Interpeting Magnetospeed Data

[Bishop]

So i got my magnetospeed V2 in yesterday and went out this evening to see what the velocity out of my .308 win was.

This is that data I gathered from 15 shots.
Series, 1, Shots:,15
Min,2790, Max,2863
Avg,2829 ,S-D, 19
ES , 73

Series,Shot,Speed
1, 1, 2815, ft/sec
1, 2, 2828, ft/sec
1, 3, 2813, ft/sec
1, 4, 2824, ft/sec
1, 5, 2810, ft/sec
1, 6, 2790, ft/sec
1, 7, 2818, ft/sec
1, 8, 2824, ft/sec
1, 9, 2847, ft/sec
1,10, 2845, ft/sec
1,11, 2849, ft/sec
1,12, 2863, ft/sec
1,13, 2837, ft/sec
1,14, 2847, ft/sec
1,15, 2837, ft/sec

First off, I am seeing some what seems to me, pretty high velocity here, I would like some input on how confident I should be in these numbers.

Also this seems to tell me that my load is complete crap and i need to do some drastic work on getting my ES down.

These numbers were shot out of a .308 win, lapua brass, 175 smk, wlr primer, 44g IMR-4064, 10 thou off lands with a 30 inch barrel. I was hoping to get close to 2800 fps with this gun and 175's but my god, according to the magnetospeed I hit 2863 fps on one shot. And the velocity seemed to increase to the shy side of the mid 2800's after the first 5 or 6 shots. And I had one round at 2790 fps? Should i throw out the outliers?

This rifle has only had 115 shots fired total out of it, is it possible I just experienced some barrel speed up? Are these numbers normal? This rifle shoots sub 1/2 moa consistently at 100, and the few groups I have shot out to almost 600 yards did not exhibit much vertical at all 2 to 3 inches of vertical normally out at 600. Certainly not what i would expect with a 70 something ES. Can anyone tell me what kind of vertical they would expect out of that much ES at 600? Did i just get a few lucky groups?

Thoughts?

 

[Bishop]

Yikes, tough questions I reckon.

 

[westcliffe01]

How fast did you shoot the string ? What were the environmental conditions for this latest shoot compared to when you did the load development ? That powder is temp sensitive and if the barrel and chamber was getting hot, it could increase pressure and thereby velocity. Try the same with Varget and take your time shooting the string. It should be a lot less temp sensitive.

 

[Bishop]

I shot all 15 shots over the course of about 2 hours. Environmentals were similar within 15 degrees. From development to now.

Would love to use varget, and will when I manage to get a large enough batch gathered up, I only have 4 1/2 lb's of varget right now vs 18 lb's of imr-4064. Once I manage to get enough varget to have a supply I wont run out of soon I will give it a shot.

The barrel is a 30 inch brux MTU contour I got the barrel ever so slightly "warm" to the touch compared to the ambient temperature with a couple of 3 to 4 shot strings. I didnt get the barrel "hot" by any means.

I suspect I either need to,

1: Back off my powder charge slightly

2:Change to Fed210M primers

3: Change Powder

I guess I am just looking for some reassurance that my magneto isnt lying to me, or having a little brain fart with the seemingly out of place highest and lowest fps shots.

 

[MMERSS]

Min,2790, Max,2863

Avg,2829 ,S-D, 19
ES , 73
These numbers were shot out of a .308 win, lapua brass, 175 smk, wlr primer, 44g IMR-4064, 10 thou off lands with a 30 inch barrel.

I don't see anything major that jumps out with what you have listed. Your AVG MV is not unrealistic. ES is high but this may be contributed to your loads and not necessarily the chronograph. I use identical components with a charge of 42 gr. and 20 thou jump in my 30" gun with an average velocity in the 2700s.

 

[bill123]

Could the accuracy of the powder scale account for some of that?

 

[HARPERC]

What's your reloading process? are you annealing necks etc.? Bushing or expander ball?

 

[liltank]

How clean was the barrel when you started to shoot? Did you do a barrel break in? With 115 rounds down a tube it's hard to say until you get some polish on the rifling. My Lothar barrel really didn't settle down until about 250 rounds. It shoots very consistent now. You may want to back down a grain to see what happens. With trying to save up Varget, they need to be the same lot or it won't matter. Try some RL15 if you can find it. If you had really clean barrel then it takes a few rounds to settle in the barrel. I noticed your last three shots were pretty close in velocity. Just some thoughts.

 

[Bishop]

I use an rcbs Beam scale and throw each charge close, and trickle up from there on the beam scale.


I did not anneal the necks as these are virgin lapua brass, I trimmed them all to the same exact length, sized with a Redding type-s F/L bushing die. I ran it with the expander ball in the die on this batch because they were all virgin cases and i wanted to get rid of any dings in the case mouth etc. Now that i have all cases sized once and no dents in the neck I will not be using the expander ball anymore.

Barrel had 20+ shots to foul it before i started shooting through the chrony, and i followed the break in instructions included with the rifle when i bought it from Len here. I also shot it some today and only had a much lower ES and SD today, but I also had a smaller sample size, only 8 shots with the magnetospeed on the barrel. I had an ES of 15 for those 8 shots with most of them being within 5 fps. I had one round abnormally low fps and one round abnormally high when compared to the rest of them.

I did however shoot a .327 3 shot CtC group with it today off the bipod with this load at 100y, so the accuracy potential is there, i just need to get the ES down as low as I can.

I will mix all the varget together in a tub once i get enough saved up and then put it back into its containers to help eliminate the lot to lot difference once i get enough bought up to warrant going through the trouble.

@liltank you mentioned the last 3 shots really close, thats what I am seeing when im chronographing this gun, I will get a few shots that are right close within 5 fps or so and then BAM i get one wacky shot that is like 30 fps slower or faster.

I really wish i could find 5000 F210m primers but they are harder to find than powder for me atm. I might try some Rl-15 if I cant get the ES down with IMR-4064 but I have plenty of IMR to work with so I will give that some time first. Since I have nice velocity as well dropping a grain might be a good idea, I will give that a shot next and see what happens, although my observed accuracy nodes were at 42.5 g of imr-4064 and 44g of imr-4064 however the gun has not shot any worse than .5 moa with any load and seating depth I have tried so far, except 44.5 g of imr-4064 there was an immediate group opening when i was doing my initial load work up when i hit this powder charge, and a plain ejector mark on the brass. I am getting a very faint ejector mark at 44g right now with some primer flattening. So I suspect I may be fine just being satisfied with .5 moa and dropping my powder charge to see if I get better ES.

Heck of a problem to have i know, having a gun that shoots .5 moa at its worst. The ES is just driving me crazy though, its fine out to 600 now, but i suspect I would start having some major issues at 700-1000 with this load with bad vertical.

Thanks for the responses guys much appreciated!

 

[liltank]

That might be a starting point. Change primers on the same load data. You don't necessarily have to use match primers. Try some CCI and any other you may have. MIGht take care of the spike. However, the spike almost sounds conducive to a load that is above max and your seeing the beginnings if diminishing returns.

 

[Bishop]

However, the spike almost sounds conducive to a load that is above max and your seeing the beginnings if diminishing returns.

Yea this load is definitely on the cusp of max/overpressure in my rifle, it is close enough that im certain I will have to drop the powder charge by a half grain or so during the summer, if not a full grain. All my shooting so far has been done between 45-55 degrees, and im like 300 feet above sea level here as well.

 

[liltank]

I bet if you back it down a half to a full grain, your numbers will be a lot better.

 

[Greyfox]

As has been previously mentioned, velocities, considering your barrel length and charge weight the 175 SMK are not unrealistic. You stated that a string of fewer shots produced better ES. One thing to check is the tightness of the Magnetspeeds mount on the barrel. I had a similar experience with a well proven load that was indicating wider velocity spreads than normal. The problem was that after repeated shots the the Magnetospeeds mount had was slightly moving on the barrel. When I tightened it up my results returned to normal. I'm not sure this is contributing to your ES but worth checking. I use the extra rubber barrel mount supplied with the unit, and put it under the strap on top of the barrel, then make it very tight for a secure mount. on another note. Myself and a few of my buddies do a lot of 308 shooting. Like yourself we have had a lot of difficulty finding Fed210M's. We have found that the more available Winchester LR primers produced very similar, accuracy, velocity and ES in our rifles when tested against the Federal 210M's using Varget, R15, and IMR4895 powders.

 

[Bishop]

As has been previously mentioned, velocities, considering your barrel length and charge weight the 175 SMK are not unrealistic. You stated that a string of fewer shots produced better ES. One thing to check is the tightness of the Magnetspeeds mount on the barrel. I had a similar experience with a well proven load that was indicating wider velocity spreads than normal. The problem was that after repeated shots the the Magnetospeeds mount had was slightly moving on the barrel. When I tightened it up my results returned to normal. I'm not sure this is contributing to your ES but worth checking. I use the extra rubber barrel mount supplied with the unit, and put it under the strap on top of the barrel, then make it very tight for a secure mount. on another note. Myself and a few of my buddies do a lot of 308 shooting. Like yourself we have had a lot of difficulty finding Fed210M's. We have found that the more available Winchester LR primers produced very similar, accuracy, velocity and ES in our rifles when tested against the Federal 210M's using Varget, R15, and IMR4895 powders.

Thanks, I will keep plugging away with the imr-4064 and try to find a slightly slower load with better consistancy untill i get a decent amount of varget saved up. Thanks for the tip on the rubber piece, i have noticed the magnetospeed likes to slide forward when shooting. I guess its because im shooting a mtu taper, i suspect this wouldnt be so bad on a straight taper barrel. The tip about the extra rubber piece on top sounds like it will help, thanks!