Ever had a successful load for short range br jumping.020 or more?

[Owens85]

In all the bullets I've used for a 6 ppc they've been in the lands. Same with the 30br with some bullets at full jam which was around 30 thou in with the neck tension I was running. In my bra the only bullet I tried that shoot better jumped was a 105 hybrid. They seemed to be happy around 15-20 thou off. The hammers Im using are in between 5 to 10 thou.

 

[Sleepyhollow]

Lots of good info here. Bullet ojive shape will dictate where in the lands it wants to shoots. Long skinny ojives like 7/10.5 will usually be about 0.006 in from touch for me. My 8/6 made on Ulrich dies seem to like a couple tho back from touch point. I let the barrel tell me what it wants. Being back out of the lands allows me to run a hotter load without the pressure issues I would see if I was into the land pretty hard. Let the barrel and target tell you what it wants.

 

[gunsandgunsmithing]

Doesn't loading into the lands increase pressure ?

It's not as simple as a yes or no answer. But if we assume it does, wouldn't that be free speed with less powder being used to do the same work, kinda thing?

I've seen peak pressures on a pressure trace occur with a short jump rather than jam. I imagine it as the bullet starting, stopping and restarting in a very short distance but more powder has burned during that little cycle time. Not sure that's 100% accurate but I think it would be similar, at least. At some point, I think I read in a loading manual, a description of this scenario. It's been a while so I don't remember the details or where it was.

I do think it can be tested either way and that's how we learn things.

 

[searcher]

Most of my barrels want at least a soft jam, though I do have one which I tried a (now) long-discontinued 62 Berger bullet. It shoots incredibly well at .025" off. You almost have to with that bullet as there is almost nothing in the case. Walt Berger told me that bullet was not meant for 6PPC at the time. Regardless, I sought out a few thousand of them before they were all gone. Was using the old "T" powder. One never knows what might work well.

 

[Longtrain]

I have never jammed bullets. Generally, I was in the school of .010-.020 off was where I found consistent accuracy. As my last Dasher barrel wore and the throat lengthened I found that rounds that were once .010 off were now .050 off. This was for Sierra 70 SMK’s and Berger 68 gr FB accuracy was excellent, mainly shot at 100 meters and as far as 300 yds.
I found this article discussing long jumps being accurate and those that chase the lands may be able to have a range of jumps that will stay accurate without adjusting seating depth.

More Bullet Jump Research!

This is the 4th article in a series on some new research on bullet jumps. Here is a recap of the pr...

precisionrifleblog.com

 

[memilanuk]

Did you miss the key part of the thread title? "short range benchrest"

Entirely different cartridges, bullet types, etc.

I'd be interested in a similar thread on 600-1k BR, but this ain't it.

 

[wildcatter]

NO, short range BR requires absolute accuracy, great accuracy is unexceptable.

 

[jackieschmidt]

Both myself and my best Friend Ed Bernabeo are jumping my 112 grain 30 BR between .015 and .020.

We have tried every seating depth imaginable, and that’s what it likes.

 

[NC/Br Shooter]

Both myself and my best Friend Ed Bernabeo are jumping my 112 grain 30 BR between .015 and .020.

We have tried every seating depth imaginable, and that’s what it likes.

This is what kind of reply s I was hoping to find

 

[dgeesaman]

It’s a tough question to answer because so many SRBR shooters never test there. Not saying they’re doing it wrong, but if some barrels like that amount of jump, it’s never known.

 

[Mark Buettgen]

In all the years I've been shooting and all the barrels I have used, there was only one 6 PPC that shot better jumping. I was ready to pull it and turn it into a Decoy anchor when a buddy suggested to try jumping. So next day, went to the range and just spun the seater and it wound up at .040" jump. First 5 shot group was about an .080" and at that setting was one of the best 100 yard barrels I ever had. I never was able to get it to shoot at 200, it just splattered, but at 100 was great. In those days, like most of us, I was using Button rifled barrels.
Later, Mark Buettgen
Bartlein Barrels Inc.

 

[gunsandgunsmithing]

In all the years I've been shooting and all the barrels I have used, there was only one 6 PPC that shot better jumping. I was ready to pull it and turn it into a Decoy anchor when a buddy suggested to try jumping. So next day, went to the range and just spun the seater and it wound up at .040" jump. First 5 shot group was about an .080" and at that setting was one of the best 100 yard barrels I ever had. I never was able to get it to shoot at 200, it just splattered, but at 100 was great. In those days, like most of us, I was using Button rifled barrels.
Later, Mark Buettgen
Bartlein Barrels Inc.

Kinda same here. When all else fails, try it. Most often, I find the best at some amount of jam but if one acts stupid and just doesn't seem to like what you're doing, by all means, try jumping. I still find it to typically repeat at only a small amount of jump as compared to what some do but jumping, nonetheless. My rule of thumb is from +.010 to -.010. A few a litlle more and a few a little less but it's always close.

edit...on a similar note, do you find any difference cut vs buttoned in regard to seating depth. I don't but wondered your view of it and if so, why do you believe so. Thanks!--Mike

 

[TTE]

No. Every competitive rifle I have ever used did best around. 020 to .040 into the rifling. One came alive at .050 into the rifling, pushing the bullet into alignment I would assume. I am sure there's exceptions to this rule, but this has been my experience with some very accurate rifles. Good luck with your testing!
Paul

I am new to this bench stuff, so please bear with me.
If you measure hard jam (where the barrel seats the bullet) how do you get .020 to .040 longer into the rifling ? Or am I not quite understanding what you are saying ?

 

[gunsandgunsmithing]

I am new to this bench stuff, so please bear with me.
If you measure hard jam (where the barrel seats the bullet) how do you get .020 to .040 longer into the rifling ? Or am I not quite understanding what you are saying ?

You don't. It's a terminology thing and the only real reason for "speaking in the various languages" regarding jam and touch etc, are for communicating numbers, mostly on internet forums. To your point...you're right. full jam, in my definition, is as far into the lands a given bullet can be pushed with a specific amount of "neck tension"...another term that gets used/misused..but we know what is meant by.

Just remember that most or all tools sold for measuring, say touch point, are comparators. They aren't intended to give actual dimensions between say mine and your comparator tool. But if we say touch, that has a meaning, regardless of what the number is on a set of calipers or whatever. So, if I say I'm .010 off of touch, we're speaking the same language is all. Not that it'll shoot best in your gun though and the actual number on the caliper will likely be different, yours to mine....but .010 off of touch is just that. Assuming the same and consistent manner of finding touch is used for both people involved. If only one person...It doesn't matter how you come to a number as long as it's repeatable.

 

[TTE]

You don't. It's a terminology thing and the only real reason for "speaking in the various languages" regarding jam and touch etc, are for communicating numbers, mostly on internet forums. To your point...you're right. full jam, in my definition, is as far into the lands a given bullet can be pushed with a specific amount of "neck tension"...another term that gets used/misused..but we know what is meant by.

Just remember that most or all tools sold for measuring, say touch point, are comparators. They aren't intended to give actual dimensions between say mine and your comparator tool. But if we say touch, that has a meaning, regardless of what the number is on a set of calipers or whatever. So, if I say I'm .010 off of touch, we're speaking the same language is all. Not that it'll shoot best in your gun though and the actual number on the caliper will likely be different, yours to mine....but .010 off of touch is just that. Assuming the same and consistent manner of finding touch is used for both people involved. If only one person...It doesn't matter how you come to a number as long as it's repeatable.

Thanks.
OK ... is jam and touch the same thing (in my rifle) ?
If so, my question still remains.

 

[gunsandgunsmithing]

Thanks.
OK ... is jam and touch the same thing (in my rifle) ?
If so, my question still remains.

No. Touch is just that...the point at which the bullet just touches the lands. There are methods to measure this to around a thou, consistently, maybe even a little less. But again. as long as it's consistent, it doesn't matter. Your gun and consistent method stands on its own. Remember, touch or jam is just terminology for conversing purposes. Nothing more. Since there's no way to know that my touch will shoot in your gun, it is nothing more than a close place to start...again, for conversing only. If I say my gun shoots best at just touching but our methods vary in how we find touch or even the actual measurement itself..but yours shoots best at your just touch point also...then who cares? You just found what matters. Most people these days consider jam to be touch plus however far into the lands beyond that they are. .010 jam= touch+.010

 

[Bill Norris]

No. Touch is just that...the point at which the bullet just touches the lands. There are methods to measure this to around a thou, consistently, maybe even a little less. But again. as long as it's consistent, it doesn't matter. Your gun and consistent method stands on its own. Remember, touch or jam is just terminology for conversing purposes. Nothing more. Since there's no way to know that my touch will shoot in your gun, it is nothing more than a close place to start...again, for conversing only. If I say my gun shoots best at just touching but our methods vary in how we find touch or even the actual measurement itself..but yours shoots best at your just touch point also...then who cares? You just found what matters. Most people these days consider jam to be touch plus however far into the lands beyond that they are. .010 jam= touch+.010

Absolutely, we have to remember these numbers are relative ONLY. Meaning each rifle will show a different set of numbers. Touch - is simply touching the lands. In the lands - is anything past touch until Hard Jam is reached and Hard Jam is as far as the bullet will go without the bolt seating the bullet deeper into the case.

 

[gunsandgunsmithing]

Absolutely, we have to remember these numbers are relative ONLY. Meaning each rifle will show a different set of numbers. Touch - is simply touching the lands. In the lands - is anything past touch until Hard Jam is reached and Hard Jam is as far as the bullet will go without the bolt seating the bullet deeper into the case.

Thanks Bill! You said it better than I did and in fewer words.

 

[NZ_Fclass]

My BR shoots from 12 to 40 off with no noticeable change on the target, with 107's I usually keep it at 18=20.

 

[Ccrider]

My BR shoots from 12 to 40 off with no noticeable change on the target, with 107's I usually keep it at 18=20.

No doubt if you are loading for minute of deer. Doubt you will ever see that tuning a benchrest rifle, even the most forgiving.

I look for a tuning seating depth window of 2 to 4 thousandths. Most of the time it ends up closer to 2 than 4.