2925 FPS in .300 win mag but no Pressure?

S

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Something kind of strange is going on with my .300 wm load development.

In a previous thread https://thefiringline.com/forums/showthread.php?t=585310 I detail some of my load workup and the cartridge specifications.

I have since moved beyond the 76 gr of H1000 up to 79 graines in 1/2 gr increments just to find where the upper range of the pressure is so that I know. This way, where ever I settle (and right now it looks like 77-78 gr), I know how far I am from too much. But so far, I have no pressure signs. 79 grains yielded about 2925 fps...This is very fast for a 225 grain bullet in .300 win mag. As I detail in the thread linked above, I am seating the bullet very long, 3.624, which is very long compared to the SAAMI spec 3.340. But it is a long bullet.

I did some calculations, and the difference between seating to SAAMI spec and my OAL is about 6.2 grains of water volume/weight. That additional case capacity essentially makes my .300 win mag load a couple grains less in volume than a .300 rem ultra mag. The .300wm holds almost 94 grains of water while the .300 RUM holds 114. That is obviously a 20 grain difference. But seating the bullet where I am closes that gap significantly when comparing the same bullet seated to SAAMI in the RUM.

Anyway, I have to believe that 3,000 fps is not attainable with a 28" barrel and a 225 grain bullet, even with the additional space. There is no manual or load information that even comes close to approaching that velocity. Also, 79 gr is beginning to compress. At that weight there is no sound when you shake the cartridge AND you can hear powder crunching when seating....I beileve 80 would be a fully compressed load.

FIFW, I have verified the accuracy of the chroney I am using (alpha model) against a caldwell, and a Gamma model chroney and they are within 20fps of each other.
 
79 grains of H1000 is 1 over current max for a 220(2,750 fps). That's not enough to matter though. Normal manual differences will do that.
How are you determining the speed?
Forget the off the lands stuff until you have a load too.
 
I am determining speed with a verified chroney (Alpha model). That has been measured against 2 other chronographs of differing models and brands. I just ordered quickload software, but the guy on the phone was nice enough and did the calculations for me and found that at 79 gr, I am only at 59500 psi...well below the 62500 max psi for the .300 win mag! Which means 3000 fps is possible and quickload was within 25fps of what I am getting.
 
Have you measured case head expansion? I have rifles that don't show the normal pressure signs and I can either tell if the load is too hot by measuring expansion or after it's too late and flogging out primer pockets in a couple reloadings.


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Nosler guy:

Yes, I have. When working up and pressure testing I measure and evaluate the usual stuff like case growth, shoulder demension, etc. I generally use an average of case measurements from cases fired at lower pressure vs higher pressure loads. In belted mags I also pay closer attention to the web for signs of bulge.

Like I said I went and ordered Quickload...The guy on the phone calculated I am below 60k psi which is mild for a .300wm, but his velocity was 40 fps below what I get.

But! There is no such thing as a free lunch. I have substantially increased case volume and that has been accounted for, but I can't be beating the programs velocity expectation by 40 FPS or so without paying a price.
So when I get the software, I will see what pressure (and powder charge) yields the velocity I am getting....I think that will be the more definative answer as to where I'm at on chamber pressure.


This may seem to some like a lot of wasted effort, but I have had experience, just like nosler guy and others I'm sure, who think they have a magic load that is screaming fast at nice safe pressure, only to find out in the summer heat they are sticking cases or after 2-3 loads the primer pocket is loose.
 
Re: "2925 FPS in .300 win mag but no Pressure?" Is there a question here?

I'm a novice rifle re-loader but maybe you are running into a wall with this load. I've heard of this before where there becomes a point where more powder has little effect on velocity yet pressure will continue to increase until it becomes erratic.

If the accuracy is OK at 79 but better at 77 - 78 i'd suggest following the obvious route and stick to the 77 to 78 range and tweak the load from there - OAL, Concentricty, Neck Tension, maybe change bullet, etc. I'm not sure what 3000 FPS could do that 2925 can't.
 
Re: "2925 FPS in .300 win mag but no Pressure?" Is there a question here?
Click to expand...

Im not a novice, but also not an expert. The reason I have a question mark on it is because that puts a .300 win mag at about the same velocity as a SAAMI .300 Remington Ultra Mag.

As for the accuracy node between 77-78 grains, that is where I will likely end up when I have finished testing.

But a common practice, while fireforming brass and before fine tuning the load, is to find the upper end of the pressure limit in THIS chamber with THIS powder lot, bullet, primer, case etc. Once the brass is fireformed, you will lose a little velocity due to increased case size, but it usually isn't much..So if the upper limit is say 80 grains in virgin brass, it might be more like 80.5 in fireformed brass.

But that is what I am trying to find out, it is just that I am getting up there in velocity with nothing telling me to back off. Usually there are little stop signs like extraction marks, heavy bolt lift, primers dimpling outward rather than inward, case head expansion etc. But so far, I am seeing none of that.

I went ahead and tested 79.5 and 80 grains.
80 grains gave 2952 fps. I finally began to see pressure signs at 80 grains.

Which means to me, that 2950 is the upper limit of velocity with my seating depth, chamber deminsions, brass, primer and powder combo.

But I must say, I am impressed....That Bryan Litz guy sure knows his stuff, I read some of his papers on seating depth, velocity, and pressure and he said that this would happen...I just didn't think it would be this dramatic.
 
Re: "But a common practice, while fireforming brass and before fine tuning the load, is to find the upper end of the pressure limit in THIS chamber with THIS powder lot, bullet, primer, case etc. Once the brass is fireformed, you will lose a little velocity due to increased case size, but it usually isn't much..So if the upper limit is say 80 grains in virgin brass, it might be more like 80.5 in fireformed brass.
But that is what I am trying to find out, it is just that I am getting up there in velocity with nothing telling me to back off. Usually there are little stop signs like extraction marks, heavy bolt lift, primers dimpling outward rather than inward, case head expansion etc. But so far, I am seeing none of that.
I went ahead and tested 79.5 and 80 grains.
80 grains gave 2952 fps. I finally began to see pressure signs at 80 grains.
Which means to me, that 2950 is the upper limit of velocity with my seating depth, chamber deminsions, brass, primer and powder combo."



Very interesting. Thanks for the detailed response and update.
 
My Hornady manual shows a max about 2800 fps with a 220gr bullet. I doubt your gonna get 3000fps even with that long barrel! I didn't see where you gave the powder your using?
 
WOW! In the Hornady manual it has 2600 fps max with that powder! They have a 225 gr bullet but don't list H1000 for it. Nosler manual for the 220 gr bullet and H1000 is 75.5 grs getting 2677 that is load density at 95%. You don't have a long throat do you? I long throated a 7mm Rem mag years ago so that I could seat a 160 gr bullet flush with the shoulder/neck junction. Upped the max load by 2 1/2 grs. No idea what it did to the velocity, no chronograph's in those day's. Lot of freebore is what allow's Weatherby's to reach the velocities they get. Be kind of neat to see someone take and have a barrel done in 300 Weatherby with out that freebore and see what it get's. Years ago a friend brought a friend of his rifle that didn't shoot well. His friend was complaining about presser to a gunsmith and told him he wanted it fixed so he could eliminate the pressure. Gunsmith told him he'd relieve the problem. Freebored it several inch's up the barrel. He's have been better off with a 7mm-08 after that! Did you get that rifle new? Can you reach the lands with the bullet seated?
 
Don Fischer: WOW! In the Hornady manual it has 2600 fps max with that powder! They have a 225 gr bullet but don't list H1000 for it. Nosler manual for the 220 gr bullet and H1000 is 75.5 grs getting 2677 that is load density at 95%. You don't have a long throat do you?
Click to expand...

I have the newest Hornady Manual also, and Sierra, and Nosler, and Speer.....and the universal Lyman 49th. I find that the Bullet maker manuels are very conservative on their Max powder recommendations. On the other hand, I find Hodgdon to be a bit too hot on their max recommendation. Hornady is one of the MOST conservative. If you find a bullet in hodgdons dataset from hornady, look at the max charge hodgdon recommends vs. hornady and you will see what I mean.

As for the Rifle, I built it. It has a Shilen #8 28" barrel, timney trigger, savage 110 action, competition recoil lug, in a aluminum pillar beded stock that takes AICS magazines. I headspaced it using the savage barrel nut method and Forster Go/No-Go gauges.

Now the freebore..The new Hornady ELD's are long with about a 0.60" bearing surface and long ogive. The 225 gr ELD-M is 1.655" long. The COAL recommendation in the Hornady Manual is 3.340, I am seating to 0.02" off the lands which yields an OAL of 3.628, or CBTO of 2.8570".
Which means I am almost 0.30" longer than the SAAMI OAL. I calculated that the amount of space I am freeing up would be about 6.5 grains of water vs. seating to SAAMI OAL.

This also means that I would have had about .302" of freebore had I seated to SAAMI. The throat of this rifle was not intentionally throated long, but the shape and design of these new secant ogived bullets from berger and hornady require you to seat well beyond SAAMI OAL. Otherwise, I would have almost 1" of bullet in the case, which would occupie a lot of space, and spike my pressures quickly with much less powder. Maybe Hornady's recommended powder charge is spot on....IF you are loading to the SAAMI OAL, which I am not...not even close. But they will feed from the mag because I am using the AICS system.
 
the shape and design of these new secant ogived bullets from berger and hornady require you to seat well beyond SAAMI OAL. Otherwise,
Click to expand...

I have 2 300 Win Mags, one shoots one hole groups and the Model 70 Winchester shoots groups that are best described as shot gun patters. Both barrels have two diameters, the large one is .308" and the small one is .300"+.

I know the diameters because I drill the flash hole/primer pockets out of the case, then sized the case and seat a bullet with all the bullet hold I can get. I then remove the bolt and chamber the test case and then push the bullet out of the case into the lands. The lands imprint on the bullet, I measure the diameter imprint.

F. Guffey
 
I have pushed bullets out of the case before the bullet contacted the lands, I found the bullet traveled .300" out of the case before the bullet hit the lands. There was nothing free about the free bore because fixing that one was very expensive. The owner ask me "How could that happen?" and I said "I do not know!".

F. Guffey
 
I have pushed bullets out of the case before the bullet contacted the lands, I found the bullet traveled .300" out of the case before the bullet hit the lands.
Click to expand...

Wow...Was it a Spitzer type or Roundnose type bullet? Because if that happened with a bullet having a short ogive, I think a re-chamber is the only option.

In this case, I don't actually have a lot of freebore, it is that these ELD and VLD bullets are so long, that if you seat them to SAAMI 3.340, the tip of the bullet is so far from the shank that it has to jump a long way before hitting the rifiling.

Perhaps your friend would have been delighted to find out his gun was throated to shoot very long VLD bullets with maximum case capacity? ;)
 
The old Mauser 243 of mine have a quarter inch of jump and a 90 gn bt hits the lands just as it exits the case.
ea906be9d4be0a208202ff51443adeca.jpg


80 bt with varget. Barrel is pretty shot out but it still puts em where you want them.

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