Jamming To Square?

[jr600yd]

Gentlemen your opinions please. German, Bryan, Laurie, and everybody else.

On jamming VLD bullets a competitor explained this theory to me. Agreed, every rifle is different but this is a place to START. Additional adjustments may or maynot be necessary. As explained, a VLD bullet is placed in the chamber then pushed forward untill it will go no futher. A light tap or two on the base with a cleaning rod will ensure the projectile is well into the lands and groves. The cleaning rod is then used to push the bullet out. Looking at the bullet one should see engraving from the lands on the bullet. The WIDTH of the engraved land is then measured. It doesn't matter if it is a 2 or 6 grove barrel it's the land width that is important. A dummy round is then made up with the bullet seated into the lands the same amount as the lands are wide. He calls it SQUARING THE JAM.

Just out of curiosity I tried this with some Berger 105 VLD's in my 6BR I was impressed! As stated above this may or maynot be the most accurate seating depth for your XXX rifle but it's an excellent place to start. What do you think?

Good shooting, Jim

 

[RonAKA]

I think all you are doing is making the jam equal to the width of the lands. Can't see anything magic about making them equal. However, in most guns that is a pretty significant jam, compared to the typical 0.010" that I use.

To my way of thinking, the factors at play in using a jam, is the clearance of the cartridge body in the chamber, the clearance of the neck in the chamber, and the concentricity of the chamber to the neck, and bore. If the chamber and/or neck are tight, and concentric to the bore, then a jam probably can make the bullet more concentric with the bore, even if it is not loaded that way. The geometry forces a concentricity straightener, reduces bullet cant, and likely improves accuracy.

However if there is excessive clearance in the body, neck, and/or lack of concentricity between the chamber and bore, then a jam likely forces the cartridge sideways in the clearance, and increases bullet cant, and reduces accuracy. In this case a jump may work better.

So, the simple answer is that "it depends".

 

[jr600yd]

RonAKA,
Your right about making the jam equal to the land width and you bring up some very good and interesting points. I was referring to a place to start the jam. Seating adjustments can and probably will be necessary to find the most accurate seating depth. Just wondering on opinions as a place to start.

Good shooting, Jim

 

[1shot]

I personally let the bullet and the reamer design in the chamber make my decision for me. If the reamer/chamber is a little off I go the jam route. But, if it’s a custom everything, I start from where you are talking about, being “square” and do my development from what I see in magnifier on the chrono and the target. I have walked on this road more than once, an if other aren’t free to talk to you about this, feel free to contact me via personal e-mail, as we all, started somewhere. I will be happy to tell you what I know and what I don’t. Someday, you will help someone else in the same situation you are in.
I hope this helps,
Lloyd
tangodown@embareqmail.com

 

[bigedp51]

Your stepping back into the 18 century and the single shot Schuetzen rifles that had a false chamber that allowed a cast lead bullet to be pre-engraved into the rifling ahead of the case. The false chamber was removed and the cartridge case (minus the bullet) was chambered "behind" the pre-engraved bullet in the bore and then fired.

Your problem is your new jacketed bullets are too hard to go any further into the bore. Therefore your new rifles are not Schuetzen rifles but do qualify as "Das Firespitenloudenboomer rifles" :

 

[tenring]

The square engraving theory applies not only to VLD's, but flat base bullets as well. At least, that is what I have read by several well known HOF 6PPC shooters, using flat base bullets. Personally, I do not feel one shoe fits all. You gotta try various seating depths in your rifle and chose the best.

 

[johara1]

All it is is a starting point,Then move. Just eye ball it no big deal, then zero and .010 out. It will tell you what way to go............jim

 

[BoydAllen]

There is nothing magic about square marks.

It seems that many times questioners, on the internet are looking for a specific load, or seating depth that will work best for their rifle, without further adjustment. Good luck with that. As a better alternative, I would suggest that shooters take their loading equipment to the range, shoot over flags, and make small moves, from whatever starting point they find works best for the particular bullet, barrel, and powder that they are using. I am always amazed at many shooters' resistance to making changes in how they do something. In many cases if you tell them how to solve a problem, what it comes down to is that they want to shoot better without changing anything.

Personally, I find that for single radius ogive bullets (that are tangent ogive) that have an ogive number around seven, shooting VV 133, in my 6PPC, that marks that are about one third as long as they are wide are an excellent place to start, having yielded test groups in the teens under good conditions, with a properly adjusted charge weight. On the other hand, for the same rifle and powder, shooting a double radius ogive bullet,that has a ogive radius of around nine where the marks will be, favors marks that are much longer than they are wide.

 

[johara1]

I've had good barrels that doesn't leave a mark,and lot to do with the reamer and the person using it. after a hundred rounds or so all you see is a dents not cuts from the lands..........jim

 

[Kenny474]

I agree with BoydAllen and what he has stated.

I think bringing your loading equipment to the range and making adjustments on the spot is the best way to develop a good load. I too have seen many people who ask for a "good load" and expect to just load it up with the specs that were accurate in some other rifle and have it shoot the same as it did in the other rifle. This is very rarely the case. Every rifle is different, and even chambers cut with the same reamer can have minor differences in dimensions in the throat area, as well as anywhere else the reamer has worn.

If you have your equipment at the range, you can load smaller test batches and make changes and see how they effect your groups. Not so when you have your stuff at home. Then you likely will not be shooting in the same conditions the next outing, and your changes may be affected by weather as well as other things, not really giving you an accurate reading of how your changes affected your loads.

But as for the technique discussed above used for a baseline on bullet jam, it is likely just as good a starting point as many of the other starting points. I really don't think it matters a whole lot about where you start, but more that you try different amounts of jump or jam and also that you try a wide range of jump or jam as well.

I feel that sometimes people put too much hope or faith in these magic starting points and trying to make them work, rather than experimenting and changing things to see what does work. Like when someone spends days working on trying to get a load to shoot with .010 jam because they they were told that is what's best for that bullet, when it would really work better with .010 jump if they only tried it.

Bottom line, most any starting point is a good starting point as long as you deviate from it and try other things if it isn't working for you, rather than fight and try to make it work. Trying a wide range of settings and understanding how things are affecting your accuracy is the key to building a good accurate load. Trying to make someone's load or some magic starting point work best in your rifle is the biggest mistake I see more often than not.

So as long as it's understood that a starting point is just that, and that it is to be changed once it doesn't work, than yes, it may work.

 

[BoydAllen]

A tip for making land marks easier to see....wrap the bullet in 0000 steel wool, and while squeezing it between the thumb and index finger of one hand, turn the loaded round with the other hand, so that steel wool lightly marks the bullet.

 

[alf]

I smoke the bullet with a Bic lighter.

The length of the marks is also dependent on the number of lands and their width. For an example, with a four groove, square marks leave the bullet seated too deep for my liking.

 

[GermanS1]

Jim, you indicated that the square mark was a starting point; that's fine. I would recommend two things: 1. after you determine where your square mark OAL is, measure with a Stoney Point/Hornady tool to put some real numbers on it, and 2. back off from there as you develop the load because it's probably a pretty deep jam, like 0.030".

The benefit of your proposal is that there's practically only one way to go from the starting point: shorter. As Kenny said, doing a bit of work at the range is really helpful, but for a place to start, a square mark is as good as any and better than some.

 

[GerryM]

German is right .
I do have my own way though. I put a bore guide in the rifle and a bullet i then push the bullet in until it just touches and start from there.
Usually i get an indication right off the bat. I then make the round longer by .005 and see what happens with a 3 shot group. Now i go the other way jumping .005 as a start and bringing it back about .005 at a time. One rifle is jumping .020 and shooting tiny groups most of the other are just touching , or just jumping .005
Jaming the bullet does square the bullet up in the lands but it also raises pressures . basicly its just like adding more powder by jamming the bullet, At least thats what i have found out The hard way.
Its best to load develope at the range. Load 3 shots at a time and measure the groups later It saves a lot of time in the long run,' Don't forget to take notes especially temperatures' and seating depths.

 

[johara1]

German, Number one i use a stub that is cut from my chamber reamer to measure with, i never found other things that repeatable.Then i make three settings in to square zero and .010 out,this will give me the direction to go. After i find the direction i need to go i move at .002 seating depth moves to find a window in the seating depth that it will shoot in. My dasher shoots from .008-.012 with the 115's jumped, so i set the seating depth at .010. This allows me seating error plus throat advancement.....jim

 

[artbosco]

Gentlemen your opinions please

On jamming bullets a competitor explained this theory to me.

#1 A bullet is placed in the chamber then pushed forward until it will go no futher. A light tap or two on the base with a cleaning rod will ensure the projectile is well into the lands and groves. The cleaning rod is then used to push the bullet out. Looking at the bullet one should see engraving from the lands on the bullet. The WIDTH of the engraved land is then measured. It doesn't matter if it is a 2 or 6 grove barrel it's the land width that is important.

#2 A dummy round is then made up with the bullet seated into the lands the same amount as the lands are wide. He calls it SQUARING THE JAM.

What do you think?

Forcing a bullet down a barrel with a cleaning rod and then removing it with one, sounds like a way to ruin a good bullet, and a little excessive.

I'd stick with using a dummy round as the better tool for finding you're intended mark. Seat bullets to varying lengths until you find what your looking for, then record that length with a measuring device. I use my Wilson Seater die's micrometer setting as my measuring tool and then record the number setting in my log book.

 

[Laurie]

I reckon a 'square jam' is pretty severe. I'd always use less if at all possible. There's nothing I hate more than unloading a 'jammed' round and getting powder loose in the lug recesses so, providing it works, I tend to use just enough bullet in the lands to make it work and hope that unloading a live round brings the bullet with it. (Sometimes it does, sometimes not!)

To be honest, if there is a tangent bullet that does the job in hand and can be jumped, I'll use it in preference to a VLD that needs to be jammed. (Next year, I'm going to experiment with Berger's recommended VLD jump steps to see if it works for me in the .223R with 90s, and if so whether it gives as good results.)

With a light jam, you do need to keep checking throat erosion and adjusting the COAL. With a really deep jam, you can likely forget it for a lot of rounds.

Laurie,
York, England

 

[jr600yd]

Thanks guy's. Lots of good info here.

Good shooting, Jim

 

[artbosco]

There's nothing I hate more than unloading a 'jammed' round and getting powder loose in the lug recesses so, providing it works, I tend to use just enough bullet in the lands to make it work and hope that unloading a live round brings the bullet with it.(Sometimes it does, sometimes not!) Laurie, York, England

The best way to prevent the mess that's created when a bullet stays in the barrel, and the extracted case pours powder into all the crevices found in a chamber, and even into trigger area, is to simply fire the round.

Make it a habit when firing jammed bullets. The only way you may get by without it, is using lots of neck tension, but even that's no guarantee.

A few cents worth of powder and bullet down a barrel is a very small price to pay to prevent a chamber full of powder.

 

[Laurie]

The best way to prevent the mess that's created when a bullet stays in the barrel, and the extracted case pours powder into all the crevices found in a chamber, and even into trigger area, is to simply fire the round. [Outdoorsman]

Ah not a regular F-Class or Fullbore type target shooter methinks!

If the Range Control Officer tells you to unload, prove weapons clear and step off the firing point, you do just that even if it leaves a bullet stuck in the barrel and powder all over the shop! On some ranges it only happens rarely, like when you get a trespasser; on some that I shoot on it happens all the time because military units can legitimately demand access in front of you to get onto / leave an adjacent range.

In BR shooting practice, it is assumed that at least some competitors will have 'jammed rounds', so the RCO will tell shooters to step back and leave rifles as they are should an on-range emergency arise. In Fullbore / Target / Service Rifle and F-Class which have their roots in service type shooting, the assumption (at least on this side of the Atlantic) is that any chambered round can and will be easily ejected on a legitimate command, and if it causes problems for the shooter and he or she has to retire, well he or she shouldn't have so loaded their ammunition! You certainly won't get any sympathy. This is one reason why many shooters in these disciplines won't use VLDs.

Then another issue that can arise occasionally with any rifle that sees a lot of rounds though it, is bolt, trigger group, or other mechanical malfunction that can only be rectified after the round is ejected and the bolt removed.

Laurie,
York, England