Another Head Scratcher

[284winner]

Here’s one analogy take a hammer and try to push in a nail then raise a hammer smack it down on the nail it drives much easier this relates to jam or jump with a bullet as well jam does not let the bullet build up speed to hit the rifling and engrave therefore it does raise pressures and then return raise velocity but I am just an old construction worker you may have a much different opinion

I have no opinion on that scenario except hammering something certainly drives it in while pushing it, not so much. This process I'm going thru isn't for load development as I stated earlier In the thread. It's to jam the bullet so the cartridge is tight in the chamber allowing a full fire formed case. Having misfires makes me think there is some cartridge play between the bolt head and case. A bullet tight in the rifling should push back the case tight to the bolt head allowing a better formed case when fired, hopefully eliminating future misfires.

 

[RegionRat]

Just food for thought.
Sometimes, but not always, those misfires have nothing to do with the ammunition but they are the result of a weak firing pin spring or problem with the firing pin or bolt.

I have had to debug many rifles, including two of my own, for these issues and some share of the issues were the rifle instead of the ammo.

 

[284winner]

Just food for thought.
Sometimes, but not always, those misfires have nothing to do with the ammunition but they are the result of a weak firing pin spring or problem with the firing pin or bolt.

I have had to debug many rifles, including two of my own, for these issues and some share of the issues were the rifle instead of the ammo.

Ya that's the other thought I had. I did measure a new firing pin to this one and there exactly the same length. Spring wise, I haven't checked it but it will be replaced if I can't fix the issue with this jam fire forming technique. I'm pretty sure this method will cure my problem BUT I'm still stumped on the OAL gauge measurement vs actual chamber measurement or better explained the closed bolt dummy round on chamber measurement.

 

[Mulligan]

I wish there was a ballistic expert that would take the time to explain the whole process while showing what happens as you increase distance into the lands. As lead and brass are softer than steel, it is hard for me to visualize or comprehend the difference between 2 and 15 thousands into the lands.

Push a bullet into the lands and they cut grooves into it. Push it harder, and the grooves get deeper.

Don't get me wrong. I have certainly expermitted with this by finalizing seating depth at the range. What I want to know is why. Is it increased pressure which should increase velocity?

I'm old and stubborn, and it might be that I think too much and should forget about the why and simply concentrate with the results. It's the stubborn part that causes me the most problem. I like to fully understand anything I do.

In the Boyer book, Tony explains it has to do with rise time. I would need to re-read that section of the book. As I recall, he has some grafts that help with the visualization .
CW

 

[284winner]

I don't want to turn this into an indepth discussion on a variant of my problem. It's fairly straight forward as to why I'm trying to get this measurement but as I explained, I'm going to go to the Wheeler method from the Stoney point method after having these difficulties getting a true measurement. I'm simply looking for an explanation or another with the same experience. Once I get the bullet into the lands even if it's by loading long and letting the bolt close method pushing the bullet to the optimum "in the rifling" spot, I'm good with that. Then just dial the micro seater to the jump I want. It's more of a curiousity as to why the measurement are so far off from each other question.

 

[Nick Caprinolo]

Here’s one analogy take a hammer and try to push in a nail then raise a hammer smack it down on the nail it drives much easier this relates to jam or jump with a bullet as well jam does not let the bullet build up speed to hit the rifling and engrave therefore it does raise pressures and then return raise velocity but I am just an old construction worker you may have a much different opinion

Apples and oranges. Wood is so soft you can drive a blunt spike into it.

 

[284winner]

Apples and oranges. Wood is so soft you can drive a blunt spike into it.

Analogies aside, I just used the bolt drop method after removing the ejector and firing pin assembly. So much better. Gonna retire the OAL gauge measurement technique and end all the curiousity and being stumped.

 

[hoz53]

Analogies aside, I just used the bolt drop method after removing the ejector and firing pin assembly. So much better. Gonna retire the OAL gauge measurement technique and end all the curiousity and being stumped.

i to went through what you did. My stoney point gage now sits on the shelf unused also. The problem is its very difficult- impossible for me - to put the exact same amount of pressure on the shaft each time you use it. and once you press on it how do you know if that is jam,touch ect ect. each bullet is different. I now use the wheeler method and it works for me. (thanks Alex) An alternative some people use is the marks on the bullet.

 

[PracticalTactical]

Using my stoney point (Hornady) OAL gauge to measure my OAL of a cartridge to load into the rifling, I'm finding this measurement to be false. Once I push the bullet into the rifling and remove the modified case and bullet, I find the measurement to be much longer than what the chamber will actually take once the round is loaded. Once I load a dummy round and chamber it, the bolt will not close without force. Once it closes, the bullet seats much deeper into the case than what the measurement started at. It has me scratching my head at this point. Not that it's a big deal as I use the new measurement of the round after closing the bolt as my "In the rifling" measurement. Just can't understand why the OAL gauge measurement is not accurate. I'm actually gonna start using the Wheeler technique from now on. It certainly is the most accurate. Thoughts ? Experience ?

Unless I'm not understanding you, It sounds to me like the datum diameter on your OAL gage is just different than the jam contact point in your chamber.

Why not just measure the length of the round (using your OAL gage) after the chamber pushes the bullet back, and use that as your base dimension for seating?

If the contact point on your throat is not the same as the contact point on your OAL gage, the value will be different. It can also change based on different bullets. All you need to know is what the offset is.

 

[284winner]

i to went through what you did. My stoney point gage now sits on the shelf unused also. The problem is its very difficult- impossible for me - to put the exact same amount of pressure on the shaft each time you use it. and once you press on it how do you know if that is jam,touch ect ect. each bullet is different. I now use the wheeler method and it works for me. (thanks Alex) An alternative some people use is the marks on the bullet.

U bet. I'm pretty sure mine is in retirement mode also but I'll use your home brew method. Thanks again. John

 

[284winner]

Unless I'm not understanding you, It sounds to me like the datum diameter on your OAL gage is just different than the jam contact point in your chamber.

Why not just measure the length of the round (using your OAL gage) after the chamber pushes the bullet back, and use that as your base dimension for seating?

If the contact point on your throat is not the same as the contact point on your OAL gage, the value will be different. It can also change based on different bullets. All you need to know is what the offset is.

I did that. Then when I loaded the dummy in the chamber, it was way too long to close the bolt. I used a big neck bushing so the bullet is not real tight in the neck. Closing the bolt moved the bullet in the case fairly easy without pulling it from the neck when I eject the round. That measurement after closing the bolt is real close to the wheeler (bolt drop) method.

 

[PracticalTactical]

I did that. Then when I loaded the dummy in the chamber, it was way too long to close the bolt. I used a big neck bushing so the bullet is not real tight in the neck. Closing the bolt moved the bullet in the case fairly easy without pulling it from the neck when I eject the round. That measurement after closing the bolt is real close to the wheeler (bolt drop) method.

Strange

 

[divingin]

As do I. Looking at the rifling marks in the bullets, it's apparent that the bullet isn't really very far in them. Too bad they don't make a jacketed bullet that's harder than copper but just softer than steel so the stop would be pronounced. One that mimics the bullet used in a loaded case

I'm not sure how something harder than a bullet would "mimic the bullet used in a loaded case" better than the bullet used in a loaded case.

That said, there's jam, and there's jam. The amount of neck tension you run has an affect on how deep the bullet goes into the rifling when soft-seating. For instance, running a neck 2 thousandths smaller than bullet diameter will soft seat deeper than running 5 thou smaller than bullet diameter.

The Hornady gauge requires a certain amount of feel to get consistent results (you need to apply the same amount of force to the back of the bullet each time, which isn't always the easiest thing to do), and, IMO, it still just gives an approximation. That's why I largely use mine to get just a rough measurement, then fine tune using the Wheeler method (looking for rifling marks on the bullet ogive.)

 

[NZ_Fclass]

yes - I have the Hornady thingy. No I don't use it to set seating/jamb depth in the chamber. A far more accurate gauge is available - the Vivid marker.

The Hornady is much more useful for checking shoulder bump and checking base to ogive after reloading - ie setting up the seating die.

Having said that - when I was shooting 105 Amax in the 6BR, it measured perfectly - but some bullets are un-coperative with the system and the Vivid works better.

 

[284winner]

Strange

Absolutely

 

[284winner]

I'm not sure how something harder than a bullet would "mimic the bullet used in a loaded case" better than the bullet used in a loaded case.

That said, there's jam, and there's jam. The amount of neck tension you run has an affect on how deep the bullet goes into the rifling when soft-seating. For instance, running a neck 2 thousandths smaller than bullet diameter will soft seat deeper than running 5 thou smaller than bullet diameter.

The Hornady gauge requires a certain amount of feel to get consistent results (you need to apply the same amount of force to the back of the bullet each time, which isn't always the easiest thing to do), and, IMO, it still just gives an approximation. That's why I largely use mine to get just a rough measurement, then fine tune using the Wheeler method (looking for rifling marks on the bullet ogive.

What I meant by a harder than copper bullet is have dummy bullets that are identical in size as the bullet you will shoot. Only difference is it has a harder jacket than copper but not as hard as metal so no damage will occur to the rifling or lands. Kinda like the modified case. It's not a case for shooting, only measuring. Offer bullets that dimensionally are identical to all other bullets for this use. That way finding the lands isn't so hard. Then measure that and load to that measurement. I'm using the Wheeler at this point as I did it this morning and found what I needed.

 

[284winner]

yes - I have the Hornady thingy. No I don't use it to set seating/jamb depth in the chamber. A far more accurate gauge is available - the Vivid marker.

The Hornady is much more useful for checking shoulder bump and checking base to ogive after reloading - ie setting up the seating die.

Having said that - when I was shooting 105 Amax in the 6BR, it measured perfectly - but some bullets are un-coperative with the system and the Vivid works better.

Yes the marker works also

 

[Webster]

Using my stoney point (Hornady) OAL gauge to measure my OAL of a cartridge to load into the rifling, I'm finding this measurement to be false. Once I push the bullet into the rifling and remove the modified case and bullet, I find the measurement to be much longer than what the chamber will actually take once the round is loaded. Once I load a dummy round and chamber it, the bolt will not close without force. Once it closes, the bullet seats much deeper into the case than what the measurement started at. It has me scratching my head at this point. Not that it's a big deal as I use the new measurement of the round after closing the bolt as my "In the rifling" measurement. Just can't understand why the OAL gauge measurement is not accurate. I'm actually gonna start using the Wheeler technique from now on. It certainly is the most accurate. Thoughts ? Experience ?

Never got reliable readings with a Stoney Point. Wild huge scatter. Now use a split neck. It works fine only if you get the ideal grip on the bullet.

 

[PracticalTactical]

I'm wondering if the the OAL measuring tool is bottoming out against the tip of the bullet and not somewhere along the diameter.

 

[284winner]

I'm wondering if the the OAL measuring tool is bottoming out against the tip of the bullet and not somewhere along the diameter.

Not sure I understand that picture