Cooper Rifles and Max Loads

[WYO300RUM]

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 have a Cooper mod. 52 in 6.5x284 that gets pressure signs with factory ammo. Norma and HSM. Haven't tried others. Just reload for it now.

 

[Coopershawk]

I can't get anywhere near top velocity!

I have a 280AI 24" that runs right about at the manual. My 270 WBY 26" hit the book velocity 1+ gr short of max. RL22 in both. Zero pressure signs and the groups were so good I saw no point in pushing it.

 

[Philward]

Max load is relative to the particular rifle you are shooting.

 

[Greyfox]

My Cooper 6.5x284 with a 1:8 twist 26" barrel has never had an issue achieving max velocity, with identical results using comparable loads used with three other 6.5x284's I own.

 

[JMB 1911]

Mine in 6.5 cm shoots factory eldm about 100 fps faster than the box says my max load of 6.5 staball is almost 200 fps faster without any pressure issues

 

[deertroy1]

Thanks for all the replies guys. It looks like it's just a matter of the barrel and not the small tenon so I guess I'll see about having it rebarreled.

 

[deertroy1]

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

Yes.

 

[smokepoler]

Yes.

I would try brand new brass to see if there's any change. Only need to load a few of the same recipe.

 

[Mikecr]

I don't usually consider this path, but in this case I would give Cooper a chance to shoot the gun & determine the issue/resolution.
If nothing else but to help them, which might help me, and other people as well.

 

[deertroy1]

I don't usually consider this path, but in this case I would give Cooper a chance to shoot the gun & determine the issue/resolution.
If nothing else but to help them, which might help me, and other people as well.

This is my second Cooper. The first one (a 7mm-08) I purchased new in 2014. I couldn't get it to shoot and it has been back to Cooper more times than I can count. I finally sent it to a Gunsmith on my dime after it refused to eject fired rounds. He said the ejector was bent and looked as though it was never heat treated. While there, I had him check it over as I couldn't get it to group. He said the chamber was not cut concentric with the barrel. I contacted Cooper and they said they would look at it but they were 6 to 8 months behind. With that and the fact it's usually another month or two in customs and shipping I decided to rebarrel it on my own dime. I'm still waiting to get it back from the Smith.

 

[JMB 1911]

For the money Cooper charges that's pretty hard to hear.

I had some feeding issues with mine I sent it back and they fixed it but I think there magazines have some design flaws.

 

[Baylor243]

I have a Copper 243, I shoot IMR 4350 with 67gr Vmax out of it, speed is just a tad over what yours shoots the 70gr Sierras at...and its plenty hot for my needs. I really think its about a grain under "max" according to Nosler but it shoots really well at that. I do think its kinda tight in the chamber, but I have no complaints there. It took me only about 20 rounds (four different loads) to get where I'm at now and I'm happy with it. I may have to switch up powder with this rifle soon, my stock of 4350 has a lot of rifles to cover on a small budget so the bigger guns will move to the front of the list.

I got very similar results with the Cooper 223 and 22-250's i used to own. I shot them both under Max loads and they got me just what I needed. Both were tight, as preferred. It's kinda hard for me to find fault in a rifle that shoots so dang well.

It also could be just my opinion, but it seems your quoted FPS for the Savage rifle is pretty dang fast. Not saying its inaccurate or bad, its just faster than I would have expected out of a 6mm Rem. with that bullet. Anything north of 3600 with a max load would be extra gravy in my world.

 

[deertroy1]

I have a Copper 243, I shoot IMR 4350 with 67gr Vmax out of it, speed is just a tad over what yours shoots the 70gr Sierras at...and its plenty hot for my needs. I really think its about a grain under "max" according to Nosler but it shoots really well at that. I do think its kinda tight in the chamber, but I have no complaints there. It took me only about 20 rounds (four different loads) to get where I'm at now and I'm happy with it. I may have to switch up powder with this rifle soon, my stock of 4350 has a lot of rifles to cover on a small budget so the bigger guns will move to the front of the list.

I got very similar results with the Cooper 223 and 22-250's i used to own. I shot them both under Max loads and they got me just what I needed. Both were tight, as preferred. It's kinda hard for me to find fault in a rifle that shoots so dang well.

It also could be just my opinion, but it seems your quoted FPS for the Savage rifle is pretty dang fast. Not saying its inaccurate or bad, its just faster than I would have expected out of a 6mm Rem. with that bullet. Anything north of 3600 with a max load would be extra gravy in my world.

It looks like there is a big discrepancy in load data with this cartridge.
For instance, Nosler list a 40gr charge as max with IMR 4895 achieving 3511 fps.
Hodgdon list a max of 44.6gr and 3735 fps with the same powder!

 

[JMW67]

a discrepancy would be if they tested the same gun and came up with this data they tested two different guns with two different barrels with different chambers with a different lot of powder and different brass and possibly two different barrel lengths