Tight Neck Chambers.. How much clearance?

[flyingfisherman]

How do all,

 

i'm shortly to pick up a new rifle, with a tight neck chamber.. I've shot the calibre a lot before but only with a SAAMI spec chamber. Now that this has been cut with a tight neck reamer, i'll need to turn brass.

 

I've heard varying opinions about how much clearance is required.. I want to be safe but want to get the best from my brass, so what would everyone recommend?

[onehole]

You wont have any issues if you run with three thou ie 249 thou loaded in a 252 neck for example.Benchresters may run quite a lot tighter but they are probably cleaning very often.At the end of the day a tight neck chamber usually demands neck turning and the major benefit of course is concenticity and in a reasonably tight environment. I would problaby never go tighter than a two thou clearance ie 250 for a 252 chamber for my own applications .My current 22PPC I am running at 249 loaded in a 252 neck and is repeatably stonking accurate.

[The Gun Pimp]

Even with short-range benchrest, ideas on neck-clearance have changed in recent years - around two to three-thou is now the preferred clearance. The no-clearance 'fitted neck' days are long gone.

 

Of course, short-range benchrest is shot undercover, away from the elements and the detritus associated with outdoor shooting. Most clean regularly - every 15 to 25 rounds so crud never builds up on the inside of the chamber neck - as it would with say an F Class shooter firing c.70 rounds in a day without cleaning.

 

If you intend to clean regularly, I'd go three to four thou. - that's two-thou. all round. But, beware at all times of the risks associated with tight necks. It's a good idea to have a spare neck-bush to slip over all your loaded rounds as a final check.

 

Outside of short-range benchrest, I no longer neck-turn for 600/1000 yd benchrest or F Class.

[flyingfisherman]

Thanks guys, great advice, that confirms what id heard from a couple of sources. I'd also heard considerably more than that.. which to me seemed to negate a lot of reasons for tight necks.. also, i would imagine that thin neck walls could be a hazard..

 

Whats the thinnest people would accept in terms of neck thickness?

[flyingfisherman]

Next question..

 

Now, I'm turning some once fired brass for the new gun, its been F/L sized, trimmed to length and now needs neck turning.. Just setting up the cutter and wanted to do it so that i should avoid doughnuts.. I noticed on some other batches of brass after 4-5 reloads that I'm starting to get doughnuts and believe that these can be avoided by neck turning right unto the neck/shoulder junction..

 

I've set the cutter up so that there is no step between the neck of the shoulder but am concerned that if i cut too far in, i could get neck separation, which would be a pain in the a**.

 

What do we think? Apologies about the pic quality.. its an iPhone so not so good at macro type stuff..

 

 

 

[Ronin]

Cutting about .025" into the neck shoulder junction will avoid donuts.

 

The brass will flow back into this space but not create the infernal internal lip...

 

 

I dont use less than .003" all round neck clearance, as others have said.

[flyingfisherman]

 

 

I dont use less than .003" all round neck clearance, as others have said.

 

How do Ronin,

 

Thanks for that.. you say all round.. just to clarify, do you mean that in a .292 neck chamber, you'd need an overall loaded round of .286?

 

Sorry if I'm being dull, but am approaching tight necks with caution..

[onehole]

 

How do Ronin,

 

Thanks for that.. you say all round.. just to clarify, do you mean that in a .292 neck chamber, you'd need an overall loaded round of .286?

 

Sorry if I'm being dull, but am approaching tight necks with caution..

Hi Onehole replying,,,,,,Ronin I,m pretty sure would mean 289 in a 292 neck.............Flyin F,,,,,,tight necks are purely done to provide a tight environment to which to turn for,,,,,,if you turned necks to obtain concentricity in a standard sized neck then you would very probably end up with massive slop in the neck dimensions,,,,,,ie 254 standard factory neck and a neck turned 246 loaded round,,,,,8 thou? or possibly more,,,not where you want to be at all.

Depth of cut,,,well you do really need to cut to feel a step,,,,comes with experience I guess but the step you feel will keep the doughnut away,,,,,,don't go too mad but yes cut into that shoulder and feel it on your finger nail quite easily.If in doubt do a couple ,,,fire em off and grind away or file off the necks in such a way as to examine how far you have cut into the shoulder.Once you,ve messed up a few cases and felt your way you will be well away ,,,,take care and hope I,ve explained this reasonably well,,,,,,,,O

[flyingfisherman]

Cheers onehole.. that all makes sense.. I've neck turned 50, another 250 to go.. i hate this bit....

[onehole]

Cheers onehole.. that all makes sense.. I've neck turned 50, another 250 to go.. i hate this bit....

Yep know what you mean and goes someway to me thinkin about annealing to rejuvenate precious turned brass,,,,,,,,,,I do have a small lathe though which takes away some of the pain and the cutter sits in the chuck whilst I feed it the brass,,,,,,,,,good investment a small lathe for doing a whole heep of things,,,,,,,,goodnight,,,,,,,O