[Darin115]

I just joined this site the other day. I already have found tons of useful info. I have not reloaded in some time but due to the increase in Federal Premium 25-06 bullets I broke out the Rockchucker a few weeks ago. I worked up a load for my 25-06.

I just purchased a Thompson Center Venture chambered in 270 Win, a box of Hornady SST bullets and some IMR 4831. I checked my old trusty Speer # 13 manual which listed a max load of 58 grains and a velocity of 2967 (if I remember correctly) . I then pulled up the data on Hodgdon's website. They list max as 55.8 with a velosity of 3002 fps. I then called Hornady and they said they listed the max at 56.2 grains and I did not ask what velocity they listed.

I started with 55 grains and worked up to 57 grains. 56.5 grains was my best group. It shot a 5 shot group around 3/4 of an inch. I noticed no pressure signs at all until I hit 57 grains. The primers flattened out. The only way you could tell where the primer stopped and the case started was the color difference. I figured it was a little to hot. 56.5 grains is the magic load in my gun. I guess I could try to dial it on in but I deer hunt with shots generally less than 200 yards. I figure I am right where I need to be.

I am stumped on the differences in the loading data. I called Speer and they stood behind their max load. Hornady said it is way to hot and I should stay below 56.2 grains. My question is how can 55.8 grains of IMR 4831 have a velocity of 3002 fps but the 58 grains is only listing 2967 fps.

Anyone have any ideas??

Thanks!

Darin

 

[broom_jm]

The equipment used to test data in your "old trusty Speer # 13 manual" has been replaced by more accurate and consistent methods. All other things aside, if your primers are flattening out that much, you are right at, or OVER maximum pressure, regardless of what any book says. I'm pretty sure your "old" manual did not have data for those SST bullets. You should always go with the recommendation of the bullet manufacturer, when it's available. In this case, both your primers and Hornady agree that you need to back your load off just a little.

 

[MikeG]

Bullets are different, so are lots of brass, chamber dimensions, primers, lots of powder, etc., etc., etc. Stick with a good grouping load and don't worry about getting every last foot-second.

Bet the three makers listed different OALs with their load data. Stay safe.....

 

[broom_jm]

And the old lawyers weren't as spooky as the current strain. If my rifle wanted 56.5 grains of coal and didn't show me flattened or cratered primers, that's what I would load. I would not care one wit that Hornady says 56.2 is max, nor that 57 grains flattens primers.

But, his primers DID flatten...badly, by his description. If 56.5 grains causes that but 56.2 doesn't, THEN would you believe Hornady data, for a Hornady bullet?

 

[Darin115]

56.5 was fine. I was surprised when 57 showed that much pressure sign with only a 1/2 grain difference.

I even checked the 14th edition of Speer and called them. They said they researched it and stand behind their data.

I am staying with the 56.5 grains because it shot so well with no high pressure sign. I just could not understand the difference. I am not overly concerned about the speed. I just could not understand why there is such a big difference in loading data. I have only loaded 30-06, 25-05, 308, 30-30, 450 Marlin and 223. I have never ran into this problem. But I never researched load date like I have for the 270.

I loaded my 25-06 super fast and got poor penetration. When I slowed it down the bullet penetrated much better. I am happy with the 270 with a 130 grain SST going just below 3000 fps. I just wanted 1 inch or less at 100 yards.

Thanks!

Darin

 

[EWestbrook]

Have you chronographed the velocity? I finally got one, and found out just what I've been missing. Your rifle is telling you what it likes, sometimes it doesn't agree with some manuals max.

 

[Darin115]

I do not have access to a chronograph. I wish I did. What is the best kind to get. I know nothing about them.

One other note the guy at Hornady said that if I shot a hot load in the Summer the pressure could go even higher due to the increase in temp. I did not think about that. I am not worried with the current load. I would be concerned if I stayed with the hotter load and the higher pressure.

The Venture has a sub moa guarantee with premium factory loaded bullets. It is shooting a sub moa with handloads. I am really happy with this gun so far. I am planning a pig hunt later this month. We will see how the SSTs perform on ferel hogs.

Darin

 

[gunpa]

I'm not buying pressure measure equipment being so much more accurate in 5 years time, especially when the measurement is still in cup. When they listed the new maximum loads for my 338 win at 3 grains less than the old starting loads and the powders haven't changed I'm caling B_____ on their "expert testing". I also use my chrono and there's. no way to reach advertised velocity with the new max loads when that's where I was with the old manuals starting loads. Alliants listed loads haven't changed but according to speer, nosler, and hogdon, I should be blowing primers, at the very least, and they aren't even flattenning! It's almost like being thrown back to the early 50's and having to start from scratch and figure everything out yourself. I think corporate attorneys have been very busy and are way over paid! Other than that -----I have no opinion

 

[broom_jm]

Read it again, Broom. "I noticed no pressure signs at all until I hit 57 grains".
I believe I would load 56.5 grains with or without the blessings of Hornady.

I stand corrected...my apologies to you and the OP, as he did the prudent thing and you smartly pointed out that his results are better than any book data. Guess I need to read a little more carefully.

 

[EWestbrook]

I do not have access to a chronograph. I wish I did. What is the best kind to get. I know nothing about them.

Got a Prochrono Digital from Midwayusa for Christmas. What a marvelous tool for $100.00. Next I'm going to get the cable that connects it to a USB so I can operate it with my netbook at the range.

 

[marsms]

The Lee manual shows only Jacketed bullets, and Barnes X in 130 grs. Anyway, for a jacketed bullet using IMR 4831, it shows a maximum load of 56.5 grains, at 3080 fps, and a CUP of 51200.

 

[Darin115]

Thanks for the info!!!!


Darin

 

[unclenick]

56.5 was fine. I was surprised when 57 showed that much pressure sign with only a 1/2 grain difference.

I even checked the 14th edition of Speer and called them. They said they researched it and stand behind their data. I do not have access to a chronograph. I wish I did. What is the best kind to get. I know nothing about them.

You need to reread Mike's post. The SST is not made by Speer, so you cannot assume the same data will apply. The jacket thickness may be different, making the Hornady harder than the Speer bullets to push into the rifling, even though the weights are the same? Or there may be a slight diameter difference, or a difference in core alloy hardness?

In addition, Hornady used a COL of 3.210". Speer used 3.240". (See the chart below for one example of the effect of seating depth on pressure. Yours won't match, but the same principle applies.) Speer used a Winchester case and a CCI 200 primer. Hornady used a Hornady Frontier case (probably slightly heavier and lower capacity than the Winchester) and a Winchester WLR primer. (Primer differences alone can cause pressure to vary equivalent to up to 5% powder charge weight). Speer used a Ruger M77 Mk II, Hornady used a Winchester Model 70.

So, you may not be using the same components either manufacturer did, and even if you are, these have some tolerance lot-to-lot, as Mike pointed out. In addition, your gun isn't either of the ones used in the tests, and I don't just mean model, here, since there are manufacturing tolerances even within a firearm model. I mean you don't have either of the exact same guns used in the tests, and that introduces a difference in chamber dimensions that also affect pressure.

In general, you have to use the exact same component brands used in the load recommendation, same bullet make, same case make, same primer make, same COL. Right now you are relying only on using the same powder make to get a matching load. It's the biggest single factor, just not the only factor, and smaller factors count as you come up on the edge of pressure limits.

Even with all the components matched, your gun's individual tolerance range can affect what it will tolerate, sometimes considerably. So, the earlier mentioned advice to check several sources (which you did) is correct. The best safety strategy is to take the smallest starting load among the several sources and begin your load workup there. 99% of the time that load will turn out to be wimpy in your gun, but every once in awhile you find a gun for which the starting load is already at its individual maximum. I've seen that twice over the years, and am darn glad I didn't follow the common and (as it would have been in those two guns) risky suggestion to start in the middle of the load range in a manual. Don't do that. It only involves the expense of firing one of those light loads to see it is wimpy. Even working up in half grain steps won't cost you more than ten rounds or so. Well worth the investment in safety, IMHO.

In your instance, the Hornady starting load is 49.5 grains. The Speer is 54 grains, and the Hodgdon is 51 grains with a Hornady Spire Point seated to 3.180" in a Winchester case with a Winchester WLR primer. The smallest is Hornady's recommendation, and they made your bullet. So the safe advice is to start with that and work up in steps not over 0.5 grains.

I suspect you were operating under the erroneous assumption that all bullets of the same weight should work with the same load data in all brass and with all primers in all guns. Not so. Expecting one manual's data to necessarily apply to all guns is expecting the manual authors to have a crystal ball and to know what the whole range of firearms and components will work the same way with all guns. All you really get in a manual is how their components worked out in their gun. It's a ballpark figure for all combinations, and not always all that precise a ballpark. Checking multiple references is an attempt to find the worst case. Then assume your gun is at the worst end of the worst case until firing tests prove otherwise.

One other note the guy at Hornady said that if I shot a hot load in the Summer the pressure could go even higher due to the increase in temp. I did not think about that. . .

You might try working up a second load with H4831? It is formulated to be less temperature sensitive, but there is no guarantee. You just have to find out how it does in your gun? One method is to wear a warm coat and put your test rounds into your shirt pocket long enough to reach body temperature before you start firing it. That warms them to 98.6 degrees, or close to it. That should be worst case for most folks not in Iraq. Re-fire the same test with cases kept on ice in a plastic baggy in an insulated lunch box to see what they will do in winter? Watch for condensation and don't let anything sit in the chamber for too long.

On a chronograph, this question gets tossed around a lot. Probably the best one commercially available is the PVM-21 sold by NECO. It is German made with a 16 MHz time base (4X faster than the usual 4 MHz time base) and infrared light sources built-in rather than optional. It is also by far the most expensive, at $750.

I have gotten near perfect agreement between my CED Millennium chronograph (the M2 is the current model) and my old Oehler 35P (long held to be the gold standard, but no longer available). The IPSC uses the CED (two in tandem in black boxes with the infrared light screen option in place) as the final arbiters of what a contestant's actual power factor is at their nationals. At just under $200, the CED is not the cheapest unit, but it may be the next best to the German technology?

 

[broom_jm]

One other note the guy at Hornady said that if I shot a hot load in the Summer the pressure could go even higher due to the increase in temp. I did not think about that. I am not worried with the current load. I would be concerned if I stayed with the hotter load and the higher pressure.
Darin

Darin,

Maybe I am misunderstanding what you're saying here, but it has always been my understanding that high temperatures actually make really hot loads safer, whereas firing those same loads on a very cold day can result in higher, potentially unsafe pressures? Is this a misconception, on my part?

EDIT: Turns out I was confused on this and hot weather actually causes higher pressures. I'm 0-for-2 on this one!