.223 No.4 Revisiting

[newcastle]

My only worry is that a 'less than stellar' example may have been used alot and not lock up nice and tight like I want. Whereas its probable that there are little used rifles out there where negligence has killed the barrel but left the rest of it in pretty solid condition.

[Peter Laidler]

Always remember this with small-arms, especially when doing a barrel/calibre change, that there are 8 important sequences during the operation of a firearm. Cock, feed, load, lock, FIRE. Unlock, extract and eject. Getting it to fire is easy. It's the other 7 that are fraught with problems.

Learned the hard way at Enfield while doing the L4 project. The smaller the base rim diameter, the greater the feed problems

[newcastle]

I am fully expecting to make many more posts on this subject Peter. and its probable that most will be asking for your advice.

[Peter Laidler]

Oh, no..............!

[Bruce_in_Oz]

Coals to Newcastle?

[newcastle]

Coals to newcastle? I will keep you psted during the project. or peter will with his commentary / abuse / advice

[Bruce_in_Oz]

Things to consider:

STRIKER profile and protrusion:

As set-up for the .303 cartridge, the striker has VERY excess protrusion and excess diameter for the 5.56NATO / ".223". The tip profile should be "adjusted" to something akin to the AR-15 striker, otherwise there will be a LOT of weeping and wailing about punctured primers and the consequent "burning" of the striker and the face of the bolt-head .

The face of the bolt-head will need "modification" to maintain a close fit of the hole around the striker, to prevent more primer ruptures; the 5.56 cartridge runs at quite high pressure.

Magazines:

Mini-14 are close to ideal but with 3 caveats:

1. The magazine must be seated as high as possible to ensure the bolt actually scoops a cartridge from between the lips.

2. The mag must also be as far forward as possible to ensure the projectile has entered the chamber BEFORE the rim leaves the mag. lips

3. Closely associated with "2", is that the standard mag. spring force is somewhat too high for use in a bolt-action. Note how "limp" the standard Lee Enfield spring is, compared to an L1A1 or M-14. Too strong a spring and, as the rim leaves the mag lips, the back end of the cartridge will be suddenly forced upward by the following stack.

Note that the mags for the AI rifles also have, besides a different (single row) feed at the top, a somewhat "softer" spring than say, the M-14 mag.

I have thought about the "single column", "politically correct" mags for some of the "sporter" AK variants; anyone played with these?

As for ejection, spring-loaded plungers are good, but can ONLY be used if the bolt "face" has a complete "collar" like, say, the Remington 700 or has an "extension", like the lower part of the front of the M-14 bolt. The biggest issue is trying to get enough "grunt" in the tiny springs to heave out the empty. One solution is to fit TWO plungers, offset by about 90 degrees. There is at least one BOLT action sporter that has dual plunger ejectors. The axes of these plungers and spring MUST go back at such an angle so as to NOT cut out through the back of the main part of the bolt-head.

Alternately, you could fit a "rocking", spring-loaded blade ejector into the left wall of the body, just like the system on the old Lithgow-built, SMLE-actioned "Hornet" rifles.

Keep us posted.

[Peter Laidler]

Believe me Bruce, this rifle project will do some of the 8 important features in thread 12. It might do many of the features. But it ain't going to do ALL of them! Been there and tried it. But it never managed to DO 'em all!

I tried SA80/M-16 magazines and even cut up a TMH to use as the magazine interface......... Nope....... Wish I'd kept the TMH/rifle and deactivated it instead. Worth more than the scrap I was left with!

[newcastle]

This is the target 8 I am aiming for : Cock, feed, load, lock, FIRE. Unlock, extract and eject. I am not too optimistic given Peter's experience but as the truck is in the shop for bpdywork for some months i have nothing to tinker regularly with so this will be my substiute.

[tiriaq]

What is the status of the Craig Whitsey 5.56 bolt head?