Tikka Tip of the Day….Ejector Roll Pin

[nksmfamjp]

It is my understanding that I need the bolt to have zero spring pressure on the action and case base. Under this condition, I can find the max cbtd that will allow the bolt to drop under its own weight. That is the only way to do this. Other methods are a guess.

With cbto, I can do the same thing, but I lift the bolt handle. When the cbto is short enough to raise the bolt without the click from the primary extraction cam, I know it is just short of max cbto.

Without removing the ejector, what can I do to determine these dimensions to the same accuracy without meaningless lower accuracy tools?

 

[FireFlyFishing]

It is my understanding that I need the bolt to have zero spring pressure on the action and case base. Under this condition, I can find the max cbtd that will allow the bolt to drop under its own weight. That is the only way to do this. Other methods are a guess.

With cbto, I can do the same thing, but I lift the bolt handle. When the cbto is short enough to raise the bolt without the click from the primary extraction cam, I know it is just short of max cbto.

Without removing the ejector, what can I do to determine these dimensions to the same accuracy without meaningless lower accuracy tools?

How far from the lands do you typically seat your bullets?

For me, I need a repeatable process that gives me a relative jam starting place. I then subtract 0.020" for the start of any of my load development. Why? Because I want my rifles to cycle reliably every single time. I know from experience, I will find a happy place away from the lands quite some distance. The best shooting rifle I have in my quiver is actually mag fed and mag constricted for OAL. I had to seat depth test starting from mag length. I didn't even create a dummy round to find jam distance as I had no interest in a single fed rifle.

If you seat away from the lands, then disassembly of the bolt is unnecessary. As you found out, there is a higher exposure of losing parts and wasting time sourcing missing parts. I'll put it this way, you can change the oil in your engine by pulling the entire engine. Why do that when it takes longer, is more complicated, and has the potential for lost parts and/or issues with reassembly? I like processes that save me time. If I have a method that is faster, easier, and gives me the best possible result, why wouldn't I use it?

Now, if you're into jamming your bullet every shot or staying a couple thou off the lands, then maybe your method is better. I wouldn't know as I don't roll that way…again, for reliability in the field and I don't "chase the lands".

As a side note, I ran the Hornady OAL tool for many years. The only plus side with that thing is you don't have to donate a piece of brass and a bullet to make a dummy round. I sit in the camp of lack of consistency with that tool. I'm glad to have moved past that thing.

 

[nksmfamjp]

How far from the lands do you typically seat your bullets?

For me, I need a repeatable process that gives me a relative jam starting place. I then subtract 0.020" for the start of any of my load development. Why? Because I want my rifles to cycle reliably every single time. I know from experience, I will find a happy place away from the lands quite some distance. The best shooting rifle I have in my quiver is actually mag fed and mag constricted for OAL. I had to seat depth test starting from mag length. I didn't even create a dummy round to find jam distance as I had no interest in a single fed rifle.

If you seat away from the lands, then disassembly of the bolt is unnecessary. As you found out, there is a higher exposure of losing parts and wasting time sourcing missing parts. I'll put it this way, you can change the oil in your engine by pulling the entire engine. Why do that when it takes longer, is more complicated, and has the potential for lost parts and/or issues with reassembly? I like processes that save me time. If I have a method that is faster, easier, and gives me the best possible result, why wouldn't I use it?

Now, if you're into jamming your bullet every shot or staying a couple thou off the lands, then maybe your method is better. I wouldn't know as I don't roll that way…again, for reliability in the field and I don't "chase the lands".

As a side note, I ran the Hornady OAL tool for many years. The only plus side with that thing is you don't have to donate a piece of brass and a bullet to make a dummy round. I sit in the camp of lack of consistency with that tool. I'm glad to have moved past that thing.

I typically shoot for 0.02" off. But My last loads are like 0.17" off. To know off, don't I need to know touch?

BTW, I haven't lost a roll pin yet. Just would like a spare. I can see how I might lose one. I use tape to catch things.

 

[FireFlyFishing]

I typically shoot for 0.02" off. But My last loads are like 0.17" off. To know off, don't I need to know touch?

BTW, I haven't lost a roll pin yet. Just would like a spare. I can see how I might lose one. I use tape to catch things.

It's all relative. Since you're not dug into the lands with your loads, it's not imperative you know the exact CBTO down to the 10,000th of an inch. You need a starting place to stay away from so you don't jam your projectile into the lands causing pressure issues and/or a seated bullet in the rifling when you eject a case. The process in the video I shared earlier will ensure this as well as ensure you don't have to disassemble the rifle to achieve great results.

There are multiple ways to test seating depth. Barnes, Berger, Cortina has a video. It's up to you to decide how finite you want to do that test.

 

[bigngreen]

The bottom line is do you want to know where the lands are at or do you just want a baseline to start from somewhere off the lands.

 

[med358-boise]

The bottom line is do you want to know where the lands are at or do you just want a baseline to start from somewhere off the lands.

I personally do not care whether my measurement to the lands is is +/- .005-.007 because 1) I am going to start .015 off the "what I measured" the lands to be and 2) finding the most accurate seating depth (measured BTO) is an empirical process; i.e., I find it thru observation of the results (the actual group size) as I vary seating depth. It is completely irrelevant whether based on measurement believe that I am 18/1000 off the lands but in fact I am 23/1000 or 13/1000 off the lands.

It seems incongruous to me that anyone would use a process with the objective of finding a very precise actual measurement but the process includes removing the ejector. The ejector forces the case forward and presses the case groove against the back of the extractor hook. The tolerance around the extractor and the case groove is probably at least .010 or more (or .005 or more per side) but the actual tolerance is likely unknown. In other words, "I am expending effort to get a measurement within .001 but I am not accounting for some unknown amount that is likely .005 or more"

edited for clarity

 

[bigngreen]

I personally do not care whether my measurement to the lands is is +/- .005-.007 because I am going to start .015 off the lands and finding the most accurate seating depth (measured BTO) is an empirical process; i.e., I find it thru observation of the results...actual group size.

It seems incongruous to me that anyone would use a process with the objective of finding a very precise actual measurement but the process includes removing the ejector. The ejector forces the case forward and presses the case groove against the back of the extractor hook. The tolerance around the extractor and the case groove is probably at least .010 or more (or .005 or more per side) but the actual tolerance is likely unknown. In other words, "I am expending effort to get a measurement within .001 but I am not accounting for some unknown amount that is likely .005 or more"

That just hurt my brain!! You don't care if your measurements are + or - .005-007 yet you start at .015 off the lands, that tells me you really are just winging it and it's working, own it for what it is!!

The case should never be pushed as far as the extractor, your headspace should be much tighter than that.

If we are using tools that measure base to ogive we need to use a base to ogive process for accuracy. If your ejector is in and your off the lands your now using a shoulder to ogive process and a base to ogive measuring tool. Your introducing that much tollerance stack to your measurement and frankly why use tools that measure to the thou then, pick a spot and rock on WHICH is completely fine just own it for what it is.

If I have a seating die that adjusts to the thou, I bump my shoulder to the half thou, I measure charge weight to the .01 grain, I'm taking half a minute to pull an ejector so I can take a measurement that has some real value and the method is repeatable across users.

 

[med358-boise]

That just hurt my brain!! You don't care if your measurements are + or - .005-007 yet you start at .015 off the lands, that tells me you really are just winging it and it's working, own it for what it is!!

The case should never be pushed as far as the extractor, your headspace should be much tighter than that.

If we are using tools that measure base to ogive we need to use a base to ogive process for accuracy. If your ejector is in and your off the lands your now using a shoulder to ogive process and a base to ogive measuring tool. Your introducing that much tollerance stack to your measurement and frankly why use tools that measure to the thou then, pick a spot and rock on WHICH is completely fine just own it for what it is.

If I have a seating die that adjusts to the thou, I bump my shoulder to the half thou, I measure charge weight to the .01 grain, I'm taking half a minute to pull an ejector so I can take a measurement that has some real value and the method is repeatable across users.

I am curious:
How far do you start off the lands? how did you determine that was a good starting point and have you ever changed it over time?
What process do you use to find the most accurate distance off the lands? (i.e., what increments of change do you use)

if the answer to any of the questions above is it depends feel free to quote a range

What is the range of the deltas between ending and starting point? In other words, I start at .010 off and sometimes I stay right there but I have ended up as little as .007 off and as much as .040 off

 

[marc357]

I only find JAM to make sure I'm not jamming the bullet into the lands. With most factory rifles a cartridge that fits in the magazine will never touch the lands anyway, and I'm not interested in single feeding.

I'll typically load .010" shy of my max magazine length (as long as that's shorter than JAM) and roll with it. I don't care how far the bullet is jumping.

Removing the ejector plunger can increase "feel " as far as determining when your case chambers freely when setting your resizing die. I prefer to use the Hornady case comparator to measure a fired case, then set the die to bump the shoulder .0015 to .002 and done. Quicker way for me to arrive at the same place, and I have an actual base to shoulder measurement to work with.

If I change brands of brass, I still need to size it to the same shoulder bump/ base to datum line measurement, but usually the sizing die setting will be different because different makes of brass behave differently.

 

[Taylorbok]

That just hurt my brain!! You don't care if your measurements are + or - .005-007 yet you start at .015 off the lands, that tells me you really are just winging it and it's working, own it for what it is!!

Basically the same thing you're doing.
Statistically 100 rounds isn't really enough to determine that the change you made actually had a significant affect, or that it needed changing in the first place. (I guess unless it was a big difference like going from 2moa groups to .5 moa but from what I've seen seating depth wont cause that large of change)

The gun is shooting well in spite of the change not because of it. correlation is not causation.

Most people are backing off some arbitrary number from the lands and going from there so it doesn't really matter the actual distance to the lands. If you are trying to maintain X distance into or out of the lands it does matter but IME and a few articles that I have seen from legitimate ballisticians seating depth has very little impact on precision

 

[pavementends]

Since the lands move slightly with every shot, I an unsure of the worth of the time expended. We again have different disciplines,
some small groups are the goal for others small groups are important but absolute reliability when magazine fed is most important. For most of us it is measuring with a micrometer, mark with chalk and cut with a chainsaw. Find what makes you feel good and enjoy.