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Them marketing people don't like it when you ask real questions...

I can't provide numbers,but my guns easily produce 150fps more with the grooved tsx or mrx than they did with the original x before showing pressure signs.

I don't have the option of getting quantified pressure tests made for my loads. But of late I have had several indications that loads with TSX or Barnes Banded Solids produce less pressure than the same loads with "conventional" lead core bullets. I have to admit, that I make the assumption: "less muzzle velocity ~ less pressure". That may well be a simplification when it comes to peak pressures, but it sounds a reasonable assumption of the whole area below the pressure graph.

Case in point: 9.3x62 - using the same load of RL15 in a 22" barrel behind a 250 grs Nosler AccuBond, a Barnes TSX and a Barnes Banded Solid produced velocities of about 2600, 2500 and 2400 fps respectively (all measured just above freezing point - 1-2 degree Celcius).

- mike

mho, are those numbers listed in the correct order?
Peter

Some real answers to a real question:

Below are pressures obtained with a variety of 500gr .458 bullets. The copper plated lead bullet was 510gr.

Bullet Type -------- Powder Charge - Velocity - Pressure PSI
GS Custom drive band- S335 78gr ---- 2201 fps - 59 755
Bronze Grooved Solid- S335 75gr ---- 2191 fps - 60 480
Copper Solid Shank--- S335 77gr ---- 2190 fps - 60 963
Copper Plated Lead--- S335 74.5gr -- 2134 fps - 60 755

In a separate test, after the above one, we wanted to determine if an experiment was moving in the right direction:

500gr .458 GSC Drive Band Bullet - S321 76.5gr - 2182 fps - 61 355 psi
500gr .458 GSC Drive Band Bullet - S321 76.5gr - 2192 fps - 60 175 psi

We felt that maintaining speed and dropping more than 1 000 psi of the pressure was an improvement.

With a 450gr .458 HV bullet, we got 2307fps at 56 056 psi. No comparative testing was done with other 450gr bullets.

Shot start pressures for a variety of bullet types have been determined as:

Copper Mono Drive Bands ------ 1450 to 2900psi
Bronze Mono Drive Bands ------ 3200psi
Copper Jacket Lead Core ------ 3600psi
Copper Mono, Grooved --------- 3700psi
Copper Solid Shank, Grooved -- 3700psi
Bronze Mono, Grooved --------- 4400psi
Copper Solid Shank, Smooth --- 5100psi
Jacketed Copper a frame type - 5400 to 6400psi
Bronze Mono, Smooth ---------- 5800psi

Pressure testing was done at Somchem Ballistic Proof Lab

Note that shot start pressure as well as maximum pressure can be reduced by using undersize bullets or bullets that effect a bad seal in the bore. This gives advantages in the short term but long term, the price will be paid in throat erosion.

The trick is low shot start pressure, low friction and a good seal.

The Bottom Line

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.............In my very limited experience ,., I have found that original Barnes X bullets tumbled in moly react very similarly to the Barnes TSX .,.as far as normal layman,s pressure signs like case expansion ,primer flow , sticky bolt lift , expanded primer pockets ..., velocity and barrel heat ..............As Alf brought up I have found that relatively soft flat base jacketed bullets seem to reach max working pressure with less powder than bullets with thicker jackets that are of the same material ..... .Since heat equals wear .And I like to shoot my favorite rifles alot . I have gone to moly tumbling All of my bullets when I had the ability to ............... ....In developing loads for my 9.3x62 Mauser CZ550 Medium FS model 2 years ago I found that with apparantly the same pressure the 270 gr Speer bullet that I molyied took 2.5-3 gr more powder than the non coated bullet and it gained 40-50 fps .........I had similar results with the regular Barnes X bullets .,. , I attained relatively high velocity with that rifle because I was able to seat the bullets out quite a ways due to its throat dimensions , magazine box length and action strength .......... , ,With my 458 Win mag . 300 gr Barnes X bullets .,., I was able to reach 2700 fps with uncoated bullets ,., . with molied x bullets the barrel gets about half as hot as the non coated ....The brass lasts longer and the shot to shot velocity variation is much less .,.,., Something that I know but really don,t understand is why the barrel stays so clean ..Why does tumbling bullets , Mono metal , jacketed , plated , or cast lead alloy.......Keep the rifle or handgun,s bore so much cleaner .........Dramatically so ..... .....since with both , the primer and powder are similar .. . there is always more junk left in the barrel after the shot with non mollied bullets ...... . ,This may just be alot of rambeling , but I have found that moly greatly reduces pressure and evens out velocities .It protects from heat inside the bore , and the barrel stays cleaner ., .,Since I don,t think alot about small group size , as I think 50 fps more velocity is more important than a 1/2" smaller group , I can,t speak to the ultimate accuracy difference between moly and not ..

quote:

Originally posted by Peter:
mho, are those numbers listed in the correct order?
Peter

Yes, those were the (approximate) chronograph readings:

Nosler AccuBond - 2600 fps,
Barnes TSX - 2500 fps
Barnes Banded Solid - 2400 fps.

- mike