Differences in velocity

[Grimm]

Alright, Wizards.. Got a question for you.

I'm pretty new to the reloading game and I'm not sure what what to make of these last two trips to the range. I'm currently working up a load for my 30.06 with 180gr Accubonds using IMR4350 using velocity to find a node with good ES and SD, then I'll move my OACL around to find accuracy. Basically, I worked up in .3 increments from 54.4 to 57.1 and found a few sweet spots, decided to play around in the 56.2-56.8 range and went out for another trip. What I'm not understanding was after the second trip, my velocities are consistently 50fps faster today than they were a few weeks ago. Not only were these last numbers higher, but they're also 60fps over the numbers in the Nosler book and their test barrel was longer. I'm not seeing any pressure signs until I've gotten over 56.8 which is why that was my max number on this trip.

I'm not really sure how I should interpret these results. My test consisted of 4 4-shot groups in .2 increments. The 56.2/56.4 loads were pretty on par with the speeds I saw a couple weeks ago. It was the 56.6/56.8 that had a pretty large jump from the first test. I know that velocity can be a sign of pressure but these loads were just fine the first time around. I plan on sticking with the 56.6 and playing around with length to find a group with it, unless that's not a good idea. I know 56.5 is a very common charge with this caliber/weight combo. I don't know if pushing the bullets into the case more is going to raise my velocity even higher or not.

Tikka T3 30.06
180gr Nosler Accubond
IMR4350
Fed 210 Winchester brass
2.729 to Ogive with 3.357 OACL which is about .020 off lands.
Magnetospeed Sporter chrono

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[Kruel J]

@No_Regerts

 

[P7M13]

Post your numbers please, meaning the entire string of shots through the Magnetospeed.
Which node gave you the best ES/SD numbers?
I've never loaded for -06, but I have seen similar results in 308, 338, 7mm and 6.5mm calibers, where velocity will jump significantly and then stay flat as powder increases.

 

[Grimm]

Post your numbers please, meaning the entire string of shots through the Magnetospeed.
Which node gave you the best ES/SD numbers?
I've never loaded for -06, but I have seen similar results in 308, 338, 7mm and 6.5mm calibers, where velocity will jump significantly and then stay flat as powder increases.

First test-
56.2gr - 2735, 2719, 2736, 2744, 2726
56.5gr - 2747, 2750, 2751, 2766, 2751
56.8gr - 2763, 2764, 2759, 2780, 2761

Second test-
56.2gr - 2699(?), 2791, 2795, 2787
56.4gr - 2795, 2798, 2787, 2807
56.6gr - 2811, 2809, 2807, 2811
56.8gr - 2830, 2809, 2821, 2803

FInding that flat spot is what I was kind of shooting for. This spot wasn't AS flat on my initial test, but had the best ES and SD numbers in the lot. They're not quite as great on this go around as the first time and have the higher velocities so I don't know what I'm doing lol

 

[bentoncity]

Temp & humidity factored in?

Dan

 

[MTpockets]

Did you control the temperature of the ammunition and the temperature of the chamber and barrel? I don't think IMR4350 is as susceptible to temperature variance as other powders, but you could use a control to verify.

 

[Grimm]

Did you control the temperature of the ammunition and the temperature of the chamber and barrel? I don't think IMR4350 is as susceptible to temperature variance as other powders, but you could use a control to verify.

Control, no. I just did the feel test on the barrel and tried to keep it about as consistent as I could. I don't have a chamber fan thing or IR thermometer yet.

 

[Grimm]

Temp is the only thing I can think of at this point. This go around I kept the barrel cooler than on the first trip because I shot far fewer rounds

 

[pharmseller]

We need to talk.

Find some Hunter powder and Winchester Large Rifle Magnum primers.

I load for three or four Tikkas using 180 AB.




P

 

[Grimm]

We need to talk.

Find some Hunter powder and Winchester Large Rifle Magnum primers.

I load for three or four Tikkas using 180 AB.




P

I'm always interested in trying new stuff! I have an awesome 165gr load with this combo so just figured I'd keep all things the same and try 180s.

What length are you loading them too? I'm .020 off the lands and it seems like it's not liking that far out. Won't know for sure until I play around with it some more of course.

 

[pharmseller]

Start low and work up or don't blame me.

180 AB (or Partition, same recipe)
59.0 gr Hunter
WLRM
3.334" oal

Expect 2750-2775 FPS mv and impressive precision.



P

 

[oremike]

In less you are in a lab and controlling all the variables there is no absolutes. A 1% difference from one day to the next as long as the load shoots good and has no other high pressure signs could just be environmental changes.

 

[Grimm]

In less you are in a lab and controlling all the variables there is no absolutes. A 1% difference from one day to the next as long as the load shoots good and has no other high pressure signs could just be environmental changes.

I guess that really is only 1.5%.. I didn't really stop to consider that. I'm just new to the game so thought I'd ask before I did something too stupid.

 

[oremike]

If it were me, I'd look at that 56.6 load as one to make. It has the least amount of difference between high and low velocities.

 

[Grimm]

If it were me, I'd look at that 56.6 load as one to make. It has the least amount of difference between high and low velocities.

Thats the one I'm going to be messing with the length on. It had a big group today but I've never been able to group with the magnetospeed on and never loaded this long before.

 

[oremike]

One thing about loading long is I've found the magazine length sets the OAL rather than the distance off the lands. I load to hunt so want to use the magazine rather that target shooting as a single shot.

 

[Whisky Tahoe]

Alright, Wizards.. Got a question for you.

I'm pretty new to the reloading game and I'm not sure what what to make of these last two trips to the range. I'm currently working up a load for my 30.06 with 180gr Accubonds using IMR4350 using velocity to find a node with good ES and SD, then I'll move my OACL around to find accuracy. Basically, I worked up in .3 increments from 54.4 to 57.1 and found a few sweet spots, decided to play around in the 56.2-56.8 range and went out for another trip. What I'm not understanding was after the second trip, my velocities are consistently 50fps faster today than they were a few weeks ago. Not only were these last numbers higher, but they're also 60fps over the numbers in the Nosler book and their test barrel was longer. I'm not seeing any pressure signs until I've gotten over 56.8 which is why that was my max number on this trip.

I'm not really sure how I should interpret these results. My test consisted of 4 4-shot groups in .2 increments. The 56.2/56.4 loads were pretty on par with the speeds I saw a couple weeks ago. It was the 56.6/56.8 that had a pretty large jump from the first test. I know that velocity can be a sign of pressure but these loads were just fine the first time around. I plan on sticking with the 56.6 and playing around with length to find a group with it, unless that's not a good idea. I know 56.5 is a very common charge with this caliber/weight combo. I don't know if pushing the bullets into the case more is going to raise my velocity even higher or not.

Tikka T3 30.06
180gr Nosler Accubond
IMR4350
Fed 210 Winchester brass
2.729 to Ogive with 3.357 OACL which is about .020 off lands.
Magnetospeed Sporter chrono

Grimm,
Note that H4350 is way more temp stable than IMR4350 so that alone might be your "speed source" if temperature has increased.

While you are testing, log the temps and pay attention to how many rounds you are shooting to gauge how hot your barrel is. Don't chamber a round until ready to fire or you can cook it and get more velocity that way as well.

In match barrels speed up is very common till about 200 rounds fired. If you have a new barrel, you might be experiencing this.

Finally, What is your goal? Accurate hunting rounds or target shooting?
The big difference is bullet construction which affects distance and ballistics coefficient.

 

[Grimm]

One thing about loading long is I've found the magazine length sets the OAL rather than the distance off the lands. I load to hunt so want to use the magazine rather that target shooting as a single shot.

I'm loading to basically max mag length in the Tikka

 

[Grimm]

Grimm,
Note that H4350 is way more temp stable than IMR4350 so that alone might be your "speed source" if temperature has increased.

While you are testing, log the temps and pay attention to how many rounds you are shooting to gauge how hot your barrel is. Don't chamber a round until ready to fire or you can cook it and get more velocity that way as well.

In match barrels speed up is very common till about 200 rounds fired. If you have a new barrel, you might be experiencing this.

Finally, What is your goal? Accurate hunting rounds or target shooting?
The big difference is bullet construction which affects distance and ballistics coefficient.

It's a hunting rifle, I'm just anal about wanting the tightest groups possible with these Accubonds. I have an area to plink around at 1000+ if I want to which is why I'm trying to be mindful of the ES and SD. I plan on switching to the H4350 (or try this hunter stuff out!) when I'm out of the IMR, I just have a few pounds of it left which will last plenty long for this hunting rig. Truth be told, I'm actually working these loads up for my brother in law and dont intend to hunt with them myself. I have a killer 165gr load for deer hunting and just picked up a 300PRC for elk thatll be my next reloading rabbit hole.

 

[pharmseller]

Do not use the Magnetospeed while shooting for groups. It will throw you off. Verify velocity then take it off when shooting for precision.



P