stiff bolt lift ?

[handwerk]

I just put together a Kimber 84M 6 cm. The load that worked in my 2 son's kimber hunter 6cm builds ( 42 RL 16
95 LRX) shoots great in mine but I am having a bit of a stiff bolt lift yet the primer and case look fine.
With the 22" proof CF barrel my FPS is between 3160-3175 which seems moving along pretty well.
I dropped down a 1/2 grain but accuracy suffered and the slightly stiff bolt lift remained.
Should I just carry on with this load or are there other pressure signs I should look for.

 

[HuntHarder]

For me, stiff bolt lift is usually where I say it's a no go. Too close to max and if a round gets wet, you may end up with a stuck cartridge in the chamber.

 

[Jebel]

What velocity does your son get with this load at what barrel length? Match the barrel-length-adjusted velocity, not the charge weight.

You don’t want a stiff bolt lift.

 

[Dmoua]

Work up a new load or you might pay the consequences when it gets wet out.

 

[SloppyJ]

Hard no go. You've got that thing cooking. Back it down and find a new load.

 

[waspocrew]

Back down until the stiff bolt lift goes away.

 

[Ucsdryder]

I’ve never had a gun show pressure without ejector marks way before heavy bolt.

 

[AkMtnRunner]

One possibility is slight difference in chamber between the two rifles. If the brass was fire formed in a larger chamber, it may add quite a bit more friction pulling out of the smaller chamber.

 

[Hudsflywater]

I would try 41 and 40.5 gn and see what you get. do you know where your at with your bullet in relation to the lands? I.e if your really close the the lands, that can increase pressure?

 

[hereinaz]

If you are reusing brass from another chamber you can’t isolate the heavier bolt lift entirely to pressure.

 

[TheWhitetailNut]

Try 40.7gr. My last couple rifles I've done the load dev. using Dan Newberrys OCW method. But in studying it I heard him say optimum charge weights are in 3% increments. I tried it first in my match rifle because I wanted to drop speed a bit to extend barrel life. I found group size, shape, and relation to POA are consistent in 3% increments. If that does work for you, you could drop the load 3% across all rifles and just readjust dope for extended ranges.

 

[handwerk]

Thanks for the input guys, I’ll keep working on a different load, just hard to leave it when it’s shooting quite well.

 

[General RE LEE]

Could be pressure but it also could be clickers due to variances in chamber dimensions between the two. Is this brass fired in the previous rifle? If so, try some new, unfired brass.

 

[jjohnsonElknewbie]

Per the comments about different chambers, if this isn't virgin/sized brass, and you're re-using between 2 rifles, it definitely could be a sizing issue. I ran into this a couple times with used brass in a .308 and a 7-08 from different rifles. Do yourself a favor before you restart load development, and turn your FL sizing die down (beyond the default shellholder to ram position) to make sure your sizing the entire case. If its a sizing issue, this will solve your problem.

IME, I had difficulty chambering even before firing and that was after FL sizing. It was a very frustrating process, and although it's cheaper, I avoid using fired brass unless it was shot from the rifle I plan to reload.

Good luck!

 

[mtnbound]

I agree with others about chamber difference and trying new brass before developing a new load.

 

[Harvey_NW]

Try 40.7gr. My last couple rifles I've done the load dev. using Dan Newberrys OCW method. But in studying it I heard him say optimum charge weights are in 3% increments. I tried it first in my match rifle because I wanted to drop speed a bit to extend barrel life. I found group size, shape, and relation to POA are consistent in 3% increments. If that does work for you, you could drop the load 3% across all rifles and just readjust dope for extended ranges.

Complete hogwash. This is simply a matter of random distribution and small sample variability. There's up to 70% variability in 3 shot groups, meaning the same load could shoot a .3" group, and a 1.7" group. If you up your sample sizes, the trends disappear.

 

[handwerk]

All the brass I’ve used is new 6 CM sig brass.both in my rifle as well as both my son’s. All barrel/chamber work was same smith who I’ve been very happy with.

 

[jjohnsonElknewbie]

All the brass I’ve used is new 6 CM sig brass.both in my rifle as well as both my son’s. All barrel/chamber work was same smith who I’ve been very happy with.

Are you full length or just neck sizing?

 

[General RE LEE]

All the brass I’ve used is new 6 CM sig brass.both in my rifle as well as both my son’s. All barrel/chamber work was same smith who I’ve been very happy with.

Just to confirm, the brass you fired in new rifle is new and has never been fired in another chamber correct?

 

[TheWhitetailNut]

Complete hogwash. This is simply a matter of random distribution and small sample variability. There's up to 70% variability in 3 shot groups, meaning the same load could shoot a .3" group, and a 1.7" group. If you up your sample sizes, the trends disappear.

Sure, but it didn't. I've fired this same load from 10F to 90F in many conditions in matches and as a pace rifle for other load dev. Constant as the moon.