Locating Bullet Touch Point in Barrel With Bolt?

[master_photog]

Regardless of the weight or length of a bullet, shouldn't the jam point be the same for each bullet (of that caliber)?

Once I locate the jam of a .204 40gr Vmax, measuring base to ogive, won't that be the same for a .204 32gr Vmax or a .204 55gr Berger BT varmint, etc.

The method I'm using in locating the jam is seating a bullet long in a case, lubing the ogive and closing the bolt. I do this with 3 cases of the same bullet.

The reason for the question, is that I get different results, with different bullets. My thinking is that I should get the same jam point every time regardless of the bullet because the ogive to base measurement should always be the same after closing the bolt, regardless how heavy or long the bullet is.

Thank you

 

[Drolds72]

there are a lot of variables in play with that method, to get same measurement. Neck tension is the big one I think. Are you using the same case over and over? Resizing? Try the Wheeler method, if goal is to have repeatable results.

 

[G Liles]

What he said ^^^^^

 

[Forum Boss]

Quote: "Regardless of the weight or length of a bullet, shouldn't the jam point be the same for each bullet (of that caliber)?"

No. Absolutely NOT.

Bullets of the same nominal diameter can vary by up to 0.001" in true (max ogive) diameter, based on our measurements with 90-108 grain 6mm bullets from five different makers.

You should re-check your "distance to first touch" whenever you change bullets. And it's not a bad idea to check with every new lot. And you may want to check multiple bullets, because the base to ogive length can vary slightly even within the same box of bullets.

This is one reason we really like Lapua Scenar bullets -- they are very consistent base to ogive.

And you also must have a very consistent and repeatable measurement technique. Using the Hornady (formerly Stony Point) tool, I will take FIVE measurements. Normally I will get at least 3 of five consistent to .0015". However I have had a friend use the same tool, and get widely varied measurements because he did not use consistent pressures on the push rod.

I also do NOT recommend the technique you are using for multiple reasons, including (but not limited to) inconsistent neck tension, bullet tilting in neck as you move cartridge forward with bolt, inconsistent lube application, inconsistent force or bolt closure -- etc.

I would NOT lube the bullets.

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Before testing, I will first measure base-to-ogive for 7-8 bullets so I have a good representative sample from the box. Then I will make sure the modified case is seated properly on the tool. Then after putting the tool in the action, I use gentle pressure on the gray rod, with a couple light taps (to ensure case is not tilted). That yields very consistent, repeatable results.

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Additionally, I do not think you are using the term "JAM" properly. That's why I prefer to say "first touch of bullet to lands". Jam can refer to a bullet that is seated to the maximum engagement in the rifling -- you can measure that but it will depend on the amount of engraving, the neck tension, bullet jacket, and other factors.

The method I use leaves a tiny mark on the bullet, so it may be a thousandth or two past true "first touch". But the important thing is that the measurement is REPEATABLE.

As long as you have a repeatable measurement of "first touch", then you can load further in or further out with confidence, understanding that the lands will migrate outward with time.

Many PPC guys use the term JAM meaning the max length they can seat their bullet.

 

[Webster]

Regardless of the weight or length of a bullet, shouldn't the jam point be the same for each bullet (of that caliber)?

Once I locate the jam of a .204 40gr Vmax, measuring base to ogive, won't that be the same for a .204 32gr Vmax or a .204 55gr Berger BT varmint, etc.

The method I'm using in locating the jam is seating a bullet long in a case, lubing the ogive and closing the bolt. I do this with 3 cases of the same bullet.

The reason for the question, is that I get different results, with different bullets. My thinking is that I should get the same jam point every time regardless of the bullet because the ogive to base measurement should always be the same after closing the bolt, regardless how heavy or long the bullet is.

Thank you

I determined the touch OAL for at least 8-10 different bullets in my 6BR. They are all different.

 

[milboltnut]

use a hornady OAL gauge just about every bullet I set are different. Ogives differ.

Forum Boss:
1. Check the Bullets by themselves first. As noted, high quality bullets will show very consistent base to ogive. With the old Scenars, nearly the whole box would be within a narrow range.

2. You need to do multiple runs with the same bullet. I suspect your method is not consistent.

 

[Bill Norris]

From time to time u may find two different ( brand-weight ) bullets come close to the same number but most of the time there will be some difference using the Hornady L & L device.

 

[master_photog]

My attempt to find the jam point was following this video. The illustration, instruction and techniques appeared to be pretty solid based on his ease of explanation. His explanation seemed to be very natural, not as if he was using cue cards, that was one reason I put a little stock on this method.

His suggestion on lubing the ogive appeared to be pretty sound too, just to prevent a jammed bullet.

I would agree with the lengthy and detailed explanation by Forum Boss that "first touch" is what I'm after.

 

[skeeljc]

Regardless of the weight or length of a bullet, shouldn't the jam point be the same for each bullet (of that caliber)?

Once I locate the jam of a .204 40gr Vmax, measuring base to ogive, won't that be the same for a .204 32gr Vmax or a .204 55gr Berger BT varmint, etc.

The method I'm using in locating the jam is seating a bullet long in a case, lubing the ogive and closing the bolt. I do this with 3 cases of the same bullet.

The reason for the question, is that I get different results, with different bullets. My thinking is that I should get the same jam point every time regardless of the bullet because the ogive to base measurement should always be the same after closing the bolt, regardless how heavy or long the bullet is.

Thank you

Seating the bullet long and lubing it with die wax is Erik Cortina's method. He is strictly interested in finding the point where the bullet will stick in the rifling and cannot be withdrawn with the loaded case. He is a F Class shooter and wants to be able to unload his rifle if need be. It represents a danger point for him.

The better way to find touch is the use the Wheeler method. Remove the firing pin and the ejector. Size a case that will allow the bolt to close just by the weight of the handle. Then seat a bullet long and continue seating it deeper until the bolt closes by just the weight of the handle. Then you have found the lands for that bullet. Low bullet to case runout is required for perfect results.

If you do not like removing the ejector just mill a clearance slot in the case head for it.

 

[master_photog]

Is the Alex Wheeler method a written document on the forum, on another forum, a video on youtube, etc.?

Based on the multiple suggestions that doesn't contain a link, I presume it's in printed book form??

 

[Dusty Stevens]

Is the Alex Wheeler method a written document on the forum, on another forum, a video on youtube, etc.?

Based on the multiple suggestions that doesn't contain a link, I presume it's in printed book form??

He took his youtube page down. Somebody may have it and can share it. I and most BR shooters always lube the bullet only for this test

 

[skeeljc]

Here is a good YouTube video on the Wheeler method:
Measuring length to the lands in your rifle by primalrights

 

[K22]

Why anyone would want to approach the jam point is beyond my comprehension but I'm not an "expert".

I've never had any problems finding accurate loads with bullets seated well off the lands but like I said, I'm not an "expert".

Forum Boss: You may be surprised. My 6BR and 6BRDX would shoot high twos (for five shots) jumping .025". However, seated in the lands, about .005-.007", these same guns would shoot a ragged hole. My last measured group was a .174" for four. YMMV... but it's always worth a try. You may be surprised.

 

[skeeljc]

Why anyone would want to approach the jam point is beyond my comprehension but I'm not an "expert".

I've never had any problems finding accurate loads with bullets seated well off the lands but like I said, I'm not an "expert".

Some BR shooters seat into the lands because some rifles shoot better that way. Be aware if you do seat into the lands you may stick the bullet in the barrel if you attempt to unchamber a loaded round.

 

[master_photog]

Why anyone would want to approach the jam point is beyond my comprehension but I'm not an "expert".

I've never had any problems finding accurate loads with bullets seated well off the lands but like I said, I'm not an "expert".

My reason for approaching the jam point is to know how far to not seat the bullet. It's a starting point, then work back from there. I won't know where to start from without knowing the jam point initially.

 

[Forum Boss]

With the method i have described using the LNL tool and gentle pressure to first touch, lube is not helpful. As noted I will measure 4-5 times. Perhaps one in 5, the bullet may stick, but raising barrel to vertical and a gentle bump on the buttpad and it comes out.

I am NOT pushing hard on the rod — that leads to inconsistent results.

The Wheeler method is also good, but I do not like disassembling bolts.

If your method is repeatable, that is what counts. If you are using the LNL tool and use gentle pressure and a couple light taps, you should achieve very repeatable results, that are not improved by bullet lube.

 

[cw308]

Using the stripped bolt method , finding the case length is with the bolt closure , pressure of the locking lugs going forward , once you repeatedly find your zero measurement you can size to your .002 . Using our of those cases finding you ogive setting is with the lightest bolt lift , pressure on the locking going rearward. With the lightest lift release that's your touch. Can jump or jam from that measurement. Same bullet same lot should be the same , same bullet different could change.

 

[K22]

My reason for approaching the jam point is to know how far to not seat the bullet. It's a starting point, then work back from there. I won't know where to start from without knowing the jam point initially.

That's exactly what I do on all my rifles and stay at least .010" from the lands.

 

[rwj]

He took his youtube page down. Somebody may have it and can share it. I and most BR shooters always lube the bullet only for this test

The video is currently on his web page... https://www.wheeleraccuracy.com/videos

 

[Bill K]

If I read you question correctly, setting the seating die for one bullet brand/weight to touch the lands, will not have other bullets brands/weights also touching at the same setting.
However slight it is, different brands will not have the same exact measurement and touch like you think.