9.3x62 300 Grain A-Frame - COL & Load data Qs

[jwp475]

Quick-Load shows increasing pressures as you seat deeper (reducing the space inside the case).
Obviously this would not be the case if you were initially jammed into the lands and just moving back from there.

Chub Eastman wrote an article years ago with pressure testing the same load each as he seated deeper and the pressure and velocity decreased as the bullet was seated deeper

 

[sestoppelman]

Chub Eastman wrote an article years ago with pressure testing the same load each as he seated deeper and the pressure and velocity decreased as the bullet was seated deeper

I get what you are saying, but that is something taking place at the other end. Seating the bullet deeper into the case reduces capacity and will increase pressure slightly and the throat distance may offset that increase and sort of break even, thats possible, but the increase is still there even if backing the bullet back from the lands decreases it slightly as well.
I think you get a bit of both.

 

[sestoppelman]

This is from Modern Reloading by Richard Lee of LEE Precision.

 

[jwp475]

This is from Modern Reloading by Richard Lee of LEE Precision.
View attachment 418335
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Exactly seating deeper straight wall cases most certainly increases pressure
Bottle neck cartridges is another matter and it has been proven that seating deeper lowers pressure, until you get farther than .2500" from the lands and then pressure starts to increase.

 

[sestoppelman]

He didnt differentiate between case styles. But you have it your own way.
Lee said the effect was greatest in pistol and revolver rounds he didnt say rifles were exempt from the effects.

 

[jwp475]

This is a post by Mule Deer (John Barsness) from a thread about bullet seating depth here not too long ago:

You're missing a couple of things. While pressure starts to build as soon as the primer ignites, it doesn't rise nearly as rapidly until the bullet hits the rifling, due to the force required to engrave the bullet. Seating bullets deeper essentially results in a longer throat, giving the bullet more room to accelerate before engraving on the rifling.

This is exactly why custom chambers for Weatherby cartridges that eliminate the longer "freebore" result in much higher pressures: The bullet hits the rifling much sooner, and pressures skyrocket. The freebore results in a flatter pressure curve.

The same effect is created by seating bullets deeper, which essentially increases case volume, rather than decreasing it as you suggest. The "pressure vessel" is essentially the entire chamber, to the beginning of the rifling, rather than the space occupied by the powder to the base of the bullet.

Second, modern rifle powders are progressive-burning: After ignition they burn slowly, due to either granule size (large granules have less surface area for their volume) or burn-deterrent coatings, or both. As they continue to burn, they burn faster--but by then the volume has increased considerably, due to the bullet being further down the bore. Like a longer throat, this flattens the pressure curve.

The opposite effect is usually seen in handgun rounds, where seating bullets deeper increases pressure. First, many if not most handgun powders are degressive-burning: They start off burning very fast, then slow as the burn progresses. Seating bullets deeper encourages this initial fast burn, increasing peak pressure. Handgun chambers also have very short throats, especially in semiautos.

John

 

[sestoppelman]

Well it is what it is I guess. Barsness is a very knowledgeable guy. I dont really care for him, but he is pretty sharp.
Wish that link was usable, like to read it.

 

[shootist~]

I ended up turning my seater stem down two full turns and did a couple of starter loads (3 rounds each) with the 300 Grain Swift A-Frame and RL-17. As previously seen, the 9.3x62 CZ 550 factory barrel is quit a bit slower than the Quick Load projections. More so as bullet weights go up, it appears. (The Swift Manual does not show RL-17 with the 300 gr A-Frames, btw.)

These had a COL of 3.217" (which averaged .082" off the lands) - and were shot at 50 Yds using my Bog Pod HD sticks from a kneeling position. (Two point hold).

56.3 Grains of RL-17 with an F210 std primer into 6th fired Lapua Brass did 2,157 & 2,156 fps (I only chronographed the last two of the three). I used a Lab-Radar Chronograph.

57.3 Grains of RL-17 with the 300 Gr A-Frame averaged 2,203 fps (3 of 3) and measured 1.05" center to center, so about 2 MOA (50 Yds/Sticks). This group is shown below. I'm not sure how much further I will proceed with the 300 AF, but it looks like *In My Rifle*, approximately 60 grains of RL17 would be needed to match the 2,300 fps / 300 grain load Kevin Roberts mentions in The Perfect Shot II.

 

[sestoppelman]

That load equates to a .405 Winchester factory load which aint too shabby. However it seems like it ought to do better than that, perhaps a little faster powder, or more of R17. Load by half grains steps until you get some pressure signs.
Max OAL is 3.30" but the throat and mag length of the specific rifle determine the proper OAL.
Have any CFE223? If it works in the Whelen it should do equally well in this round.

 

[shootist~]

That load equates to a .405 Winchester factory load which aint too shabby. However it seems like it ought to do better than that, perhaps a little faster powder, or more of R17. Load by half grains steps until you get some pressure signs.
Max OAL is 3.30" but the throat and mag length of the specific rifle determine the proper OAL.
Have any CFE223? If it works in the Whelen it should do equally well in this round.

Yes on having some CFE223 - though not much.
I tried a few loads with 250 grain Accubonds, but RL17 seemed to do a better job for me (good velocity and accuracy).

 

[shootist~]

300 Grain Swift A-Frame, still .082" off the lands. Finally got it up to my target velocity of 2,300 fps at 60.0 grains RL17. Note my barrel is slower (takes more powder) than Quick Load indicates. Lapua Brass and F215 primers.

Four shots - 50 Yards, from the bench.

 

[baxterb]

That’s a good load. How compressed it that?


my 286 Norrh forks shoot at 2505 from my 25” barrel. The 9.3 x 62 is a very capable cartridge.

 

[shootist~]

That’s a good load. How compressed it that?


my 286 Norrh forks shoot at 2505 from my 25” barrel. The 9.3 x 62 is a very capable cartridge.

Quickload shows it at 100.9%. Visually I would have thought it to be a little more.
One of my fired Lapua cases held 75.7 grains of water, btw.

That Northfork load would be a serious Cape Buff load, IMO.

Elevation was set at 0.5 Mils higher than my standard 250 gr Accubond load (zeroed at 200M).

 

[AZDAVE]

I have shot and tested many different powders with, 286, 300, 320gr bullets in the 9.3x62 and 9.3x74. The two best powders I have found that give good velocity with the lowest pressure signs, and best velocity have been RL17 and Ramshot Big Game. Have tried slower and faster powders but the results weren't acceptable to me. Haven't tried CFE223 as haven't been able to source enough to do a proper load work up.

I start off with every rifle and determine the Max length for each different bullet that I plan on shooting. Measure the length of the magazine box to ensure it can be loaded to that length. I start load development with bullets seated 30 thousands off the lands and work my way up to 15 thousands. I use the hornadat OAL case gauge to measure this. Then mid bore rifle cases I start at min, load reccomend and go up a grain at a time looking for pressure signs. I always use a chronograph to determine velocity, ES, and Sd. For each load. The two loads with the best ES and SD. I then shot for accuracy. I always take the load that gives the best accuracy vs highest velocity. Sometimes you get both together. Also measure the case volume, I use privi, hornaday, and lapua in the x62 and there is enough volume to affect pressures, so develop your loads for the same make of brass for the most consistent and safe loads.

All rifles are individual characters, I have 2 custom 9.3x62`s with 25in barrels and they shoot the same load 96 fps different.
The chamber was cut with the same reamer and the OAL is within 3Thousands. One has a paid-for barrel and the other a shielen.

When I get time to check my load development book in the shop I will PM you what loads work for my rifles. Again all best loading practices when you develop loads for your rifle.

The other comment I have is that several of the comments on seating depth seem to contradict each other. So I will put things into a basic physics statement. When you reduce the volume of a container and burn the same volume of a comuustable substance the pressure increases. Ie when the bullet is seated deeper into the case you reduce volume of the container. With different burn rates of powders you will see small changes in very slow powders like RETUMBO and very large changes with fast powders like titewad. So please be careful.

 

[baxterb]

@AZDAVE

I began with Big Game and just stopped there. That’s great powder for the 9.3.

I’m about to try it in my 06 with the 175 LRX as well. I hope it works, I like simplicity.

 

[shootist~]

@AZDAVE
Thanks for the informative and well thought out post.

My decision to use RL-17 for the 9.3x62 was in large part due to posts from you and @dchamp

Having a decent supply on hand helped as well.

 

[AZDAVE]

Happy you found the information helpful

 

[shootist~]

Back to seriously shooting the 9.3x62 300 grain A-Frame load again (.082 off the lands in my CZ550).

Did a check to see where a 275 grain Norma Solid (factory load) would print in comparison.

50 Yards off the sticks. Two 300 gr A-Fs, then two 275 gr solids, then two more A-F. The two solids went ~2.6" high (and a bit right).

Also dialed up 0.5 mils per my ballistics app, and did two more on our 165 yd steel. They went right where they were supposed to go.

Tempted to keep tweaking things, but I had probably better quit while I'm ahead.

 

[Puddle]

Possibly I practiced with the 9.3 a little too much. (700+ rounds at the 1 year mark.) As mentioned elsewhere, I have become a recoil sissy in my old age. But enough history.

My goal is to work up a lower recoil practice load with 286 grain bullets (I do like to practice) - and then develop a hunting load that duplicates Dr Kevin Robertson's favored 9.3x62 loading - the 300 grain Swift A-Frame at 2,300 fps. He mentions this load as working well on buffalo for numerous clients in his The Perfect Shot II.

And I thought I was a bit OCD putting 200 rounds down the tube in field practice!

My 300 grain A-F load is 56.80 grains RL-17 which hovers right at 2,300+ fps MV from my 24" barrel. This is using new Lapua brass.

I use all manner of practice bullets from 185's, 232's, 250's, 285's & 286's that I load to around the classic 2,360 fps MV using mostly H4895. I do use some R-15 and R-17 for practicing, but generally save those for hunting loads. I'm hoping to use the 250 grain AccuBond at ~2,500 fps MV on a Sable hunt one day.