30-06 reloads seem too fast.

[Gs11gk]

Hello everyone.

Been reading quite a bit here the past few weeks and wanted to ask a question related to a curious observation with my 30-06.

i have been loading 57.5 grains of imr 4350 under a Sierra 165 grain HPBT. The rifle is a savage 111, totally stock, with a viper pst 6.5 x 24 scope with a 1/4 MOA click. After zeroing at 100 yards, I took some shots at 200 and 300 yards to determine drop. The drops were about 2.5” and 10” respectively. Groups are about 1.3 MOA.

i then took some more shots- 5 clicks at 200 and 14 clicks at 300. Elevations were seemingly bang on... so I was happy.

i don’t have a chrono so I was attempting to deduce my bulllet speed and create a drop table based on what I observed at 100, 200 and 300 yards. Using the iSnipe app, plugging in the bullet data (165 grains, BC .363) and zero at 100 yards with the scope 2” above the bore, I manipulated the muzzle velocity such that it lined up with the observations. To my surprise, the app suggests my muzzle velocity would need to be 3000 FPS, which is considerably higher than I would expect for this load.

Is this possibly right or am I not accounting for something? I’m wondering if my Tupperware stock is whipping my barrel and pushing it higher than it should. I have a Bell and Carlson stock in the way and will hopefully get a chance to install and shoot next week.’

what do you think?

Thanks. David

 

[supercorndogs]

Is your scope center line really 2 inches above your bore? My remingtons with low rings are about 1.5. Run your numbers out further.

 

[black5.3]

How long is the barrel on your gun? I dont keep up with savage much so i dont know... with a 165gr bullet it wouldnt be crazy to have 3000fps.. i have some factory hornady superformance 165gr sst i used to hunt with and the muzzle velocity on the box is 2960 i think.

 

[Gs11gk]

Thanks for the thoughts. The barrel is a 20” inch sporter barrel and I just verified the scope height at 2 inches from the axis of the bore.

 

[black5.3]

I agree shoot them out farther if you can and retry your calculations.

 

[McNamara0851]

I used a cheap chrony that I got second hand for a long time. If I were to do it over again I would have bought a magnetospeed the day I started shooting. You cannot put a price on good data.

 

[308pirate]

I'd expect 2950 - 3000 fps out of a 26" barrel. That out of a 20" is suspect. I agree on shooting farther and verifying dope again. Or if you can use someone's magnetospeed or labradar that will pretty much put the speculation to rest

To give you an example, Hodgdon's reloading data shows your bullet hitting 2934 fps out of a 24" barrel with 60 grains of IMR 4350.

 

[Yondering]

I use iSnipe as well and get really good results with it, but with any ballistic app, all your inputs have to be right on to have any hope of estimating velocity accurately. Frankly it's a pretty poor way to check your velocity, with far more potential for error than even a cheap chronograph. (And a decent chrono can be had for as little as $100, check out the ProChrono Digital at MidwayUSA.)

Are your weather conditions correct? That's a big one; for example using the drop values you stated in the OP, but my weather conditions (close to sea level, ~40* F temp) would need closer to 3,100 fps with your bullet.

Agreed with the other comments that 2" scope height above bore seems like a lot. Even if it's correct, dropping the scope in lower rings should help you in other ways.

Another source of error is your zero. The app assumes exactly zero at 100 yd, if you're off by 1/4" or 1/2" that changes down range drop values a lot. This one is a big reason why this method of velocity estimation is prone to lots of error.

Finally, you're using a publized b.c. value, and assuming it's correct in your rifle. It might be different, and probably is to some degree. IMO you'd be better off to actually measure velocity, and use that (along with all the other app inputs) to figure out the correct b.c. value. Of course, the actual drop values you measured are what's really important, and the app is just a way to predict changes to those values for different atmospheric conditions.

 

[Gs11gk]

Thanks again. I think Yondering’s point about the zero being off is on the money. On further review, I suspect my zero at 100 is an inch high with this load, which has a significant effect. Plus, I agree that I need to take more shots to get better sample sizes at the various distances.

i have thought about a chronograph. My challenge there is a good place to use it. Never seen one used at my local range. I’ll have to look into that. No doubt it could make my shooting life easier.

 

[spife7980]

i have thought about a chronograph. My challenge there is a good place to use it. Never seen one used at my local range. I’ll have to look into that. No doubt it could make my shooting life easier.

Magneato speed. I’ve shot rounds out the back door into the dirt before a hunt with a new rifle just to get a ball park of what I had. And you dont have to wait for a cease fire like with the opticals since you have a public range. Lab radar also has that benefit but I already had a magneato before they came out and I really like it’s convenience and idiot proof factor.

 

[Gs11gk]

Just looked at magnetospeed. Given the barrel mount, hat’s just the ticket for the range. They should have them available to rent. I would happily rent one and I think any reloader would.

 

[Gs11gk]

I took the plunge and ordered the magnetospeed sportster model. Will report back. Thanks for the tips.

 

[Gs11gk]

I got my magnetospeed and put it to use this weekend. I took two shots with the load in question and it registered 2887 and 2896 FPS. That still seems fast for 165 grain bullet out of a 20” 30-06 barrel.

The day before the magnetospeed arrived, I went to the range. After a five shot group, I made a slight adjustment to my zero at 100 and took a couple more shots at 300 yards. They both dropped 14 inches. That made me think that this load was actually moving at about 2600. Now the chrono says it is quite a bit faster... closer to what I originally thought.

I’m not sure what to make of the chrono, drop observations and ballistics calculator. Any suggestions? I am growing a great appreciation for the skill of long range shooting.

 

[black5.3]

I would trust what the magnetospeed and target are telling you first. I rarely use any app other than to get me in the ballpark of my dope at distance and then i fine tune my dope on the target.