Stiff Bolt Close

[harry.hacking@kiewit.com]

I just chambered a sporter in 6.5x284 norma, and I bought 50 pieces of norma brass sized it and chambered it to check for fit. It slid right in bolt closed no problem. So I loaded up a Dummy round, 120gr a-max Col 2.90, when I went to close the bolt the last little bit of close was hard. I pulled it out and it did not appear to be touching the lands at all, and it looked like the should had been slightly rubbed. I am puzzeled to what is causing this? Has anyone else had any problems such a this, the reamer used was a match reamer so it has tight specs but when should I get worried about how tight? Any help would be appreciated.

Thanks,

 

[Preacher]

Is the reamer a tight necked reamer ?
It sounds like the bullet in the case is causing the problem, seeing it chambers easy with out one..

 

[fdshuster]

As preacher said, it could be a neck clearance problem with the loaded round. What is the chamber neck diameter? Should be shown on the reamer. What is the neck diameter of the loaded dummy round? You might try painting the neck of the dummy round with black magic marker and chambering it. I would not expect to see any rub marks. Also try seating the bullet back about .010" or .015". You could have a minimal throat depth. The Stoney Point/ Hornady chamber O.A.L. gauge would provide a good indication if you're seating the bullet out too far. Just some thoughts: none of which may work.

 

[harry.hacking@kiewit.com]

I don't believe it is the OAL. I started the dummy round out at 3.110 in and I thought that might be the problem so I incremented it down to 2.90 in. What is the difference between the 6.5x284win and the 6.5x284 norma. I rented a 6.5x284 norma reamer but I don't recall ever seeing Norma on it, if the reamer was indeed a winchester version would this cause the problem I am having.

 

[fdshuster]

Hack: You may have hit on the problem. A few years ago a friend bought a used Remington 700 chambered in 6.5 x 284. Bought Lapua brass and it could not be chambered. He had to have the chamber re-cut with a Norma spec reamer. I'm grasping at straws here, since I have no personnal knowledge of a 6.5 x 284. ???

 

[spclark]

I believe the Winchester cartridge had a slightly smaller neck diameter than the Norma, 0.295" vs. 0.297".

Reamers will differ for this reason as well as because the Norma's throat was designed longer to better utilize heavier bullets.

For safety's sake please try to learn what the neck dimension is on the reamer used to cut your chamber, or plan on turning your cartridge necks to provide a safe loaded case-to-neck clearance (0.004" ought to be minimum for a sporter) before touching off a chambered cartridge.

 

[oneflyer]

The standard 6.5/284 WINCHESTER has a SMALLER base than the Norma case dimensions. The difference is in the base not the neck resulting in hard bolt close.

 

[spclark]

The standard 6.5/284 WINCHESTER has a SMALLER base than the Norma case dimensions.

I've heard that before. What doesn't jive is 284 Win cases are 12.72 mm or .5008" in the C.I.P-approved drawings, also shown here:

http://accurateshooter.net/pix/sae284winx350.png

- while the 6.5x284 Norma is the same:

http://accurateshooter.net/pix/65x284.png

Where ease of chambering (and safety) is questionable, carefully obtained case measurements are required along with a reamer print or better yet a chamber casting for comparison.

 

[harry.hacking@kiewit.com]

I found a print of the reamer that I used and my chamber is .001 to .0005 shorter to the shoulder than my norma brass. So with the stiff bolt I assume I am crushing the case .001 to .0005. My next question is this safe? It feels like my crush to fit for fire forming 6mm AI brass when closing the bolt (for those who have AI). My next question if this is safe will they fire form to the cut chamber and be perfectly sized for the next firing?

thanks to those who have responded and those who will,

 

[Laurie]

I found a print of the reamer that I used and my chamber is .001 to .0005 shorter to the shoulder than my norma brass. So with the stiff bolt I assume I am crushing the case .001 to .0005. My next question is this safe? It feels like my crush to fit for fire forming 6mm AI brass when closing the bolt (for those who have AI). My next question if this is safe will they fire form to the cut chamber and be perfectly sized for the next firing?

Hack,

if it just a small touch of 'negative headspace', it is quite safe. The key thing is to ensure you have enough neck clearance - since you've found the reamer drawing you can now easily compare the neck O/D of a loaded round with your chamber. It should be at least 0.002" smaller than the chamber, better still a fair bit more in a sporting rifle.

Firing a case that is a slight longitudinal crush fit won't fireform it shorter - sorry, it only works the other way! The only cure is to full-length resize (or resize with a neck + shoulder 'bump' type like the Forster Bushing-Bump model) and push the shoulder back marginally. Your aim is to have 0.001-0,002" clearance at the shoulder which gives easy and reliable chambering but minimal clearance for good results and minimising case stretching on resizing + firing.

I wondered if this was the problem area when you said in your original post that the shoulder looked like it had been lightly rubbed.

 

[harry.hacking@kiewit.com]

thanks Laurie,

Print shows the chamber necks at .301 and the cartridge diagram here shows .2969 giving me a neck clearance of .0041. I'll measure a loaded case to be sure my necks truly are .2969. So I should be ok with the necks. I am going to run everything through the full length die and see where that gets me. One thing I have noticed is that the Norma brass appears to have a thicker than normal rim compared to some of my other calibers, I am new to the 6.5x284 is this the norm?

 

[spclark]

Were I using your hardware I'd bump the new case shoulders back .001" if only to take the strain off my bolt handle... it wasn't intended for resizing cases.

Might want to check your case OAL once that's done too, against the maximum case length indicated on your reamer print. .015" is kinda the minimum clearance if you want to guarantee your cases (I assume you'll check them for OAL every time you resize & trim accordingly?) never grow too long for your chamber. That's something you most assuredly want to avoid.

As for the rim thickness: there's a spec for that too (.0539") & your extractor should be OK with it but you may want to take your bolt out & try it on an unloaded case just to see what kind of conclusions you might draw from the fit & feel. Try some of your unloaded but fired brass too & compare the differences.

(I measured a few Lapua 6.5x284 case rims just for grins. I have two batches; one I bought new, one bought used with a turn-neck barrel. The new measures .053" the old .052" while Lapua's new Palma brass & new 6BR measure .052".)

I think you're good to go now that you know what you're dealing with.