Variables in velocity in load development for 270WSM

Pineman

Beginner
Dec 20, 2021
66
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Ok. So I have a great load for my 270WSM with 140g Accubonds and Magpro. I thought I would try and see what I could do with 150G Accubonds and Magpro. I went to the range today and was very happy with my initial loadings but not the velocities I was achieving. I need to fine tune but I was getting 0.525 inch groups around 2950fps. I did try Remington 91/2 M primers instead of WLRM and Browning and Hornady Brass instead of my go to Nosler and Winchester just for development purposes. I guess my question boils down to this: would brass and primer choices make a significant difference in velocities? I was hoping to get around 3100fps. Like I said, accuracy was very good just wish they shot alittle faster. Looking forward to comments. TIA
 
While velocities may not be as high as you want, that degree of accuracy with that particular velocity will allow you to show easily to 450 yards or more. To answer the premise you suggest, yes, primer choice and brass can make some difference in velocities. A hotter primer can boost velocity by as much as 100 fps, but you can't predict what impact such a change will have on accuracy. Brass choices will have a much smaller impact on velocity, but can provide a measurable difference.
 
Good advice above. The answer is yes. A safe and accurate load with xyz brass may very well be unsafe to an extreme degree with abc brass. Especially if you’re inclined to shoot your rifle at the top end of its safe pressure range. It’s not as pronounced with mid level loads. Brass can and will also impact group size. Basically, if you use different brass you are firing a completely different load. Primers will change a load as well, especially when using slow powders.

Edit: I recommend consistency when running near redline.
 
Ok.. Thanks for the replies. In regards to hotter primers: can someone rank the magnum primers from slow to fast, etc? I have all the major brands of primers so I could experiment but i don't know where the 9 1/2 M compares to the WLRM and 215M. Once again TIA.
 
On all the WSMs, I have found that standard large rifle primers will work just fine due to the shorter powder column. You can use magnum primers, but they aren't necessary for full ignition. I've hunted with my 270WSM in temps as low as -30 C, and never had a problem with ignition or with massive shifts in ballistics. In terms of standard primers, the hottest are WLR followed by Fed 210 and/or CCI200, with R 9.5 showing the least brisance. When weighing magnum primers, Fed 215 is generally revealed to produce the most brisance, followed by CCI250 and/or WLRM, with R 9.5M having the least brisance.
 
Thanks Dr Mike. I was surprised in that my 270WSM was really easy to find to work up a load with very good accuracy with the 150AB. I will try some standard primers when I tweak my loads.
 
Sounds like a great load so far, congrats. Going to pick up some Magpro for my 6.8 Western for when I start reloading for it shortly.
 
Gerry,
I know so people don't like Magpro but my 270WSM really likes it and I guess that's all that matters. Try some in the 6.8 Western, I think you will like it.
 
Looks like I can actually buy some Magpro locally, should be as good in the 6.8 W as it is in your 270 WSM.
 
There are multiple reason you feel the load was slow. Yes brass internal capacity makes a difference along with primers as Dr. Mike covered. Your style chronograph you’re using and lighting condition if it’s an optical.
Most rifles will have an accuracy node well short of max pressure.
The one thing nice with QL is you can match bullet and powder to a BT node. I have select barrel lengths I purchased to help them match up.
 
On all the WSMs, I have found that standard large rifle primers will work just fine due to the shorter powder column. You can use magnum primers, but they aren't necessary for full ignition. I've hunted with my 270WSM in temps as low as -30 C, and never had a problem with ignition or with massive shifts in ballistics. In terms of standard primers, the hottest are WLR followed by Fed 210 and/or CCI200, with R 9.5 showing the least brisance. When weighing magnum primers, Fed 215 is generally revealed to produce the most brisance, followed by CCI250 and/or WLRM, with R 9.5M having the least brisance.
I only use standard rifle primers in all my WSM cartridges. Mostly GM210M.

I recently substituted 9 1/2m primers in place of 210M primers in a 300 wm. Lost 65 fps. In most primer tests involving 9 1/2 M primers I believe they are one of the mildest primers magnum or not. My results were in larger capacity cases. Not sure how smaller cases would react.
 
Thanks for the helpful replies. On my load development, they were all seated the same length so next time I will use the same brass and just try different primers. I will report back with my results but it won't be for a couple weeks. I appreciate all knowledgeable guys on this forum.
 
Keep in mind that new brass will have some variables in velocity as well, once fireformed it will have a more significant reading on your chronograph. As Mike already mentioned that different brass will have different impact on velocity due to volumes of the case, some brass are thicker or thinner. Thicker will give less powder volume and thinner brass will have a larger powder column. If a certain case brand shoots well, stick with it. a half MOA @ 100 yards is great. Good shooting, and good luck on your next development.
 
As you have noted, the AccuBond bullet is easy to develop loads with. I have found it to be the easiest bullet to quickly find accurate loads, regardless of cartridge/caliber and weight. Using in .257-.375 calibers.
I know that the Federal Premium factory ammo with the 140gr AB was very accurate in my 270WSM (0.415" @ 100 yards) but was also slow...by about 100 fps. I did have a recipe for 69.5gr of MagPro in WW cases with WLRM primers that were supposed to produce 3237 fps...but I never got around to trying that load while I had the rifle as I had a good supply of the ammo on hand (sold rifle as it was RH and I'm a lefty).
At the end of the day I didn't worry about the velocity as the accuracy was so good and a 140gr bullet at 3100 fps is no slouch, and no animal is going to notice the difference in velocity at the ranges I normally hunt within!
 
On all the WSMs, I have found that standard large rifle primers will work just fine due to the shorter powder column. You can use magnum primers, but they aren't necessary for full ignition. I've hunted with my 270WSM in temps as low as -30 C, and never had a problem with ignition or with massive shifts in ballistics. In terms of standard primers, the hottest are WLR followed by Fed 210 and/or CCI200, with R 9.5 showing the least brisance. When weighing magnum primers, Fed 215 is generally revealed to produce the most brisance, followed by CCI250 and/or WLRM, with R 9.5M having the least brisance.
Years ago I tested most of the available primers (yes, back when they were ALL available and AFFORDABLE) in my .270 WSM with my favorite load and was surprised that the standard Federal 210 primer gave the most consistent results vs the various magnum and even the bench rest versions. I didn’t have a chronograph back then, so I went with best accuracy. My son’s favorite load in my old .270 WSM consists of MagPro and the 150 gr Nosler Ballistic Tip. It chronographs around 3200 fps, but that is out of his 27” Lilja barrel.
 
Follow up from range day. I tried Federal nickel cases today with both Fed 210M and Rem 9.5M primers. All the bullets were seated the same and fine tuned powder charge in 0.3 increments from last range day. I guess I was pleasantly surprised but a few questions came up. My best group came in at 0.313 at 2976fps in my 270WSM and 150g Accubonds. This is what I was really happy about: SD was 1 and Extreme Spread was 3fps. Can someone interpret that very low SD and ES for me--I just know the lower the better. In the Nosler Book it says my charge of Magpro from a 24 i1 inch barrel will be around 3175FPS. What is the rule of thumb: 1 inch barrel length = 100FPS? If so, I have a 23 inch barrel and my altitude is 1230 feet so when you factor those 2 in, probably not to bad. Going to try Winchester and Nosler brass but other than that, going to use this for a cow elk this fall.
 
Follow up from range day. I tried Federal nickel cases today with both Fed 210M and Rem 9.5M primers. All the bullets were seated the same and fine tuned powder charge in 0.3 increments from last range day. I guess I was pleasantly surprised but a few questions came up. My best group came in at 0.313 at 2976fps in my 270WSM and 150g Accubonds. This is what I was really happy about: SD was 1 and Extreme Spread was 3fps. Can someone interpret that very low SD and ES for me--I just know the lower the better. In the Nosler Book it says my charge of Magpro from a 24 i1 inch barrel will be around 3175FPS. What is the rule of thumb: 1 inch barrel length = 100FPS? If so, I have a 23 inch barrel and my altitude is 1230 feet so when you factor those 2 in, probably not to bad. Going to try Winchester and Nosler brass but other than that, going to use this for a cow elk this fall.

Great shooting. Typically, you will see about 25 to 50 fps= for each 1" of barrel length. Those 150 AB at that speed will be deadly on a cow elk. Here is a good read on SD/ES: https://www.gunsandammo.com/editori...-extreme-spread-and-standard-deviation/247510
 
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