This is a very long post, but I think it will be worth your time.
I was interested in the .300 Varminter and noticed there is substantial controversy on this forum concerning it. After reading quite a few posts, I broke out QuickLoad and decided to see if it was even close for a .300 WSM to drive the 125gr Nosler BT to 4000fps. At first glance it seems it is not, at least with reasonable pressures.
However, QuickLoad is just a model. Professionally I am an engineer and I have done quite a bit of modeling/simulations and analysis across many different fields; I still have much to learn. One of the things that is often forgotten is that most of the equations we have from physics and we engineers use are simplifications, models. They only work under a given set of assumptions. Should be common sense, but if I had a nickel for every time someone refused to believe what they were seeing because the model said it couldn’t happen…
It is also important to build the right kind of model. Too often engineers get caught up in our models and want to model/simulate everything, even when there are other more accurate/reliable solutions. A wise, old engineer/physicists told me a story once about how a particular government program wanted to build a simulation. It was going to take a significant amount of money and time to build the simulation and test it. Then even more money and time to actually run the simulation and get statistically valid results. This older engineer pointed out that a simulation was pointless because there was an analytic solution and you usually use the analytics to validate the simulation. So he got some paper and solved it analytically in a day.
The moral of the story is only build a model/simulation when you need too and only trust it when it agrees with the analytics and the real world. Now that that bit of modeling philosophy is out of the way, let’s take a look at the .300 Varminter claims.
It seems some of the .300 Varminters critics like to cite the Hodgdon reloading data. Unfortunately, the Hodgdon data does not specify barrel lengths nor twist rates. To evaluate this data I used QuickLoad, the Hodgdon reloading data for the 125gr Nosler BT in .300WSM, and the Modern Reloading Second Edition by Richard Lee.
The data for the .300WSM and a 125gr jacked bullet (page 459) is identical to the Hodgdon data. Unfortunately, no barrel or twist rate is given. Using QuickLoad, I played with the barrel length until I was able to minimize the error in pressure and velocity on all of the Nosler 125gr BT loads from Hodgdon (both Min/Max loads):
QuickLoad Data Bullet 125gr Nosler BT Starting Pressure (PSI) 3626
Everything is default QL except the COL and barrel length. I tested other cartridges with the Nosler 125gr BT and the starting pressure seems correct for this bullet and QL (data presented further on). It appears that the Hodgdon data is from a 24.5” barrel (+- 0.5”). Interestingly, Varget and H4895 both have substantial differences in pressure/velocity between QL and Hodgdon/Lee.
Returning to the QL defaults (COL 2.860” vice 2.810”) and a barrel length of 24.5” I get 3371fps, 53314psi for 70gr of N550. This is Richard Franklin’s suggested starting load. However, his .300 Varminters are built on 30” barrels yielding: 3579fps, 53314psi, for 70gr of N550 in QL. A far cry from 4000fps, but still not close to max pressure either.
Richard’s 4000fps load is supposed to be 75gr of N550. QL results are: 3610fps, 67226psi for a 24.5” barrel and 3773fps, 67226psi for a 30” barrel. Still 250fps shy of 4k and already approx. 3000psi over CIP MAP. If we stopped here it would be easy to say someone is a liar or the loads are easily over 70k psi. I decided to push onward and check some base assumptions and things get interesting.
I decided to pull up Lapua/Vihtavuori reload data. At least in theory, their data should be spot on for their powders. Fortunately, Lapua specifies barrel length and twist rate. It should be noted that the twist rate for the .300 WSM test barrel (1:10) is tighter than optimal for the 125gr Nosler BT and much tighter than the 1:15 Richard uses. I compared the Lapua data for N550 (Richards recommended powder) against QL:
Test Barrel: 24.5” 1:10 twist
Otherwise QL defaults
Interestingly, QL is giving 101fps lower for the starting load and 210fps lower for the max loading. Just for fun I wanted to see what the max load was under QL was: 74.4gr of N550 for 3580fps in a 24.5” barrel. About the same as what I got for the Nosler.
Again, QL gives data that is much slower then Lapua’s N550. Max loading in QL was: 67.1gr for 3130fps in a 24.5” barrel.
Bullet Grs FPS Delta PSI
Lapua 185gr Mega 52.6 2572
Lapua 185gr Mega - QL 52.6 2454 -118 35031
Lapua 185gr Mega 59.1 2844
Lapua 185gr Mega - QL 59.1 2727 -117 47836
QL is still 100fps lower in the .300 WSM than the Lapua factory data. It does seem the heavier bullets give less error in velocity than the lighter bullets. It is also possible Lapua’s data is junk (not likely). It should be noted that Lapua wasn’t specifying pressures, so I have no idea if the QL number above are even close. Nearly every Lapua factory load I tested during this inquiry QL calculated the pressure right at MAP – 25%.
To test the quality of QL predictions with Vihtavuori powder and the .300 WSM I tried comparing some more loadings.
Cartridge 300 WSM Test Barrel 24.5" 1:10 COL 2.709" Powder N150
This is only two other factory Lapua loadings, but both are showing similar results to N550, 200+fps low in QL. It doesn’t seem to be a problem with the 5 series of powder, but most comparisons are needed.
Fantastic data! The .308Win results are extremely close and this is the factory data for the Nosler 125gr BT. The starting pressure was set to the QL default of 3626psi. As I stated before, the QL default starting pressure for the Nosler seems to be correct. The interesting thing is that these are Vihtavuori powders again, but the data is spot on. Granted these are faster burning powders, so more analysis is required.
How does the .300WM compare?
Cartridge 300 WM Test Barrel 24.5" 1:10 COL 3.224" Powder N150
The QL data for the .300WM seems to match slightly better than the .300WSM data does for N550, but there is still about 150 fps differences. The other Vihtavuori powders also seem to be off by substantial amounts too. So far anything with Mag in the name seems to be way far off with light bullets.
How about one of my favorites .338LM?
Cartridge 338 LM Test Barrel 27.5: 1:10 COL 3.681" Powder N560
Huge errors again! Either Lapua magnum data is junk or QL is having an issue with magnum velocities and Vihtavuori powders. To see if this problem is a QL and magnum issue or if Vihtavuori powders are part of the issue I pulled up some other factory load data.
How does Nosler’s own data for their 125gr BT sound? I used the QL defaults for COL, etc., but played with the barrel length as Nosler didn’t specify it. To match the velocities IMR4064 needed a 32” barrel and RL-15/Varget needed 29” barrels. It is unlikely that Nosler tested these lengths, but we don’t really know. I put the barrel length back to 24.5” because I thought that was reasonable and probably closer to what they tested. Only max loads shown:
Cartridge 300 WSM Test Barrel 24.5" COL 2.86" Powder IMR4064
Again the .300WSM data in QL is much slower than the factory data. I don’t think QL pressures are that far off as all of these Nosler factory loads are right at MAP – 10%. Let’s take RL-15 (because it is in the middle of velocity loss and I like this powder) and put a 30” barrel on the gun (like Richard’s 300 Varminters). Also, according to QL 68gr of RL-15 is the max before breaking the MAP.
Cartridge 300 WSM Test Barrel 30" COL 2.86" Powder RL-15
70gr of N550 is the starting charge; it reaches mid 3700s when corrected. 74.1gr is right under the CIP MAP; it is good for mid 3900s corrected. 75gr is Richard’s hot loading; it is good for 4000ish. 75.4gr is the MAP that Norma brass is suppose to handle safely (I heard this from people. I have no insider knowledge and it could be completely wrong); it is good for just over 4000fps. However, if the Norma brass MAP is correct than it would explain why Richard’s 300 Varminters were not seeing pressure signs with 75gr N550 and BAT actions.
Last edited by gunderwood; 07-07-2009 at 10:46 PM.
Given this data I think QL is under calculating the velocity for magnum cartridges with light bullets. I think it is clear that to get 4000fps hot loads must be used, but Richard said he was seeing around 3800fps with 70-72gr of N550. The corrected velocities seem to be real close to 3800 with 70gr. Without going over MAP and with corrected velocities it seems 3900+fps is achievable with some assumptions.
First, even if the QL velocity correct is accurate, the correction for velocity would have to be constant, it won’t be. Richard is throating these guns for these bullets, he is also using high quality SS barrels which factory data probably isn’t. A slightly longer COL? Any of these things can change the pressure/velocity significantly. Etc. Etc.
E.g. Cartridge 300 WSM Test Barrel 30" COL 2.91" Powder N550
If you don't want to read and analyze all of that, here is the short story.
Richard Franklin's .300 Varminter should be able push the 125gr Nosler BT to 3800fps easy and probably 3900fps without breaking CIP MAP according to my QL analysis. This is because QL seems to be under calculating the velocity of all magnum cartridges with light weight bullets when compared to factory data. 3900fps takes the pressure right to max. To reach 4000+fps the QL analysis suggests that CIP MAP must be exceeded, but it will still be within wildcat cartridges MAP range of 68k psi.
QL numbers vs Sierra's, COL 2.76":
H4895 -239fps 49,042PSI
IMR4350 +98fps 67,232PSI
RL-19 +64fps 62,192PSI
IMR4831 +169fps 70,318PSI
So 4895 shows similar results as the Lapua data, slower by 200+fps, but everything else is faster. 4831 is much faster (169fps vs. Sierra), but the pressure of RL-19 and 4831 are well over CIP MAP of 64, 542PSI. Think QL is a little off on the PSI? Or is Sierra publishing 70k+ PSI loads as "safe?"
QL is a great tool, but it seems to fail on these .300WSM loads. Always check your models against measured data or analytics to verify they are producing good results.
Interesting stuff. Anybody know if Richard has ever put a strain gauge on one of his rifles and shot it over a chronograph? That would shed more light and would seem to be more concrete evidence one way or another (anecdotal as it would be though, if done with just one rifle).
The critters have to win every time, I only have to win once.