Finding the jam.. again.. sorry

[Rsadams]

I use Sierra matchkings and finally getting into trying to tune the seating depths useing a bullet comp. instead of measurements from the tip which of course is never the same..

I seat a bullet long but of course the bolt will not close it seems like it would take a hammer to close it to push the bullet in and I really don't want to force or break anything.. should I just take a dremel tool and cut a slit in the neck to release some tension?? I use rcbs full length dies , of course barely setting the shoulders back but can not control neck tension..

Should I just seat , pull the bullet and reseat till some tension eases up?? I just don't want to stick or break anything I am just trying to move on and learn something new.. I am useing a Savage 10 T-SR.. am I starting by seating way to long or something... I am just trying to see how much jump to use it's just a guess measured off the tips ( COAL )..

I am not a competition shooter like you guys I just enjoy shooting and reloading...

Thanks in advance
Shawn

 

[BoydAllen]

When your length is close to jam, the closing cams will be engaged and you should be able to close the bolt. Be sure to have a film of bolt grease on the backs of your lugs when doing this. Also, the whole jam narrative and method came from short range benchrest where thin necks are the norm. One can only have so much seating force with necks that are that thin. On the other hand with much thicker necks that are too clean and not lubed inside one can get into a situation where it may be more practical to work out from touch rather than in from jam.

 

[243winxb]

 

[Rsadams]

Thank you everyone... I just need to find when the bullet touches so I actually know how much jump I am useing.. I am sure my terminology is not correct... I think I can get it done now..

 

[Tim Singleton]

Thank you everyone... I just need to find when the bullet touches so I actually know how much jump I am useing.. I am sure my terminology is not correct... I think I can get it done now..

All that matters is to find a starting place. Finding touch is a good method then just keep good records and go into and away from the lands a few thousands at a time

 

[Zero333]

Another link to a video showing a "good enough" method to find the lands...

The Video link that Joe R posted is one of the best ways of going about finding the lands but it doesn't work very well with bolts that have floating bolt heads because the bolt head retaining pin is held in place by the firing pin. So with out the firing pin the bolt head retaining pin slides out.

Another method is with the Hornady OAL tool. That's what I use because I've developed a good feel for it and comparing it against Alex Wheeler's method (Joe R's video link) my results are identical.

 

[Webster]

I use Sierra matchkings and finally getting into trying to tune the seating depths useing a bullet comp. instead of measurements from the tip which of course is never the same..

I seat a bullet long but of course the bolt will not close it seems like it would take a hammer to close it to push the bullet in and I really don't want to force or break anything.. should I just take a dremel tool and cut a slit in the neck to release some tension?? I use rcbs full length dies , of course barely setting the shoulders back but can not control neck tension..

Should I just seat , pull the bullet and reseat till some tension eases up?? I just don't want to stick or break anything I am just trying to move on and learn something new.. I am useing a Savage 10 T-SR.. am I starting by seating way to long or something... I am just trying to see how much jump to use it's just a guess measured off the tips ( COAL )..

I am not a competition shooter like you guys I just enjoy shooting and reloading...

Thanks in advance
Shawn

If it's very difficult to close the bolt the COAL is way to long. Yes cut the neck with a Dremel tool to determine COAL. The bullet needs to slide with some grip but not too much. A few tries you get the feel. Start short and work longer to determine the range you need to be in so you don't stick the bullet in the bore. I use diagonal cut pliers on the tip to pull the bullet longer for repeat tries. Getting the correct neck tension makes it easier. After about ten tries I pinch the Dremel cut gap a little smaller to get the tension I like back. If the bullet comes out the same length it went in it was too short to touch the rifling. If it comes out longer than the in COAL it stuck then was released from the rifling. It was too long.

 

[Texan]

I used the slit case method for years, but recently got the Hornady OAL gauge.

I can now measure with the action open (which saves a lot of trouble in of itself), and by alternately pushing the bullet towards the muzzle with the tool, and back out with a cleaning rod, I can feel exactly when the bullet contacts the rifling.

According to an individual's finesse, all the methods may be equally accurate, but I've found the Hornady tool to be faster and easier.

I'll never go back to the slit neck way again.

 

[47WillysGuy]

There’s the hard jam that takes a hammer to close the bolt with a distinct click upon extraction.

Then there’s the soft jam where the bullet just touches (lightly) the lands. There will be very tiny land scrape
marks on the bullet ogive. There is no click of the bolt upon dummy case extraction.

That’s about 0.025 of an inch difference for my method.

Your jam can be whatever you want to use as a reference.

 

[Mozella]

........ snip.......... I am sure my terminology is not correct... I think I can get it done now..

Don't worry too much about terminology because some words associated with our sport are confusing. For example, why is the case head the same as the case base? Why is the head at one end of the case, the neck at the other, and the body in the middle?

When it comes to bullet seating, people use the same terms to mean different things. The people I shoot with generally measure the point where the bullet just touches the lands and they call that point 0.000". Any cartridge shorter than that, (i.e. it doesn't touch the lands) is considered a "jump". Longer is called "Jam".

Most people measure the CBTO (Case Base To Ogive) in thousands of an inch. Bullets seated longer than the "touch" point will obviously be pushed into the lands when you close the bolt. The guys I shoot with call that "Jam" even if the cartridge is only slightly longer than one which just barely touches the lands. Others consider "Jam" to mean something different.

When I make entries in my electronic log book, I personally label short seated cartridges with a positive sign, which is to say a cartridge seated so the bullet is twenty thou. short of the lands is called +0.020". Like wise, a cartridge with a bullet seated ten thou. longer than the touch point is logged as -0.010"; however, plenty of other people use just the opposite signs. In other words, they label their long cartridges as "plus" and the short ones as "minus". Suit yourself. As far as I know there isn't an industry standard for this, but I could be wrong.

The point to remember is that you should find a reliable way to find that "touch" point. I prefer a Hornady tool for that. Depending on the rifle, bullet, powder and other factors, you may find that your groups are smaller when the bullet is seated longer or shorter than that. Sometimes the improvement in group size can be surprisingly significant.

By the way, it is normal to get slightly different measurements when repeatedly measuring your seating depth using either a Hornady tool or a home brew rig to find that 0.000" touch point. A clean chamber and sometimes a tiny bit of lube may help. Long skinny bullets can be tricky. Don't be discouraged if it takes you 20 tries to get readings which give you confidence that you've found the exact measurement.

Sometimes a jump much longer than you might imagine works best with certain bullets. Read this article by Berger which I found enlightening. http://www.bergerbullets.com/getting-the-best-precision-and-accuracy-from-vld-bullets-in-your-rifle/

It's also good to remember that seating bullets long can produce higher chamber pressures than listed in your reloading book, so work up to your personal maximum charge weight carefully while checking for pressure signs.

 

[Texas10]

I dunno, I found Joe R's video about seating to the lands a bit confusing as far a obtaining a reliable CBTO (cartridge base to ogive) measurement. Measuring to the tip of the bullet and using that to discern the CBTO is to me, a bit like attempting to measure you car engines horsepower by checking the pressure in the tires.

I think most are aware that both the base of the bullet and the tip vary in distance from the ogive from bullet to bullet within the same box or lot, and any measurement that uses either of these points will be subject to dimensional errors.

As proof, do we not know from experience that bullet seating dies that use the tip most portion of the bullet to seat will produce the greatest errors in CBTO?

How may have modified a seating stem to bear upon the bullet closer to the ogive in oder to get more consistent CBTO during seating? I, for one have, with good results. Better results came from buying a better die set that did the same thing.

If I were loading only one bullet brand and wanted the best consistency during seating, I would bed the seating stem to the bullet with something like Devcon 10110.

As far as maintaining a consistent seating depth to within a few thousandths, in or off the lands, is something that requires frequent and reliable measurements due to throat erosion. Looking at all the possible measurement errors in the video's methodology, one can't help but conclude that there has to be a better way, especially with small "pointy" bullets that are the hardest to get consistent results with.

I have a Savage action, so I can't use the "bolt drop" method demo'd with a Bat action. The two are not comparable. I've used the Hornaday modified case method that resulted extreme variances in dimension because the amount of force used to push the bullet bears greatly on seating depth. Some say they develop a repeatable technique. I couldn't on small "pointy" 224 cal bullets. 308 cal bullets, yes, much easier.

So I developed a method similar to using the Hornaday Modified case but neck sizing it and seating a bullet long. Mount it on the tool and shove it up the pipe, then try to extract it. If it wants to stick, seat the bullet a bit deeper and repeat until it no longer tends to stick upon retraction. That is my "touching lands" dimension. It is quite easy to feel the difference produced by a .001 change in CBTO as the bullet engages the lands.

Only I don't use the Hornaday modified case, I use one of my fire formed cases to get the best consistency and good, accurate, repeatable measurements.

YMMV.

 

[chop house]

my apologies if one of the videos describes the following technique i've been using - with good repeatable accuracy - for years and years. my connection won't allow viewing them right now.

works with bolt, break action, and msr style actions... requires only calipers, cleaning rod or other steel rod with two stop collars (like used on drill bits) and a chopstick. The rod must not have female threads, or you can modify an attachment such that it will have a BLUNT TIP. NOTE: measure, record and SAVE a bullet you wish to seat.

(run through this mentally, and you'll see what is being accomplished)

close action, engage safety with rifle cocked. insert rod with both collars installed until it bottoms on bolt face. lock the second (furthest) collar on the rod. open action, remove bolt, drop bullet in bore. lay rifle on bench and push bullet into lands with chopstick while resisting with cleaning rod from the other direction. feel the contact point. lock the second collar onto the rod against the muzzle. measure BETWEEN the two collars and this is COAL for this individual sample of bullet in this chamber with this headspace at this point of throat erosion, with bullet either kissing lands or firm into lands (your choice). seat THIS bullet or one with THE SAME base to tip measurement in a case. you may use a comparator to measure CBTO. After you get data on a few dfferent styles of bullets, compare CBTO and they will track closely within bullet designs of like ogive (secant, tangent, VLD, etc.) COAL can be computed for the variance in bullet tip to base length by doing some math if you lose your 'coupon' bullet.

DONE.

took as long to type as it does to get COAL for a bullet. repeat for all bullets you intend to use. RECORD bullet base to tip, COAL, date, barrel round count if known. track the erosion, play with seating depth, tune your rifle/load, AMAZE your friends.

 

[chop house]

oh, i should add that if you use the 'firm' method, and bullets with exposed lead tip, ensure you did not blunt the lead, thus altering the coupon bullet's base to tip measurement. this can happen if you have to tap the bullet out of the lands. the COAL measurement previously taken will still be correct but now this bullet will measure short. if seating this particular bullet one would need to adjust COAL to compensate for bullets 'new length'

 

[gotcha]

Hi Shawn ! I don't think anyone has mentioned this yet, not even the Videos. .................. Your factory barrel, unlike a hand lapped match barrel, is likely to have machine burrs on the Leade of your rifling. Though very small they tend to be "grabby" and cause bullets to stick in the rifling adding frustration to the process of finding your 0.00" measurement. It's a good idea to put twenty or so rounds through your rifle to iron out and remove the burrs prior to doing any definitive bullet seating depth testing. ................. If your 1st bullet sticks in the rifling or you can't seem to find a consistent 0.00" measurement the burrs are most likely the reason. Even with a hand lapped barrel I put a little smear of case lube around the ogive to promote more consistent seating depth readings. I just thought this was worth mentioning. Have fun with your experimenting

 

[Rsadams]

my apologies if one of the videos describes the following technique i've been using - with good repeatable accuracy - for years and years. my connection won't allow viewing them right now.

works with bolt, break action, and msr style actions... requires only calipers, cleaning rod or other steel rod with two stop collars (like used on drill bits) and a chopstick. The rod must not have female threads, or you can modify an attachment such that it will have a BLUNT TIP. NOTE: measure, record and SAVE a bullet you wish to seat.

(run through this mentally, and you'll see what is being accomplished)

close action, engage safety with rifle cocked. insert rod with both collars installed until it bottoms on bolt face. lock the second (furthest) collar on the rod. open action, remove bolt, drop bullet in bore. lay rifle on bench and push bullet into lands with chopstick while resisting with cleaning rod from the other direction. feel the contact point. lock the second collar onto the rod against the muzzle. measure BETWEEN the two collars and this is COAL for this individual sample of bullet in this chamber with this headspace at this point of throat erosion, with bullet either kissing lands or firm into lands (your choice). seat THIS bullet or one with THE SAME base to tip measurement in a case. you may use a comparator to measure CBTO. After you get data on a few dfferent styles of bullets, compare CBTO and they will track closely within bullet designs of like ogive (secant, tangent, VLD, etc.) COAL can be computed for the variance in bullet tip to base length by doing some math if you lose your 'coupon' bullet.

DONE.

took as long to type as it does to get COAL for a bullet. repeat for all bullets you intend to use. RECORD bullet base to tip, COAL, date, barrel round count if known. track the erosion, play with seating depth, tune your rifle/load, AMAZE your friends.

Hi Shawn ! I don't think anyone has mentioned this yet, not even the Videos. .................. Your factory barrel, unlike a hand lapped match barrel, is likely to have machine burrs on the Leade of your rifling. Though very small they tend to be "grabby" and cause bullets to stick in the rifling adding frustration to the process of finding your 0.00" measurement. It's a good idea to put twenty or so rounds through your rifle to iron out and remove the burrs prior to doing any definitive bullet seating depth testing. ................. If your 1st bullet sticks in the rifling or you can't seem to find a consistent 0.00" measurement the burrs are most likely the reason. Even with a hand lapped barrel I put a little smear of case lube around the ogive to promote more consistent seating depth readings. I just thought this was worth mentioning. Have fun with your experimenting

Ya jam was not what I meant..lol , just the touch or 0.000 as described above.. I broke the barrel in and it turned out nice... If you subtract the one I always seem to pull the gun is grouping around a .500 at worst .600 or so , last group I shot was .313 center to center in .308 now that I found the charge.. so I think it will be even better with a little seating adjustments..

I got bit by the .308 bug and wanted to see how good I could get it.. useing the book seating of 2.800 so I thought it might get better if I knew exactly what worked best useing sierra 168gr matchkings that like a jump normally... Plus it would be another skill in reloading... I am so close to getting it's load done and then I need to finish my .223 load for my M4s..

I really appreciate everyone's replies thanks for sharing you knowledge and time.. I am a teaching myself and don't have anyone to ask... I started with pistol 3years or so and this last year I moved on to rifle.. I like meticulous work and with rifle reloading that's what you need..

 

[T-shooter]

This is the method I use.. I bought some drill depth stops and use them on a cleaning rod that is close to the bore diameter. I also got a kit several year ago that had some flat tip screw in plugs for the cleaning rod but they also had some flimsy plastic stops that I don't like to use. On a bolt gun, I sometimes use a rubber band just strong enough to keep the bolt against the case and the case in the chamber.

Close the bolt and run the rod in until it touches and make sure it's not on the ejector pin. Run the (#1) stop up against the muzzle and lock it. You need to make a dummy bullet that is seated too long to chamber. Lightly run it into the chamber until you feel it touch. Now add the second drill stop on the cleaning rod, then insert and lock it in place when it lightly touches the bullet tip. The headspace/COL is the distance is from outside to outside the drill stops minus the thickness of the last one (#2 here). By being careful, I can repeat measurements to .001". This will work on one exact bullet and sometimes only with one lot number. You can now seat the bullet to the same overall length you measured and take your measurements from there. Maybe use the Hornady bullet insert/comparator from your dummy test round to get a reading and then subtract what ever jump you want to have. Keep in mind, the overall length of the bullets can vary several thousandths even in the same lot. It takes a light touch not to jam the bullet into the rifling or to move the bolt backwards when the dummy round is in the chamber. Sometimes I use my finger instead of the bolt so I can feel when the rod makes contact. If you use another rod (aluminum would probably be best) instead of a cleaning rod, you won't need to plug the threaded end.