Quickload questions

[DPSTX]

I am new to quickload software and I’m trying to learn how to interpret the information and compare to actual chronograph info.

Here is my situation. I have two 243 Win chambered M70’s, one is my hunting rifle and one is my new match rifle. I have listed the Specs for each below, including the brass used and measured grains of water for the brass.



I have been loading rounds for both rifles using the same bottle of powder (h4350) and both using 210M primers (although the primers are not from the same lot). The chronographed velocities from the hunting rifle are usually ~150 to 200fps faster than predicted by Quickload. I have verified that the barrel length, COAL, case capacity, etc are accurate for both rifles when using the software. I have tried both rifles with several different loads and bullet combinations and seating depths, and while the changes result in corresponding changes in the measured and predicted data, the measured velocity for the hunting rifle is always much higher than the predicted while the match rifle is always pretty close, only 25 to 50fps faster than predicted, which could be attributed to variation in powder lot if it didn’t create so much more velocity in the hunting rifle. In fact, the match rifle has 5.5inches more barrel, and other than the variation in the brass brand and capacity, the hunting rifle velocity will be right with the match rifle with the same load. In order to have the velocity of the hunting rifle predict closely, I have to adjust the burnrate of the powder significantly (>10%) and adjust it back down to predict the match rifle velocities correctly; all this with powder from the same bottle. Am I missing something?? I would expect that once all the specs were sorted out in the software that the predicted velocities would be closer to the actual, and that any adjustments to the burn rate of the powder to bring the software to the measured would be pretty close to each other.

Any ideas??



Hunting rifle.

Pushfeed M70A, 22 inch factory barrel, 1in 10 twist

Winchester brass

56.4 gr water capacity



Match rifle

Pushfeed M70, 27.5 inch Kreiger barrel, 1in 8.5 twist

Lapua brass

54.0 gr water capacity



Thanks in advance

DPSTX

 

[TheBlueEyedBear]

You forgot one key ingredient,,,,, the bullet. What bullet are you using in each gun. Sounds like one is developing more pressure than the other. Have you noticed 'cratered ' primers or hard bolt lift in either gun?
As far as Quickload, it is not an exact science. When using magnum primers I alway adjust the burnrate + 8-10% depending on cartridge.
Also, what are the chambers like on each gun? Are they identical as far as the neck dimension, and freebore?

 

[Erik Cortina]

What is the relation of the bullet to the lands in each rifle?

 

[DPSTX]

Thanks for the replys, guys. I have tried several bullets in the hunting rifle and the velocities are always higher than expected or predicted by Quickload, like I said, on the order of 150 to 200fps. The rifling in the hunting rifle begins about 2.225" and the loads I put in that gun are always about .040 off the lands. The rifling in the match rifle begins about 2.400" and I seat them currently about .080 off of that. The one load that I tried in both rifles that was identical except for seating depth (and brass) was 40.5grains of H4350 with 95gr Berger VLD's. not a very hot load at all, (I'm just starting to work with quickload, so I wanted to gather data and try to get a fix on my powder, and due to the difference in performance between the 2 rifles, I'm being conservative at this point) The measured velocities of this load in the 2 rifles is very close, (mid 2900's) even though Quickload predicts about mid 2700's for the hunting rifle. With its much shorter barrel, I would expect there to be a significant difference.

The hunting rifle has a factory (1973) Winchester chamber. The match rifle has a Chamber that according to my gunsmith is pretty close to SAAMI except for the leade. I know that a neck sized case that has been fired in the hunter will chamber in the match rifle but the handle is a bit tight going down.

My previous loading experience with the hunter has shown that it does tend to produce higher pressures ( due to case evidence, primer pocket stretch, flattened primers, etc) than other 243's, I can't use some of the loads that other guys use, 'cause as I work up toward those loads, I start to get high pressure signs before I ever get close to their powder quantity.

I guess I'm just trying to find out what the variable is that is causing the hunter to have higher pressures and is making it difficult to have a stable number for the burn rate of this powder. I realize that the burn rate somewhat dependent upon conditions in the chamber at the time, but these chambers seem to be fairly close and there is a bit of difference between the lapua and Win brass.

I look forward to your ideas/suggestions.

DPSTX

 

[mkihne]

Could be barrel difference or as stated above, the freebore. Also groove/lands dimensions might vary by a small degree between barrels, twist rate, etc. Barrel length also plays a factor. I think you can eliminate powder and primers if, as you say, you get a reproducable difference with load variation. You could also mike your fired cases(base, below shoulder, etc) to roughly assess chamber dimension variables. Headspace too. With consistent variation, it has to be one or more of the above.

 

[kelbro]

You might try tweaking to coefficient of friction for the bullet to see if you can get it to align with your chrono.

 

[pmarauder]

Looks like your only neck sizing your cases.....your water capacity test says it all... You have a large chamber on the hunter (larger combustion chamber) I bet if you full length size your cases, your velocity will also become lower. I would bump your hunter brass back .002 at the shoulder if you have a way of measuring that (headspace comparator insert) and see what happens.
Derek

 

[TonyR]

Did you adjust the case water volume in QuickLoad for the differences in the two chambers?

 

[DPSTX]

Did you adjust the case water volume in QuickLoad for the differences in the two chambers?

Yes, and the Lapua brass in the match rifle is a bit smaller inside (and heavier, they weigh more than the hunter's Winchester brass) The Lapua is 54gr water capacity and Win is 56.4gr.

I'm not really trying to get the 2 rifles to perform equally, in fact, I trying to figure out why 2 rifles that are so different perform the same and more importantly what the factor might be that I am not properly entering in Quickload.

I have not yet tried the bullet coefficient of friction adjustment that was suggested. The match rifle's barrel is a lapped Kreiger with 243 grooves and 236 lands and only four of each as opposed to the 6 of each in the hunter. I hadn't thought of that as a potential cause until it was suggested, but I did kind of wonder, if it was important, why it wasn't available as an entry in the software.

From what I have read, many people do not get the "advertised" velocities from factory ammo with a 22" barrel, but my hunting rifle does. I've always wondered why. If I'm not able to isolate the cause so that I can use a consistent powder burn rate in the software, I'll just have to keep the numbers separate for each rifle and not correlate them.

The only indication I have of headspace or chamber variation between the 2 rifles is that I can chamber the necksized cases from the hunter in the match rifle and they will go in,they just take more force to pull the bolt handle down. I've had cases that were fired (in my hunting rifle) with a bit too much powder that were harder to open the bolt on than this was to close. Nothing beats proper measurement but I don't have the tools for that.

I suppose that it could also be a stack up of several of the factors discussed but all in the direction of increasing the velocity/pressure in this old rifle.

I really appreciate ya'll's input, I've got a lot to learn, and I'm enjoying it!!

DPSTX

 

[whiskey08]

wow, in this case the causes are literaly infinite. Number one reason in my opinion for differences is the barrels and chambers.

As far as the difference between your chrono, and quick loads chrono differences it could be specific lots of powder, primers, etc..

Chronos vary alot, your chrono might be way off from what theyre using. My buds CED vs. my cheap chrony arent even in the same galaxy. Granted both guns are different but I think its a matter of two guns, two barrels, two chambers.

If you get a chance run you numbers thru JBM caculator, and see if your trajectory matches what your chrono says your velocity is. In my experience I use the JBM caculator and real world trajectory to tell me how fast my bullet is doing.

lastly, I appreciate a handloaders mental sicknesses when it comes to perfection, but there's comes a point when your causing to much brain damage and could do much better with working on something more tangible e.g why does fred flinstone continously order the big slab of ribs when he knows its going to tip his car over????????????