Finnish M39 - struggling with seating depth

[Ritterbruder]

I've been trying to work up a handload for my Finnish M39 Mosin Nagant, and I am struggling to make sense of why my bullets keep touching the lands.

I took a factory PPU round and measured the base-to-datum at 2.437" (with a Hornady bullet comparator). The PPU load uses a 0.310" diameter bullet. It does not touch the lands when I chamber it.

The bullet for my load is a 0.312" Hornady 174 BTHP. I have it seated down to 2.210" base-to-datum, and the bullet still has rifling marks on it.

My bore slugs at 0.313".

Just for kicks, I seated a standard 0.308" diameter bullet down to 2.300", and it still has rifling marks.

I can't make sense of why my handloads keep touching the lands even after being seated way deeper than factory ammo. Am I missing something?

 

[gunsnjeeps]

Sounds like something else is going on. Do you have an Over All Length Gauge or can you sacrifice a shell to chamber a round to see where it pushes a bullet back to?

PS: Could you be hitting the neck shoulder junction and scraping the bullet and seeing it as rifling?

 

[Ritterbruder]

I have a Hornady OAL gauge, but I don't have a modified 54R case to use with it.

I did try to push the bullet back by jamming it into a case, and it ended up at around 2.330". I seated a few bullets to 2.310" and I still get scrape marks.

 

[918v]

Your gauges suck.

Take a FL sized case and cut a slit lengthwise through the neck. Seat a bullet long and insert the dummy round into the chamber. The rifling will push the bullet deeper into the case. Push out the dummy round carefully with your cleaning rod from the muzzle. Measure the oal. That is the only way to get a true distance to lands.

 

[gunsnjeeps]

That's the plan. I recommend measuring a few of times when you do this. A couple to get the feel for it then a few to get the measurement. Some will say average the measurements. I go more with the repeatability of the measurements. When you do it and get the same measurements your doing it right.

 

[M77]

What M39 is it ? Sako or Vkt

 

[M77]

I use the 174gr Hornady fmj and I sent them fairly past the canelure with no issues . Usually they are throated fairly Long

 

[Ritterbruder]

I use the 174gr Hornady fmj and I sent them fairly past the canelure with no issues . Usually they are throated fairly Long

Mine's a 1967 "sneak". I believe Sako made those.

I was going to try the Hornady 174 FMJ next. The cannelure is located pretty far forward on those right?

 

[Clark]

I have a rifle with a neck that is 0.338" go 0.340" no go, that should be big enough, but I have had serious neck pinching problems causing pressure spikes.
The chamber must be short for the brass.
The groove on the barrel measures 0.309"

Mosin Nagant

Sako VKT M39 Westinghouse 1915-18

7/62x53r

$90

$0

1/1/2004

PS

1944

Westinghouse made receiver (1915-18),