Brux Barrels - UPDATE
- Thread starter Steve Blair
- Start date
Some have asked what is meant by "off jam"? To me finding the "jam" is much easier than finding "just touching". I use a dummy round which has very little neck tension and I seat the bullet long and chamber it....allowing the bullet to be pushed back by the rifling. I do this about three times to be certain that the bullet was not pulled back out of the case. I measure with a Stoney Point device and record that information for the particular bullet. Also, I note the setting on the seating die and move it to the new setting after the "set-back" is determined. James
James, I guess i'm old times but i use seating dies made from chamber reamer and a K&M Press. zero is easy to find after break in with a split neck case and a little wax to keep it from sticking. Then i start with the real ones and they will be about.001-2 long then i adjust from there.I use shims to set the die. My run out is .001 or less.....jim
BoydAllen
Gold $$ Contributor
James,
It has been my impression that the more common definition of jam (in the tradition of short range benchrest) has specified the use of neck tension that is the same as will be used in loaded rounds. This is not to quarrel with anyone's method. Obviously there are several approaches to describing seating depth that can be used, and although it may make answers a bit longer, I think that including ones own definition of the word is always a good idea, especially if the object of the exercise is to enable the duplication of what one is describing.
On a related matter, since I use an arbor press die to seat my 6PPC bullets, and it does not have a micrometer top (a very closely fitting custom seater) I record the combined length of the stem and cap. This can involve a little visualization and math that recently resulted in me making an error that shot very well.
The intent of the exercise was to end up with the bullet off of the lands, but to use jam (determined with actual loaded round neck tension) as the starting point. The target seating depth was .030 off, or shorter than jam. I set the seater to produce a length that would have the bullet pushed back when the round was chambered, loaded the round, measured the length, and the combined length of the stem and cap at that setting. Then I chambered the round, and remeasured its length, noting the exact amount that it was shortened.
It was at this point that I made my mistake. I should have added the difference of the lengths to the amount that I wanted to be off jam, and added the total to my starting stem and cap length to get the setting needed to be .030 off jam. (Longer stem and cap measurements produce shorter loaded rounds.) What I did was to get in too big of a hurry and add the difference in measurements and then subtract .030. It wasn't until I had shot a couple of test groups that I it started to dawn on me that I had made a mistake, and set my die to seat the bullets .030 longer than jam, effectively loading my rounds to "soft seat" the bullets. The fact that I was using a bushing that produced medium neck tension had made my error less obvious, although I should have picked up on it when I chambered the first round, from the slight additional effort that it took to close the bolt.
Anyway, just as I was about to correct my mistake, it occurred to me that since the object of the exercise was to find a seating depth that gave good accuracy, and the test groups appeared to be good, that perhaps I should stick with the mistake, since the results were what I was looking for.
At that point, I determined that it was about time to pack up, and made a note to see if there would be a problem with bullets being pulled from case necks when unloading the rifle, on my next trip to the range, as well as correcting my mistake, and doing the test that I had originally intended.
Boyd
It has been my impression that the more common definition of jam (in the tradition of short range benchrest) has specified the use of neck tension that is the same as will be used in loaded rounds. This is not to quarrel with anyone's method. Obviously there are several approaches to describing seating depth that can be used, and although it may make answers a bit longer, I think that including ones own definition of the word is always a good idea, especially if the object of the exercise is to enable the duplication of what one is describing.
On a related matter, since I use an arbor press die to seat my 6PPC bullets, and it does not have a micrometer top (a very closely fitting custom seater) I record the combined length of the stem and cap. This can involve a little visualization and math that recently resulted in me making an error that shot very well.
The intent of the exercise was to end up with the bullet off of the lands, but to use jam (determined with actual loaded round neck tension) as the starting point. The target seating depth was .030 off, or shorter than jam. I set the seater to produce a length that would have the bullet pushed back when the round was chambered, loaded the round, measured the length, and the combined length of the stem and cap at that setting. Then I chambered the round, and remeasured its length, noting the exact amount that it was shortened.
It was at this point that I made my mistake. I should have added the difference of the lengths to the amount that I wanted to be off jam, and added the total to my starting stem and cap length to get the setting needed to be .030 off jam. (Longer stem and cap measurements produce shorter loaded rounds.) What I did was to get in too big of a hurry and add the difference in measurements and then subtract .030. It wasn't until I had shot a couple of test groups that I it started to dawn on me that I had made a mistake, and set my die to seat the bullets .030 longer than jam, effectively loading my rounds to "soft seat" the bullets. The fact that I was using a bushing that produced medium neck tension had made my error less obvious, although I should have picked up on it when I chambered the first round, from the slight additional effort that it took to close the bolt.
Anyway, just as I was about to correct my mistake, it occurred to me that since the object of the exercise was to find a seating depth that gave good accuracy, and the test groups appeared to be good, that perhaps I should stick with the mistake, since the results were what I was looking for.
At that point, I determined that it was about time to pack up, and made a note to see if there would be a problem with bullets being pulled from case necks when unloading the rifle, on my next trip to the range, as well as correcting my mistake, and doing the test that I had originally intended.
Boyd
I often use a Wilson seater with shims to seat bullets for my Dasher. I use the RCBS (shown) seater to get the depth right and it seats bullets very straight. I have founnd that runout is often caused more by the sizing die and the neck turning. Both operations are very critical to having straight ammo. James
PS My rifle is a BAT B with Terry Leonard stock. The scope is an IOR Valdada 36X. The Brux barrel is 28" and is a .236/8 twist.
PS My rifle is a BAT B with Terry Leonard stock. The scope is an IOR Valdada 36X. The Brux barrel is 28" and is a .236/8 twist.
James, You are spot on the sizing die, all i'm saying is that there are may way to start but all are subject too change. mine is throat advancement. Yours will change with throat adv. and neck tension, bullet diameter and the smoothness of the leade. I had ppc barrels that the leade was so smooth that it didn't cut the jacket,it like little dents but still formed cases. Now if that works for you fine but for me i have one that also tells me how much the throat moves.This just more information you can kick around or delete but, i have been shooting competitively since the 60's In the USMC...... jim
Bradley Walker
Re: Brux Barrels
Could you please tell me your setup?
I find this thread amazing... So cool...
johara1 said:
Could you please tell me your setup?
I find this thread amazing... So cool...
Bradley Walker
johara1 said:
Just your rifle, etc...
Upgrades & Donations
This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.