Sticky bolt.

[AFA82]

Hello ladies and gents,

I have been playing around with 170gr Lapua Lock Base bullets for a bit recently (in a .308).
My load is 44.5grs of N540 in Lapua cases with cci br2's.
I get 2840fps with minimal variations, in other words its very accurate out to 1200m.
The rifle in question is a Weatherby Vanguard with a 27" Lothar Palma match barrel (1:13 twist)
This load pretty much replicates the HPS factory Lapua ammo.

HOWEVER!

The issue is that I get pressure signs in the form of a sticky bolt, not much but enough to call it a "sticky bolt". With the Factory HPS ammo I never have this.
Since 44.5grs according to the big book is well under max pressure, I am at a lose as to why I'm getting this excessive pressure sign.
I've tried neck sizing and full length re-sizing but same result.
Primers look fine, not pancaked.
Could I just simply have a roughly cut chamber that needs polishing or should I look elsewhere to solve this problem.
I would love to make this combo work since its so accurate to long ranges and I have recently stashed up on 170 LB's and N540.
Many thanks, and if someone could be kind enough to run this load through Quickload I would very much appreciate it.

After shooting these possible over pressure loads, would the rifle still be safe to shoot?

Cheers.

 

[davkrat]

2840 sounds smoking fast for a 170 in a .308 to me. I'm not familiar with that powder but a quick look at hodgdon's data shows most 168-175 grin loads maxing out about 100-150 fps lower. You say your well below book max but I'd double check that if you're getting those kinds of speeds. As for damaging your gun it's my understanding that the proof testing loads are significantly higher pressure than a slightly sticky bolt. Might put a little extra wear on some of the parts not sure it will make it unsafe to shoot. If I were you I would take that load down a bit you're getting up into .300 Win Mag starting load speeds out of the little .308.

 

[royinidaho]

First off, I'd say your rifle is plenty safe to shoot.

Take note of how the reloaded cartridges chamber. If they chamber a touch firm they may well extract a touch firm. This is the case with all of my rifles that I load on the warm side.

When I resize sufficiently to have "factory feel" chambering there is no extraction pressure. I use this "feel" as a guide to determine FL sizing is needed.

I load warm enough that I play close attention to case separation indicators. I think you are a long way away from those pressures.

In one custom rifle a change in sizing die made a big difference.

Good luck.

 

[AFA82]

Hi Guys,

Thanks for the replies.

Factory Lapua 170 gr HPS ammo chrono's at 2850fps with this rifle.......that is factory loaded ammo.

I've since talked to my gunsmith and he seems to think that the chamber might need polishing because of the grooves that are present on the fire formed brass.
Either way I'm going to have this load pressure tested at the National Firearms testing facility. It doesn't cost much and its done by professionals, just to be on the safe side.

Cheers.

 

[gohring3006]

I would make sure your cases are trimmed to specs. I would check a trimmed case to a fired case and compare lengths. Also I was always told never to polish a chamber that the hash marks from reaming allows a little friction to the case actually lowering back thrust on the bolt....

 

[AFA82]

I would make sure your cases are trimmed to specs. I would check a trimmed case to a fired case and compare lengths. Also I was always told never to polish a chamber that the hash marks from reaming allows a little friction to the case actually lowering back thrust on the bolt....

Interesting point regarding the chamber, I'll take that into account with I see my smith.

 

[gohring3006]

Interesting point regarding the chamber, I'll take that into account with I see my smith.

Its OK to get deep scratches out but I wouldn't polish to a mirror finish I have seen people use cylinder hones that are used on break calipers and hydraulic valve body cylinders it leaves a cross hatched pattern but I heard mirror finish is bad.

 

[Unofficial Gun Addict (UGA)]

I'm not sure if I have the 170 lapua lock base bullets in my quickload database, but if you shoot me over your specs, I'd be happy to check.

Need your Coal and case length. Think I can get by with the rest of the data you've provided.