Seating shorter than mag length

[PD Gohil]

Working on tightening up groups, and disadvantage to seating deeper than mag length? Obviously this is going to increase pressure and increase the jump. But I'm trying to chase a little tighter group. Thanks

 

[Ned Ludd]

When using mag length as your working MAX COAL, there is only one direction you can go. You should still be able to find an optimized seating depth, but the increase in pressure will largely depend on how far off the lands you have to seat the bullet to find the sweet spot. I have found that I can generally moved a jumped bullet about .010" to .015" in either direction without changing the pressure enough to reliably alter velocity. If you have to seat the bullet .020" to .030" deeper (or more) to find the sweet spot, I would suggest reducing the charge weight sufficiently to maintain the same velocity you had with the bullet seated out farther. In my hands, that might typically be only a few tenth grains at most, because I usually don't have to seat bullets that far from the lands in tuned loads. However, if you find it necessary to seat them much farther off the lands, the load may need to be reduced even more.

 

[Richard Coody]

My hunting rifle likes berger vld's 0.130 off the lands. Considerably less than mag length. Never would have thought it. Tried the berger seating depth test. All i can say is it works.

 

[PD Gohil]

I haven't tried finding the lands, as I have no desire to shoot this rifle hand fed. Should I anyway? Just to find and know ? What good would come of it?

 

[D-4297]

Ned Ludd gave a excellent response to the general topic , but having some specifics to work with would allow for more definitive and accurate responses from all corners . How bout telling us caliber , cartridge , powder / load weight , and bullet used . There are many highly skilled and knowledgeable people here who could help resolve your issue . Help us out here ...

 

[Ned Ludd]

I haven't tried finding the lands, as I have no desire to shoot this rifle hand fed. Should I anyway? Just to find and know ? What good would come of it?

Finding the distance to "touching" lands in such a situation is not essential. Use the MAX COAL that will reliably feed from your mags as the starting point to work up the charge weight. Then, do a seating depth test with the bullets seated incrementally farther off the lands. If you have to move them farther than about .020" to .030", then a reduction in charge weight may be in order. Alternatively, you can use the MAX COAL for mag length and carry out the Berger VLD seating depth optimization as Richard suggested, which is designed to cover a very wide seating depth range in coarse increments. Again, you'll moving the bullet quite a ways in/out in that test, with MAX COAL for mag length as your baseline, so charge weight may need to be adjusted.

https://bergerbullets.com/getting-the-best-precision-and-accuracy-from-vld-bullets-in-your-rifle/

 

[swd]

I’ve seen some rifles shoot extremely well at over .250” off so don’t be shy about pushing them back.

 

[dellet]

I haven't tried finding the lands, as I have no desire to shoot this rifle hand fed. Should I anyway? Just to find and know ? What good would come of it?

It’s always a good idea to find the lands. Depending on the cartridge and bullet combination, it’s possible to have bullet that will jam hard at less than mag length. A good example would be 150-155 grain .308 bullets. Between hunting bullets, VLD and solids, length will vary more than .250”. Nose profile and base to ogive length can surprise you every now and then.

There are also bullets known to be more jump tolerant than others, so don’t be afraid to try something that might not be your first choice, that is a known performer.

 

[PD Gohil]

Savage 10 BA Stealth. 24" barrel. Once fired Hornady brass full length sized Shoulders .003 back.. 002 neck tension, 156 Berger's, rl16 working 2 loads one at 39.2 and one at 41.0 grains Federal 210 primers.. I have not seen any signs of pressure yet. I had some errors on my chronograph so I have to reshoot again. But over the course of the last range sessions the 41.0 grain groups are tighter but with a higher SD.

 

[David Christian]

Savage 10 BA Stealth. 24" barrel. Once fired Hornady brass full length sized Shoulders .003 back.. 002 neck tension, 156 Berger's, rl16 working 2 loads one at 39.2 and one at 41.0 grains Federal 210 primers.. I have not seen any signs of pressure yet. I had some errors on my chronograph so I have to reshoot again. But over the course of the last range sessions the 41.0 grain groups are tighter but with a higher SD.

@PD Gohil, powder nodes are typically 3% a part. So if 41.0 is correct, your next lower node should be at 39.8. Or if 39.2 is spot on, your next higher node should be around 40.4. As @Ned Ludd stated earlier, play around with your seating depth to work with in your mag length and tweak your powder charge appropriately.

 

[PD Gohil]

@PD Gohil, powder nodes are typically 3% a part. So if 41.0 is correct, your next lower node should be at 39.8. Or if 39.2 is spot on, your next higher node should be around 40.4. As @Ned Ludd stated earlier, play around with your seating depth to work with in your mag length and tweak your powder charge appropriately.

I was doing ladder tests and pick those weights as the middle of relatively close velocities. Maybe I should restart my ladder test and do it differently.
I read the article on the berger seating depth test and we'll do that for sure once I settle on a charge weight.

Thanks all

 

[RegionRat]

Don't be afraid to explore larger jumps. Some of the nicer sporting rifles back in the day used to come with lots of free bore. The Weatherby Magnums come to mind and were way above average for accuracy when compared to the context of off-the-shelf sporting guns.

There is nothing new or wrong about searching for a deeper seating depth before drawing conclusions and bulk loading. It was news to me that the current thinking was to get close to the lands and chase them. That isn't new either, but can be a real pain in a match gun that might run for several days in a row at some of the bigger matches. By then, those lands are out farther than when the week began and the ammo loaded ahead of time no longer reaches the intended gap.

Here is a little more reading on a seating depth exploration that just proves everything old is new again...

https://precisionrifleblog.com/2020/04/15/18-shot-bullet-jump-challenge/

 

[tirednlost]

Personally I have always found the lands. I’ve never shot from there but I like to document the info in my notes. If some day down the road I have load issues, I have a reference to see if the throat is starting to go. Maybe it’s not important, just my thoughts. I just like to track a good amount of info Incase I run into issues

 

[Zero333]

I have a 300winmag deer load with 130 TTSX jumping more than 0.200" and it's the most accurate load in that hunting rifle.