Stumped! Chamber pressure

[rcol317]

As a shooter and reloader for more than 40 years I'm stumped today with an issue. I just purchased a Cooper 52 Excalibur in a 6.5X284 Norma. The gun is used but looks as new. First shots down the tube and stuck case. After attempting several rounds I found Lapua new brass @ minimum load didn't stick but increase it by only one grain and brass sticks. 130 gr AccuBond with 49.5 grains H 4831SC sticks 48.5 grains OK. 140 gr Sierra HPBT 47 gr. H4831SC sticks 46 grains some OK and some stick. Tried Winchester brass and 140 gr Sierra with 45.5 gr. H4831SC sticks 45 grains OK Tried Retumbo and even with minimum load sticks brass. Tried 142 SMK, 140 VLD and 120 Nosler Bal. Tips all the brass sticks. I have two other 6.5's and have had three others and none of them have given me pressure problems until max. Any suggestions would be appreciated. The pressures great enough that you can't neck size the brass and get it to chamber must be full sized and then it's tight.

 

[green 788]

when you say the cases stick... do you mean it's a sticky bolt lift, but it'll still extract?

or do you have to punch the case out with a rod from the muzzle?

do you have any scratch marks on the case wall or neck area that would indicate where the cases are hanging?

 

[rcol317]

No stiff bolt lift like normal pressure sign but case sticks need ram rod to tap out. Case does not show any other than normal marks, that was my first thought a rough chamber.

 

[PaLuke]

About 3 years ago my son got a A Bolt in 338 win mag and had
The same issues. When it was first purchased we loaded for
it with starting loads and every once in a while we had the
case stick. I tried loading 1 grain more and all of them stuck.
Different powders and different bullets gave the same results.
Funny thing was that was the only pressure sign. Cases measured
fine, primers looked good and no ejection marks. Took it to a smith
and he found nothing wrong. Ended up trading it on a X bolt
and did tell the shop owner of the issues. To this day I think it was
a rough chamber or that far out of line that it stuck everything.
Along with that when it did shoot the groups were 10" at 100 yards.
I know this isn't the answer your looking for but I hope it helps somewhat.
PaLuke

 

[green 788]

check your bolt lugs for marks which could come from a screw in the scope base... not sure if the Cooper could have this issue, but give the bolt lugs a good going over. Sometimes this will only come up after the round is fired and bolt lugs are pressed hard under pressure...

 

[Coyboy]

a loose extractor and not enough primary extraction on the bolt handle to cam surface, sounds like the problem, look at the bolthandle to cam angle contact the next time you fire a stuck load, if you open the bolt and the cam runs out and the case is still stuck it is likly those 2 things in combination.

 

[rcol317]

It's got Talley one piece ring/base and the screws are plenty short and don't stick through, great idea though. I re examined the brass and can't see any sign of sticking from rough chamber. I have 9 other Coopers so I'm sure I can send it back to them. In my conversations with them they seem very good about customer service. Don't really want to send it back, don't want them to tell me to shoot minimum load cases. Really makes it hard to do load development. I'd like to figure it out.

 

[rcol317]

Thanks Jim, The cam issue may be the problem, when I chamber a spent piece of brass there seems to be a hangup on the bolt lift to eject it. But does that explain the case stuck on the chamber? It takes a pretty hard tap on the ram rod to get it out. Sounds like it's something I'll need to have Cooper resolve.

 

[BountyHunter]

carbon rings in chamber throat will cause pressure issues also

 

[Freebore]

rcol317

I have the same issue with a rebarreld BLR in 7mm-08 I had actually shot the barrel out that's how much I shot that rifle. The gunsmith is very well known in benchrest circles. The barrel is a Krieger. He could not explain it either.

Lapua, W-W, R-P brass all stick with very light loads. Had chamber repolished still the same, sticky brass.

I had some old nickel plated Federal brass laying around. I Can Not stick these cases even when at max+. So that is the brass I use.

I'd be real interested in your info if you get yours figured out.

 

[rcol317]

Thanks for all the input. Called Cooper today and was again pleased with the customer service but a little surprised by the response. After discussion their response was the gun probably will only shoot light loads and you can't push it. I disagreed and asked what load they used to test fire. They gave me the information and I loaded it as suggested. First load no problem, good, second and third stuck brass. I've shipped the rifle back to cooper and it will be interesting to see what comes of it. I hope they don't go with minimum loads and tell me thats what I'm stuck with. I'm not sure about industry standards but I hope it isn't load as low pressure as possible.

 

[cowboy]

You will soon find out what kind of company Cooper is - shooting min. loads would not fly very far with me. A person shouldn't have to even put up or deal with something like this but I guess all companies have something slip out the door that is not normal. The good companies take care of any problems. We'll see.

Good Luck.

 

[kjcpoint]

I sent 2- 6.5x284 rifles back to cooper for the same problem. Cooper said to shoot mild loads and the chamber was a 6.5x284 win and not norma? Go figure, the only difference I could find in Dave Kiffs reamer prints was the Free Bore. Also sent them a 22 250AI for the same problem?

 

[boomtube]

Maybe your rifle has a too tight neck or short chamber that fails to release the bullet properly.