Question about seating pressure

[deadon]

I know that smokeless powder needs a certain amount of seating pressure to go boom. I have been thinking and wonder if I have gotten all wrapped up in this so much that I am not thinking straight. Some powders need much more pressure to ignite that others. I am now shooting 4759 and never had a misfire as long as I poured powder down the barrel Are there reasons other gun goes BOOM to need so much pressure. I shot some 250 shock waves with supplied easy glide sabots. I pushed them down the barrel with one hand, They fired, Shot 1 1/4" group. If one sticks with 4759,5744 or N110, why does he need to pull his shoulders out of their sockets loading bullets? Please help me understand all this?

[artjr338wm]

So far to date I have shot my 10ML-II almost 700 times. 90%+ of those shots were made up of a combination of 300XTPs, 290TMZs, 245SFs, and to a lesser extent of about 10% or more of Barnes Os, S-eaters Mod/Rems, 250XTPs, and a few 300/SSTs. Used in order of amount and use H-4198, 10X, IMR-4198, 4759, N120, H-4198, RL-7, and N110.

Sabots used in order of preference & accuracy, Harvester BLK CR, Yellow CR, Harvester made for Knight Yellow NON-CR, plane BLK, and Red CR. From MMP, HPH-12, HPH-24, MMP 3-petal EZ black. My 10ML-II prefers Harvester Sabots like we humans prefer O2 over C02.

After all that and having them load from easily with one hand only to all my strength and two hands + all my body weight I can bring to bear, I have yet to suffer a miss fire with my 10ML-II.

Also based on the extensive amount of info I have read here on miss-fires, I'd estimate well over 95%+ of all miss-fires are due to a to loose a sabot/bullet fit to supply the back pressure needed for the primer to ignite the powder, as smokeless powder is markedly more difficult to ignite than BLK-PWDR or BLK-PWDR subs, at least that what I have read over and over, but have no 1st hand experience to know that is in fact the cause.

So in short, based on my experiences, unless while loading a sabot-ed bullet it literally almost falls down your barrel, it should fire.

Now for a trick I was taught here I will share with you now. Long before any bullet or sabot combo I am considering firing at the range actually is shot, I subject it to test loading in my basement first. A loooong time ago I developed a feel for what should be the minimum amount or loading resistance and or tightness that is needed for a bullet/sabot combo to shoot accurately.
If during 3 or so test loadings I do not strongly feel a bullet sabot combo meets my tightness requirements, I do not bother with it at the range. You be the judge, but if you also adopt the habit of test loading sabot/bullets at home first, it will most likely serve you as well as it has me at preventing miss fires.

As I knurl about 75% of the bullets I shoot, test loading is a absolute must for me.

I feel with out a doubt, doing this test loading will eliminate the chances of a miss fire due to too loose a sabot/bullet fit by at least 95% or more.

I do this test loading on a 100% clean and dry oil free barrel.

I truly wish I could offer a specific pressure in pounds that my
sabot/bullets load at, especially my most accurate loads, but I broke my high $$$ scale for weighing people years ago and never replaced it.

[deadon]

Is knurling just to make the bullet fit tighter OR could it also help keep the bullet seated to the sabot wall? What I am thinking is, If a combo loads at say 20#s of pressure which WILL go boom with 4759,will knurling keep the bullet from slipping inside the sabot which would effect accuracy?

[artjr338wm]

Deadon, anyone who knows better feel free to correct me, but as I understand it and believe as true, knurling a bullet will accomplish two things:
#1-Knurling will definitely increase a bullets OD (of this I am 1000% certain as I measure after knurling)
#2-Knurling a bullets copper jacket will dramatically increase its roughness causing it to go from baby-butt smooth to sand paper roughness and there by also cause it to bight into and grip a sabot much better and consequently ensure it spins or orbitraits(sp?) down the bore as well as possible. I also know this to be true because my recoverd sabots all show clearly defined inprints of the knurling on the inside of the sabot petels.

[deadon]

Art, God bless ya ;D It makes since to me and that is why I got good accuracy with the lose fitting SWs. When I say lose I mean nice firm loading pressure that I could do on a stand with the factory ramrod. Thank you Sir, very much, Rusty

[artjr338wm]

You are welcome Rusty. As a added note, I'm sure you have seen my posts about my results of shooting knurled TMZs and Spit Fires. Knurling both of these all copper bullets from .450" up to .4535-.4545 served to cut my 200yrd groups from 3.5-4.5" down to 2.5" and less, quite a bit less.

I have no doubt what so ever the increase in accuracy was due 100% to knurling as knurling= a much tighter fit and also insured the bullet spun well enough to be stable in flight and in truth [glow=red,2,300]especially when shooting all copper bullets[/glow], knurling = tight fit and tight fit and good spin are IMHO one in the same.

Arthur.

[deadon]

Arther,What sabot did you use with the barnes boat tails? Harv has new one they may sell, if the test work out, especially for the boat tail bullets. Boarhog and a couple of others are testing them

[artjr338wm]

I am using their new (well it was new about 7-8 months ago) Yellow CR sabot for use only with boat tailed bullets, and to be ultra specific according to the Harvester Rep I spoke with was desigh specifically for use with Barnes all copper BT bullets. I have enjoyed excellent accuracy using the new Yellow CR sabots with 290grn TMZs knurled up to .4545" from a factory OD of .450".

To my knowledge you can only by them direct from Harvester.

I also discovered by experimentation that the factory supplied sabot made by Harvester for Knight that came with the bullets (these are also yellow, but smooth sided with no ribs and visibly thicker) I bought from Cabelas on C/O Knight called them something else but they were actually Barnes 290grn TMZs and 245grn Spit fires made for Knight ML by Barnes. I though what the heck I have 100s of them give them another try. Well it turns out they work even better with the 245 Spit fires than the Harv/Yell-CR sabots do. The Knight supplied sabots are with out a doubt a more durable sabot.

[deadon]

Art, The sabots that came with the barnes 245 semi spitser HPs packaged by Knight are Blue and are made by MMP I think. If you turn them upside down the bottom cup is sort of stepped down. Like miniature stair steps all the way around going down into the cup. Are they the ones that shot better than the Have yellow CR

[ozark]

When I shot the ML I learned much from members of this board. One thing I recall being set solid in my three brain cells is that loading pressure and compression applied to the powder are different animals. Example: If loading requires say 30 pounds of pressure to push the bullet down the bore when the sabot/bullet contacts the powder it stops. Additional force is needed to apply pressure to compress the powder. To insure this occured I was taught to use the palm or heel of my hand to give the ram rod a couple or three downward blows. Is this still a good idea? This idea deals with loading pressure plus additional pressure to compress the load. The practice may be obsolete now.

[deadeye]

my opinion on seating pressure is at least approx 30lbs or more. i feel consistency is the key whether it be 35,50,80lbs. i have even put so much pressure i could feel the sabot cup give a little-thats the breaking point imo