.120" Jump

[Piotrowski]

I'm looking for a little advice/comments...
Shooting a stock Savage F/TR in .308 prone.

I spent part of yesterday (when the wind dropped off) doing the Brian Litz Test (calling it that because it was his article that got me to try this) with various lengths of bullets. Of the 4 groups (.010 long (yeah, I had to work the bolt handle down), .040 short, .080 short and .120 short from jammed), the shortest bullets shot way better than any of the others...

I mixed up at batch of 10 of the Shorties and took them back to the Range this morning. With not a breath of wind, this was by far the best group I've ever shot at 600 yards. My calculation called it a 99-6X. (I have a tendency to lose focus and it takes a crappy shot like the one I jerked to wake me back up!)

Enough of the bragging and down to the question/comment: I'm thinking this might have more to do with Pressure than Jump or Jam... I'm also thinking 120 thousandths is one heck of a Jump. Should I settle for this and call it a Good Load for my rifle, or should I work the power load at longer COALs? (The Lazy Person in me says settle since I really don't like all this experimentation...)


This is the group I shot this morning... 10 shots @ 600 yards:

 

[Keith Glasscock]

Shoot it the way it is. If it needs any adjustment, it will tell you.

Keith

 

[Shynloco]

Now see if you can repeat that group and if so, leave it alone. Don't need fixin! My .308 loved that jump too before I rechambered her.

Alex

 

[timeout]

I have two rifles that loved the "long jump". Latest one doesn't. Shoot what works.

 

[L-46]

Not sure how you can improve on that at 600?
just saying

 

[eric32]

What bullet/powder/primer are you using???

 

[CaptainMal]

That's so nice others will try to find a way to get that gun from you.

You shoot what works in that gun. That group tells me - it works.

 

[nastynatesfish]

What's the coal? What bullet ? In my old ftr I shot 175s like that too but it was at 2.79" 2.80 was in the lands. I never worked 155s cause the 175 a shot so well

 

[Piotrowski]

First off... Thanks for the kind words and comments.

Second, I should have said something about my thinking that pushing the bullet that deep into the case will cause an increase in pressure due to compressed powder? I realize that jamming the bullet into the lands also builds pressure in the chamber.

Third, the load:
Gold Medal Match Clone from Newberry.
~41.75g of IMR-4064
Sierra 175g SMK HPBT
~2.116 to the Ogive (with my tools).

My tools measure a real GMM at 2.225 to the Ogive and my F/TR loves them too, but they've never shot like this for me.

I made up a new batch today and have a four-day weekend coming up in a few days, so I'll get to try them again soon. It will be interesting to see if I can repeat this. If so, I'm going to have a good time with the Guys that (basically) forced me into buying an F-Class rifle so I can participate in the mid-range matches at our range. (Almost all of the matches take a break thru the hot summer months and restart in October, so I rarely see them in summer.)

 

[r bose]

Jamming bullets into the lands increase pressure A WHOLE LOT MORE than pushing bullets further into the case. (jumping) IN my experience, jumping bullets at any length dosen't justify a change in powder charge but jamming WILL cause you to creep back on your charge. I like to find a load that is NOT JAMMED just in case you have to unload when the range is called "COLD". You don't run the risk of pulling out the bullet (that is lodged into the lands) and dumping powder into your action.

 

[NorCalMikie]

From looking at your 600 yard target, LEAVE IT ALONE! Looks real good from here. Don't fix it if it ain't broke! 8) Looks to me like you've found your load. ;D
Got a shooting buddy with a H.S. Precision in .308. .100 + jump to the lands. DEADLY ACCURATE!
Seems like the larger calibers prefer a jump to the lands.
I start with all my rounds jammed into the lands (small calibers ).
No problem working up loads from there. Bullet stuck in the lands and powder dumped into the action on extraction??? Been there, done that.

 

[Piotrowski]

Thanks again.

BTW, the primers are Federal GM210M. I have some Wolf, Winchester and S&B primers that I was going to try out to see if there's a difference, but if the next round of shooting this load works as well as this past weekend, I'll probably just keep using the Federal primers and hope I can get some more when I get close to running out.

 

[BradY]

I thought that test was for VLD bullets. The 175grSMK is a fairly jump tolerant projectile. Still if it works where you have it, dont mess about.

Ive done that test on a few rifles that I use VLD's in. While alot of people say the 10 thou jam or thereabouts in a VLD is a good seating depth, you would be amazed at how well some loads work with 40 thou jump.

 

[Piotrowski]

Don't recall the mention of specific bullets in either article I read, but we all know he works for Berger...

http://www.bergerbullets.com/effects-of-cartridge-over-all-length-coal-and-cartridge-base-to-ogive-cbto-part-1/

http://www.bergerbullets.com/effects-of-cartridge-over-all-length-coal-and-cartridge-base-to-ogive-cbto-part-2/


Shot some again this morning... 91-0x.

Out come the excuses: breeze blowing to 8mph, ran out of bullets while reloading, so I had two mixed lots, some of the Federal Brass had started to stretch, so I had to trim...etc.

More likely: I'm not shooting, or reloading, consistently enough yet.