25 Pronghorn

[CurrentTX]

I was recently helping my dad sight in his 25 Pronghorn, or a .300 WSM necked down to 25, and noticed an extreme inconsistency between shots at 100 yards. The rifle was my grandpa from 12 years ago, along with all the ammo that was hand-loaded around the same time. We would have a POI where aimed; then the next shot was 10" left or right of the aim location. The 5-shot group had a 20" spread. Could this be due to the powder being expired or something else? I attached the load data from the box.

If I were to create some new loads to test this, what would be a comparable powder? Does anyone have any load data on this rifle?

 

[SJB358]

Scope is my first inclination. Mounts next, and then stock screws. It’s mechanical. Unless the barrel is bent it’d be hard to believe it’s the load if it shot decent in the past. I’d be hard pressed to think the propellant is bad.

 

[CurrentTX]

Scope is my first inclination. Mounts next, and then stock screws. It’s mechanical. Unless the barrel is bent it’d be hard to believe it’s the load if it shot decent in the past. I’d be hard pressed to think the propellant is bad.

I checked for wobble at the range; everything seemed tight, but I will run through it with a torque wrench and see what happens. Thank you!

 

[SJB358]

Maybe it’s worth it to put a known good scope on it, just to check.

 

[FOTIS]

What scope are you running?

 

[JD338]

I agree with Scotty and Fotis, try a different scope and make sure the mounts and rings are torqued to the proper spec. Same with the action screws.
You might also want to try the Nosler 115 gr BT.

JD338

 

[300WSM]

I was recently helping my dad sight in his 25 Pronghorn, or a .300 WSM necked down to 25, and noticed an extreme inconsistency between shots at 100 yards. The rifle was my grandpa from 12 years ago, along with all the ammo that was hand-loaded around the same time. We would have a POI where aimed; then the next shot was 10" left or right of the aim location. The 5-shot group had a 20" spread. Could this be due to the powder being expired or something else? I attached the load data from the box.

If I were to create some new loads to test this, what would be a comparable powder? Does anyone have any load data on this rifle?

STOP RIGHT THERE!

Something is wrong.

First thing to check.

Scope and it's mounts.
Mounts don't go bad. They CAN loosen....but I doubt this is the problem.
Scopes on the other hand...can have a reticle walking around inside the tube.
They lose their effective adhesive properties and then you have a reticle moving about and it can be difficult to detect at times.


I will touch on the hand loads...
Get the powder expired thought out the window.
That is NOT a problem nor will you be the first to have such an issue.

that said.....
It CAN be an adventure using someone else's hand loads. Unless you were there and a witness to the process you don't really know how consistent the loads really are.

So many intangibles when using another's reloads.
Just because they "reload" doesn't mean they are any good at it.

They might be great at it....but how do you know their scales wasn't giving fictitious readings. It can happen although mostly with digital scales.

That said, I have my doubts that even a variance if a few grains will throw your group out to a 20" size.
Inconsistent powder charges will expand your group size but it would have to be by a significant difference. 10-15 grains might do that.

2-5 grain variance will not make your group grow to 20'".

Focus on the optics.

An easy test for you...

Install a bore sighter...
Check the reading.
Take your palm and bump the scope on the sides of it.
You won't hurt anything so don't be shy.

Then check your bore lighter again.

YOU WILL HAVE TO REPOSITION YOUR BORE SIGHTER AFTER YOU BUMP IT A FEW TIMES.

You're trying to simulate vibration from a scope after firing.

I wouldn't be surprised if you find the scope reticle moving around inside the tube.

Good luck and keep us posted.

 

[clearwater]

Ladder tests of loads don't produce that large a spread. Other than scope problems, the only time I have seen groups like that was from unstable bullets tumbling due to a slow twist and low velocity. The bullets whet thru the paper sideways.

Just for curiosity you could pull some of the loads and examine and weigh the powder charges. I have found some mystery loads with wet/clumped powder. When i receive others reloads, I generally pull the bullets and start over.

For powder i have been liking the Staball series of powders by Winchester since Alliant is not around.

 

[CurrentTX]

What scope are you running?

It’s an older Leupold scope, maybe they will service/warranty it. Gonna look at the rifle tonight

 

[CurrentTX]

STOP RIGHT THERE!

Something is wrong.

First thing to check.

Scope and it's mounts.
Mounts don't go bad. They CAN loosen....but I doubt this is the problem.
Scopes on the other hand...can have a reticle walking around inside the tube.
They lose their effective adhesive properties and then you have a reticle moving about and it can be difficult to detect at times.


I will touch on the hand loads...
Get the powder expired thought out the window.
That is NOT a problem nor will you be the first to have such an issue.

that said.....
It CAN be an adventure using someone else's hand loads. Unless you were there and a witness to the process you don't really know how consistent the loads really are.

So many intangibles when using another's reloads.
Just because they "reload" doesn't mean they are any good at it.

They might be great at it....but how do you know their scales wasn't giving fictitious readings. It can happen although mostly with digital scales.

That said, I have my doubts that even a variance if a few grains will throw your group out to a 20" size.
Inconsistent powder charges will expand your group size but it would have to be by a significant difference. 10-15 grains might do that.

2-5 grain variance will not make your group grow to 20'".

Focus on the optics.

An easy test for you...

Install a bore sighter...
Check the reading.
Take your palm and bump the scope on the sides of it.
You won't hurt anything so don't be shy.

Then check your bore lighter again.

YOU WILL HAVE TO REPOSITION YOUR BORE SIGHTER AFTER YOU BUMP IT A FEW TIMES.

You're trying to simulate vibration from a scope after firing.

I wouldn't be surprised if you find the scope reticle moving around inside the tube.

Good luck and keep us posted.

Good advice, thank you. I’ll open a few loads and see what they look like, but I have a spare scope I’ll throw on there first and see what happens!

 

[FOTIS]

It’s an older Leupold scope, maybe they will service/warranty it. Gonna look at the rifle tonight

Try a proven scope you have on hand

 

[RL338]

5” group at 100yds , something is loose or bad scope. What brand of rifle is it? Is the barrel a nutted or shouldered install?
Hopefully it turns out to be a simple fix.

 

[CurrentTX]

5” group at 100yds , something is loose or bad scope. What brand of rifle is it? Is the barrel a nutted or shouldered install?
Hopefully it turns out to be a simple fix.

It was a factory Tikka rifle, from what I understand, he took many guns to the same gunsmith that shot half MOA., and it’s a shoulder install done by the same guy. I don’t know much about the rifle since my grandfather has passed away. But I do know he was a complete snob for grouping. At one point I’m sure this rifle shot really well. I really do think it’s a scope issue, so I will do as others have suggested and try a proven scope

 

[300WSM]

Good advice, thank you. I’ll open a few loads and see what they look like, but I have a spare scope I’ll throw on there first and see what happens!

Very welcome and wish you the utmost luck.
Things like these can become tail chasing

 

[Firebird24]

Send the scope to the manufacturer and let them know it won’t hold zero any longer. Even if this isn’t the problem it might have a very happy solution. . .
Any chance the throat is getting burned out and the barrel needs replaced?

 

[Guy Miner]

BTW, Reloader 22, the powder your grandfather used (me too) is almost impossible to find anymore.

Unless you have a good supply of it on hand, when you start handloading for that rifle you'll likely need to turn to some other fairly slow burning powder.

I hope you get the mystery solved and that rifle starts grouping like it used to!

Guy