Shoulder bump testing in a blaser?

[Petehack]

So having starting to relearn a few things recently from Erik cortina and the guy that makes the cps priming tool. So the main thing I learnt with regards to shoulder bump is the cps guy is saying you should never just measure off once fired brass, bump 2thou then call it a day. As the shoulders will not be filling the head space in the chamber and that depending on brass it could take 2-4 firings before the case is actually fire-formed to the chamber and then you’ll be actually getting the consistent 2thou shoulder bump you want. Now In a regular bolt guy you can check this with removing the firing pin and ejector plunger, and feeling the bolt close. Cortina also places a piece of tape on the back of the case to check this. My question is, is there a way to this with a blaser?? If my explanation is unclear let me know and I can link the two videos. Any advice is appreciated.

[stokesrj]

You can remove the firing pin and extractor from a Blaser R8 also if you wish but I have found it totally unnecessary to do so as you can feel any resistance to the bolt closing very easily without doing so.
Also to the notion that it takes several firings for a piece of brass to reach a state of stability, that may be true for some cases but certainly isn’t so for Lapua or Alpha brass I’m currently using in my 223, 308 and 300 win mag. One firing and it stays consistent. I prefer .003 set back for my hunting Guns but sometimes go to .001 or even .000 for my match rifles.

[Corjack]

I agree with Stokes, I run full power loads in Lapua brass and it is annealed in the shoulder area from the git go. I figure two firings max and it is fitting the chamber. I periodically spot check as well. Might make a small adjustment when setting up a die, then I forget it. Have two barrels in one caliber cut with two different reamers. They are about a half thou different in shoulder bump. I just split the difference between the two. I bump mine back 3 thou even for my match rifles. Eric Cortina I know personally, and is a good guy. Trust what he says. The other fellow I do not care much for, so pay him no mind.

[Petehack]

Okay sounds good. So you’re saying you can feel if your shoulder is not bumped enough just with soft closing of the bolt? Would you not be feeling the fingers of the collet on the bolt engaging?

[stokesrj]

You can feel both but the tolerances are so tight the bolt will not rotate forward if the case is even .001” too long.

[Babcock21]

Corjack and Mr. Stokes, thank your for your input in this thread. This is good information to know.

[9.3x64]

I am not at the same level as you guys, but this is what I do with my R8.
Screw the Full length die down until is kisses the shell holder when the ram is in its fully elevated position. I then back it off 1/4 of a turn and chamber the case with that particular barrel. Most often it will not chamber at all. I then turn the die down and try again with a different case until the bolt closes reliably with just the slightest resistance. Almost always it seems to be that reliable feeding is when the die is about 1/16 of a turn backed out from touching the shellholder. I cannot get a 2 thou feeler gauge between the shell holder and the bottom of the die.
Am I good?
Thanks Allan

[secondtry]

I am not at the same level as you guys, but this is what I do with my R8.
Screw the Full length die down until is kisses the shell holder when the ram is in its fully elevated position. I then back it off 1/4 of a turn and chamber the case with that particular barrel. Most often it will not chamber at all. I then turn the die down and try again with a different case until the bolt closes reliably with just the slightest resistance. Almost always it seems to be that reliable feeding is when the die is about 1/16 of a turn backed out from touching the shellholder. I cannot get a 2 thou feeler gauge between the shell holder and the bottom of the die.
Am I good?
Thanks Allan

Perhaps not quite as precise as it could be, but huge improvement over simply crunching to minimum.

The Redding shellholders with varying thicknesses can be quite handy once you have worked out where you want to be.

[SPEEDY]

That's actually the same way I do it, I ain't no competition shooter so I tend to take a close enough is good enough approach to it.
Only difference is once it chambers I give it a tad more of a turn just to make sure every round will chamber then I put some glue on the ring so it won't budge.

[Datchew]

Bringing this thread back from the dead! MWA-HA-HA-ha

I'm used to handloading and headspace measuring in bolt guns and even falling blocks like ruger no 1's. Typically, you can very carefully feel when the brass shoulder is too long when carefully closing the bolt or the block and then adjusting accordingly.
For bolt and block guns (unlike gas guns) I typically re-size with the redding shell holders to 0.002" below the headspace.

I'm new to the blaser R8 - upon observation and reading this thread, it seems the bolt slides forward far enough for the collet to be in the engagement zone to the barrel and THEN the bolt will rotate in order to expand the collet. But it also looks like the bolt simply "bottoms out" moving foward and then any hand force rotates the bolt lever to expand the collet because the bolt cannot move any further forward.
Am I looking at this right?

My reason for scratching my head is I can easily chamber a spent casing and that's not my experience with bolt and block guns unless there is a VERY generous chamber headspace.
So i'm curious to hear how you guys match your brass to the chamber.

Also - bonus question - can you use the same technique for COAL adjustment of the bullet seating? I.e., leave it long and assume the bolt lever wont rotate until the bullet is seated enough to not hit the riflings as part of the overall bullet being too long?

[gearguywb1]

To set the COAL without an actual gauge, I use a long loaded (with no primer) round. Mark the ogive area with black magic marker. Gently feed it into the chamber and close the bolt. Extract. Shorten the length as necessary until you don't see rifling marks on the round. Then back of further to get the "jump" you are looking for

[9.3x64]

You can feel both but the tolerances are so tight the bolt will not rotate forward if the case is even .001” too long.

Hi Bob, apologies for digging up an old thread. But I have read this thread many times over, and would just like some clarification.
When you say above “the bolt will not rotate forward if the case is even .001” too long.” Are you saying that the bolt will not make that final push home into battery? That second “click” you feel just before the bolt will not travel any further?

Thanks in advance Allan

[stokesrj]

Hi Allan,
The Blaser action locks by an expanding collet which uses lateral force unlike a conventional bolt action that uses a cam that pushes the bolt forward as it rotates into locking position. The Blaser lacks this ability to force a cartridge into the chamber. That is not to say that you cannot force a Blaser to close on a cartridge that is just a little long but with the R8 it is done by the forward momentum of she bolt by rapidly working the action forward, you can do so. But if working the action at normal speed the bolt handle will stop before fully rotating forward and the safety mechanism will not allow the firing pin to contact the primer because it senses an out of battery condition. This safety mechanism is the little pin at the top of the bolt housing that contacts the barrel shroud at top dead center.

[9.3x64]

Hi Allan,
The Blaser action locks by an expanding collet which uses lateral force unlike a conventional bolt action that uses a cam that pushes the bolt forward as it rotates into locking position. The Blaser lacks this ability to force a cartridge into the chamber. That is not to say that you cannot force a Blaser to close on a cartridge that is just a little long but with the R8 it is done by the forward momentum of she bolt by rapidly working the action forward, you can do so. But if working the action at normal speed the bolt handle will stop before fully rotating forward and the safety mechanism will not allow the firing pin to contact the primer because it senses an out of battery condition. This safety mechanism is the little pin at the top of the bolt housing that contacts the barrel shroud at top dead center.

Thankyou Bob, very much appreciated.

[9.3x64]

After reading the first two comments in this thread by Bob Stokes and Corjack I decided to do some testing of my own.
I choose to use RWS brass, because as far as I am aware it is the thickest brass available. The cartridge was the 7x64 Brenneke in a R8.
The first firing was RWS loaded 159 grain Evolution ammo.
The rest were Handloads.
Headspace measurements were taken with a Hornady comparitor.

Original nominal headspace 2.0790”
Once fired. 2.0840”
Twice fired. 2.0850”
Third fired. 2.0850”
Fourth fired. 2.0850”

So, in other words even with thick RWS brass, after two firings the case had filled the chamber and grew no more after further firing.