Author Topic: Bullet seating depth (Read 1259 times)

quickdtoo · « **on:** November 24, 2004, 05:47:11 AM »

Here's an interesting link with bullet seating depth pressure differences.

http://www.shootingsoftware.com/pressure.htm

Fred M · « **Reply #1 on:** November 24, 2004, 06:19:59 AM »

Quick
This is pretty deep stuff, more than I can use or need to use. But a great tool for a scienetific experimenter. 25 years ago I would have entertained the idea. Besides being retired where would I ever find the time to use this intrument, ha?

I aquired another sublimental deer tag and I go hunting this pm with a friend who needs the venison.

quickdtoo · « **Reply #2 on:** November 24, 2004, 06:39:47 AM »

The reason I posted it was the big difference in pressure created when the bullet is seated into the lands compared to off the lands, it's towards the bottom of the page under other traces.

Fred M · « **Reply #3 on:** November 24, 2004, 07:57:01 AM »

Quick.
You will note that the pressure variation with bullets on the lands are more uniform and with less diiference than the bulllets 30 thou off the lands.

A 10% difference in pressure is not abnormal and as a matter of fact quite common. If you tune a rifle like I do with the bullets into the lands than there is no problem. It is a well known fact that loading bullets into the lands will provide more uniform ignition and better accuaracy.

In a normal tuned load the higher pressure of perhaps 10% is inconsequential when it is taking with that in mind. Quick Load points this out and advises of the 10% differenc in pressure.

I know there is a difference in pressure when loading into the lands because it shows up clearly on the Chrono with higher velocities but not a whole lot. Also it is there but I have never worried about it with tuned loads.

That is not to say you can indiscriminatly change seating depth with max loads into the lands.

Mac11700 · « **Reply #4 on:** November 24, 2004, 08:05:20 AM »

Quote

That is not to say you can indiscriminatly change seating depth with max loads into the lands.

That's why a beginner reloader should follow the recomended cartridge overall lenght provide by the bullet manufactures...until such time as he/she has aquired the means and knowledge of diserning pressure signs for that paticular rifle...since each rifle will be different...the suggested O.A.L. is a safe guideline to follow.........

Mac

Quick....thanks for the link...lots of information to go over..

quickdtoo · « **Reply #5 on:** November 24, 2004, 08:15:03 AM »

Since seating the bullet too deep can also increase pressure, does one offset the other to the same degree? I've read a bunch about seating to or into the lands increasing accuracy but others say it doesn't always hold true and just depends on the particular rifle. It's almost as controversial as the nickled brass topic! :? My particular interest lies in the fact that my .45-70 barrel has a long throat, contact with the lands comes at 2.575". To me that means I could load to slightly longer COL than 2.55" but well short of the 2.575" and reduce pressure slightly but maybe increase accuracy a little. This all assumes that the load I work up from the start always uses the same COL.

Donaldo · « **Reply #6 on:** November 24, 2004, 12:59:29 PM »

I was loading for my 223 UV the other night with some 40 gr. Vmax's. Thought I might seat them as close to the lands as possible. So I got out my handy dandy home made cartridge length gage to check the OAL cartridge length. (gage made from 2 223 cases) On my rifle the throat is so long you cannot seat the bullet in the neck and have it contact the lands. Seating the bullet only minimally still leaves a good jump to the lands. Maybe a long bullet, 60 or 70 grns could be seated long enough to contact the lands, but I think it might wobble a bit coming out of the Handi barrel.

Fred M · « **Reply #7 on:** November 26, 2004, 10:23:43 AM »

Quick.
There is a bit more to the seating into the lands. One overlooked factor is case neck concentricity. An eccentric case neck and a bullet loaded into the lands will worsen accuracy in most instances. This of course is also dependable on the amount of eccentricity. Just visualize what is happening specially in a Handi where the lands are mostly out of reach except with very long bullets.

The bullet is cocked from the beginning and is slammed sideways into the lead so to speak. So it is best to put it straight, that is deep into the case neck so it gets a halve ass straight start.

I just prepared another box of 25-06 for the Ruger #1. To get the best possible case necks I start with Win 30-06 new brass.

I neck this brass down to 25-06 in one operation. When you do this you end up with thicker case neck walls that the straight 25-06 brass.

What you will find is an exaggerated case wall variation, because necking down will increase the neck wall thickness. I found as much as .0025" difference.

Next I outside neck turn the case necks to .0138". This will almost do the whole circumference of the case neck except for a few low spots. 75% of the circumference will do quite well in a hunting rifle loads.

In the Ruger chamber the loaded cases will end up with a most ideal .0015" radial neck clearance

A loaded shell will in most instances with a concentric necks shoot very well indeed when the bullets are loaded into the lands with a developed
load. I have quite a few rifles when so loaded and prepped will shoot extremely tight groups, and these are no flukes.

quickdtoo · « **Reply #8 on:** November 26, 2004, 10:53:48 AM »

Well, I'm sure I can't get even close to the lands with the "little" 300gr bullets in the .45-70, just thought it may make a bit of difference with slightly less pressure if I'm pushing the envelope trying to reach the 22-00-2300fps goal. :wink:

Fred M · « **Reply #9 on:** November 26, 2004, 01:23:13 PM »

Quick.
What do think the pressure is with that 300gr bullet. With that huge expansion ratio your pressure should not be very high. I would seat the bullets as far out as you can and still maintain a good bite on the bullet in the neck. O.A.L in a single shot can be quite flexible, me thinks.

Are you in the 35-40 kpsi range which I doubt very much? 55gr of H4198 with 300gr bullet will get 2221 in 24" barrel at 27600cup and that is not stretching anything in a Handi, but perhaps do a number on your shoulder.

I hate that cup and psi data mixed on the same page.

quickdtoo · « **Reply #10 on:** November 26, 2004, 01:56:23 PM »

My starting load will be 50gr H4198, not worried about recoil, with a 12 lb handi and a limbsaver recoil pad, recoil won't be a problem! That's what my new scale says it weighs! When I hunt, I'll take the 2.5lbs of lead out of the stock! :wink: Thanks Fred!

Tim

Fred M · « **Reply #11 on:** November 26, 2004, 03:41:52 PM »

A 12lbs Handi, man you must be strong like bull. Here I am squawking about a 9 lbs Ruger #1 that I can barely hold up for any amount of time.
My 25 Hunter weighs 8.5 but feels a lot lighter and seams more agile.

I lost a lot of strength in my left arm when they they operated on the rotator cuff. Not anywere near as strong as it was. Have to keep my hand way in to shoot off hand. But you get a fast swing. It works ok.

Mac11700 · « **Reply #12 on:** November 26, 2004, 06:39:25 PM »

Quote

Are you in the 35-40 kpsi range which I doubt very much? 55gr of H4198 with 300gr bullet will get 2221 in 24" barrel at 27600cup and that is not stretching anything in a Handi, but perhaps do a number on your shoulder.

I hate that cup and psi data mixed on the same page.

Fred:

Don't be so quick with the pressure data...if I'm not mistaken...Quick is using the Nosler Partiton...and also the Lee Factory crimp die...and that 55 grains of H4198 will be close to pushing the pressure envelope of the class 2 45-70 loads...the partition has a longer and thiicker bearing surface on it than any other 300 grain 45-70 bullet out there...and that does make a huge difference in pressure with this combination...I've been loading it for 2 years now...and have discussed this with not only the techs at Hodgdon's but also those at Nosler...it's still safe...per Hodgdons tech's but the folks at Nosler want you to stick with their recomended loadings...

Mac

Fred M · « **Reply #13 on:** November 27, 2004, 02:49:15 AM »

Mac
55 grains of H4198 with a 300gr Sierra HP bullet is a recommended load by Hodgdon and 27600 cup is not even close to Handi's nominal strength.

Being an HP it would even have more bearing surface than a Nosler partition. Even at that 27600 cup has to be quite docile in a rifle in spite of the kick.

Mac11700 · « **Reply #14 on:** November 27, 2004, 05:12:01 AM »

That's true Fred...but like I said...I do believe he's using different components than what the data was made for...and that does make a huge difference...also...when you use the Noslers and a heavy crimp by the factory Lee crimp die.. you will notice a significant increase in pressure,same too for changing the brass...to say...the Remington nickle cases...I'm fully aware of the changes...and use this powder and the mentioned components...and while I didn't send in my loads to be actually tested...another person did...he was trying to get into the commercial reloading buisness...and the results he got where a-lot higher than using the Hornady or Seirra 300 grain bullets..One would think that you can just substitute a Nosler bullet for a Hornady...or a Seirra....you can...but a major increase in pressure will result...this has been proven time and again by differnt folks testing the load themselves and then sending it in...this has been knocked around on the Marlin forums for sometime...so you can check with the guys on that forum...like I said...earllier...the load is safe...but the pressure is near the max of the class #2 loadings...the velocity I get from that combination is right at 2300 fps from a 18" barrel out of a 1895GS...do the math...theirs was from a 24" barrel...

Mac

quickdtoo · « **Reply #15 on:** November 27, 2004, 05:20:49 AM »

I am using the components Mac has mentioned, but I'm starting at 50gr and working up slowly, this old boy don't want to get hurt anymore than you fellas. And I certainly don't want to hurt my Handi! :eek: I've invested in all the equipment necessary to do the load work up as Mac has suggested and do it safely. Even bought a bullet comparator so my COL measurements will be accurate and consistent.

Thanks,

Tim