Some insight on jamming please

[BigBamBoo]

I talk to folks at the range and read about how most folks "jam" their bullets. I am looking for some insight/clarification on this practice.

When I start load development on a given round I always start with the bullet seated in lands/jammed. By this I mean I seat a bullet on the first load long and try and chamber it. I keep seating the bullet deeper until I can chamber it/close the bolt.
I them work on powder charges till I find a promising charge weight and then start seating deeper o find where that load and seating depth shoot the best.

I personally have never had any of my rifles shoot "the best" with the bullets jammed into the lands. And this has me wondering why? As stated above, from what I read/hear, most folks claim to be shooting jammed with best results.
Is there something I am overlooking in my reloading practice?

Jamming has yielded ok groups for me at different times but the problem I have ALWAYS ran into with jamming is flyers. I ALWAYS get a random flyer while jamming. And again....this has been the results on 5 different custom (not factory) rifles.

All my rifles seem to tune best with some sort of jump....I know I am a vortex of "if it is going to happen to someone it will be me"...but it seems like there must be more going on here that I am overlooking (would not be the first time).

Input/direction please.

Take care.

 

[7x57 Shooter]

I have seen bench rest shooters do this before, I don't care for the procedure as it raises pressures. Bench rest shooters that jam their bullets don't use full loads that you would find in hunting ammo, they shoot for accuracy rather than velocity.
For hunting I full length resize to ensure the rounds will chamber and extract properly. For range work I have a bunch of neck sized brass for different the cartridges that I shoot.
Hunting ammo shouldn't be loaded the same as bench rest ammo, the applications are totally different. Follow your reloading manuals, always start at the starting loads and work up to accuracy of your rifle without exceeding the manual.

 

[4xforfun]

I have seen bench rest shooters do this before, I don't care for the procedure as it raises pressures. Bench rest shooters that jam their bullets don't use full loads that you would find in hunting ammo, they shoot for accuracy rather than velocity.
For hunting I full length resize to ensure the rounds will chamber and extract properly. For range work I have a bunch of neck sized brass for different the cartridges that I shoot.
Hunting ammo shouldn't be loaded the same as bench rest ammo, the applications are totally different. Follow your reloading manuals, always start at the starting loads and work up to accuracy of your rifle without exceeding the manual.

BUNK!!!!

Benchresters (at least LR benchrest) shoot as fast as possible. They will find 3 or four "nodes" and use the top nodes even if they are at the ragged edge!!! A lot of guys I know shoot loads that would SCARE most hunters. I have only had ond BBl that I shot slow. The rest are at the edge!!! I have several tubes that need to be loaded down when it gets warm out, and can not be shot when it is hot out with out sticking the bolt. And most JAM their bullets to some degree (at least for VLD bullets).

Also...I am pretty sure that the PPC guys run at 60000 + psi.

 

[TerryPohl]

I load my hunting rounds the exact way I load my bench loads for the utmost accuracy I can get out of that rifle, weather it be fast, slow , jump are jam.
Terry Pohl

 

[deadlyswift]

I'm not so sure that it has as much to do with a particular barrel as to weather it shoots good with a jump or a jam. Now days I seem to believe that it comes down to what bullet make you shoot. As far as jamming them or jumping them goes. My .308 shoots the 175gr bergers really good. With the same powder charge and with the 175gr SMK they must be seated with a .030 jump to achieve the same accuracy as the berger's. Something I found a cpl of weeks ago was that I can achieve the same accarcy with the 175gr SMK's with a .010 jump as well, But I have to up the charge .6 gr of powder. What I noticed as I was shooting over the chrony is that the SMK will shoot good when they get up to the same volicities as the berger's do. It just takes a different seating depth or powder charge if not both to get into the same accuracy node that the berger's are in. I really don't know if I'm 100% right but the evidencie of my findings is pointing me into that direction. I could be just as confused about it all myself so don't hold me to this. Just passing along what I have experienced lately.
Mark

 

[deadlyswift]

OOPs, I forgot to add that the berger's are jammed .010! Sorry about that ;D

 

[jo191145]

60,000 PSI in a PPC is just a starting load ;D


Most over the counter huntin style bullets such as Sierra, Hornady etc usually like a little jump. A good place to start is -.020" from just touching.
Bergers or custom or VLD usually like a little jam. A good place to start is +.010" past just touching.
None of that is carved in stone anywhere. Whatever works works.

I would suggest you buy a Hornady Cartridge OAL set and comparators. Its the best way to find "just touching"

Speaking of pressures tho. I can't recall ever having a "jammed" load that worked at anything less than competitive pressure levels. Anyone have a jammed slow load that shoots consistent?
Just wondering.

 

[deadlyswift]

I also believe that the design of the ogive from the berger and the SMKs have a lot to do with rather they are jammed are not. I do remember someone on this site sent me a screen shot from Quickload on the load that I'm shooting the 175gr. bergers with and it seems like Quickload says I'm running around 59,000 psi.
Mark

 

[7x57 Shooter]

I have seen bench rest shooters do this before, I don't care for the procedure as it raises pressures. Bench rest shooters that jam their bullets don't use full loads that you would find in hunting ammo, they shoot for accuracy rather than velocity.
For hunting I full length resize to ensure the rounds will chamber and extract properly. For range work I have a bunch of neck sized brass for different the cartridges that I shoot.
Hunting ammo shouldn't be loaded the same as bench rest ammo, the applications are totally different. Follow your reloading manuals, always start at the starting loads and work up to accuracy of your rifle without exceeding the manual.

BUNK!!!!

Benchresters (at least LR benchrest) shoot as fast as possible. They will find 3 or four "nodes" and use the top nodes even if they are at the ragged edge!!! A lot of guys I know shoot loads that would SCARE most hunters. I have only had ond BBl that I shot slow. The rest are at the edge!!! I have several tubes that need to be loaded down when it gets warm out, and can not be shot when it is hot out with out sticking the bolt. And most JAM their bullets to some degree (at least for VLD bullets).

Also...I am pretty sure that the PPC guys run at 60000 + psi.

I don't shoot bench rest, but the ones I watched said they shot for accuracy with velocity being second.

 

[4xforfun]

Jo,

My very first...and best to date....1000 yard comp bbl...a Spencer 1-10, just loved 74.0 g RL 25........WAY slow....around 2700 fps. I had gone as high as 85 gr RL 25. I used Berger 210 VLD bullets jammed 20 thou......I pretty much cleaned up that year. Of course, silly me shot it in F class, hunting....plinking...ect...WASTED A TRUE HUMMER BBL JUST F&*&%#G OFF!!!!!

7x57 shooter,

Yes they do shoot for accuracy.....but in a PPC that is usually WAY HOT.

 

[BigBamBoo]

Thanks Lynn. I have been doing it this way (starting jammed and working down) since I started reloading. I too see a lot of folks start with a jump seating depth and only play with powder charge weight. I guess what ever works, but for me that technique never has worked for me.

Yep...I sort my bullets by ogive. I REALLY....did I say REALLY....dis-like reloading. Or at least the whole case prep, bullet sorting, etc.,etc. part of it. Makes me want to shoot a .308 with FGGM ammo and call it good!

I do not know where the hunting stuff came from in all the post above...this is a bench rest forum I thought?? I am reloading for 600 and 1000 yard target shooting only.

Take care,Stan

 

[45bpcr]

Interesting. For target guns I've always started with the bullet touching the lands and then worked up with charge weigts. I'd never thought that varying deating depth by .001 would make that much difference. Guess I'll have to try it!

Thanks,
Craig

 

[gunrac]

I do not know where the hunting stuff came from in all the post above...this is a bench rest forum I thought??

Take care,Stan

: Shame on me, a hunter-reloader, for wanting to get prospective view's from the BR guy's.

Nearly 12,000 member's. Do you seriously think they are all BR shooter's? ID ten T.

 

[mikecr]

The real question that should be in everyone's mind is; Why does distance X w/resp to lands make such a huge difference?

I know it does. But clueless as to how...

 

[stgw77]

The real question that should be in everyone's mind is; Why does distance X w/resp to lands make such a huge difference?

I know it does. But clueless as to how...

It is explained here why is so:
http://www.the-long-family.com/OBT_paper.htm
Hope it helps.
Klemen

 

[Dgd6mm]

lynn, that is excellant info. I've never started working up a load with it being jammed to start. Now I can't wait to do it.

 

[mikecr]

IMO, even if the OBT 'theory' had ever been proven, it hardly relates to distance from the lands as a tuning adjustment. In the article, it is implied that you can move in and out and back into another OBT while adjusting seating. I have never seen this.

Seating isn't minute tweaking of timing(I used to think this).
I could go through full increments of a powder, and never affect grouping like a few thou of seating depth change!
I've even re-load-developed at different seating depths to conclude that there is ONE best seating depth for a given combination, and that it could never be predicted.

In other words, I could not pick just any 'preferred depth' and work up an equal performing load by other means. It's too major of a change. I know multiple nodes are reachable with powder, but not seating depth adjustments.

So I just don't buy into any particular depth being right for any particular bullet, as a general rule of thumb.

 

[Clark]

I jam most bottle necked rifle cartridges, for increased accuracy.

I don't jam 44mag or 45 Colt rifles. They are more accurate with a jump.

 

[BoydAllen]

First of all, let me define my terms. To me,as gathered from early issues of Precision Shooting, jam is the greatest length that a bullet may be seated to, for a particular neck tension, without being seated farther into the case neck as the round is chambered. Form this definition the use of the word has been (in my view) corrupted by using it to mean any seating depth that is longer than "touch". Within my set of definitions, one may describe a seating depth as so many thousandths of jump, touching, so many thousandths longer than touch, so many thousandths off jam. or at jam. One can also use relatively light neck tension, and intentionally load longer than jam so that bullets are set back in the case as a round is chambered. In the world of position shooting, this is referred to as soft seating. The current and three time NRA National Long Range Champion, John Whidden used this technique.http://bulletin.accurateshooter.com/2010/08/whidden-shares-secrets-of-championship-long-range-rifles/ The starting place for my personal load work up technique involves a short range (100 yd) one shot per load, ladder/pressure test, using a seating depth that is chosen based on previous experience with bullets of similar ogive shape. For instance, I usually find that many varmint bullets seem to do their best when seated .006 to .010 longer than touch. On the other hand, for my 6PPC single radius ogive bullets seem to do their best when the rifling marks on the bullet are about one third as long as they are wide. For double radius bullets, for the same caliber, a longer seating depth, usually a few thousandths shorter than jam, seems to work best. For any of this, loading at the range, using a chronograph and wind flags is the fastest way to get the job done. Ultimately, one needs to try different loads, in an organized manner, and keep notes that anyone could understand, for future reference.

The short answer to why different seating depths change accuracy is that they change the timing of when the bullet exits the muzzle in the barrels swing cycle, and since some points in the swing of the barrel produce better accuracy than others, loads that time the exit so that it happens at the best point are more accurate. Since the barrel continues to vibrate at a regular frequency, there are multiple opportunities for bullets' exit timing to occur at the most advantageous point it the cycle.

 

[fayettefatts]

OK... so if you want to test loads to determine which seating depth is best and start by soft seating the bullets, how much should the length be changed for each subsequent load? Increments of .001, .005, .010?