Seating against the lands???

[Powder Burn]

I have been reading about bench rest shooters seating the bullet into the lands. I'm wondering if this will create more pressure. I am breaking in a new Model 12 Savage in a 6.5 x284 . Anyone know what is the best seating for load development and the seating question? ???

 

[RossL]

Many seat their bullets into the lands of the rifling. Bergers often shoot their best that way.

As for pressure: if you start working up loads with the bullet already into the rifling it will work fine. At some point you will get signs of high pressure just as you would with a bullet seated away from the rifling. The bullet manufacturers books caution against doing this because their load data is done with all bullets seated to a much shorter OAL/sammi spec.

What my friends and I like to do is seat .010" into the rifling and work up a load getting an idea of what charge weight works best. Then we move the seating depth so the bullet is seated deeper into the case and away from the rifling in small increments to see if that fine tunes the load. In a few cases the load actually got better with the bullet seated deeper INTO the rifling. If you go too deep and you have to remove a unfired round the bullet could be left in the rifling spilling powder as you pull out the case.

Another interesting method is to soft seat the bullet. The neck tension has to be low but enough to hold the bullet in place for handling etc. The bullet is seated out far enough so it will bump into the rifling and as you cam the bolt shut the bullet will move deeper into the case. When the bolt is fully shut the bullet is barely touching the rifling. The advantage here is that as the throat wears the bullet will continue to have the same relationship to the rifling. I read that Dave Tubb does this with his 6XC and 115 DTAC bullets. This would not be a good method for repeaters. It also might now allow you to remove a loaded round, you would have to check to see.

Hope this helps

 

[TonyR]

+1 on Ross's comments. Generally, I have found that VLD type bullets work better jammed 0.010-0.015 inces into the rifling and conventional boat-tail bullets work better off the lands. If I am doing load development, I will start off with an 0.010 jam with the VLDs and either touching or a bit off the lands with the conventional BT bullets. I proceed as Ross has outlined. An exception would be new cases. I was firing forming yesterday some 6.5X284 Lapua cases for my 284 Shehane and the new cases had about 0.008 inches of headspace compared to my fired cases. So, I loaded the Sierra 168 MKs I was using to a hard jam just to control the headspace even though it is a conventional BT design. I have had mis-fires with new cases in another chambering I shoot and that one required a false shoulder to control the headspace but jamming has always worked with the 6.5X284 brass.

 

[Laurie]

+ 1 on what Tony and Ross have said. Also, read the 6.5-284 section on the main 6mmBR site - there are several comments on this issue with people's pet loads for various bullets.

If you do seat the bullet into the lands, you must beware of pulling it on extracting a live round and leaving it stuck in the barrel. A cleaning or drop rod quickly and easily sorts that but cleaning every last powder kernel out is another matter!

Finally, either seat them well in or well out. Trying to be just off the lands or just in with people on the forum quoting single figures (in thou') risks having some touch and some not - a cast iron guarantee of increased group sizes.

Laurie,
York, England

PS nowadays, many if not most, BR shooters keep them off the lands.

 

[artbosco]

I have been reading about bench rest shooters seating the bullet into the lands. I'm wondering if this will create more pressure. I am breaking in a new Model 12 Savage in a 6.5 x284 . Anyone know what is the best seating for load development and the seating question?

I'm a benchrest shooter that seats bullets into the lands because it's part of my fine tuning process with both my 6PPC and 30BR. It does raise pressure as does increased neck tension through the use of bushings. The reason it's done is to fine tune the BARREL. The best seating depth [on or off the lands] for your 6.5X284 will be determined by your particular barrel. Each one is unique. Here is a sample method, there are many more, that will help you determine your tune. Watch for your barrel's response on the target.

Working Up a Load …. by Lee Euber

1. Polish bullet with steel wool. Initial seating depth achieved when bullet is marked by all lands.

POWDER

2. Load 3 cases in a low grain load. Increase each 3 case load by .5 of a grain, and then shoot. Increase loads until primers show pressure.

3. Identify shots that grouped well, not so good, and then good again.

4. Pick load that shot the best. Load 3 cases with .1 grain less, and 3 with .1 grain more, for another comparison.

5. After picking charge for use, load 30 cases with the same powder charge.

SEATING DEPTH

6. Load the 30 cases in groups of 3, increasing the seating depth from touching the lands to jumping about .040 of an inch, in increments of .005 of an inch.

7. Shoot all 30 rounds without cleaning or clean after each 10.

8. Use ONE fouling shot after each cleaning.

9. Select load that shot best. Load 5 cases with that powder charge and seating depth.

10. Load 10 cases, 5 with seating depth .005 less than benchmark figure and 5 with .005 more.

11. Can compare more than once or change seating depth by .001 or .002.

12. Once you’ve picked the best seating depth, load 15 cases at that depth.

POWDER

13. Check first test by varying charge by .1 grain, for each 5 shot group.

14. Shoot in a medium wind condition, letting the gun do the work.

SEATING DEPTH

15. After picking the best load jumping the lands, compare it with the load that touches. Compare these loads again and again, on different days, in varying conditions, deciding which one is best.

16. If it doesn’t shoot to your satisfaction, restart with a different powder.

NECK TENSION

17. If you decide on the load that puts the bullet in the lands, be sure neck tension is tight enough to hold the bullet uniformly.

 

[artbosco]

PS nowadays, many if not most, BR shooters keep them off the lands.

To the Contrary. Not at point blank / short range.

 

[Laurie]

PS nowadays, many if not most, BR shooters keep them off the lands.

To the Contrary. Not at point blank / short range.

That's what I was always given to understand too, but my enquiries amongst the small UK 100yd BR shooting community suggest more than a few jump bullets a bit. But maybe I've misunderstood them. I know that Mike Ratigan (Extreme Rifle Accuracy) says:

"There's an overwhelming majority of rifles that when tuned to there [sic] best, the bullet will be in contact with the rifling."

I'll found out what works for my own rifle sometimes in the coming weeks when I prepare brass and work up loads for a secondhand 6PPC HV-class rifle for 100yd benchrest. (We don't have any 200yd BR in the UK.)

 

[TonyR]

Laurie.
Is there some sort of regulation in the UK which prohibits or discourages jamming bullets?

 

[Laurie]

Tony,

no not at all. Many people won't do it for disciplines other than benchrest (which is small here, numbers wise) because many ranges can see the command given to unload and stand back. Most of the ranges used by civilians are Ministry of Defence military ranges and shooting is regularly disrupted on some by units moving across the field of fire. Civilian club owned ranges don't have this problem, but walkers trespassing by accident or design across range boundaries, farmers or livestock appearing etc can see a complete halt and unload ordered.

We live in a small set of islands with a lot of people and 'right to roam' legislation was introduced over all open spaces a decade ago. Although there are 'exempt areas' which for obvious reasons include firing ranges of all types, the more militant 'ramblers' are very hostile to moorland and other open unfarmed areas being closed to them for any reason, and then there are the many stupid individuals who simply don't check maps and believe they have a God-given (or at least, Parliament-given) right to walk absolutely anywhere that takes their fancy!

The one thing you can be sure of here is that if you do jam-seat, you will eventually have a problem as a result. Our only two ranges that regularly see benchrest shooting work on the step-back and leave the loaded rifle on the rests and bags if an emergency halt is required.