because of the shape of RL17 it is able to burn it all but at the last second. With tiny powders it is easier to finish it off at the muzzle without making a big show of it.

2. Where the powder is burned. Our sims and pressure sensors arn't quite advanced enough to show where this complete burn occurs. You think, o well it burns it all, thats optimum. Then you have a huge fireball and think you arn't. Call it a 24" barrel. It genereates pressure, we can see that at the muzzle and then down every inch to see a curve. I don't think that necessarily means that it burns perfectly even. You have 100 burning paper towel rolls that will catch fire and be thrust through a 10 foot PVC pipe. You have 2000 burning pieces of confetti that is thrust through the same pipe. Which is going to take longer to burn out when the atmosphere comes into play?

Naturally going with Weatherby ammo and load data, that is some high pressure awesome stuff. But they are known for twice the amount of free-bore as others. Bet their curves and test equipment show some Area 51 type firearm stuff.

 

[yorke-1]

So 145 ft for 4 inches. 35 ft per inch. That is in line with normal. If I remember right it gets down to about 25 or so as you get longer. Being we are having this discussion I am curious about something. Let,s use a 300 weatherby for an example. Why is it a 24 inch gun has so much more blast and fireball than a 26? If all the powder was burned the muzzle pressure should not be much different. Correct? And if all the powder was burned why so much more muzzle flash? The 264 was really bad for that. Cut one shorter and you have a noisy 270 win.

The blast is more substantial in part because it's just closer to your face. Also, the muzzle pressure is higher. The fireball has a lot to do with the specific powder you use. here are a couple examples of relatively large capacity cases shot from short specialty pistols.

20" VS 30" barrels on a 338 SnipeTac (140gr H50bmg powder). The shooting starts at 2:00.


338/375 Ruger in an 18" barrel (76.5gr H4350)


18" 300 RUM in an 18" barrel (101.2gr Retumbo)


I have more videos of more mild chamberings like the 6 BR, 284 Win and 260 Rem as well but they were filmed mid day and there's really no significant muzzle flash. Note the relatively mild muzzle flash even from 140gr of one of the slowest available powders in a 20" barreled 338 SnipeTac.

 

[David Emerson]

Well this could get deep in the thick of it. Good thinking. I have owned a few weatherbys and see eye to eye with what you mention.

Couple theories -

1. Powder shape/size. We have a few that are fireballs, even through a silencer, that burns all the powder. 338 WSM does that with RL17 and an 18" barrel. The longer powders seem to do that. We use W748 in the 458 WSM. Have never seen a fireball out of that. CFE223 and H110, same thing. I think because of the shape of RL17 it is able to burn it all but at the last second. With tiny powders it is easier to finish it off at the muzzle without making a big show of it.

2. Where the powder is burned. Our sims and pressure sensors arn't quite advanced enough to show where this complete burn occurs. You think, o well it burns it all, thats optimum. Then you have a huge fireball and think you arn't. Call it a 24" barrel. It genereates pressure, we can see that at the muzzle and then down every inch to see a curve. I don't think that necessarily means that it burns perfectly even. You have 100 burning paper towel rolls that will catch fire and be thrust through a 10 foot PVC pipe. You have 2000 burning pieces of confetti that is thrust through the same pipe. Which is going to take longer to burn out when the atmosphere comes into play?

Naturally going with Weatherby ammo and load data, that is some high pressure awesome stuff. But they are known for twice the amount of free-bore as others. Bet their curves and test equipment show some Area 51 type firearm stuff.

I learned something. So N570 in a 264 would be worse than us869. I am surprised that you can get pressure with 748 in your short 45. I am not sure but I believe Winchester used it in the 458 and compressed it so much was what caused the trouble with the 458 and squib loads.

 

[David Emerson]

The blast is more substantial in part because it's just closer to your face. Also, the muzzle pressure is higher. The fireball has a lot to do with the specific powder you use. here are a couple examples of relatively large capacity cases shot from short specialty pistols.

20" VS 30" barrels on a 338 SnipeTac (140gr H50bmg powder). The shooting starts at 2:00.


338/375 Ruger in an 18" barrel (76.5gr H4350)


18" 300 RUM in an 18" barrel (101.2gr Retumbo)


I have more videos of more mild chamberings like the 6 BR, 284 Win and 260 Rem as well but they were filmed mid day and there's really no significant muzzle flash. Note the relatively mild muzzle flash even from 140gr of one of the slowest available powders in a 20" barreled 338 SnipeTac.

I guess I have been living in a cave. I never dreamed I would see a pistol chambered for a gun like that!!!!!

 

[David Emerson]

The blast is more substantial in part because it's just closer to your face. Also, the muzzle pressure is higher. The fireball has a lot to do with the specific powder you use. here are a couple examples of relatively large capacity cases shot from short specialty pistols.

20" VS 30" barrels on a 338 SnipeTac (140gr H50bmg powder). The shooting starts at 2:00.


338/375 Ruger in an 18" barrel (76.5gr H4350)


18" 300 RUM in an 18" barrel (101.2gr Retumbo)


I have more videos of more mild chamberings like the 6 BR, 284 Win and 260 Rem as well but they were filmed mid day and there's really no significant muzzle flash. Note the relatively mild muzzle flash even from 140gr of one of the slowest available powders in a 20" barreled 338 SnipeTac.

I have never used H50BMG but I have used the old 5010. That stuff was like pencil lead. The new powder granules like that?Or much smaller?

 

[SENAL]

N570, 78.5gr, is a 60k psi load 3360ish FPS, burns 98% and fill is around 97%

You would get 120FPS slower with US869 and burn 94%. Fill is 104%. Yikes for FPS drop.

458 WSM, W748 is a big compressed load 105% fill, burns 98% 60k PSI load 2275FPS/4600ftlbs of energy out of an 18" Barrel. We can't put that sucker in the smaller ammo machines we have. We single stage it. Plus its not like that caliber is flying off the shelf. We use a little more H335 than the W748 though. We have an Africa trip on the schedule. I don't trust W748 for temp issues or sitting too long. I have heard the stories.

H335 Little less fill, slightly less speed. Same burn. If we go heavier, have to use W748 or BLC2 as H335 can't push 480gr/500gr as well. That is the fun of short barreled magnums and trying to make them live up to the long mag potential. Some we surpass. Others, super close.