Home Forums Hunting & Shooting Ask The Gunwriters Anyone seen oddly high velocities with certain powders in a particular round?

I have a M70 in .300 Winchester Magnum. Using RL 17, RL 22 and H4350 - velocities by chronograph are about on par with what the books say they should be using 150g Barnes TTSX, Nosler 165g Accubonds, and Nosler 180g Accubonds. However - when I use IMR 7828 with 168g Barnes TSX and 180g Accubonds, I'm literally 125 to 150 fps above the max published velocity with 2 to 3 grains under the published max loads with a 24" tube. Now - I understand that rifles are different and that's why you start low and work up but IMR 7828 seems oddly energetic in my .300 Magnum more or less producing close to 300 Weatherby velocities without obvious pressure signs (other than the recorded velocity) with powder charges that are 2-3g below the max published load.

Is this a common occurrence? .

Are you following the recipe exactly, or substituting bullets, primers and/or cases? Those things can matter a lot, or not much. Powder lots vary too.

I loaded some 6mm CM carts with I4350 and 103gr ELDXs. The Hornady data didn't specify the primer they used, and I only had Starline cases at the time. I got a sticky bolt 1.5 grains under their max, and ended up about 3.5 grains under for best accuracy (nothing to write home about BTW). Those SL cases turned out to be a lot heavier than Hornadys and less roomy.

In the case of the TTSX - the TTSX differs from the source that was a TSX but the Accubond loads it was a Winchester case instead of Nosler with a Fed 215 Primer. The only thing that makes me think it's odd is that the the particular rifle is pretty much spot on with RL 17, RL 22, and H4350 with multiple bullets (in each powder) using Winchester cases and Fed 215 primers. I've only tried two bullets with IMR 7828, and both were far more energetic than I would have expected. It just struck me as particularly odd, and I've had almost the same results with 2 different lots of 7828 with 180g Accubonds.

I had the same thing happen with IMR 7828 in my 300 win mag, at first I thought my chrony was not right but it is,, its my go to powder in that cartridge.

I had similar issues with a 300 WSM and RL17. The Winchester 70 gave me velocity almost exactly where the books said it should be with 180's and a max load of H4350 with good accuracy. Looking at the manuals it showed about 75 fps more speed was possible with RL17. I was 2-3 gr below max, and getting speeds above where I should have been even with a max load. Accuracy wasn't anything to brag about either. When I backed off on the RL17 to where accuracy was acceptable I was right at the same speeds I was getting with H4350. I just stayed with H4350.

If you are getting speeds 100fps faster than expected you are over pressure. Just not enough to show traditional signs. YET.

Are you using data specifically for the Barnes bullets, or generic data for any 165/168 gr bullet. The copper bullets are different and load data always calls for less powder for a given bullet weight.

Leverevolution with 200gn Ballistic Silvertips in a 338 Federal. No published data, only published for 210, 215 and 225gn bullets. Sticking to data for the 215s, the 200s are much faster than other powders. Nice round primers, no ejector marks, stiff bolts, etc. So much faster I wonder what I’m missing...

JMR40,

No, data for copper bullets doesn't always call for less powder for a given bullet weight.

That pretty much used to be true, before Barnes started grooving the shanks of their solid-copper X-Bullets back in That was because copper was harder and "grabbier" than lead-cored bullets with gilding-metal jackets.

With the grooved shanks, however, pressure dropped considerably. In fact, the head tech at Western Powders' ballistic lab told me years ago that TSX's usually produced a little less pressure than most other bullets of the same weight and diameter--and light-for-their diameter TSX's produced about the least pressure of any rifle bullets. This is because the grooves resulted in less bearing surface between the bullet and bore.

This often isn't obvious when comparing data from two different sources, say the Barnes manual and some other manual, because of the differences in individual pressure barrels. But if we compare data from the SAME barrel it shows up.

An appropriate example here is the .300 WSM data for 165-168 grain bullets with Hunter powder in the Western manual. Maximum charges run from 68.3 to 71.4 grains, producing around 64,000 PSI. The second-highest HIGHEST maximum charge, 71.0 grains, is with the Barnes 168-grain TAC-X BT--and the highest is with the 168 Nosler E-Tip. (The E-Tip, however, is seated a little deeper, which also has a effect on pressure.)

The two lowest maximum charges for the six 165-168 grain bullets in the Hunter data are for the 165-grain Nosler Partition (69.0 grains) and 167-grain Lapua Scenar (68.3).

Another factor is that all handloading powders will vary some in burn rate from lot to lot, even though companies try to blend them to produce a reasonably consistent product. Generally different lots will vary no more than about 2% in burn-rate, though sometimes they vary more. Buzz probably has a slightly "warmer" batch of 7828.

What is your seating depth compared to the published data? I often follow John's advice of seating close to the lands (which raises pressures) and then "tuning" by seating deeper. But if the data you're using has a bullet seated much further from the lands than you're loading, that can make a difference as well.

Two examples for me that immediately come to mind are IMR 4955 in 6.5x55 and Reloder 23 in 7mm Remington Magnum.

Hodgdon shows a max of 48.0 grains of IMR 4955 in the 6.5x55 with a 129 grain Hornady will give 2,827 fps. I got 2,831 at 46.5 grains, or 1.5 grains below max. This could possibly be explained by the differences in seating depth though: 2.935" for Hodgdon and 3.090" (about 0.010" off the lands) for mine.

Alliant shows a max of 65.1 grains of Reloder 23 in the 7mm RM with a 160 grain Speer BTSP will give 3,001 fps. I used this data for a different, but lighter bullet; the 154 grain Hornady Interlock. The Interlock often has a reputation for showing lower pressure than some bullets and so I loaded up 5 shots at 1 grain increments to give an idea of velocity.

61.5 2,955 fps
62.5 3,007 fps
63.5 3,032 fps
64.5 3,045 fps
65.5 3,103 fps

So here I reached max velocity about 2.5 grains below max. Again, the seating depth varied (along with the bullet) with Alliant using 3.210" and me using 3.300 (I think about 0.015" - 0.020" off the lands).

Usually, even with slightly different components I don't see those big of differences. So those are some of my "worst case" examples.

Different lot of powder, different brass capacities even if the same make will make a difference. I have had changes from the powder absorbing moisture enough to increase the weight so I am sure the opposite could be true of very dry powder like if the powder is stored with a dehumidifier. I have also had very old powder do funny things. I think an old lot of H870 the exterior deterrent started to go and the powder shot faster and with higher pressures than previously. It took a magnifying glass to see any difference and I tossed the rest of the powder.

Case neck thickness especially if paired with a tight chamber can make huge differences. Just ask Steve Timms who touched off a load in a tight chambered Kimber of Oregon that they neglected to tell him that it had a neck turn only target chamber.

Happened to me recently with a Marlin X7 in 25-06.
About 2 grains under max with RL22, Fed 215M and 115 Nosler Ballistic tips.
Chrono showed 3345, 3350 and 3342 which is quite a bit faster than book showed.
No pressure signs at all.

R22 can vary so much from lot to lot that it is like a different powder. I believe they had one lot that was so fast they re-called it but not sure of this.

I think I mentioned it earlier but if not here again. The excessive velocities I ran into shooting 180g Accubonds happened with 2 different lots of IMR 7828 likely made several years apart


Rifle is a M70 Winchester with a 24" Pac Nor barrel in 1-10" twist

Going back to my notes -
75g of RL 22 seated to 3.380" produces an average velocity of 3005 fps. I was able to work up higher but this load produced the best groups in the rifle at that charge
70g of RL17 seated to 3.380 produces an average velocity of 3021 fps, but the extreme spread was a bit higher than I prefer

The odd one
Started at 73g of IMR 7828 (Nosler lists 77g as max) in Winchester cases with a Federal 215 Primer at 3.380" OAL, The initial velocity of the 73g loads was approx 3050 fps and I worked up to 76g before I stopped
Velocity at 76g averaged 3175 fps which is flat out smoking a 180g bullet. Even at 75g it was close to 3150 fps (didn't average), I honestly wondered if the chronograph was malfunctioning because there didn't appear to be any pressure signs in the rifle. Shooting a standard velocity .22 LR through it indicated it was pretty much spot on.


These loads are within the max charges published by Nosler - I've always found their published velocities to be a bit optimistic and this is first time I've exceeded them considerably under the max charge. The results from the second lot of 7828 were only chronographing the low end of the powder changes and they were pretty close to what I saw in the first lot.


Both Nosler and Hogdon have max charge of 80g of 7828 for 168 bullets and Nosler includes the E-Tip in their loading data. Somewhere I have my old Barnes book but at the moment I can't locate it.

I started at 76g of 7828 with a 168 TSX and it was approx 3120 fps, 77g was 3210+ fps. I stopped and didn't work up any further, again no pressure signs apparent while shooting but at least to me that seems oddly energetic for a .300 Win Mag given the powder charge. I'm going to try some H4350 this weekend and see what kind of velocity / accuracy it produces.

https://load-data.nosler.com/load-data/300-winchester-magnum/

I have used a lot of RL 22 in the past but one thing I don't like about it is that if I work up loads in the summer it seems to have a significant difference in velocity in cold temps. It doesn't really get that cold here but I don't want to work up a load here then take to Colorado or Canada on a hunt where the temps could be 80 degrees different!

On a different note - I noticed Barnes Loading data for 180g bullets is WAY different than Nosler using RL 22. Nosler's starting charge for 180g is more than 2g higher than the max load listed for Barnes. Of course compounding the odd is that Barnes lists a higher max charge weight with IMR 4350 than RL 22, despite RL22 being a considerably slower powder.

I am liking R23 a lot and where it performs the same or better than R22 there is no going back. The temperature consistency is amazing and since I don't have any Artic hunts planned R23 will vary less than 10 fps in the temperatures range I hunt in which can be damn hot at times. MRP has been a little more consistent than R22 so I will not quit using it but 23 beats the snot out of both of them.