Bullet jump

[AlNyhus]

Depending on the cartridge, neck tension, neck prep, bullet shape and bore size I have had cartridges with a hard jam of .015" on the low end to over .050" on the high end. Its nice to know your hard jam, but I never work from it because of that reason.

Absolutely. Most don't consider how the different angles interface. A 10 ogive bullet in a 1.75 degree throat is very different from a 7 ogive in a 1.5 degree throat, for example.

As to the high pressure boogey man that somehow magically comes to life when the bullet touches the rifling.....

 

[hpshooter]

Absolutely. Most don't consider how the different angles interface. A 10 ogive bullet in a 1.75 degree throat is very different from a 7 ogive in a 1.5 degree throat, for example.

As to the high pressure boogey man that somehow magically comes to life when the bullet touches the rifling.....

A lot of common sense and wisdom in one concise sentence. Angles of interference do matter.

 

[skeetlee]

One day when you're restricted to magazine COL you'll have no option other than to jump projectiles.
Start developing loads for magazined hunting rifles and you'd find this out real quick.

You are correct if you’re talking about factory rifles. The custom rifles I build in my shop I try and keep these types of facts in mind. Proper reamer selection is key!

 

[skeetlee]

I'd say 99%+ of handloaders jump bullets. If your testing it, especially in non BR rifles your missing out on some of your most accurate loads.

Why would a non BR rifle be any different than a BR rifle? Magazine length I’m assuming? I just personally haven’t ever found the need to jump a bullet. This doesn’t mean I wouldn’t I just haven’t had too.

 

[ballisticdaddy]

IMO it has a lot to do with the type of bullet being used, if its a VLD (Secant) then close to or into the rifling works well but if utilizing a hybrid (Tangent/Secant) then jumping is what it was designed for!

 

[skeetlee]

I do appreciate the discussion. I do t want to imply that I’m against jumping a bullet. I’m not against it and I know several shooters that do this with success. I also understand completely if your situation leaves no other choice. Magazine length or whatever the situation. For me I just think being in the lands at least a little seems like the better idea. I don’t play with many factory made rifles these days so I don’t have a lot of knowledge other than I’m usually disappointed in the accuracy. I don’t give much thought in to loaded round concentricity, but I do check mine from time to time. I never have much but there always seems to be a little. I just can’t see why this wouldn’t compound in .020 to .040 or however much one jumps. I like things to be as straight as I can control I guess.
This is just a topic that I thought would provide for a good topic and it has. Keep your thoughts coming.

 

[std7mag]

I just bought some Nosler ABLR 142 bullets to try in a 6.5 Creedmoor. Nosier recommends to use their COAL for the SAMMI length chambers, because this bullet likes a lot of jump. I think I’m going to try it and not re-invent the wheel.

Shooting a lot of 7mm ABLR from 150-175gr, they generally give me best accuracy about 0.02" off the lands.

As for the general jump vs jam, I see both useful but in different circumstances.

For a hunting situation, the last thing I want is the CHANCE for a bullet to possibly stick in the barrel and dump powder in my action.
Bear in mind reliability trumps absolute accuracy.

While I can load to the lands in my Weatherby Mark V, and it fits in the magazine, I can't then unload a live round. The ejection port is too short.
150gr ABLR is 3.630" to the lands. To eject a loaded round is 3.360"

Going to touch, or "jam" the lands for a competition rifle, I can also understand.
Your going for absolute accuracy.

But I'll ask any competition shooter this.

Those who say that they do a "hard jam" of 0.05-0.06" "into the lands ".
If you can unload a live round from the rifle, measure it and compare to the measurement to the lands.

 

[Bill Norris]

Depending on the cartridge, neck tension, neck prep, bullet shape and bore size I have had cartridges with a hard jam of .015" on the low end to over .050" on the high end. Its nice to know your hard jam, but I never work from it because of that reason.

Yea, I'm sure he was speaking about the 6PPC but that is some idea of one particular scenario.

 

[Bc'z]

I was running Bart's 105 hammer @.003
ITL from touch, until I investigated jump, .012 out shot the best testing @300.
I guess you'll never know what's around the corner if you don't take a peak.

 

[Bc'z]

After last post I got to thinking bullet may have a bit to do with where it wants to be.
Same 6br likes Vapor Trail 103's .012 ITL

 

[HTSmith]

Going to touch, or "jam" the lands for a competition rifle, I can also understand.



Those who say that they do a "hard jam" of 0.05-0.06" "into the lands ".

I'm confused on nomenclature here. To me "jam" is as far out as I can possibly seat a bullet out and still manage to close the bolt. "Touch" is the longest I can seat the bullet and the bolt handle (minus firing pin assembly) drops freely. I usually seat between those two points, whatever you call them, for the VLD bullets.

 

[Homerange]

You are correct if you’re talking about factory rifles. The custom rifles I build in my shop I try and keep these types of facts in mind. Proper reamer selection is key!

Which might impact on versatility.
What might suit 130gr won't suit 180gr in a hunter that you might use on small deer and moose.

Everything is a compromise.

 

[Alex Wheeler]

Why would a non BR rifle be any different than a BR rifle? Magazine length I’m assuming? I just personally haven’t ever found the need to jump a bullet. This doesn’t mean I wouldn’t I just haven’t had too.

As you get into larger bores, and longer bullets I find theres more tendency to like a jump. For example, one of my favorite big cartridges is the 338 Lapua imp. For me its both a "BR" and a LR hunting round. I have tight neck reamers and no turns. Build them for elr and 2k group matches as well as for hunting. I have put a lot into them because to me its the 6br of 338s. They will shoot in the lands and off. But most of them will shoot better off than in. That big bullet just like to jump a little. You will also see this in 30s. Even in 1kBR with the 300 wsm. A much higher % of guys will jump then you will see in the 6mm. The only reason I will jump or jam is accuracy. When you get to the bigger bores you just see more of them like to jump. In a 6mm, I dont even test jump anymore. Even though I should and recommend to do it. But the chance of a 6mm not shooting best in the lands is less.

 

[D-4297]

Been shooting Berger 185 OTM's , and Berger 185 Jugg Targets for most of my seven years of TR , and I went through a very extensive testing of seating depths in relation to Target accuracy , and found that this bullet seems to like .005 off touch , for the most consistent scores .
Also ; Powder choice does make a difference , as does primer , so you have to match things up .
All of my barrels are done with a Manson 2013 FTR Reamer , with a adjusted Freebore set at .190 , so I can shoot the 200 Hybrid , or the 200.20x .
Barrels tend to last roughly 3,500 rounds , and when they go "Bad" , they go in less than 100 rounds , and GONE !

 

[Alex Wheeler]

Yea, I'm sure he was speaking about the 6PPC but that is some idea of one particular scenario.

I have no idea, but the .050" hard jam I mentioned was a 6ppc. Theres so much that changes jam a huge amount. Nothing changes touch.

 

[BoydAllen]

Here is a little jumping story, about a .222 varmint rifle that a friend built for California. He was concerned about the barrel heat issue when shooting when there are a lot of targets. (Richardson ground squirrels in N. CA) Nosler makes a 35 gr. no lead ballistic tip that is similar to their lead core 40. He had worked up a very accurate load that gave him about 3,650 FPS with good case fill. What he ran into is an issue with muzzle flip when shooting off of his field rest tripod. It caused him to loose his target at impact. To solve this he built a muzzle brake for the rifle, which ruined the tune, but did solve being able to see his hits. Not wanting to mess with charge weight, he decided to try changing seating depth. Starting at Hornady tool snug touch, he shot two shot tests in increments of .010, giving progressively more jump. In the past I would have quit by say .020 jump, but he is a hard core tester so he kept going well beyond that and found overlapping bullet holes again at about .080 jump. I would have never tried that in a million years, but he is a serious experimenter. Later I loaned him some LT30 to test and he was able to get another hundred FPS with out strain. In reworking the load for that powder, he found his accuracy at about .060 jump. He also shoots sanctioned short range benchrest at the Visalia range. Last match, he came in third in the two gun and I think that except for a strategy decision, he would have come in higher. My point being is that he is a serious shooter who does his own machine work, and who shoots, and tests a lot under excellent conditions, which we are lucky enough to have fairly often.

 

[Steve Donlon]

I do appreciate the discussion. I do t want to imply that I’m against jumping a bullet. I’m not against it and I know several shooters that do this with success. I also understand completely if your situation leaves no other choice. Magazine length or whatever the situation. For me I just think being in the lands at least a little seems like the better idea. I don’t play with many factory made rifles these days so I don’t have a lot of knowledge other than I’m usually disappointed in the accuracy. I don’t give much thought in to loaded round concentricity, but I do check mine from time to time. I never have much but there always seems to be a little. I just can’t see why this wouldn’t compound in .020 to .040 or however much one jumps. I like things to be as straight as I can control I guess.
This is just a topic that I thought would provide for a good topic and it has. Keep your thoughts coming.

You don't have to jam the bullet to have very little run-out if any to speak of using the right seating die. It does take more time and skill. If you do not jam, you can get more velocity without sacrificing accuracy. I'm not saying the upper node is always the most accurate, but more velocity is not a bad thing if it's accurate. I load every bullet the same way, regardless of the rifle, from a 300 BLK to a bench rest rifle. I have to add that I do not turn the necks on the AR brass. I just would never consider jamming a bullet into the lands. I'm very happy with the accuracy I can achieve and is beyond what I thought was possible before I had a friend of mine put together my first bench rifle, a 30" straight tube 30-06 with all the bells and whistles. I really can't imagine how jamming a bullet could improve the accuracy. But when you guys compete, it's like driving a race car, some will do what ever it takes to win. I get it. But for me , a one hole group is good enough. Also, how long have shooters been jamming bullets? Maybe they dd not make the same style of seating dies they make now.

 

[boltfluter]

You don't have to jam the bullet to have very little run-out if any to speak of using the right seating die. It does take more time and skill. If you do not jam, you can get more velocity without sacrificing accuracy. I'm not saying the upper node is always the most accurate, but more velocity is not a bad thing if it's accurate. I load every bullet the same way, regardless of the rifle, from a 300 BLK to a bench rest rifle I just would never consider jamming a bullet into the lands. I'm very happy with the accuracy I can achieve and is beyond what I thought was possible before I had a friend of mine put together my first bench rifle, a 30" straight tube 30-06 with all the bells and whistles. I really can't imagine how jamming a bullet could improve the accuracy. But when you guys compete, it's like driving a race car, some will do what ever it takes to win. I get it. But for me , a one hole group is good enough. Also, how long have shooters been jamming bullets? Maybe they dd not make the same style of seating dies they make now.

With all due respect, a .30-06 and a 6PPC are worlds apart when it comes to absolute accuracy. A .30-06 doesn't have the inherent accuracy to be able to see the benefit of seating bullets into the rifling. That's all.
Paul

 

[Dimner]

With all due respect, a .30-06 and a 6PPC are worlds apart when it comes to absolute accuracy. A .30-06 doesn't have the inherent accuracy to be able to see the benefit of seating bullets into the rifling. That's all.
Paul

I agree with this, although I have found certain 30-06 loads that like the bullets in the rifling. When I first started this trek down better rifle accuracy (when I first found this site), the only halfway accurate rifle I owned was the 30-06. I was eager to learn and having nothing else to use, I tried many of the methods found on this site to tune loads.

I found that some bullets with my 30-06 did the best when seated into the lands. It seemed specific to the type of bullet. Standard flatbase soft points did not seem to care one way or the other. I suspect there is an accuracy/precision ceiling that one reaches with these kinds of bullets. On the flip side, some sierra match kings and Nosler bullets I tried did better in the lands.

However, circling back around to your main point. Loading an 06 into the lands is just not worth testing. Any load into the lands is not practical for hunting purposes, and the 06 is not even the 2nd, 3rd, 4th choice of anyone doing any kind of competition format.

 

[L.Sherm]

I've found in multiple cartridges like Alex mentioned in stuff from 17-6mm that with boatail and flatbase bullets .005 in to .005 off has been the sweet spot.
My LR Hunting rifles 30- 28 Nos with the 215 is .030 off and my 6.5x300wsm with 140 Bergers are .027 off