How far with 180 grains and a 300 rum?

[MontanaRifleman]

I was given a small number of the 177 grain GS bullets for testing in my 300 ultra's. I was getting good accuracy with them at 3515 fps. With the high BC they carry this is one of the best long range killers in the business. The only thing I saw is they do not open up as well as I hoped they would at slower velocities. They are a monometal bullet and will not come apart though which is a huge plus. I did not see the huge double caliber type mushrooms of the Barnes bullets but they did seem to be adequate for hunting. I used Retumbo, RE25 and H-870.

What media and what velocities did you see the expansion results with?

 

[jcathunter]

My wife shot this bull at 842yds this year with a 165gr accubond from her 300rum. 95.5gr of RL25. Its a roosevelt bull and it went about 50yds after her one shot. Elk out around 700-800 haven't been a problem for that combo but black bear seem to soak up the 165s pretty well so I went to a 338 cal for my hunting rifle.

 

[elkaholic]

Congratulations! What a girl! Can she cook too

 

[jcathunter]

Um, cooking???? Well....um... because she can shoot, I'll choose not to answer that. I'll just say that the kids are good cooks. lol

 

[jwp475]

I plan on trying the GS HV 177's in my 300 RUM. With that bullet, a little faster powder than Reumbo will probably work better, such as H1000. Retumbo was my go to powder for 180 E-Tips, 200 AB's and 210 Bergers. H1000 was right there with it, but I liked the Retumbo results a little better in *my* rifle. The GS bullets will fly faster with less pressure and my do very well with RL17. I would expect to see 3500 - 3550 with H1000 and maybe up to 100 fps more with RL17. There would be nothing in the 30 cal world that could match that performance if it happens... 3600-3650 fps with a .6 plus BC. This is just "educated" speculation, but I think it's doable.

I have tried RL17 with 180 E-Tips in my 300 RUM and matched Retumbo and H1000 velocity. If you want to try it with the GS bullets, 80 grs would be a good place to start. I found max @ 87 gr and 180 E-Tips with my rifle. I suspect it would be a little higher with the GS bullets.

-Mark

Velocity is a function of gas volume and pressure. Since the volume will be about the same for different bulets at the same wieght how is the bullet going to go faster with less pressure. That defies internal ballistics

 

[elkaholic]

Velocity is a function of gas volume and pressure. Since the volume will be about the same for different bulets at the same wieght how is the bullet going to go faster with less pressure. That defies internal ballistics

Some bullets are designed with less friction thus it is easier to get them moving.

 

[jwp475]

Some bullets are designed with less friction thus it is easier to get them moving.

With lower pressure the velocity will be lower. If friction is lowered with the same powder charge then the pressure is lower with the same gas volume and so is the velocity. More powder must be added to increase gas volume and pressure inorder to get back the velocity. I have experience this before.

 

[elkaholic]

With lower pressure the velocity will be lower. If friction is lowered with the same powder charge then the pressure is lower with the same gas volume and so is the velocity. More powder must be added to increase gas volume and pressure inorder to get back the velocity. I have experience this before.

Try pushing a toboggan on gravel and on snow with the same amount of force and see which one goes the fastest. If you want to keep it in the bullet realm, why do moly coated bullets attain higher velocity than non coated of the same brand and weight?

 

[jwp475]

Try pushing a toboggan on gravel and on snow with the same amount of force and see which one goes the fastest. If you want to keep it in the bullet realm, why do moly coated bullets attain higher velocity than non coated of the same brand and weight?

And that relates to a specfiic volume of gas pushing a bullet down a bullet, how? It doesn't.
For instance we have 50 grains of powder in the case producing 60,000 PSI of presure and this is producing 3000 FPS. Now lets reduce the bearing surface of the bullet which reduce the friction, now our 50 grain of powder is going to produce less pressure and of course less speed. We will then have to add more powder inorder to get back to 60,00 PSI and our original 3000 FPS

 

[MontanaRifleman]

Generally speaking, when we decrease pressure we also decrease velocity. But different bullet/powder combinations will have different pressure/velocity ratios.

If we look at Hodgdons load data for the 300 RUM and 200 gr AB, we see that 92.5 gr of H1000 produces 62800 psi and 2975 fps while 95.5 gr of slower burning Retumbo produces 62,400 psi and 3050 fps - lower pressure and greater velocity. If we go to the 200 gr Barnes XFB and Retumbo, we see 62,800 psi and 2988 fps - more pressure, less velocity than the 200 gr AB and Retumbo.

The GS bullets are moly coated and banded and designed in such a way as to produce minimum friction while the bands seal the escaping gasses behind them. They can be easily tapped down a bore with a cleaning rod.

Reducing friction can increase velocity with same or lower pressures.

Changing burn rates can accomplish the same thing which is why we see different velocities with max loads of differnt powders in the same bullets.

 

[jwp475]

200 GR. NOS AB Hodgdon Retumbo .308" 3.600" 89.0 2904 56,400 PSI 95.5C 3048 62,400 PSI



200 GR. BAR XFB Hodgdon Retumbo .308" 3.555" 81.0 2852 56,200 PSI 86.0 2988 62,800 PSI



You didn't tell the whole story.. Yes the pressure is less for the 200 grain AccuBond by 400 PSI which is rather meaningless. But the powder charge for the AccuBond is 9.5 grains higher also. The top load for the AccuBond is 95.5 grains and the top load for the Barnes X is 86 grains. The difference in velocity is 60 FPS at near equal pressure. I am sure that you have chrono'ed enough rifle to know that the fastes load in one rifle is ofton the slower load in another rifle. The AccuBond load has an aditional 9.5 grains of powder, the added gas volume is needed in oroder to keep the pressure up

As I stated eairler reduce the friction and pressure drops and to get back to the csme velocity one must add more powder to regain the lost pressure

 

[MontanaRifleman]

200 GR. NOS AB Hodgdon Retumbo .308" 3.600" 89.0 2904 56,400 PSI 95.5C 3048 62,400 PSI



200 GR. BAR XFB Hodgdon Retumbo .308" 3.555" 81.0 2852 56,200 PSI 86.0 2988 62,800 PSI



You didn't tell the whole story.. Yes the pressure is less for the 200 grain AccuBond by 400 PSI which is rather meaningless. But the powder charge for the AccuBond is 9.5 grains higher also. The top load for the AccuBond is 95.5 grains and the top load for the Barnes X is 86 grains. The difference in velocity is 60 FPS at near equal pressure. I am sure that you have chrono'ed enough rifle to know that the fastes load in one rifle is ofton the slower load in another rifle. The AccuBond load has an aditional 9.5 grains of powder, the added gas volume is needed in oroder to keep the pressure up

As I stated eairler reduce the friction and pressure drops and to get back to the csme velocity one must add more powder to regain the lost pressure

JWP, I didn't say anything about powder charges in my post. I said the GS bullets will get higher velocities with lower pressures than other bullets. I didn't mention anything about powder. In fact, I believe a slightly faster powder would be better with the GS bullets than other bullets of similar weight.

Meaning, one can produce better velocities with the optimum powder for the bullet. In my case, I can get 3400 fps with 180 E-Tips with Retumbo. I would expect to get a higher velocity with the 177 GS bullets and Retumbo and even better with other powders like H1000 or RL17. I have a hunch that RL17 will work very well with the GS 177's in the 300 RUM. Just a hunch.

Bottom line, you will (should) get better velocites with the GS bullets and equal pressure and if you split the difference, you will get a little better velocity with less pressure from the same rifle.

 

[elkaholic]

JWP, I didn't say anything about powder charges in my post. I said the GS bullets will get higher velocities with lower pressures than other bullets. I didn't mention anything about powder. In fact, I believe a slightly faster powder would be better with the GS bullets than other bullets of similar weight.

Meaning, one can produce better velocities with the optimum powder for the bullet. In my case, I can get 3400 fps with 180 E-Tips with Retumbo. I would expect to get a higher velocity with the 177 GS bullets and Retumbo and even better with other powders like H1000 or RL17. I have a hunch that RL17 will work very well with the GS 177's in the 300 RUM. Just a hunch.

Bottom line, you will (should) get better velocites with the GS bullets and equal pressure and if you split the difference, you will get a little better velocity with less pressure from the same rifle.

+1....The defense rests

 

[jwp475]

JWP, I didn't say anything about powder charges in my post. I said the GS bullets will get higher velocities with lower pressures than other bullets. I didn't mention anything about powder. In fact, I believe a slightly faster powder would be better with the GS bullets than other bullets of similar weight.

Meaning, one can produce better velocities with the optimum powder for the bullet. In my case, I can get 3400 fps with 180 E-Tips with Retumbo. I would expect to get a higher velocity with the 177 GS bullets and Retumbo and even better with other powders like H1000 or RL17. I have a hunch that RL17 will work very well with the GS 177's in the 300 RUM. Just a hunch.

Bottom line, you will (should) get better velocites with the GS bullets and equal pressure and if you split the difference, you will get a little better velocity with less pressure from the same rifle.

If the velocity is significantly higher then the pressure is also, just like the Hogdon data shows. I have no dought that you get 3400 in your RUM with an E-Tip and Retumbo I have gotten 3425 with the 180 TSX in my RUM, but makw no mistake the pressure for this velocity is above SAAMI ma avereage of 63,000 PSI. You can't get higher than normal speeds without higher pressure. These claims have been made for decaqdes and will continue to be made.


I'll tell you what you work your load up and then send me a few and I'll shoot them in my 300 RUM through my Oleher 43 and we'll get velocity and pressure readings as well as the BC. Then there will be no question in anyones mind.