Lesson Learned

[SD Handgunner]

I finally was able to do some shooting this past weekend. I worked up a new load for the .30-30 AI (long and complex story). At any rate in talking to my cousin in law (who also has a .30-30 AI Contender) he was telling me he was getting radically different pressure signs and velocity readings with his .30-30 AI at different ambient temperatures.

We talked about this on a couple occasions, and I had decided to switch from the IMR-4198 I was using to H-4198SC (which is part of Hodgdon's Extreme Line of Powders that are said to NOT be temperature sensative).

In the mean time I re-read an article written on Contender Pressures and picked up on something I had totally missed the first time I read the article. Without being too long winded basically the author come to the conclusion that with cartridges using Large Rifle Primers a mark from the Rimfire Firing Pin Hole on the Contender Frame starts being visible on the fired primers at about 45000 CUP, and seemed to coincide with the determination he had made from case expansion measurements.

In examining the fired cases (as I sized and deprimed them) I could detect this mark on about half of my cases. To make a long story shorter, I started over with H-4198SC with the 125gr. Nosler Ballistic Tip. When I got to the same charge weight as I had been using with the IMR version the pressure indicators were still much less. Accuracy was good, so I decided to chronograph the loads. Velocity with H-4198SC and the 125gr. Nosler Ballistic Tips averaged 2597 FPS, but the extreme spread and standard deviation numbers were almost half of what they had been with the IMR version.

I then ran a Ballistics Chart with the 125gr. Nosler Ballistic Tip at 2597 FPS (average velocity) and it appears that I will still have the performance level I was after when I started this project.

Now is when things get interesting. Yesterday afternoon after I finished up loading ammo with H-4198SC I decided to shoot some more groups. I fired several groups with H-4198SC with the 125gr. Nosler Ballistic Tips. accuracy while not quite as good as I had previously obtained with the IMR powder was still quite good. (Yesterday I could shoot 3 shot groups great, but not 5 shot groups for some reason.) I then decided to shoot some of the remaining ammo I had loaded with IMR-4198. Now at this point I should note that I had never shot the ammo loaded with IMR-4198 at temperatures this high before, and here is where the lesson is learned. Yesterday it was 30 degrees hotter and with high humidity than when I had ever shot these loads before.

Yes IMR-4198 is indeed temperature sensative (just like Bob had told me), and I could see the slight imprint of the rimfire firing pin hole on every fired primer. In addition while the Contender action broke open smoothly, I had two of these fired cases in which I felt slight resistance when I pulled them free of the extractor, where at cooler temperatures they had always just fallen free from the chamber.

According to the article I had read I was right on the edge, and the increase in temperature did apparently raise the pressure of this load. It wasn't until I packed up and was at home that I thought I should have chronographed the IMR-4198 Loads at this same temperature

Even with the change in powder the .30-30 AI is still providing a substantial increase over the .30-30 Winchester, and provide adequate performance for what I need it to do.

SD Handgunner

[22hornet]

Very good information.

[Hopalong7]

Thanks for sharing SD Handgunner.  I've only tried Rel7 w/ the 125 BT's in mine...2600+...good accuracy.  Have not shot in hot weather though.
GOOD SHOOTIN', Walt  :grin:

[Hopalong7]

I've not used the 125BT's actually on deer w/ the 30-30AI.  I have w/ the .30Herret with good results.  In the 30-30AI I've used the 150BT on two good size bucks.  WHAMO!! Shootin'm just shot of 2400fps.
GOOD SHOOTIN', Walt  :grin:

[SD Handgunner]

I used the 125gr. Nosler Ballistic Tips out of the .30-30 AI last year on two Whitetails. One at 286 yards (lasered) and one at 126 yards (lasered). Both were one shot kills, and bullet performance was quite good. In both instances the bullets exited so none were recovered.

On the buck at 286 yards the Buck was quartering towards me. The bullet hit right behind the front shoulder and exited through the off side rear quarter (missing the hip bone by an inch or so) leaving about a 2" exit hole. On the one my daughter shot at 126 yards the shot was high hitting the top of the near side shoulder, clipping the very bottom of the spine and exiting through the top of the off side shoulder leaving an exit hole about the size of a quarter.

Not sure if it makes a difference or not, but these were fired from a 1 in 14" twist barrel.

SD Handgunner

[SD Handgunner]

You're very welcome.

I have also used the 125gr. Nosler Ballistic Tips out of a Super 14 .30-30 Winchester, but never did get to smack a Whitetail with them from the .30-30 Winchester.

SD Handgunner

[xphunter]

I have to the Hogdon Powders.  In fact, all of my specialty pistols use Hogdon.  There was supposed to be another powder out there that is not temp sensitive, but I'm unsure who it is.

[grovere]

One of the powders that I have found not to be temp sensitive is Ramshot.

[mudriver]

Quick question on this topic:  I put a new scope on my 30-30 AI barrel and sighted in with 30-30 factory loads (while fireforming).  I also shot some newly loaded 30-30 AI loads with 150g BT using 35g of 3031.  For some reason when I aimed at the same point with both factory and the AI loads - the 30-30 factory loads (also 150g bullets) hit about an inch higher at 70 yards than the 30-30 AI.  I don't have a chronograph but my instincts tell me that whatever is faster hits higher.  Is that true and why would this happen (there must be more powder in the AI loads)?

[SD Handgunner]

Now I confused.

I went out and did some more chronographing today with the H-4198SC Loads in the .30-30 AI.
 
OK the other day (8-30-04) when I chronographed the loads the results I obtained were as follows :
1st Shot = 2588
2nd Shot = 2616
3rd Shot = 2599
4th Shot = 2592
5th Shot = 2589
AVERAGE = 2597
Extreme Spread = 28
Standard Deviation = 6.56
This was done Monday morning at 9:30 AM at approximately 58 degrees.

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Today (9-4-04) I chronographed the rounds that have been in the freezer since Monday night at 11:00PM. The results were as follows :
1st Shot = 0 (forgot to turn on the Chrony)
2nd Shot = 2665
3rd Shot = 2666
4th Shot = 2620
5th Shot = 2615
AVERAGE = 2642
Extreme Spread = 51
Standard Deviation = 9.80
I didn't have a thermeter in the freezer, so we'll just call these 32 degrees.
 
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Then I also shot some rounds I placed in a plastic bag this morning (9-4-04) and laid them on the front step in the sun for 1 hour. The results were as follows :
1st Shot = 2712
2nd Shot = 2693
3rd Shot = 2717
4th Shot = 2728
5th Shot = 2698
AVERAGE = 2710
Extreme Spread = 24
Standard Deviation = 7.48
The ambient temperature when I shot these loads was 82 degrees, they had been sitting in the sun for an hour, and were quite warm to the touch so I am guessing they were at least 82 degrees.
 
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 When I add all 14 rounds chronographed together and average them I end up with an AVERAGE VELOCITY of 2650 FPS, with an extreme spread of 124 FPS and a Standard Deviation of 6.87 FPS. These were fired at vastly different temperatures.
 
HOWEVER the important thing about all of this is IN examining all of my fired cases with H-4198SC the primers are quite noticablly less FLAT than with the IMR-4198.
 
When all is said and done, and I average all 14 rounds chronographed I ended up loosing 33 FPS from the load I was using. Not sure what is different between the rounds I chronographed the other day and the ones I chronographed today, all of the powder is from the same can, and all of the primers & bullets I chronographed are from the same boxes.
 
Next is shooting some groups with different bullet seating depths to see if I can shrink the groups a little. Then I can move on to the 6mm T/CU next week, as I have a lot of work to do with that one.

SD Handgunner

[Lone Star]

I don't have a chronograph but my instincts tell me that whatever is faster hits higher.  Is that true and why would this happen (there must be more powder in the AI loads)?

Actually the opposite is usually true.  A slower load will keep the bullet in the barrel longer, meaning that the barrel has rotated higher by the time the bullet exits the muzzle and is pointing higher.  A faster bullet has a shorter barrel time so the muzzle is pointed closer to horizontal and the bullet will land lower on the paper.

However, this isn't always true.  A load which produces significantly more recoil will rotate the barrel higher by the time the bullet leaves the muzzel, meaning that the bullet lands higher on paper.  IME the former is more common.

[mudriver]

Thanks - I wouldn't have considered recoil in the equation.

[Majbg]

SD, Thanks for the information.  I am also working on a 30-30AI project, but out of a 23" bbl for my contender.  Appreciate all the work you've shared on this.  bg

[Major]

I don't have a chronograph but my instincts tell me that whatever is faster hits higher.  Is that true and why would this happen (there must be more powder in the AI loads)?

Actually the opposite is usually true.  A slower load will keep the bullet in the barrel longer, meaning that the barrel has rotated higher by the time the bullet exits the muzzle and is pointing higher.  A faster bullet has a shorter barrel time so the muzzle is pointed closer to horizontal and the bullet will land lower on the paper.

However, this isn't always true.  A load which produces significantly more recoil will rotate the barrel higher by the time the bullet leaves the muzzel, meaning that the bullet lands higher on paper.  IME the former is more common.

OK, think about this.   A bullet drops because gravity pulls it down.   If a barrel is clamped so it can’t move then the faster a bullet can get to a set fixed distance (say 100 yards) then the less time gravity can pull on it and the higher that bullet will strike.   A slower bullet will be pulled on by gravity for more time and will hit lower.   That is why a faster bullet is said to shoot flatter, regardless of what barrel it is fired in or how much recoil there is.

Therein lies the whole reason for the quest for speed.   That is the main way to overcome gravity.   The other way is to shoot at an up angle so the bullet will cross the line of sight twice.   That is what actually happens in most guns by the way.   So we seek a combination of the two and the flatter (faster) a bullet shoots then the less time it has to be pulled off target.

But, since we do not live in a perfect world then wind, barrel vibration, mirage and a hundred other things enter in to it to move that bullet and we will forever be chasing that perfect group we want down range.

         :roll: