Ok, this is weird

[RCMSTER]

So I was out shooting my Ruger no 1, in 25-06. Trying to find an acceptable load with 100 gr swift a-frames. I have a good load with norma 100 gr soft points and 56.5 gr of accurate mag-pro. Last 3 shot groups have averaged 3/4" @ 100, and the rifle is sighted in @ 2" high at that distance. Average velocity according to labradar is 3111 fps, with an SD of 13.8.

Tonight, I load up 4 rounds with 55.5 gr of R-26. 3 of 4 shots were at slightly less than 5/8" @ 100. Average velocity by labradar was 3206 fps, with an SD of 18.7. But here's where I'm bewildered. POI of the swift a-frame was 5" south of the same grain norma bullet, while leaving the muzzle a full hundred fps faster. Anybody able to explain to me how this is? Thanks in advance for theories.

 

[JMW67]

barrel whip or harmonics

 

[243winxb]

while leaving the muzzle a full hundred fps faster

Bullet exits muzzle before muzzle rise from recoil.

 

[RCMSTER]

Hmmm? Interesting. Guess I'm learning something new on this little venture. Guess I just figured with both bullets being the same weight, and generally, but not exactly, the same flat base and profile, that the swift would have the same, or slightly higher POI.

 

[243winxb]

The above works for hand guns at 25 yards. Same bullet, different velocity.

There are no set rules for rifles and different bullets.

 

[LVJ76]

Barrel Harmonics

Example: in my 7mm-08 I shoot the 139gr SST sighted in at 200m. When I shoot the 120gr Ballistic Tip load the POI is 1" higher and 6" to the left, every shot every time. Then shoot a 139gr SST and dead center hit again.

 

[Jud96]

Yes as others said, barrel whip/harmonics. Remember taking a new pencil between your thumb and index finger and wobbling it up and down and it appeared to bow and flex. Your rifle barrel does the same thing. It's a sine wave. One load might be exciting at the top of the wave and hitting dead on, and the other is exciting at the bottom of the wave and causing the low impacts.

 

[RCMSTER]

Thank goodness for the smart people on this forum. I'm really getting educated with this thread. Thanks much to everybody. This is alot of fun learning stuff. Wish school would've been this interesting.

 

[LVJ76]

Wish school would've been this interesting.

You and me both LOL

 

[Stammster]

5" is a little much, but I routinely see 2-3" POI shift between different loads/bullets. Seems to be worse, the lighter the barrel/gun.

Also, why are you wasting precious RL26 on a 25-06 with 100gr pill? Stuff it with IMR-4350 or similar.

Also there is no mulligans with shots unless you pulled it. How far out was the 4th of the 4? Was it the cold bore shot 1? Also some times when changing bullets, it takes a few shots for the barrel to foul the same, vs the old bullets.

 

[RCMSTER]

5" is a little much, but I routinely see 2-3" POI shift between different loads/bullets. Seems to be worse, the lighter the barrel/gun.

Also, why are you wasting precious RL26 on a 25-06 with 100gr pill? Stuff it with IMR-4350 or similar.

Also there is no mulligans with shots unless you pulled it. How far out was the 4th of the 4?

I'm pretty sure I choked on the last shot. It was 2 3/4" to the 2:00. My Ruger no 1 is an AH model. Alexander Henry forend, light contour barrel. 1 of about 250 made with the circassion walnut stock, or so I was told. As far as using R-26, why not? However, I originally bought several pounds of Norma MRP, and a guy I work with knows a guy that spends alot time at gun shows, and about a month ago, Came across a stash of R-26, and so I traded the guy I work with a pound of MRP for a pound of R-26. I was planning on using the 26 for my 6.5-06, but it's shooting so well with H100V, that I thought I'd try it in one of my 25-06's. The other 25-06, a Winchester 70, is doing real well with the MRP and 115 gr Remington ultra-bonded.

 

[rammac]

It takes approximately 0.006" of movement at the muzzle to move the bullet 1 inch at 100 yards. That means that the muzzle would have to move about 0.030" for a 5" error at 100 yards. There is no way that barrel harmonics would move the muzzle that far.

 

[David Emerson]

It looks like you found a load the rifle likes. My first rifle was a 25/06 bought when I was 13. I have reloaded for it my whole life. The best I have found is H4831. 57gr with a 100 gr bullet. Smoke your bullets and seat just so no rifling marks. Of course I am partial to 4831. My brother bought a 50 pound keg for 52 dollars in 1971. Hahahaha try that now!!!!! As for your drop with 2 different bullets. Others said it first,harmonics. Who cares? Sight it in and go hunting.

 

[hunter0528]

Bullet exits muzzle before muzzle rise from recoil.

I agree. I did some testing years ago with a 220 swift and 7mm RM and found that the longer the round stays in the barrell (micro seconds) the more or less the recoil will effect the rounds at the target. It is even noticeable on the muzzle loaders.