Chronograph issue or is H4350 very temp sensative?

[ken226]

A few weeks ago I worked up a load for my Obermeyer 5R barreled Weatherby .260.

I ended up with R&P brass, R&P primers, 42 grains of H4350 and 140 Amax bullets seated at 2.825. This load shoots really tight and chronographed at 2745 average at the time, velocity deviation was within 12 fps.

Due to recent events, jackasses have been panick buying just about everything gun related, including H4350. Since i couldn't find any, i picked up 8 lbs of the closest thing i could find, which was AA4350.

I loaded 5 rounds with 41.6 grains, [email protected], 5@42, [email protected], all seated to 2.825 like my H4350 load and went to the range. Here were the results.

41.6 AA4350 = 2700 fps ave
41.8 AA4350 = 2500-2525
42.0 AA4350 = 2500-2525
42.2 AA4350 = 2500-2530

Pressure signs were fairly normal, looked just like the primers on my H4350 loads. They shot to the same zero/poi as my H4350 load. Accuracy was good for all loads, about .5-.7 moa, with most of the group error being horizontal due to a 10 wind.


So I was thinking this AA4350 stuff must really be slow compared to H4350, so i broke out some of the H4350 loads from a few weeks before and was surprised when they also chronographed @ 2500 fps.

The chronograph is an RCBS. The plastic one that all fits into a bullet shaped housing and feels like it was made in china for about 50 cents.

It was weird that the 41.6 grain load showed 2700 fps, which is about what I expected from that load, but the hotter loads were significantly slower. All the loads powder charges were hand weighed individually.

Could my scale be screwed up, or the chronograph? It was 30 degrees this morning and 60 3 weeks ago when i came up with the h4350 load. 200+ fps difference over a 30 degee temp change seems to defy physics.

 

[psinclair]

Re: Chronograph issueor is H4350 very temp sensative?

Chronographs......I hate them.

I've shot H4350 in both of my .260's from 100F to minus 40F. It's one of the most stable powders I've shot. Varget is the same way...boot heel the chronograph!!

 

[ctressler]

Re: Chronograph issueor is H4350 very temp sensative?

What chronograph are you using? It could make all the difference.

 

[Engine 22]

Re: Chronograph issueor is H4350 very temp sensative?

I have found that my crappy crono reading varies depending on amount of light hitting the crono. Maybe something there? ie: direct sunlight vs. overcast days??

 

[lanwickum]

Re: Chronograph issueor is H4350 very temp sensative?

I have played with plenty chono's. now have a Oheler 35P and a magnetospeed. Those are the only ones I would come close to trusting that I have used. I still don't trust them. I have a targets from 100-800 at my shop. Then can shoot as far as I want if I drive a mile or 2. I get my dopes and make sure the velocity works in my ballistic programs. Offten don't even use a chrony anymore. It is the end result that counts. Varget is one of the least sensative powders I have ran over a chrony with 308. Now, when I lived in town and had to shoot at a 300yard range or drive 60 miles. The chonographs were used a lot. You get what you pay for is fairly true in the chrony world.

 

[ken226]

Re: Chronograph issueor is H4350 very temp sensative?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: CTressler</div><div class="ubbcode-body">What chronograph are you using? It could make all the difference. </div></div>

Its the RCBS plastic model that looks like a giant bullet. It uses two optical sensors.

This thing:

http://www.pyramydair.com/s/a/RCBS_AmmoMaster_Chronograph/3962?gclid=CKWn9YPc4bQCFQmCQgodFG8AZg

 

[ctressler]

Re: Chronograph issueor is H4350 very temp sensative?

H4350 is great powder, I don't find it to be temp sensitive, at least not bad. As was stated above, I wouldn't trust anything but an Oehler. I chased velocities just like what you described above, then I got an Oehler and everything fell into place.

 

[bward]

Re: Chronograph issueor is H4350 very temp sensative?

4350 is as stable as it gets.

 

[Huckleberry75]

Re: Chronograph issueor is H4350 very temp sensative?

^^^^^^yep, what he said

 

[jfseaman]

Re: Chronograph issue or is H4350 very temp sensative?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ken226</div><div class="ubbcode-body">...
Due to recent events, jackasses have been panick buying just about everything gun related, including H4350. Since i couldn't find any, i picked up 8 lbs of the closest thing i could find, which was AA4350....</div></div>It seems like you just called all of us jackasses.

Please be civil, we are all in this together. The "anti" people are demonizing firearms owners as a way to create a division in society. Creating "them vs. us" tactics are the new normal for the "anti" groups and media. You are buying into the "anti" rhetoric and demonizing your own kind.

Myself, I was already in the process of "stocking up" long before recent events perpetrated by <span style="font-weight: bold"><span style="font-style: italic">non-gun owner sociopaths</span></span>.

Combined with the mid winter low stocks, well...

Supplies can be hard to come by.


Now for your load.

I shoot a Pac-Nor barreled Weatherby in 260 Remington. 140 A-Max's over H4350.

Your load is in the same realm as mine and my best accuracy is in the low/mid 2700fps.

I have had this experience with "Chrony" brand devices.

With H4350 I never see that kind of temperature sensitivity. AA4350 is expected to be more sensitive than H4350 but not that bad.

I believe it is battery or lighting issue. Temperature can really bring down a battery's ability to put out power.

If it were me I'd:
Put a new battery in the chron
Make a sun shade out of cardboard slipped over the side support rods.

 

[9H_Cracka]

Re: Chronograph issue or is H4350 very temp sensative?

B2B your current chrono w a CED. Make sure the CED is closest to the muzzle and the wires between it and the keypad fully extended (OK to drape down to the ground).

Distance from the muzzle can give you erratic readings. Make that a constant and test against the CED.

Also, I have written up here many times how to set up your chrono for good readings. A good tripod, bench rest setup, target as hold point - you need the bullet flying directly over the sensor cutouts just a few inches above for your most consistent readings.

Lastly, comparing different brands of powder with similar numbers on them - does not make sense to expect one powder to be the same as another. Also, lot testing from lot to lot - it is a baseline expectation that you need to test any new lot against a known lot to determine the new lot's burn rate and density.

 

[ken226]

Re: Chronograph issue or is H4350 very temp sensative?

I went back to the range this morning and put more effort into setting up the chronograph. It worked, I angled it so that an object passing through the screens would cast a shadow on the sensors.

So @30f this morning, 42 grains of H4350 was giving me 2700fps, and I worked up to 42.2 grains of AA4350 to get the same velocity.

I appreciate the help.

As to the "jackass" statement, I stand by that for those who earn the title.

When a guy who goes through a few pounds of powder or a thousand primers a year suddenly freaks out and charges $20,000.00 in reloading supplies on thier Visa card, then lists it on gunbroker for 80.00 per pound, or 110.00 per thousand primers, I firmly believe that person to be a Jackass with a capital J.

I'm sure that none of my fellow Snipershide members are doing that, and im not picking on the guys who go buy a couple 8lb jugs so they will have some just in case. I'm talking about guys like this one:

http://www.gunbroker.com/Auction/ViewItem.aspx?Item=325122934

I'm a big fan of capitalism and allowing the market to set the price, but sometimes it goes beyond reason. A friend who works at Sportsmans Warehouse in Tucson said they have had several guys come in right after the truck shows up and charge up huge multi-thousand dollar carts of .223, magazines, semi-autos and reloading stuff. I hope they lose thier butts in thier gun/ammo speculating ventures.