Tuning to Conditions

T

tiny68

Member
Ok....newbie questions again. I was trying to reproduce a good tune I had last year with my 30BR. Same temperature. Same bullets, powder and lot of primers. Way out of tune. I don't own a weather station yet, but I see many with team at matches. What environmental factors do you keep track of when you work up a load and which is most the most critical on your tune? Temperature vs. Atmospheric Pressure vs. Relative Humidity vs. Altitude? I have only been tracking temperature.

Thanks for input, Tim
 
Tiny you said last year....
Did you shoot the load the entire year/season last year?
What month did you originally develop the load?
If you did shoot it all year then it had to work in a wide variety of conditions.
When you say same power bullets etc. Are these the exact ones that you put away last year or simply the same brand but new bottle/box?
 
Vern said:
Did you shoot the load the entire year/season last year?
Click to expand...

I have only shoot this barrel 3 times. We had a lot of family illness to deal with and I never even made a match last year. I tried a different bullet each time I shot, BIB 118-10s, BIB 118-7s, & Cheeks 115s. The BIB-118-10s shot the best in limited tuning. It was a September day - low 70s. Same temperature as earlier this week. Tim
 
Last edited:
"I have only shoot this barrel 3 times. We had a lot of family illness to deal with and I never even made a match last year. I tried a different bullet each time I shot, BIB 118-10s, BIB 118-7s, & Cheeks 115s"

I'm guessing your tune from last year might not have been as good as you thought - especially if you did not have a chance to prove it several times. It should be a decent starting point this year though.
I use Gene Beggs tuner and a Kestrel 4000 to keep track of Density Altitude. Hope things are better this year and you'll be able to shoot more.

Stanley
 
Hi Tim,

The good news about the 30BR is that you do not have to fret about your "tune" once you find it. I would suggest that you ignore the meteorological stuff at this juncture

Suggestions:

1-Determine the soft jam for your chamber and record. Start here with your seating depth or .003" down/back further in to case.

2- Ladder H4198 between 34.3gr and 34.7 gr.& look for consistent grouping regardless of the wind flags or other conditions _ looking for a wide window of forgiveness.
See www.6mmbr.com and the 30BR page on left for much good information as well. There appears to be a lower "node" around 33.7 gr. also if you prefer.

3- Once the H4198 powder charge window is found, begin to back off of jam or push bullets into case by .003" increments untill best combination or "tune", if you like, is found.

Most have found that not much other fiddling with loads or "tuning" is necessary for the 30BR _ load 'em and shoot'em ~ KISS.

Most also seem to favor the 7R ogive with bullets in the 112-118 Gr. range.

Bill

PS If can assist further, let know.
 
Hi Lee,

Seat a bullet into a case overally long or just enough to hold it in the case.

Chamber this inert round, close bolt with some difficulty, remove and measure with your choice of tools from the cartridge base to the ogive of the bullet.

using a barrel stub gauge, the Sinclair "nut" or one of their similar devices.

This is your "soft jam" for this rifle chamber and this particular bullet configuration.

Hope this helps.
 
I personally would call that hard jam but it is the same way I check jam. Size the case with your normal neckbushing and seat the bullet long and let the rifling seat the bullet when you close the bolt, that is as far into the rifling as you can push the bullet without increasing neck tension so you only have one way to go and that is too seat bullet deeper in the case. People use different termanology and sometimes that gets confusing without a complete explanation of the process they are using. This jam number needs to be established for each bullet that you use. Good luck with your load development, Steve
 
You can skip a lot of that if your Gunsmith furnished you a "thingy", that piece of barrel stub that has your chamber established in it to the shoulder.

Just seat a bullet untill it leaves just a thin circle around the bullet as you twist a loaded round in it. That is pretty close to your soft jam in a fresh chamber.

That is about where I shoot my 30BR. I have been known to increase the charge about 1/2 grn if the temperature drops below 60 degrees. I have not noticed that humidity and dew point affects 4198 like it does 133 in a 6PPC.

One question I could ask is, are you shooting the same lot of bullets? I have found that bullet quality, (ie, jackets), means a lot more in a 30 than it does a 6mm or 22 cal. I have had bullets of the same maker but a different lot, and one simply shoot better. It ain't tune, or any other magic. The simple fact is, if you score a great lot of bullets, cherish them.

One thing that I do that seems to be opposite of many is I do not use a lot of neck tension. About .0015 is all I use. My loaded round measures .328, when I run a case in my sizing die, the neck measures about .3265. That is not a lot. I have found that you get better consistancy in the loaded round with lighter tension, you simply tune with the charge, and of course, the tuner......jackie
 
Jackie,
Do you happen to know the jacket lot # of the 112gr BIB's that you shot in Midland so well? The lot # of jacket that I have are 2797. I have a lot of these in stock, and am just curious if you have shot any bullets on a .925" jacket of this lot #.

Michael
 
jackie schmidt said:
One question I could ask is, are you shooting the same lot of bullets? I have found that bullet quality, (ie, jackets), means a lot more in a 30 than it does a 6mm or 22 cal. I have had bullets of the same maker but a different lot, and one simply shoot better. It ain't tune, or any other magic. The simple fact is, if you score a great lot of bullets, cherish them.
Click to expand...

Yes Jackie, the bullets are the same lot, heck same box. I have more on order, by I think your success with the 30BR last year will keep Randy busy for a while. I am running a lot of neck tension compared to you.

Thanks to everyone for the tips and ideas. I will see how the neck range trip turns out.

Best wishes, Tim
 
Michael, the lot number on those bullets is 0905-570J4. I ahve about 420 of them left, and will shoot them in Group Matches this year when I shoot the 30 in HV.

I just got 2000 new bullets from Randy, lot #1101-797, and I shot some really nice groups with them last week end testing. ........jackie
 
jackie schmidt said:
Michael, the lot number on those bullets is 0905-570J4. I ahve about 420 of them left, and will shoot them in Group Matches this year when I shoot the 30 in HV.

I just got 2000 new bullets from Randy, lot #1101-797, and I shot some really nice groups with them last week end testing. ........jackie
Click to expand...

I'm a newbie to benchrest and as usual have a question. I understand the value of "good" bullets coming from a particular lot. How then can you get just enough from a lot to verify its from a lot you would want alot of? That make sense?? Buy 1000 from a lot and the whole lot is poor. Crap, why did I buy that many...Or buy 100 and get good results and say ok I want another 1000 from that lot? Thanks and I have even dumber questions that that I'll bet.
 
mdevers49
That is a great question. This is an issue that plagues most benchrest shooters. Many shooters buy a lot of everything and hope they stumble on a great combination. For others its a crap shoot, hoping to buy a good bunch of bullets from a custom maker. My belief is that, most barrels are good and most hand made bullets are good > the object becomes getting the combination to work. All of the things we talk about here come into play > Powder charge, seating depth, neck tension, loading habits etc. the list is long. A 1000 bullets doesn't last very long with practice and matches, if you can, buy 5000 at a time and that will add to some consistency. Get your equipment combination to work with the bullets you select. Most barrels will shoot most bullets well if tuned properly. Every day is different, can't say if its the Temp, humidity, air density or what but every day is a little different for the tune-up. Its hard to figure, but I guess that's what makes it fun! Have fun getting to be a better shooter.
 
You must log in or register to reply here.
Back
Top