What tolerance for tight necked 6.5 x 284?

[Ronin]

I have just had a tight neck (.291") 6.5 x 284 built around a blueprinted Rem 700LA, Kreiger fluted No7 barrel - 1 in 8.5 twist, sako extractor, modified bolt handle, oversize recoil lug, shilen trigger, etc, etc.

I have neck turned some Lapua brass to .289" using my K&M tool. When sized in redding comp neck die using .288" bushing the unfired case neck is .287".

Loaded case neck is .288" and fired case neck is .289".

My question is, do I have enough clearance with the loaded round (2thou) to not worry about excessive chamber pressure.
I have worked up from 46 to 50 grains of H4831sc under 142SMK whilst running in the barrel with NO signs or flattened primers, no imprint of bolt face on base of brass or hard extraction. The rifle is grouping well - for me anyway at .425"with only 40 or so rounds through it that have all been under the breakin process.

I wonder if I should leave things as they are or take another thou off the necks to allow a bit more "give" on ignition. Fired cases cannot have bullets push fitted by hand into the case if this helps. I have read some where that 1 thou each side of the case neck is desirable but wonder what everyone else who have more experience than me thinks.

Thanks Andy /ubbthreads/images/graemlins/smile.gif

 

[Ballistic64]

With your loaded rounds being .288 and your chamber neck being .291,you actually have .003" clearance.Generally a tight neck wont cause a press. problem,youll experience chambering problems if you try to go too tight.
Not an expert,but if your bullets wont fit into a fired case,you may want to experiment with your neck tension of your reloads.

 

[chris matthews]

I have gone to as little as a 0.0015" clearance on some BR guns, but where you are setting with 0.003 clearance is about perfect.
50 to 52 gr of 4831SC is what most guys run- sounds like it is working for you right now- and sounds like you can go up a bit more also- just depends on what speed and accuracy you want. But basically if it ain't broke don't fix it.

 

[nowler]

hey massy

it's a small world eh?

i sent you an email for info from you bud.

cheers

 

[308sako]

Another thing to consider is that the brass is springing back a bit after firing, so .290 0r .291 for the cut chamber is possible... therefore you have .001 per side already. I shoot a 6mm/284 with .0005 per side with no problems and no split necks. pay real close attention to loaded rounds neck diameter though! Centers the bullet and helps with accuracy.

 

[jb1000br]

i run just under 3 thou total (.2911-.2912 loaded in a 294nk chamber)

works for me with 51.6-51.9 h4831sc

ymmv,
JB

 

[Ronin]

Many thanks for the replies. I was concerned about being too close toleranced, but my fears appear unfounded. Nice to hear that for once I seem to be on the right track /ubbthreads/images/graemlins/laugh.gif

Dezzy, you too, have mail /ubbthreads/images/graemlins/grin.gif

 

[redbone]

your rifle looked good on 6.5 284 load data I am look at bulding a 6.5/284 on a Rem action can you tell me about your rifle specis Did you have it biult GOD BLESS

 

[Ronin]

Rifle is L/A Rem 700, it was a Sendero in 25-06, my smith has trued and blueprinted action, conical bolt handle fitted, bolt handle moved to maximise secondary cam, Speedlock pin and spring, Sako extractor, .375" stainless recoil lug, barrel is Kreiger no7 light target, which has ten flutes, chambered in 6.5x284 with .291" neck / 1 in 8.5 twist. Standard HS Precision stock, which I have bedded the full action and formed a barrel pad to about the front of the chamber in SS Devcon, Ken Farrel 20moa base, Leup QR rings and Leup 8.5-25x50 LRT. Tape on windage cover is to stop ejected case necks deforming as they strike the cover on the way out! All smith work was done by Norman Clark of Rugby, Warwickshire, UK. His work is exceptional, but as with most smiths- he has a long waiting list! /ubbthreads/images/graemlins/cool.gif