Help needed please ( 7mm Rem Mag ).

[Roy Sparks]

I have a 7mm Rem Mag with a Shilen stainless barrel. It was originally a bull barrel and i believe it was 26". It has been turned down to more of regular hunting profile and is now 24 " at my request. It has a 9" twist rate. The barrel is free floated.

I want to achieve optimum accuracy with this rifle ( Win pre '64 action ). I am currently using 75.5 gr of Somchem S 365 powder driving a 162 Hornady interlock with a COL of 85 mm. I have some federal premium cases and some local PMP cases. The primers I'm using now are Federal Premium Large Rifle Magnum Match. I would like to if possible have at least the first 3 bullets within a 1/4 " at a hundred meters.

Understandably I have to bring my side as the shooter. I dont believe the barrel has had over 500 rounds through it. Am I asking to much or could i achieve my objective ?

When the barrel was still original ( bull barrel ) I achieved 1/4" groups at a 100 meters with Federal Premium Factory Ammo with 160 gr Nosler partitions. I want dearly for the rifle to do this again.

Thanks Roy.

 

[Jluck]

SO....What is the problem currently?

 

[MudRunner2005]

My feelings might be different than some others...But I feel you may have hurt the accuracy due to turning the barrel down to save on weight.

If you had left it a bull barrel, then it would be alot less susceptable to barrel whip.

I would say, if you've tried everything to make that barrel shoot good and it won't...Buy an aftermarket barrel. And even then I wouldn't get anything smaller than a magnum sporter contour. If I were you, I'd go with like a Krieger #3 (like on the Weatherby Accumarks), or possibly even a Remington Sendero contour bull barrel.

I also wouldn't go less than 26" on a 7mm RemMag, but that's just me.

 

[thatguyshm]

What powders are available to you? I am not familiar with Somchem. Do you have a relative burn rate for it? What projectiles are available to you?

 

[USCGLongBow]

A few things come to mind, one how small is the contour? As Mud said you could have affected the accuracy by turning it, especially if one side of the barrel is even slightly thicker than the other. Two, it doesn't seem like much but the 2" you took off the end will effect where and how the bullet leaves the barrel in relation to the twist, so you might need slightly different bullets than what you used before. And the third and most important thing I have, goes back to the barrel contour. How long between shots with the new barrel? A bull barrel dissipates the heat over more metal meaning the barrel heats more slowly, a hunting contour is more likely to heat immediately and need more time to cool between shots to remain accurate. I have a 270 with a very light contour that groups in the same hole every time, BUT I have to wait 30 minutes between shots to be accurate, and longer if the temp is above 80.

 

[Roy Sparks]

Thanks for the advice I'm recieving.

Somchem S 365 is compared to IMR 4350 and Hodgdon 205 in the Somchem manual.

I have since read that Somchem S 361 = H4831 may be a better alternative in a 24 " barrel with 9" twist rate - How do you feel about this ??

I believe I am being too hasty between shots on the range firing 3 shot groups with tiny intervals between shots.

What I have noticed if I return to the range like the next day my first shot always seems to hold the same POI as the first shot the previous day.

If I fire 5 shot groups at short intervals the group tends spread horizontally from left to right +/- 1/2 " spacing often two bullet holes cutting then the next two 1/2" off to right cutting with the 5th jumping back to the first two !!

Looking forward to your advice , thanks - Roy.

 

[thatguyshm]

I would opt for the slower powder. 4831 is closer to RL22 in burn rate, albiet slightly faster. My go to 7mm is 66.0gr RL22, Winchester Large Magnum primers and the 160gr Accubond. I have shot it in several rifles and it seems to always provide sub-MOA grouping without much trouble. Just what worked for me, it been years since I've dug out my 7mm though.

-SHM

 

[Roy Sparks]

Thank you SHM , I'll certainly try that. Much appreciated.

 

[AZShooter]

There is possibility you have a bedding issue if the bullet impacts are moving left and right of center. It could be you are not placing the stock in the shoulder pocket the same for each shot. I used to do that with a 338 win mag and the flat Past super magnum recoil pad which prevented consistent form.

Sounds like you might have the right load. Don't get that barrel hot! Try shooting one shot and letting the barrel totally cool then shoot another. At most shoot two and let it totally cool. I used to shoot two from a cool barrel and save the target and quit. Next range session shoot two and save target. Did this for five sessions putting the targets over one another. It proved to me that the rifle was indeed consistent.