15 thou. headspace on M1917... what to do?

[Patrick Chadwick]

and the second bolt, from a GunBroker seller, arrived today in a parcel weighing a total of 4.5 ounces (including the box).

Don't tease us! What was inside? Just the striker?

[CouldBeWorse]

1911 magazine. It sounds like both were honest mistakes, and I'm just "unusually lucky" this week.

[CouldBeWorse]

There's a happy ending to this one: the rifle passed a field guage test with the third bolt I bought. With the firing pin and extractor removed, the bolt handle stops leaving about 1/4" of space under it, instead of fully closing like before. As a bonus, the bolt is an Eddystone, like the barrel.

I haven't been to the range with it yet, but feeding from magazine is working properly. I also bought a Lee collet die, and am thinking of backing it off 0.010" (1/8 turn?), and making a Lee case trimmer that is 0.010" longer, to minimize unnecessary brass trimming.

[Bruce_in_Oz]

Be VERY careful with case length.

Trimming is not just done to make things look tidy.

Case necks WILL flow during firing AND sizing, be it full or just neck.

At some point, the stretched neck will start to be forced inwards during bolt closure. On a helically-locked system like an M-17, you will probably not feel this extra resistance. You WILL notice the blown primers and bulged primer pockets, however.

What happens is this: With an over-length case, the angled step at the front of the "case" section of the chamber acts as a forcing cone on the cartridge case. Thus, the case is forced INWARDS; into the bullet jacket. This MASSIVELY increases peak pressure on ignition because the bullet is not able to start a gradual acceleration immediately after the primer has ignited the propellant.

Note that if you ever forget to load powder in a case, you may find yourself with a bullet wedged in the throat of the barrel, having been driven there by the power of the primer alone. It gets a LOT more exciting if you fail to notice the lack of recoil, noise and impact and ram another round up behind the stuck bullet and pull the trigger. It's one way to disassemble a rifle without a toolkit.

[bob308]

a way to take up headspace and i have use it before. is to have the back of the locking lugs on the bolt built up with hard chrome. it goes on in layers of about .004-.oo5.

[fguffey]

.015"? I have an Eddystone with a chamber that is .016" longer than a minimum length, full length sized, new factory loaded round, My chamber is longer by .016" than new (SAMMI) ammo. In the perfect world one school of thought says my chamber should be .005" longer than a minimum length sized case, that would make my chamber go-gage length and my new ammo minimum length, problem for everyone else, not me.

I am a case former, I am not a fire to former, I form first then fire, I am the fan of cutting down on all that case travel.

My favorite case is the 280 Remington, the 280 Remington is longer than the 30/06 from the head of the case to the shoulder of the case by .051", By adjusting my sizing die off the shell holder .014" I can off set the length of my chamber with the length of the case. I have sizing dies, I have forming die, the forming die is the best choice to start with, then finish with the sizing die. again, I adjust the die off the shell holder by setting the die gap with a feeler gage, after sizing I chamber the formed case to determining if the case will chamber.

I do not secure the lock ring to the die, I secure the die to the press with the lock ring.

The P14 and M1917 has a unique design, a go, no or beyond gage is not necessary when I determine the length of the chamber from the bolt face to the shoulder of the chamber, a smith at the Utah Arsenal took a lot of flack from other smiths, he did not use the go-gage, he did not use the no go-gage. I do not use any of the three.

When forming 280 Remington cases the reloader with a good understanding of the incline plain has 51 options from .000 off the shell holder to .051" off the shell holder, with 51 choices I can not see how they can miss.

I am the fan of forming cases from new/unfired brass, I have no problem using fired brass for determining the length of the chamber.

F. Guffey

[Patrick Chadwick]

and making a Lee case trimmer that is 0.010" longer,

You don't need to make a complete case trimmer. All you need is a 0.010" washer on the threaded spigot of the trimmer mandrel, between the mandrel and the cutter. The practical problem is that most washers are too large in the diameter, and you will probably have to turn one down.

[fguffey]

There are not many case trimmers I do not have, I will assume you are referring to the lee screw-on with the universal base. If I wanted to raise the cutter to add .010” to the length of trim I would add the shim in the form of ‘shim stock’ below the shell holder in the bottom of the universal holder, If I was R.Lee I would make a thicker universal holder then drill and tap the bottom of the holder ‘THEN’ add a screw for adjustment with 40 threads per inch as in one turn = .025”.

The same adjustment could also be made with a micrometer if the user understood the concept of .000 (zero).

F. Guffey

[fguffey]

Bad habit: Need a bolt? Order a bucket of bolts.

Must have been and keep a secret, I have 25+ Springfield bolts, the maximum/minimum effect on head space between the longest? and shortest as in the effect each one has on head space is .001”. Not a problem for me, my problem would come when I wanted one bolt instead of a bucket full, I do not know one person anywhere that could compare my measurements with the their bolt measurements.

Again, I find it easier to adjust the length of the case than adjusting the length of the chamber.

F. Guffey

[Col. Colt]

Two things - Don't rely on "experts" without verification! That is a fine old gun that would have always been "defective" to some. It just needed the right bolt!

Secondly, I have read great things about the RCBS "X-Die" that prevents case growth if used as per instructions. M14s - normally 3 or 4 reloads and scrap the case - up to 15+ with the X-dies. CC