300 PRC

[FrankG]

I see everyone is comparing this 300PRC to 300win and 300wsm but why not the 300RUM? Pardon my ignorance on the subject I am just curious.

If I remember correctly the .300RUM will produce more velocity but at a cost of about 10+ grains of more powder. More powder again means less barrel life. If you want the velocity then I'll say .300RUM will get the nod.

I've never loaded .300RUM but if it's kinda like the .300 Norma I feel there are not suitable powders out there to take advantage of the larger case capacities. The .300 Norma at a normal max working pressure will only push a 215-230gr. bullet no faster than the PRC.

Yes guys can push the Norma faster and have but I'll say they don't have a clue as to the chamber pressures that are happening. You hear guys pushing the Norma at 3000fps or faster with a 215gr. bullet. I'll say with the data that I currently have the pressures on that type of a load is/can be well past 70k psi.

 

[FrankG]

Frank,
Say I wanted to keep the barrel I have but wanted to change the cartridge - Is it possible to have my 300WM rechambered to the 300PRC? From comparison of the saami specs it appears on paper this would work... although my thought is to just shoot out the WM and replace with a PRC when it gets to that point. Lose the belt and gain other perks...

Sam

Sam, The back of the chamber will clean up but just for a rough ball park measurement you will have to push the chamber forward about a .100" for the shoulder/neck area to clean up to go to the PRC from the WM. So you would have to set the barrel back a little in order to do this.

I don't see any way around just running a PRC reamer into the chamber to set headspace to your existing thread/breech length spec. and have the chamber clean up all the way. Unless I'm missing something you will have to set the barrel back about a .100", then chamber and set head space.

Burn up your WM barrel as it sits. When that happens then decide if you want to change over to the PRC. That's what I would do .

Take a look at the attached picture of a WM and PRC round. Yes the overall case length of the PRC/chamber is technically longer but not to the shoulder/neck junction area.

Also notice the PRC has less body taper and is bigger in diameter of the main body area.

Hope that helps!?

Later, Frank

 

[SAPenguin]

If I remember correctly the .300RUM will produce more velocity but at a cost of about 10+ grains of more powder. More powder again means less barrel life. If you want the velocity then I'll say .300RUM will get the nod.

I've never loaded .300RUM but if it's kinda like the .300 Norma I feel there are not suitable powders out there to take advantage of the larger case capacities. The .300 Norma at a normal max working pressure will only push a 215-230gr. bullet no faster than the PRC.

Yes guys can push the Norma faster and have but I'll say they don't have a clue as to the chamber pressures that are happening. You hear guys pushing the Norma at 3000fps or faster with a 215gr. bullet. I'll say with the data that I currently have the pressures on that type of a load is/can be well past 70k psi.

Frank - this is an eye opener (!) Are you saying that we simply don't have powders slow enough for this type of cartridge? Even something like Hodgdon H-50BMG or maybe US 869?

 

[FrankG]

Never played with H-50bmg or 869 in what I will call normal types of cases. I've only used powders like that in big stuff like BMG. So I cannot comment personally on that as well as I've never seen test data with those powders in some of these larger cases to give any accurate info. on it.

With in the last two years or so a test was run in a ammunition pressure test barrel in .300 Norma. The data I have is about low to mid 2800's and your at max pressure. Believe it was a 26" finish length barrel. They tested to 2900fps. and pressure hit right about 70k. It was estimated to hit 3000fps. it would be right about 80k psi.

I'll back up maybe just say about 3-4 years ago with the PSR solicitation. The goal was to have a sniper rifle that could keep the rounds to speed of sound at 1 mile in calibers like .338 Lapua. There was no box ammo out there at that time that could do it at normal working pressures with the components that where available.

.26 Nosler in my opinion is a good example. Way overbore on case capacity vs. bore size. I don't feel there is a good enough powder out there to fill the case properly and push a 140gr. type bullet at a velocity you should be able to get out of it with out pressures going up.

Let's look at .223 Rem. the loads I see some of the guys running with a 80gr. bullet.....I know for a fact some of these loads are running at about 65k-70k psi. Saami spec. is 55k for the .223 rem. and 62k for 5.56 Nato. Just because your not getting heavy bolt lift and or the double click, or flat primers etc...doesn't mean we're not running stuff over max. pressure. I just made a post about this on the in another F Class forum as well. About 24.5gr. of Varget or a tad more and your about at the max. pressure limit but guys are running loads up to about 25.7gr. of powder.

We all push the envelope. I myself do it at times. I also deal in the world of reality as well.

Now factor in actual bore and groove size of the barrel, what chamber reamer/throat spec. was used to cut the shooters chamber, diameters of bullets, how the gun is being cleaned and how often, coated bullets/naked bullets etc.... more variables to contend with.

 

[SAPenguin]

Frank, thank you for this... Fascinating stuff. This is why I come to these forums.

One thing that really stood out to me above was this "just because you aren't getting flat primer / heavy bolt lift does not mean that you are not over max pressure".

I suspect that 90% of my shooting peers out there will ladder test right up till these signs present themselves, then back off a little, thinking they are now "safe"... but that might not be the case at all...

 

[DaveTooley]

I'm guilty. I run pressures just below the yield point of the brass on a regular basis.

 

[dkhunt14]

I'm guilty. I run pressures just below the yield point of the brass on a regular basis.

Dave, I believe most 1000 yard shooters have done that at one time or another. Some on a regular basis. Matt

 

[FrankG]

Totally off the subject kinda......

Guys shooting 6ppc. That round was originally designed at max. Pressure to give a velocity of about 3150fps. Most guys are running it at 3400-3500 or even higher range with the same bullets.

We made a pressure test barrel and one of the makers are going to run sample lots of ammo that Mark at work loaded up being as he shoots short range BR.

When you hear things like guys are using small electronic tools like razors etc....turn them on and touch the side of the case to settle the powder so they can get more in or using a really long drop tube or even better yet there is so much powder in the case that when they seat the bullet the pressure of compacting the powder is pushing the bullet back out.

I’m kinda worried but curious about the data we’re going to get back on the pressures of these loads.

 

[Shrek]

What is the point of worrying about pressure if you’re not getting pressure signs and case life is acceptable ? Really just a bunch of hand wringing imo.

 

[Shrek]

Worrying about pressure without pressure signs is like bore scoping your barrel all the time and then pulling the barrel because it looks bad but still shoots fine.

 

[rpierce]

Worrying about pressure without pressure signs is like bore scoping your barrel all the time and then pulling the barrel because it looks bad but still shoots fine.

I agree. My norma improved is pushing a 215 at 3125 fps in a 26" barrel w h1000 and zero pressure signs. Case web didn't expand at all compared to a load several grains lower, primer pockets are still very tight, primers are rounded and bolt lift is butter. I didn't hit pressure w h1000 until 3200 fps and with 2 gr more powder. Slight increase in bolt lift, primer pockets opened up a bit and the web expanded a bit. As soon as I hit that I knew it was max and didn't go up from there. Now if I was to use Reloader 33 or VV N570 its safe to say id hit close to or around 3300 before seeing any pressure signs at all. I will be using VV N570 in my lightweight norma improved im finishing for myself in a week or so. That will be the ultimate lightweight long range big game killer. 1540 ft lbs of energy at 1400 yds. Lapua brass, sub 1/4 moa accuracy off a bipod, and better ballistics than a 338 lapua without the recoil. Now I will say that Lapua and Peterson making brass for the norma was a complete game changer since the norma made brass sucked and wouldn't last very long at all. Most guys were only getting 4-5 firings out of the norma made brass before the pockets were loose.

 

[D.Stone]

I am getting 2950fps from an A191 Chambered 300WM with no issues in 95 degree weather without any functional issues with 215gr Hybrids. I have also tested ammo up to 3000fps where pressure signs begin.

I wouldn't be surprised if my ammo is over pressure, but it works fine, and I have yet to wear out my first 100 cases.

My question is there a realistic downside to shooting ammo that is over-pressure, but not to the point where it effects function in any type of weather?

 

[FrankG]

I am getting 2950fps from an A191 Chambered 300WM with no issues in 95 degree weather without any functional issues with 215gr Hybrids. I have also tested ammo up to 3000fps where pressure signs begin.

I wouldn't be surprised if my ammo is over pressure, but it works fine, and I have yet to wear out my first 100 cases.

My question is there a realistic downside to shooting ammo that is over-pressure, but not to the point where it effects function in any type of weather?

A close number based on ammo run in a pressure test barrel and 2950fps....your in the mid 75k-80k range for pressures and that was in pressure test barrels with the A191 chamber in it as well.

Normal max. Working pressure for .300wm is about 65k psi.

 

[FrankG]

People should be concerned about pressures.....even if you don’t have any visual signs.

Running a gun at 75 to 80k psi you have no room for any error in your load or not keeping up with cleaning or changes in the environment conditions effecting it because the ammo sat in the sun for a few extra minutes etc....or you get a new lot of bullets and the new lot the bullets are fat (bigger in diameter) even by a .0003” or .0004” bigger and your pressures get driven up even more.

Too many times I’ve seen guys at a match having to beat the bolt open because rounds are over pressure, bolt handles getting broken off, primers/primer pocket having excess gas leakage and etching the bolt face prematurely.

I’ve seen lugs set back on the receivers and or bolts.

I’ll post a pic tomorrow of a bolt face that the brass engraved itself into the bolt. When that happens your getting into the 80k psi range.

 

[D.Stone]

People should be concerned about pressures.....even if you don’t have any visual signs.

Running a gun at 75 to 80k psi you have no room for any error in your load or not keeping up with cleaning or changes in the environment conditions effecting it because the ammo sat in the sun for a few extra minutes etc....or you get a new lot of bullets and the new lot the bullets are fat (bigger in diameter) even by a .0003” or .0004” bigger and your pressures get driven up even more.

Too many times I’ve seen guys at a match having to beat the bolt open because rounds are over pressure, bolt handles getting broken off, primers/primer pocket having excess gas leakage and etching the bolt face prematurely.

I’ve seen lugs set back on the receivers and or bolts.

I’ll post a pic tomorrow of a bolt face that the brass engraved itself into the bolt. When that happens your getting into the 80k psi range.

I guess the next question is how much the difference in case capacity between different manufacturers effects pressure?

For instance Norma brass seems to be 20gr lighter than anything else so my assumption would be that if I were to switch brands of cases I would be starting probably 5 grains below my current load. That's not based on anything scientific; I would just be sure to be well within safe territory and start from the bottom.

My 215gr load data mimics that of what the guys on the Longrange hunting forum were using. I've only tested up to around 3000fps, and that's as far as I went because I just don't think 300WM needs to be going that fast.

Even Bergers new ammo is around 2900fps if I read the info right.

Sorry we're getting sidetracked.

 

[FURMAN]

A close number based on ammo run in a pressure test barrel and 2950fps....your in the mid 75k-80k range for pressures and that was in pressure test barrels with the A191 chamber in it as well.

Normal max. Working pressure for .300wm is about 65k psi.

What overall length was this testing done at?

 

[FrankG]

What overall length was this testing done at?

24".

With that being said the length will have no effect on pressures. Just velocity.

 

[FURMAN]

Sorry, cartridge overall length?

 

[FrankG]

Take a look at the picture of the attached bolt face. Pressure is up there.....shortly after this and things start coming a part.

 

[FrankG]

Sorry, cartridge overall length?

For the .300wm it was tested at a spec. of 3.475" avg. O.A.L. if memory serves me correctly.

I've got test data on Saami min. spec. chambers and the A191. They are pretty close over all. The A191 helped a little with pressure on a new barrel if the ammo was loaded to max. spec. length. The A191 helped as the throat is a tad longer than Saami min. spec. but it didn't change a ton.

For a reference....at a velocity of 2850-2900fps. with a 220gr. bullet the pressure on average will be around 72k psi. give or take a little with type of powder, bullet and chamber being used, rounds on barrel, how being cleaned etc....

Here is a little more food for thought....I've seen instances where a .0001" tighter throat diameter with a bullet at the max. tolerance diameter drive up pressures 4k-6k psi. You wouldn't think a .0001" would make a difference but it can.

Also seen examples where a barrel was made with a bore and groove .0005" under min. spec. and it drove up pressures 8k-10k psi.