300 wsm chamber issue

[Dieseltwotone]

I have a 300 wsm f class rifle. This is lapua brass with 215 hybrids going 2800fps. The chamber is dry, free of lube and the brass is virgin. This also happens with Norma brass. The gunsmith that chambering the barrel said it may be slow ignition. The measurement with calipers above the web measure .560 on some brass after firing. Any help is appreciated.

 

[Mulligan]

This is an interesting post, I am tagging in to learn,

CW

 

[Leeman]

I have a 300 wsm f class rifle. This is lapua brass with 215 hybrids going 2800fps. The chamber is dry, free of lube and the brass is virgin. This also happens with Norma brass. The gunsmith that chambering the barrel said it may be slow ignition. The measurement with calipers above the web measure .560 on some brass after firing. Any help is appreciated. View attachment 1736111

That's the classic sign of low pressure, brass not obturating to seal the chamber. Assuming there are no other pressure signs on the brass or primers I'd start slowly increasing the powder charge or try the next faster burning powder to what you are currently using.

 

[antunRC]

How old is your brass? can you give us some measurements of your brass before/after firing (neck, shoulder and .200 line).
Another thing what powder are you using?

I have a 300 wsm f class rifle. This is lapua brass with 215 hybrids going 2800fps. The chamber is dry, free of lube and the brass is virgin. This also happens with Norma brass. The gunsmith that chambering the barrel said it may be slow ignition. The measurement with calipers above the web measure .560 on some brass after firing. Any help is appreciated.

 

[antunRC]

How old is your brass? can you give us some measurements of your brass before/after firing (neck, shoulder and .200 line).
Another thing what powder are you using?

Oh, sorry Virgin brass. You are mentioning .560" at .200 line after firing. this is a lot of expansion (0.005") that explain slow speed too. If I remember virgin bras is .5545" (Lapua)

 

[243winxb]

web measure .560 on some brass

Secondary pressure spikes in the .300 WSM, often referred to in the context of abnormal pressure excursions, are dangerous phenomena typically associated with using too slow a powder, reduced loads, or specific combinations of slow powder and seating depth issues.

 

[Chuckhunter]

What powder and what charge are you shooting also are you seated into the rifling?

 

[Dieseltwotone]

64 gr RL22, 215 hybrids cci 200 Lapua cases. Those were jumped

61gr N160 208 hornady, norma brass, win magnum primers. These sealed better but not 100% of the time.

 

[Dieseltwotone]

64 gr RL22, 215 hybrids cci 200 Lapua cases. Those were jumped

61gr N160 208 hornady, norma brass, win magnum primers. These sealed better but not 100% of the time.

The N160 loads were jammed.

 

[X Count]

Too much neck clearance, too much jump or too much head space or a combination of all 3.

As a first step, Set your projectiles to jam or .010 jump and see if it goes away..

 

[243winxb]

Now is neck tension/bullet hold? .002" or more?

 

[Chuckhunter]

I personally would shoot 60.0 Gr's of N-160, with your Hornady's seated in .010 to .015 and if it continues, try increasing your neck tension .001 to .002 thou. if that doesn't help, take a closer look at your head space.

 

[Dieseltwotone]

Neck tension is .002 maybe a tad more. I was jamming .013. Sealing wasn't 100%. It would be fine then it wouldn't. I'll check the head space.

 

[swd]

Ask the gunsmith to measure the neck diameter of his reamer and compare it to one of your loaded rounds and get back to us.

 

[Dieseltwotone]

Neck is .340 (barrel is marked). Loaded round is .338

 

[medicineman]

What's the barrel length?

 

[Dieseltwotone]

What's the barrel length?

32"

 

[243winxb]

Head to datum measurement , before and after firing?

brass is virgin.

Excessive headspace, brass having to blow forward, .010" or more?
Freebore to long?
Must us a Magnum primer.

 

[Elwood]

I have had this problem. My issue was excessive free bore. The reamer used was for Bergers 230's, so basically not enough bearing surface in the case neck.
I only found out after trying some Hornady 220's which are basically small torpedo's! my problem of sooted cases and bolt face went away. Like you I was shooting F class and the Hornady's weren't well suited. In the end I had it re chambered with a suitable reamer for the 215's and the problem went away.