Home Forums Hunting & Shooting Hunting Rifles Cooper 6.5-284 chamber to tight?

I just got this gun. I went to reload some rounds and found out the the once fired Nosler Brass neck to be to small for a bullet. And when reloading have to apply a lot of pressure to the press. Does this seem right. Do I need to trim some of the case? Or do I need to call Cooper and ask about it?

What dies are you using? What bullets are you seating? Did you chamfer the brass mouths?

The die will open up the neck diameter when the button is pulled back through. If you are using a bushing die, then sounds like you have the wrong bushing.

I have the Foster Benchrest dies. Yes chamfered. And tried Barnes TTX, LRX, Hornady, Nolser BT, none will slide into by hand. Most fired cases I have used in other rifles I was able to put a bullet in. The new Nolser brass seems to fit the bullets better than the once fired in the rifle. The factory and reloads seem to chamber alright.

If you cannot slip a bullet into a fired and unsized case mouth then you have a tight necked chamber, or the brass you are using is too thick. Either way there is not enough bullet release clearance. I think you will have to neck turn the Nosler brass for more clearance or switch brands of brass.

I suggest you measure a the neck OD with a seated bullet and then call Cooper to ask them for the chamber neck dimension. Also ask what brass they use. Lapua and Norma have different neck wall thicknesses. IIRC Lapua is thicker than Norma.

IMO you should have at least .002" clearance per side .003"to .004" might be better if the brass isn't going to be turned for uniform fit.

I helped a friend work up a load for his 6.5-284 with Norma brass. Encountered the same situation. I noticed erratic velocities with flyers in the load workup. Finally I tried to fit a bullet into a fired case and it wouldn't go! The brass had very slight variances in neck thickness with some measuring the same dimension as the chamber specs!!!! Neck turning solved the issue.

My Cooper 6.5-284 uses Nosler (reported to be made by Norma) and Lapua brass without neck turning, but the best accuracy is .284 Winchester necked down. I found Lapua brass a bit heavy and harder than the Nosler, I'm not really a fan of Lapua brass due to oddball issues with distorted primer pockets and an unidentified problem where it wont rechamber in the same rifle that all the others work normally in. My friend has the same problem with Lapua brass, we are left scratching our heads.

I remembered reading an article about the 6.5-284 and neck thicknesses, here it is in case you haven't seen it: http://www.accurateshooter.com/cartridge-guides/65x284/ Scroll down to the Preferred Neck Diameter section.

Good luck.

Thanks everyone. I am trying to find a neck turning tool. Talked with cooper today and said thier chambers are very tight. So, stop at Cabelas, Gander, and Fleet Farm. Nothing..... Seem 6.5 pilot is also hard to find. Going to do some net shopping tonight.

"their chambers are very tight" Is that all Cooper said? You are going to need the actual dimension of the chamber neck.

Go here for your turning tools. I would call them and explain what you are trying to do then they can advise on what tools to buy.

https://www.kmshooting.com/index.php

Make sure the brass is not getting a little bit of dent when you are trying to eject it. I had this happen with a no turn 6BR and I thought I was going to have to turn necks. I removed the ejector so it wouldn't drag the case along the receiver as it ejected. Bullets would enter fired cases easily after I did that.

Regardless of what Cooper said I would ask them to issue a call tag to pickup the rifle and to make it right. I am a Cooper fan but that is not right and they should take care of shipping and repair on their dime, you should not have to neck-turn brass for a factory chamber.

drover

I'm positive you should NOT start neck turning for this rifle. Not yet at least.

What is the outside diameter of a once-fired case? Whatever that measurement your chamber neck area would be 0.001 inches bigger.

Saami neck says 0.297. Bullet 0.264. That leaves 0.0155-0.016 case neck thickness before I would consider neck turning. Do you know the brass thickness?

I echo Drover's comment. If I want to turn necks I buy a reamer and specify a neck diameter. Otherwise you should be able to run factory ammo.

SAAMI never standardized the 6.5-284. http://www.saami.org/specifications_and_information/index.cfm?page=CC

I am going to do some measurements. And try norma brass they stated that no standardization. And also the Nolsler brass maybe a tad thicker. They were very helpful. I have always been satisfied with the Cooper Customer Service and they work they have done for me, I am sure if there is an issue they will fix it.so, far everything they have told me has been truthful. So that goes along way. Europe it is a standard case. That is what they chamber for. And they said I shouldn't have any issues with European Brass. Be nice if SAAMI standardized it,

Called Cooper. The tech said they use PT&G's 6.5-284 Norma reamer. PT&G calls it a match chamber. The neck dimension is .297".

Called Nosler and talked to Mike. He took some measurements and said their loaded 6.5-284 ammo averaged .2943" which computes to an average bullet release clearance of .0027" total or.00135" per side. This is roughly 1 and 1/3 thousandths per side. Any pieces of brass that are thicker are going to affect accuracy and possible extraction.



Now you have the dimensions so you can figure out what to do. I would still measure a few of your loaded round's neck diameters and compare.

I would not use the Nosler brass until it is turned. Personally I would turn them so a loaded round's OD is 292". This would also require coming up with a new bushing to properly size the thinner necks.


Please share with us what you end up doing.