Powder Charge With Jammed Bullet

[4xforfun]

I start off at a .020 jump, do my powder charges then do seating depth test .020 jump to .020 jam.

I know that you are way up the food chain when it comes to shooting/reloading.
My question is this....lets say that you found a killer load at the top end of the PSI range with a .020 jump, but, you want to tweek that last little bit of accuracy out of it, so , you decide to test a .020 jam. What is your next step?

 

[Jason Boersma]

Tod, as an example let's use a dasher
I'll start at a .020 jump and let's say at 33.4 gr of varget it shoots the best. So I'll go home and load up enough cases to test seating depths at that same charge, then I find out the rifle shoots best at a .020 jam and lets say it still doesn't have single digit ES so I will then loade up some at 33.42, 33.44, 33.46, and 33.48 and see if they still shoot as good as before and if the ES got any better.
Remember when you are seating the bullet out from the powder the pressure drops until the bullet reaches the lands then the pressure goes back up. If it didn't get any better I might try a different primer or different neck tension but usually it does get better. I do all load development at 600yds.

 

[4xforfun]

Tod, as an example let's use a dasher
I'll start at a .020 jump and let's say at 33.4 gr of varget it shoots the best. So I'll go home and load up enough cases to test seating depths at that same charge, then I find out the rifle shoots best at a .020 jam and lets say it still doesn't have single digit ES so I will then loade up some at 33.42, 33.44, 33.46, and 33.48 and see if they still shoot as good as before and if the ES got any better.
Remember when you are seating the bullet out from the powder the pressure drops until the bullet reaches the lands then the pressure goes back up. If it didn't get any better I might try a different primer or different neck tension but usually it does get better. I do all load development at 600yds.

I guess my "what's next" was referring to any concerns with a PSI spike caused by going from a jump to a jam. Others above ( and regarded as common knowledge) claim that PSI can SPIKE with a jam, and an already "on the edge" load which is jumped my become a dangerous load when jammed. Seems like good logic to me . Do you reduce your load or just shoot em?? I start jammed and move to a jump, which will negate my need to worry about PSI.
As far as your load development..you and I must have went to the same school!! Of course, I am old enough where my school was a log cabin in the hills!!

 

[Jason Boersma]

I haven't found any problems with this method, I used to do it your way then started going jump to jam and found it works better for me.

I see a gradual fall in psi/fps when I get close to the lands then a gradual rise in psi/fps when I go into a jam, haven't seen at bad effects yet. Try it sometime.

 

[BoydAllen]

I have never had an issue as long as I drop back and work up when making a change that is likely to produce an increase in pressure. Once I knew a fellow who was shooting top pressure loads in a couple of AI varmint cartridges. He ran out of Federal primers, and switched to some Winchesters that he had a good supply. The result was that he blew primers clear out of cases.

 

[22BRGUY]

I guess my "what's next" was referring to any concerns with a PSI spike caused by going from a jump to a jam. Others above ( and regarded as common knowledge) claim that PSI can SPIKE with a jam, and an already "on the edge" load which is jumped my become a dangerous load when jammed. Seems like good logic to me . Do you reduce your load or just shoot em?? I start jammed and move to a jump, which will negate my need to worry about PSI.
As far as your load development..you and I must have went to the same school!! Of course, I am old enough where my school was a log cabin in the hills!!

You had a "LOG CABIN"????? WOW! You must have been one of the rich kids with really rich parents.

 

[dmoran]

I do not use neck tension, I use bullet hold. When it comes to bullet hold I want all the bullet hold I can get. For me there is no such thing as too much bullet hold. When it come to sticking the bullet into the lands I have to think, or ask; Do I want my bullet setting still at the lands with out the running start? I know pressure is going to build behind the bullet, I want my bullet to hit the lands a moving.

F. Guffey

​

 

[dkhunt14]

I prefer to save the jam for toast and seat the bullet where it just touches. Nothing worse than being at the range, loading a round, then having to unload it before firing and have the bullet pull out because it is jammed into the rifling.

I like winning so I go in the lands .010 to .015. Matt

 

[dkhunt14]

First off, I START all of my load development with at least a .010 jam. Never, ever "just touching the lands" or .001, .002....that has it's own set of problems. That way, if I decide to test the other way (jump...at least .010) I do not need to worry about reducing my loads in fear of a PSI spike.

As a side note, I have never found a jumped load that worked as well as a jammed load at LR...and I do ALL of my testing at 750 yards. On the other hand, I have never tried more than a fifty thou jump....it could be that I am missing something.

Tod

I agree with this. In 15 years of 1000 yard BR I never had one barrel that liked it off the lands better then in. Matt

 

[dmoran]

^^^^ +1

 

[sawacs]

Great information fellas.

So, if I decide to start off load development jammed, would running the neck through the expand mandrel create enough of a lack of neck tension to close the bolt and seat the bullet into the lands or should I use more neck tension (.002 or .003)?

Thanks,

Shawn

 

[4xforfun]

Great information fellas.

So, if I decide to start off load development jammed, would running the neck through the expand mandrel create enough of a lack of neck tension to close the bolt and seat the bullet into the lands or should I use more neck tension (.002 or .003)?

Thanks,

Shawn

That is called "soft seating", and I have never had good luck with it. It does make sense though...in my mind it would mitigate run out in the shape of the nose of the bullet, along with the run out of the reloading press itself. Of course, then again, you are depending on brass that has to be EXACTLY the same as far as neck tension, thickness, and probably six other things that allude me at the moment.