Can anyone estimate my fps for this load?

[JimGnitecki]

I have a TRG 42 in 338 Lapua, so a 27" barrel.

The load that seems nicely accurate (best 3-shot group at 100 yards = less than 1/4") is:

Case: Lapua
Primer: Federal 215 Large Rifle
Bullet: Sierra 300g Matchking
Powder: 87 grains of Hodgdon Retumbo

Anyone out there experienced enough to predict what muzzle velocity is?

My chronograph has not arrived yet, and the other day my friend and I were trying get me to hit at 1000 yards, and the guesstimates on muzzle velocity just weren't good enough.

Jim G

 

[Fuzzball]

Re: Can anyone estimate my fps for this load?

"Anyone out there experienced enough to predict what muzzle velocity is?"

No. Anyone with experiece knows it can't be done with sufficent accuracy to matter.

 

[JimGnitecki]

Re: Can anyone estimate my fps for this load?

Really??

Am I even speculating too much when I look at the Hodgdon loading manual, see that 85 grains supposedly deievrs 2375 fps and 94 grains delivers 2650 fps, and guess that 87 grains might be somewhere between 2425 and 2500? I base the 2425 on the velocity increase being linear with powder added, and I base the 2500 on the fact that with most loads I have seen data for in the past, increasing the powder charge brings diminishing returns, so increases from the "minimum" tend to be more effective than increases from "almost maximum" to "maximum" safe load.

I thought this was at least a LITTLE science., but you appear to be saying it is not.
Is it really THAT impossible to estimate??

Jim G

 

[Fuzzball]

Re: Can anyone estimate my fps for this load?

"Is it really THAT impossible to estimate??"

Oh no, it's so easy to estimate velocity that anyone can do it. Any guess within a range of maybe the book value on the high end to as much as 400 fps slower is as good as any other.

Your extrapolation would be valid for the same rifle Hodgedon used to develop their data but your's isn't their's. And, as you note, the change in power vs. speed isn't liniear.

It was a LOT easier to expertly guess velocities until we got some affordable chronographs; they blew a lot of wildly hopeful guesses out the window. Bottom line, if you want to know how fast a load's going, clock it.

 

[milo 2.0]

Re: Can anyone estimate my fps for this load?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Fuzzball</div><div class="ubbcode-body">"Is it really THAT impossible to estimate??"

Oh no, it's so easy to estimate velocity that anyone can do it. Any guess within a range of maybe the book value on the high end to as much as 400 fps slower is as good as any other.

Your extrapolation would be valid for the same rifle Hodgedon used to develop their data but your's isn't their's. And, as you note, the change in power vs. speed isn't liniear.

It was a LOT easier to expertly guess velocities until we got some affordable chronographs; they blew a lot of wildly hopeful guesses out the window. Bottom line, if you want to know how fast a load's going, clock it.
</div></div>

I've shot one of my guns through 4 chrono's, Oehler P35, CED, Chrony ?, RCBS bullet looking thing. Four different readings, a 130fps spread between them. Which is correct????

Jim,
If you have shot your gun to a certain distance and recorded your dope's, come up's, drop's or what ever you call them, and if you trust your BC of your bullet, you can manipulate a ballistic program to come close to your velocity.
Don't let the fuzz imtimidate you.
I've never had a ballistic program be spot on based on my velocity and bc, I shoot the the yardage, then adjust the DA on given days.

 

[X-fan]

Re: Can anyone estimate my fps for this load?

Why such a mild load Jim?

Is it really shooting well there or something??? Kind of a odd load?
Doesn't seem like you would get a clean burn (enough pressure for proper ignition and accuracy) with that load?

I don't have much experience with the Lapua and Retumbo (tried some hunting weight loads). If it were me I would try the 90-94grain range that will get you 2700-2750fps max velocity.
IIRC I seemed to get best accuracy with the 300s at 2700ish.

My guess is 2550fps+-

 

[JimGnitecki]

Re: Can anyone estimate my fps for this load?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: X-fan</div><div class="ubbcode-body">Why such a mild load Jim?

Is it really shooting well there or something??? Kind of a odd load?
Doesn't seem like you would get a clean burn (enough pressure for proper ignition and accuracy) with that load?

I don't have much experience with the Lapua and Retumbo (tried some hunting weight loads). If it were me I would try the 90-94grain range that will get you 2700-2750fps max velocity.
IIRC I seemed to get best accuracy with the 300s at 2700ish.

My guess is 2550fps+- </div></div>

There are multiple reasons for the mild load.

First, as everyone says, load for the range you have available to shoot at. The longets local range, (63 miles away!!), goes to only 1000 yards. Why reduce barrel life, and raise powder cost, and reduce case life, by loading hotter than I need to shoot at the maximum range available to me?

I also fed the 87g and 94g laod statistics into the barrel life worksheet that someone posted the link to on this forum recently. At 94g, the projected barrel life is 1544 rounds. At 87g, it is 2347 rounds! Don't take the number too literally,but DO consider the RELATIVE difference!

Second, yes, the rifle is VERY accurate, but particularly so with that load. I examined and measured closely one target sheet I fired last Saturday, using 3 loads: 85g, 87g, and 89g. There were 9 3-shot groups on the target sheet. ALL were sub 3/4 inch. 3 were sub 1/2 inch. All 3 were the 87g load. The best was less than 1/4 inch.

The 87g load is 2 grains over the minimum in the Hodgdon manual. The cases fired using this load are clean - no soot. The accuracy is superb. The rifle/ammo/scope combo has been shooting extremely well at 250, 500, and 750 yards, and even at 1000 yards despite my not yet having a 20 MOA rail under the scope and thus having to hold over a ridiculous amount at 1000 yards (remedied for NEXT weekend - I installed a 20 MOA Larue scope mount that will work on both the TRG and my LMT MWSE!). The chamber pressure is in the low 40,000s. The cases grow almost none at all during firing. The rifle cleans up quickly, with no copper showing in the barrel. The case life will likely be "lengthy". I can probably full length size even less often than normal. If your velocity guestimate, and mine, are anywhere near correct, even at 1000 yards the bullet will deliver over 4000 ft lb of energy at 50 yards and STILL deliver 1570 ft lb at 1000 yards. That's about 3 times what my 308 LMT delivers at 1000 yards, and about 2 1/2 times what a 357 Mag revolver, the all time knockdown handgun champ, delivers at MUZZLE. What's not to like?

Jim G

 

[JimGnitecki]

Re: Can anyone estimate my fps for this load?

Milo-2: I recieved my CED M2 chronograph the other day. I will test it out this weekend, so by Saturday or Sunday evening, we should know the velocity of this load!

Jim G

 

[Fuzzball]

Re: Can anyone estimate my fps for this load?

<span style="font-style: italic">"I've shot one of my guns through 4 chrono's, Oehler P35, CED, Chrony ?, RCBS bullet looking thing. Four different readings, a 130fps spread between them. Which is correct????"</span>

None of us knows do we? Do we average them? That's no good if only the high reading is closer to correct. Do we drop the high and low and average what's left? Not if we dropped the only one that is closer to correct. It's long been understood that a man with a watch knows what time it is but a man with two watches never quite knows what time it is.

It's not my intent to intimidate anyone but to inform: Guessing at velociites for long range shooting is hopeless. I submit <span style="font-weight: bold">milo-2's</span> excellant quote to support that, and add that even clocked speeds aren't totally precise no matter what clock we use. Same as rifles, there will be some speed differences even between two of the same chronographs with consecutive serial numbers. From all that, it should be recognised that attempts to produce an accurate long range drop chart by computer calculations based on a clocked speed can't be trusted either.

One thing a lot of people don't understand about chronograph 'sky screens' is the look-angle of the sensors and their cheap plastic lenses are not precise. We can shift clocked speeds a little in the same unit by simply exchanging or rotating the 'start' and 'stop' sensors.

Bottom line, if we want a long range drop chart we will have to do some long range shooting and record the results.

 

[Clark]

Re: Can anyone estimate my fps for this load?

Quickload thinks that 338 Lapua, 3.381" OAL, 27" barrel, 87 gr Retumbo, Sierra 300 gr MK 9300, 3626 psi start pressure [bullet not touching lands] will produce 2600 fps, 51,690 psi, 10,335 psi muzzle pressure [loud], and the case is 102% full of powder [still room for a little more if compressed].

Retumbo is an extreme powder. The Quickload library has Varget nailed to within 1%, but H4350 is a couple percent wimpier than Quickload expects. I have no experience with Retumbo reality vs Quickload.

Quicktarget thinks that if the scope bore is 2" above the barrel bore and the rifle is zero'ed at 200 yards, then the the bullet will be 1944 fps and 12 moa low at 600 yards.

A 338 Win Mag can get long brass life at 72,000 psi.
Many powders with a 27" barrel will push that bullet at 2600 fps. Like 68.2 gr H4381sc.

If I were shooting a 338LM with brass costing over $2, I would not settle for performance that I could get with 338WM at $0.6 brass.

Pushing 338LM at it's registered 60,916 psi will only get 2700 fps, which slows down to 2600 fps in 100 yards.

But the 338LM is a very strong case head. I would push it harder than registered pressure. At 70,000 psi 95 gr Retumbo 2800 fps if you can get 111% powder fill to fit , and that would have 180 yards before it slowed down to the 338 Win Mag class.

 

[JimGnitecki]

Re: Can anyone estimate my fps for this load?

Clark: You make decently good points.

But, the Lapua brand 338 Lapua cases only cost $2.38 if you fire them only ONCE. With the 87g load, I can probably fire them at LEAST 10 times, and maybe many times more.

And, I bought the 338 Lapua caliber so that I would have a different shooting experience than I alreayd get with my 308,and so I could be sure of being able to get to the 1000 yard maximum available to me without dirivng more than 1 1/4 hours each way.

Your stance, taken to a car analogy, says basically that if you buy a high powered car, you should not settle for driving it at speeds that are more than adequate for locally available roads, but should rather ensure that it can hit the 180 mph it is capable of doing! I've owned 400 to 575 hp vehicles, and while I've occasionally had them into triple digits, I've never felt compelled to run them at 150 mph+. I'm not a good enough driver to do so, there isn't a road closer than 120 miles away that would be good enough and safe enough, and if I tried and got caught, the penalty would be severe. But, I nevertheless enjoy the engines, occasionally DO exercise them "enthusiastically", and always enjoy the process of driving them.

My TRG 338 Lapua is like that.

If I ever get a chance to go somewhere where 1500 yard ranges are available, I'll "load stronger" for the trip out there.

Jim G

 

[milo 2.0]

Re: Can anyone estimate my fps for this load?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JimGnitecki</div><div class="ubbcode-body">

If I ever get a chance to go somewhere where 1500 yard ranges are available, I'll "load stronger" for the trip out there.

Jim G </div></div>

Jim,
Might not have to load up, consistancy wins most of the time.
If you and your lovely bride tour the northern wild west, give me a shout, we can bang some steel to 2100 yards.
There is nothing like shooting a full size IPSC at a mile or greater. I would have to say this fulfills a unspoken fantasy of 98% of the members on this site.

 

[JimGnitecki]

Re: Can anyone estimate my fps for this load?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: milo-2</div><div class="ubbcode-body">[If you and your lovely bride tour the northern wild west, give me a shout, we can bang some steel to 2100 yards.
There is nothing like shooting a full size IPSC at a mile or greater. I would have to say this fulfills a unspoken fantasy of 98% of the members on this site. </div></div>

I LOVE that Wyoming area. Karen and I lived very briefly "out in the middle of nowhere", 40 miles north of Cody, and 40 miles west of Powell, just a few hundred yards from where Casull was doing his thing at the time. I would have loved to stay there, but finding work there in my field was a real problem, and the nearest airport of any cosnequence was Billings, Montana.

We were only about 10 miles as the crow flies from Beartooth Pass, but 70 miles by road and a full MILE lower in elevation, and right near where Butch Cassidy and The Sundance Kid were fleeing from the Postal Inspector posse. I loved the wide open spaces that were wide open but full of CHARACTER, and mostly unspoiled by the marring actions of Man (Wyoming as a state in total has under half a million people population!). It's an area I really want to spend time in in the future after I retire, or sooner on vacation, and shooting is what I would do a lot of there!

Jim G

 

[Clark]

Re: Can anyone estimate my fps for this load?

At 2800 fps, only down 10 moa at 600 yards.
Generally, I can kill if if I only have to adjust 8 moa or less. 308 guys on this forum would laugh at that.


The wife and I drove up Beartooth pass in 1984.
At the top the car filled with the smell of Chlorine.
A sniff test traced it to my wife's skin.
She had quit a year earlier, swimming in a pool every morning before work. The stuff must be fat soluble, and have a high vapor pressure.

 

[X-fan]

Re: Can anyone estimate my fps for this load?

Don't get me wrong Jim I wasn't crapping on your load...Just curious.
Your dream you live it.

I think you will get less vertical at 1000+ with the better ignition 60Kpsi will give you.
With my limited Retumbo/300gr experience I might be wrong here, but I bet your new CED will reveal some larger velocity variation than you might think normal.
If I'm right you might want to try H-1000 and even H-4831. H-4831 would run higher pressure, but 15 or so grains less powder.

 

[JimGnitecki]

Re: Can anyone estimate my fps for this load?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: X-fan</div><div class="ubbcode-body">Don't get me wrong Jim I wasn't crapping on your load...Just curious.
Your dream you live it.

I think you will get less vertical at 1000+ with the better ignition 60Kpsi will give you.
With my limited Retumbo/300gr experience I might be wrong here, but I bet your new CED will reveal some larger velocity variation than you might think normal.
If I'm right you might want to try H-1000 and even H-4831. H-4831 would run higher pressure, but 15 or so grains less powder.
</div></div>

I should be able to chronograph the load this weekend. I'll report the results.

Jim G