Cooper Rifles and Max Loads

[deertroy1]

How do you know that you have max pressure?
Less barrel steel around a chamber (smaller tenon) can lead to early popping extraction, but does not change load pressure.
This is an example of an often declared pressure problem, that is not caused by pressure.

Also have ejector mark on brass! The same brass that shows no evidence of any kind in the Savage with much higher loads!

 

[deertroy1]

Hmmm....does the Cooper have a tighter twist?

No Cooper has a slower twist. 1-10" for the Cooper vs 1-9" for the Savage.

 

[Hunterjones]

Very tight bore perhaps

 

[ksshooter]

Are you determining max loads by what your book is telling you? Or with a chronograph? Or using signs of pressure to dictate what max really is?

 

[deertroy1]

Are you determining max loads by what your book is telling you? Or with a chronograph? Or using signs of pressure to dictate what max really is?

I use varios reloading manuals, Quickload, Oehler M35 and pressure signs.

 

[deertroy1]

Are you determining max loads by what your book is telling you? Or with a chronograph? Or using signs of pressure to dictate what max really is?

However, that is the reason for my post. I'd just like to know what others are able to get out of their 6mm Rem's with 65-70gr bullets.
3750 fps is no problem in my 22" barreled Savage.
3450 fps is a struggle in the 24" barreled Cooper?

 

[ksshooter]

I have talked to Glenn at cooper a few years back. He told me to start at the bottom and work up. He said that in most cases you will find max is usually around a grain under what your book will say due to having a tight chamber. I experienced this when I obtained reloading data from Berger for a cooper Excalibur in 6.5x284. I found that I was actually 2 grains under what they recommended and still experiencing minor pressure signs. I chronographed the load. 100fps faster than what Berger said max load velocity should be. I backed it off to the next node and I believe I'm Around 3-3.5 gr under max and still maintaining Berger's published max load velocity for this caliber. I have owned several coolers over the years. All shot lights out. Most were 1-2gr under published max load data. Hope this helped. Good luck with your loads.

 

[Tripodmvr7]

That's the thing. I can't reach max velocity. I get max pressure nut velocity is lagging 200 - 300 fps?
Yes, the loads were chronographed with an Oehler 35
24" Cooper 70gr Sierra 3450fps Max
22" Savage (McGowen) 3750fps Max

Same brass, primers and powder. Bothe rifles headspace within 0.001" according to fired cases. Savage has a bit more leade but bullet seated nowhere near lands in either rifle.

What propellant are you using to get these results? Are you using the 70gr Blitz?

 

[Ron Milby]

I have owed many Cooper Rifles and I have never had a problem with achieving max velocity and accuracy.

I would call Cooper's customer service. They have always been very helpful.

 

[JC in Calif]

Any of you Cooper rifle owners having difficulty reaching maximum loads? I just got a new to me Cooper in 6mm Rem and it will not reach anywhere near what my other 6mm rem will achieve even though it has a 2" longer barrel. I thought it may be a carbon ring but after a thorough cleaning and verification with a borescope it still won't accept anything near max.
My gunsmith said Coopers can be notorious for that as they have a small barrel tenon vs other brands. I read a little about this phenomenon here!

I own some Coopers. I have not had problems reaching maximum loads. .257wby, .20 Vartar, 6BR, .240wby

 

[deertroy1]

I have talked to Glenn at cooper a few years back. He told me to start at the bottom and work up. He said that in most cases you will find max is usually around a grain under what your book will say due to having a tight chamber. I experienced this when I obtained reloading data from Berger for a cooper Excalibur in 6.5x284. I found that I was actually 2 grains under what they recommended and still experiencing minor pressure signs. I chronographed the load. 100fps faster than what Berger said max load velocity should be. I backed it off to the next node and I believe I'm Around 3-3.5 gr under max and still maintaining Berger's published max load velocity for this caliber. I have owned several coolers over the years. All shot lights out. Most were 1-2gr under published max load data. Hope this helped. Good luck with your loads.

I'd be okay with that. I have a 300 Win Mag that gives me max velocity with a couple grains less powder. This rifle, however, is 200 - 300 fps under max velocity. I guess it's a really slow barrel.

 

[deertroy1]

What propellant are you using to get these results? Are you using the 70gr Blitz?

I've used both IMR 4064 and RL-16

 

[deertroy1]

Maybe tight match chambers. I get top velocity with my two model 52's with less than book max loads.

I can't get anywhere near top velocity!

 

[smokepoler]

Are you using brass shot in another rifle? If so, I would try new brass.