Fire Formed Cases for M1917 Enfield

[RSAPD]

Hopefully this is the right forum for this thread. I couldn't find any prior threads that could answer my question. I'll try to be short and clear. I have just been neck sizing my brass with a Lee die since I only use it in this rifle, so everything is fire formed.

I was measuring my rifle for OAL and made a dummy round. After I would seat the bullet .020 from my OAL measurement, I noticed the round did not easily slide out, so I thought the bullet was in the rifling and I measured incorrectly. However, it was the fire formed cases catching in the chamber. I double checked with a FL size dummy round to verify and the round falls out easily. Of course, I would expect fire form cases to catch since they are shaped by the chamber.

I measured the OAL with ogive just touching the lands at 3.29 (this is base to tip but I will actually measure and seat based on base to ogive). So, I want to start at 3.27. I have seated at 3.24 in the past and I saw flat primers meaning increased pressure and I was not even at max loads. My question is, can a fire formed case require a shorter OAL than a FL sized care to not have incorrect pressure? I should be able to seat out to 3.27 no problem but if I am seeing pressure increases at 3.24 with a fire formed case, then 3.23 seems to be the limit. I thought about loading a few FL sized cases to 3.26 as check them for pressure signs. Any thoughts or ideas in regards to this issue? Thanks.

[TurnipEaterDown]

You don't state what cartridge, presuming 30-06.

No, using a case formed to chamber & neck sized should have no effect on pressure when using a commercial cartridge and an in spec chamber.

Keep in mind that primers can flatten for a number of reasons, and that no reloader knows actual chamber pressure unless they have actual pressure measuring equipment.

One of the most common causes of flattened primers (seen most commonly in a revolver) is to have the primer back out some small amount during initial pressure rise, and then the case slide back (or stretch) as the pressure increases further, thus turning that primer cup into a rivet before it is extracted. This should Not be happening though if your cases are really sized properly.
Do you have a Stoney Point / Hornady case comparator around? If so, use a insert capable of bearing on the case shoulder (375 is great for 30-06) and measure your fired and sized case lengths. You only need 0.0015 - 0.002" clearance for easy reliable chambering.

Rarely in a bottleneck case is pressure increase by small changes in seating depth where the bullet is moved Further from the rifling. Freebore (which decreases pressures) is done purposefully to get the bullet further from the rifling.

Do you have a chronograph? What are your velocities when comparing same load in new vs sized cases and change in seating depth? Pressure change is most often indicated by mean velocity shift.

Think I'd look elsewhere other than case or seating depth if you really have high pressures.

[racepres]

How many firings?? after awhile, even fireformed rounds get too big.. as the brass quits "relaxing", or "shrinking" , completely back to original size.. especially with full power(or higher) loads... I simple partially resize until chambering/extraction ease is restored..
Just the way I do it.. Good luck

[RSAPD]

Sorry, yes 30-06. I do have a comparator and I'll take your advice on that. Thanks. They have been fired only 4 times and I've only had to trim a few. This all helps, thanks.

[WRideout]

Just a guess, but if your cases are just a bit too long, the chamber may be "helping" to crimp the neck tighter, and thereby drive up pressure. This happened when I was making 7.65 Argy cases from 30-06, without turning the case necks or trimming to consistent length.

Wayne

[Bigslug]

It's not 100% clear from your post if your primer flattening is with FL or NS cases.

In your other thread I mentioned that my Remington 1917's have generous headspace. My thought is that if you are reducing your COAL with full-length sized cases by seating your bullets deeper, what's actually happening is that your rounds are shoved forward by the firing pin into the oversize chamber, allowing the primers to start backing out on ignition, and the flattening gets completed when the case fully pressurizes to fill the chamber and slams the case head back. What I think you have is NOT excessive pressure; what's happening is your longer COAL rounds end up in the lands and hold the case head closer to your bolt face, preventing that primer setback.

When you're fire-forming cases in big chambers, very close or slightly into the lands is the way to go to prevent web stretch / case head separation. After that, it's about seating for feed function, then accuracy.

[RSAPD]

It's not 100% clear from your post if your primer flattening is with FL or NS cases.

In your other thread I mentioned that my Remington 1917's have generous headspace. My thought is that if you are reducing your COAL with full-length sized cases by seating your bullets deeper, what's actually happening is that your rounds are shoved forward by the firing pin into the oversize chamber, allowing the primers to start backing out on ignition, and the flattening gets completed when the case fully pressurizes to fill the chamber and slams the case head back. What I think you have is NOT excessive pressure; what's happening is your longer COAL rounds end up in the lands and hold the case head closer to your bolt face, preventing that primer setback.

When you're fire-forming cases in big chambers, very close or slightly into the lands is the way to go to prevent web stretch / case head separation. After that, it's about seating for feed function, then accuracy.

The primer flattening happened with NS cases. I think what you bring up may be the case. No pun intended. I'll monitor this situation. I did up several variety of loads and will take good notes. Thanks.

[ipopum]

I think most of the 1917`s that I have shot had very generous chambers. I did not FL resize when reloading.

I liked the case to take just a little bit of pressure on the final bit of the bolt close.