Thread: .284 Chambering & Freebore Specs

Hi team,

about to do another .284 build converting a 7mm08 Tikka. I will be running 150-162gn ELD-X pills. People talk about running long throats for the 162's has anyone got specs on a similar build that I can share with my gunsmith?

Yep, you want to seat pills out long to get best out of the 284. Make up a dummy round with your projectile of choice seated so the end of boat tail is just below the neck/shoulder junction. In your case choose the longest pill you intend running 162ELDx . In my experience this should end up somewhere around 3.120 or maybe as long as 3.150”

Yep, and supply said dummy round to your smith and discuss with him. Depends upon whether you jump or jam. Unless target shooting you're very unlikely to jam.

My smith that did my 284 within 1 thou of what was agreed.
Likewise my 308 FTR with a different smith. The 308 was more difficult as I shoot from 155gr up to 200gr so some do not end up at optimum seating depth. (The 200gr does.)

For the 284 I found a lot on google. Had to dig though. I anguished for quite a while deciding my freebore.

Few different neck specs for the various 284w reamer too from memory, for a hunting rifle pays to go for the roomier one to avoid issues. Have a search on here - was a good thread awhile back.

You can find reamer drawings on google. Unfortunately Pacific Gauge don't publish theirs anymore but will supply on request. You will see variation from standard for neck' (There used to be theory that the 284 liked a certain neck clearance.)
Both my 284 and my 308 had throats extended with throating reamer but would not expect this with a sporter chambering.

I agree with above - nice and long but not too long to fit in a Tikka long mag. I’m 3.1 or 79mm. Also give yourself some room to avoid next turning

Have you seen the one on trade me already done as it actually seems a good package deal with good scope and all the work sorted

A standard reamer in 284 has a neck of around .322 which is very wide , specifically if using necked 6.5-284 brass.
You have to decide what brass you are going to use and then you can measure the diameter of the neck with the bullet of your choice seated inside. Add 0.03 or 0.04 inches to that measurement and that won’t be far off. I think both gunworks and true flite have different reamer specs in 284 that suit different options among other gunsmiths

0.003" to 0.004"?

I'll dig out my reaner drawing tomorrow.