Guesses on muzzle velocity, 300 RUM

[Moman]

I think those two items would be a great setup.

 

[TyIdaho]

Crop Damage, I am betting you are indeed very close to 3100 fps with that load.

Exbal is good but you should also take a look at Loadbase by Patagonia Ballistics.

Ballistics Software from Patagonia Ballistics.

Especially if you are getting into reloading, Loadbase has the most comprehensive ballistics that I have found and allows you to save all of your load development and targets. It also has a reloading library in it, I found your load in there at 87.5 rather than 88.0 and it shows 3100 fps. The library is not designed to replace your reloading manuals but it is a handy feature when you are doing some winter day comparisons because it has a HUGE database.

Like everyone has already said, nothing takes the place of actual field testing, I have a 308 Norma with a Leupold scope, that would not match the drop data produced by Exbal, I chronographed the load kept track of environmental conditions and tried to use the trajectory validation tool in Exbal. It adjusted by changing my velocity, making it 200+ fps faster than the load actually is in order to make it match my drops (no fault of Exbal). Turns out my scope is not adjusting exactly 1/4 minute increments as it should.

Loadbase has a turret function so that you can input your actual turret increment. My turrets are supposed to be 0.250 (1/4 minute) but are actually 0.290. Now my drop charts match my scope adjustments at the correct bullet speed rather than some fictitious speed.

 

[Crop Damage]

Loadbase looks impressive too. I'm not sure if I can justify to my wife the extra cost vs exbal now, but that might be worth trying in the future. I do like that you can get load data from other sources besides just bullet manufacturers using Loadbase. Either one of these programs will make me the highest tech redneck in the area. The fanciest trick I could pull would be to whip out a hand held device with a ballistics program on it, I'd be a legend for a month or so. Thank you for the info.

 

[TyIdaho]

"...highest tech redneck in the area"

Lol I know what you mean!!

The price is actually about the same as Exbal if you want the Mobile and Desktop version of Exbal, with Loadbase you must by both.

I too took a step back at the price, but now that I bit the bullet so to speak and bought it, I could not be happier and customer support is second to none.

 

[Moman]

TyIdaho, that's an interesting point you bring up with exbal and your Leupold scope. I really like the exbal program and am using it for two guns. One is a 308 topped with a Sightron SIII and is dead nuts. I've never had to validate with it, it's always been right on the money. My 300 WM has a VX-III on it and I have had to validate it with every load I have used. It changes the velocity to a much lower number and I could never figure that out being the same chrono. I am glad you brought this up, I will have to do some testing with this scope.

 

[TyIdaho]

Moman, I tested my drops at 300, 610, 756 and 950 yards (hard to find places to shoot distance where I live, that's why the odd ball numbers). I was very perplexed to find that my load was hitting high at all distances compared to the calculated drops. (This is a Leupold 4-12 with target turrets installed by Leupold just 8 months ago).

I then clamped my rifle in a gun vise in my shop pointed it out the door and set up a target that I made with a 1" grid on an 8.5x11 sheet at 50 yards, adjusted out the parallax, then carefully ran the scope from the bottom to the top and counted the number of clicks per 8 inches, did the math and it matched what I came up with in Loadbase!. Walla, 0.290 increments instead of 0.250, it tracks consistently but not the advertised amount.

Exbal was able to match the drops pretty well with the exception of the 950, (the unrealistic speed was starting to show) just by adding velocity, so much velocity I knew it could not be correct plus it did not agree with my chrono. But now with Loadbase I matched the drops by adjusting the turret increments, and I now longer care that the scope is not adjusting exactly 1/4 minute.

I'll bet this problem is more common than we know.

 

[Moman]

Definately sounds similiar to what I have gone through with the exception that all of my hits are low. Maybe our scopes are considered 1/4 MOA clicks, give or take a little. LOL. When I get a chance, I'll try your test and see what I come up with. Thanks.

 

[Fitch]

I'm very, very new to reloading. I do not have a chronograph, I could probably use one if I called several people. I've got a hunting load that's working really well for me, and I'm not sure what kind of velocity I'm getting. Was hoping some more experienced people on here might have some better guesses at it than I do. Trying to make a rough ballistics card out to 700 yards.

Load is

300 RUM
190 Berger VLD Hunting Bullet
88.0 gr 7828
Rem Brass
CCI Magnum Primer

Rifle is Remington 700 APR w/ 26" barrel
Temps average 50 degrees
About ten feet above sea level, on the high ground.

I modeled that load in QuickLoad as well as I can with out knowing the COL at which you are seating the bullet. The COL has a noticable effect on both pressure and velocity. The model is not a replacement for a chronograph but it is a good place to go for an estimate if one doesn't have a chronograph. I use IMR7828 in my .243 with 95g Nosler BT bullets and the QuickLoad models are for that cartridge are within 2% on MV.

Results of modeling your load:

First, at least in QuickLoad, that looks like a pretty hot load. At 50F the calculated peak pressure is within 600 psi of max at 64,400 psi in a rifle that has a 65,000 psi maximum. The muzzle velocity is predicted to be 3,082 ft/sec.

At 70F the predicted pressure goes up to 66,790 psi and the MV goes to 3107 fps.

At 90F (not an uncommon summer temperature) the pressure goes up to 69,215 psi with a muzzle velocity of 3,131 fps.

I have two recommendations: First, definitely shoot that load through a chronograph and compare your measured MV with the predicted values in the manual for the bullets. If you are higher than the velocity predictions in the manual for your powder charge using the same length barrel, you might consider backing off on the powder charge.

Second, make darn sure your bullet is not touching or seated into the lands. That will increase the peak pressure another 6,000 to 7,000 psi.

Fitch

 

[Crop Damage]

Thank you Fitch. Now I'm slightly concerned! My COAL is 3.70". I don't know what pressures the barrel can withstand, the rifle is the african plains rifle from the remington custom shop, and the barrel is 26" long, if that helps.

As far as I can tell the bullet is not touching the lands. I marked the bullet with black marker and ejected the cartridge without seeing any marks. There is probably a better way to check that though.

I have not got any load data from Berger, which is why I'm having to guess the figures for this load. Looks like the chronograph will tell me a lot, and I'm going to have to get a ballsitics program.

I definitely do not want to have the rifle blow up in my face later this summer. I can step it down some, but how are there people claiming to get 3400 + FPS from this bullet using different powders, when I'm maxed out at 3100? Longer barrels maybe? I think I saw those loads on another reloaders website. I don't really need any more speed or power out of this round, if I can get it to group well at 700 yards. Thats as far as I want or need to shoot, and more speed won't help me too much I don't think. Thank you for the good info, that's very helpful.

 

[Fitch]

Thank you Fitch. Now I'm slightly concerned! My COAL is 3.70". I don't know what pressures the barrel can withstand, the rifle is the african plains rifle from the remington custom shop, and the barrel is 26" long, if that helps.

As far as I can tell the bullet is not touching the lands. I marked the bullet with black marker and ejected the cartridge without seeing any marks. There is probably a better way to check that though.

I have not got any load data from Berger, which is why I'm having to guess the figures for this load. Looks like the chronograph will tell me a lot, and I'm going to have to get a ballsitics program.

I definitely do not want to have the rifle blow up in my face later this summer. I can step it down some, but how are there people claiming to get 3400 + FPS from this bullet using different powders, when I'm maxed out at 3100? Longer barrels maybe? Thank you for the good info.

The load you have calculates as over pressure in 70F and warmer conditions, or if you let a cartridge soak in a hot chamber. But it would be good to get chronotraph data to see if my predicted velocities are correct. If the predicted velocities are correct, the predicted pressure probably isn't far off either.

The 3.7" COL is longer than I used and acts to reduce pressures significantly because it increases the initial chamber volume behind the bullet. The only data that would improve my prediction now is an accurate water grain capacity for your as-fired brass. The capacity I'm using now is 112.5g which is the QuickLoad default value for that cartridge.

The updated results I get with that COL and a 26" barrel:

90F 66,617 psi 3.101 fps
70F 64,294 psi 3,077 fps
50F 62,000 psi 3,051 fps

I have no explanation for anybody else's data. I only go by what I measure myself. I will say that there are a lot of folks on the internet that are getting higher muzzle velocities and smaller groups than I am.

Getting yourself a good chronograph, like a CED M2 will let you get your own data. If it were me, I'd definitly e-mail Berger as they suggest on this page

http://www.bergerbullets.com/Information/FAQ.html

and ask them about load data for the bullet in your cartridge (besure and give them the COL you are using) and get starting and max loads from them. \

The best powders, according to QuickLoad in descending order of maximum muzzle velocity (which says nothing about accuracy), are Vihtavouri N570, Hodgdon H870, Hodgdon Retumbo, Vihtavouri N560, Accurate MAGPRO, IMR7828 and IMR7828SSC.

I hesitate to recommend it with out knowing your background but the QuickLoad software, which my estimates above are based on, used correctly (it comes with an excellent manual), can be a huge assett when it comes to understanding internal ballistics (that which happens between the time the primer fires and the bullet leaves the muzzle). It comes with two excellent external ballistics programs as well. Like any other simulation modeling tool it's output is only as good as the input. I treat it's output like I do the load maps in reloading manuals which means I never start at a QuickLoad predicted max load. I start 10% low and work up while documenting the chronotraph readings, looking at primers, checking for sticky extraction, etc. This SW is one of the better investments I made in reloading equipment.

I have come up with a lot of good starting load and probable max load for a lot of cartridge bullet combinations using QuickLoad. I've selected cartridges, bullets, powders, barrel lengths and a number of other things based on combining QuickLoad studies, QuickTarget external ballistic results, data and equations in EXCEL from "Applied Ballistics for Long Range Shooting" by Bryan Litz. The result allows comparison of optimum game weights, point blank ranges on different game, for the various cartridges of interest.

However, if you aren't an analytical type (I'm a retired engineer) you may not find that approach to be your best approach to learning.

A few rainy/snowy days at the computer with some good coffee, pencil paper, and calculator, doing what-if studies on powders and experimenting with the effect of seating depth and bullet selection has given me the opportunity to learn and gain mor indepth understanding. I'm definitely not an expert, but I'm finally at the point of appreciating how much I don't know.

Fitch

 

[TyIdaho]

"...I don't know what pressures the barrel can withstand, the rifle is the african plains rifle from the remington custom shop, and the barrel is 26" long, if that helps."

And you don't want to find out by pushing it too far!!

"...I can step it down some, but how are there people claiming to get 3400 + FPS from this bullet using different powders, when I'm maxed out at 3100? Longer barrels maybe?"

Every gun is different, usually pretty close, but still different and thus will shoot at different speeds. Because of this (in part) you can not depend on a chronograph to tell you when you are at max pressure. You need to examine your fired cases very carefully, if you use a hand primer seater like the Lee, you will notice less effort to seat the primers when loading a case that was shot with fairly high pressures. Don't forget that you will usually, not always, but usually find your most accurate load is not the fastest. Bullet placement is much more important than an extra 50 to 100 fps that you might get by pushing your gun to the limit. Also your brass will last much longer if you back it down some, and as you know, brass aint cheap.

Your cartridge started out life at what some would consider (me included) to be over-bore capacity, which tends to make them less inherently accurate and not as forgiving at close to max pressure (notice how accurate most .308 Win. Rifles are, same bore less capacity = more efficient). That doesn't mean it won't be accurate, some guy's are shooting really good with this round, but you should be very careful, because a round that is over-bore capacity may tend to spike pressures near max rather than climb up consistently and predictably.

You are ultimately the judge, but I vote for less pressure, more accuracy and longer brass life.

Good luck and keep us posted!

 

[Crop Damage]

You guys are great. Thanks for all the info, I've learned a lot from this thread. I will contact berger for load advice, as recommended. I've been cleared by my "war dept" to get a chronograph, and I'm comparing exbal vs loadbase vs quickload.

Thanks for the warning about the chamber pressures, I had no idea that temperature could affect it that much. I'll have to come up with a summer load for this rifle. You're right about accuracy and lower pressures being better than higher velocity and a rifle bolt through your face. I think I'm now more aware of these issues than my buddy who is helping me with the reloading. He usually starts off at max and works down. Don't think I'll be doing that.

 

[Fitch]

I think I'm now more aware of these issues than my buddy who is helping me with the reloading. He usually starts off at max and works down. Don't think I'll be doing that.

Right on.

+1 for what TyIdaho wrote.

The .300RUM is a very overbore cartridge. In addition to what TI wrote, be aware that overvore cartridges, especially severly overbore cartridges suffer from significantly reduced barrel life. The .300 RUM has an overbore index of ~1510 which places it significantly above even a .220Swift or a .22-250 (both at 1218) or a 7mmMag (1326). For more on overbore see

Defining "Overbore" Cartridges via Comparative Index AccurateShooter.com Bulletin

That link isn't anything "official" in terms of being a standard but it is quite useful. I experimented with it for a while and find it to be a rather useful predictor of barrel life. Barrel life is affected by more factors than the geometry however, bullet weight (powder burn rate), loading at less than maximum, and a number of other things have an effect. The .300RUM is a Big Game hunting rifle so it doesn't get shot as much as a varmint rifle, PD rifle, or target rifle. At a dozen rounds a year 1200 rounds of barrel life is good for a 100 years. But be advised there is some motivation to find your accurate load with out putting 300 rounds down range.

Keys to this are picking the bullet with care to match the game that will be hunted, and being systematic and organized about load development. The experience, skill and ability to do what-if analysis on the computer to narrow down choices will help with this. If you have a .223, it is a nice high barrel life rifle to use as a teaching aid for the load development process.

This isn't anything to worry about, but it is a factor to keep in mind. It says if you are efficient and manage to get to your desired hunting load in a hundred rounds or so you will have plenty of hunting barrel life "in the bank" so to speak.

Fitch