PDA

View Full Version : Bullet seating



Lucky Shooter A
08-13-2013, 11:07 PM
I seated a series of 8 bullets bullets and increased the seating depth in increments 0f .010"----220 Beggs, 52 Sierra MK.

The starting seater adjustment was at .070" longer than "just touching the lands" and the final adjustment was for "just touching the lands".

Each round was measured across a Sinclair Comparator, before and after chambering with the following results:

MEAS MEAS CHAMBER
FROM FROM PUSH
DIE CHAMBER BACK

2.727 2.701 0.026


2.718 2.701 0.017


2.708 2.701 0.007


2.697 2.697 0.000


2.687 2.687 0.000


2.679 2.679 0.000


2.669 2.669 0.000


2.659 TOUCH 2.659 0.000


Did I achieve "full jam" in this sequence ? If so, at what point ?

Thanks for any info.

A. Weldy

abintx
08-14-2013, 12:01 AM
Jam is a relative term and has different meanings among shooters. Some start inward and work their way out calling their most inward position, JAM.

Personally, I never use the word. I'm just looking for the seating depth where my barrel produces the best results. I start at just touching, and work my way inward at .003" increments until I seat my last at either .015" or .018". Shooting 3 3-shot groups with each seating depth. [They won't get any smaller with 5-shot groups]

My 30BR shoots it's best just touching. My 6PPC shoots best around .012" into the lands. It's trial and error until you find what your barrel likes. Once I find my best grouping with the above, I try .001" on both sides of what appears initially to be the best.

Another issue is finding the best neck tension that compliments seating depth.

Somewhere, amongst all the forums is a comprehensive discussion of seating depth. Try the Advanced Search feature above. :)

alinwa
08-14-2013, 05:58 AM
Your 'Full Jam' is 2.701 as I see it :)

Boyd Allen
08-14-2013, 09:41 AM
I agree with Al. Going back to the old days, when Precision Shooting magazine was mostly about benchrest shooting, and there was no internet, the word was taken to mean the maximum length that a bullet could be seated to without being pushed into the case as the round was chambered, this being at the neck tension that was actually being used for loading the rounds that would be shot.

The procedure for finding it was simple and quick. If you were at the range, with the rifle on the bench, and the range hot, you would load one round with the bullet seated long enough to be able to close the bolt, but longer than you thought jam would be, measure it from tip to head, note the measurement, chamber the round, extract the loaded round, (There is the possibility that at light neck tensions that the bullet would be pulled and powder spilled in the action, so one needs to become familiar with the feel that the bolt has on opening when the case is turning on a stuck bullet, so that if it is the rifle can be pointed up, after the bolt is opened, but before the bolt is moved to the rear.) and the round remeasured, and that noted. If the second measurement is shorter, then that measurement is jam, and the difference between it and the first one is used to adjust the seating die, adding any amount that one wants to seat shorter than jam. I usually measure the combined length of the stem and cap that produced the long loading, subtract the amount that the bullet was pushed back (plus any amount that I want to seat short of jam) and reset the stem in the cap (if the adjustment is not in the body of the die) to the required length. At that point I use the caliper attachment to measure from head to ogive of the round that is at jam, and note that, as well as the combined length of the stem and cap, that would seat to jam (or micrometer top or die body setting). This all took much longer to write than it takes to do, and probably reads as if it is more complicated than it actually is. I have a range notes book that lists loads by powder, bullet, for my Nielson seater the combined length of stem and cap, and how much shorter (if any) than jam that the bullet was seated. as well as the temperature and humidity, and how the load performed, including in a few cases the velocity.

WoollyMonster
08-14-2013, 10:27 AM
Take this from a relative newb to the benchrest sport because to date, I have shot in only one match! But, I have been reloading hunting, plinking, tactical, and competition pistol rounds for 29 plus years. I have always searched for the perfect method to accurately seat bullets. I have used the Sinclair, Hornady, and other gauges to do this. But, even using the Sinclair gauge, I could measure a bullet and fired case five time and get five different readings that would vary by .005". Better than nothing but not the accuracy I was looking for.

After shooting in that one match (and getting hooked) I bought and read Tony Boyer's book. When I got to the bullet seating section it was an "ahaaa!!!" moment. I had to jump up in the middle of the night and go try it out. It is too lengthy to go into here but pretty much the same as Boyd describes in the above post. It works easily and perfectly. Using my JLC Seater die, I can now confidently and accurately seat the bullets anywhere I want. Best part is that it does not involve fooling with some gauge.

As Tony explains in the book, the "jam" that you find will be for a specific chamber, throat, bullet, neck tension, etc. All recordable, and repeatable. Easy to re-do once the throat wears. Dang, had I only known.

Cheers,
Woolly

abintx
08-14-2013, 11:04 AM
Take this from a relative newb to the benchrest sport because to date, I have shot in only one match! But, I have been reloading hunting, plinking, tactical, and competition pistol rounds for 29 plus years. I have always searched for the perfect method to accurately seat bullets. I have used the Sinclair, Hornady, and other gauges to do this. But, even using the Sinclair gauge, I could measure a bullet and fired case five time and get five different readings that would vary by .005". Better than nothing but not the accuracy I was looking for.

After shooting in that one match (and getting hooked) I bought and read Tony Boyer's book. When I got to the bullet seating section it was an "ahaaa!!!" moment. I had to jump up in the middle of the night and go try it out. It is too lengthy to go into here but pretty much the same as Boyd describes in the above post. It works easily and perfectly. Using my JLC Seater die, I can now confidently and accurately seat the bullets anywhere I want. Best part is that it does not involve fooling with some gauge.

As Tony explains in the book, the "jam" that you find will be for a specific chamber, throat, bullet, neck tension, etc. All recordable, and repeatable. Easy to re-do once the throat wears. Dang, had I only known.

Cheers,
Woolly

Mr. Boyer's book is certainly a wealth of information.

Take a look at page 131 FINDING THE BULLET "TOUCH" the opposite of jam.

Then take a look at page 254 at the top under AN EXAMPLE OF TUNING where TB explains using that method, since 2008, for cut-rifled barrels in conjunction with boat tail bullets.

Now you've got two methods at your disposal depending on which barrel and bullet combination you're using. :cool: