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#5094069 - 03/29/11 Re: 243 Ackley [Re: HuntKY]  
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Jim in Idaho Offline
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Brand new to the .243 AI so take this FWIW. Just got my LH M700 SA back from the smith and finally got it to the range this weekend. Barrel is a 24Ē Remington factory take-off I bought from the classified here a couple of years ago.

After fireforming 50 cases this past Sunday, I checked the capacity increase from cases of the same lot. Notes are at home, but the average gain in case capacity (weighing cass water filled to the base of the neck) was about 2 grains of water, or a whopping 3.8% capacity increase.

Using the 1 in 4 rule, that should allow about a 1% increase in velocity. Figuring around 3000-3050 with 100 grain bullets for the parent, that gives us 3030 to 3080 fps. Obviously not something to write home via Priority Mail about.

Factory ammo, Remington 100 gr. Core-Lokts, gave just over 3000 fps in the original chamber, about 3020 IIRC, and rounds from the exact same box of ammo gave 2949 fps in the improved chamber, a velocity loss to be expected.

But in fireforming, my velocities were a bit puzzling. I was using max book loads (for the parent case) of RL-22 and H-4831 under Sierra and Hornady 100 grain bullets, 44 and 45 grains each. 45.0 grains of H4831 with a Hornady 100 BTSP in my 23.75Ē barrel gave 3135 fps, it gave 3096 fps with the sierra bullet. Thatís cooking. In previous trials with this rifle Iíve gotten 3050 fps pretty easy with the same bullets and loads of 42.5 grains of IMR-4350 and (the exact load escapes me here) IMR-4831.

Now, this is a little fudgy logic, but the .243 loads have been tamed due to itís propensity for wider pressure swings in any given string. So, Iím using loads that the books claim to give 3000 fps from their 24Ē test barrels, in a larger chamber, and getting 100+ fps more. Pressure signs (yeah, I know) were totally missing. Primers had a good, well rounded radius, bolt lift was easy, every subjective indication said pressure was very civilized.

Not that Iím unhappy, just cannot explain the increased velocities from this enlarged chamber. Well, maybe Ė I had the bullets seated to touch the lands for fireforming, that would be the only difference over the normal loads where bullets are about .020Ē off the lands. That alone would be telling evidence of being careful when you seat any bullet hard up against the lands. Oh well, something for more experimentation.

Anyway, my whole reason for AIíing the .243 was not for increased velocity anyway. I just wanted to tame itís internal ballistic weirdness and itís humongous appetite for eating throats. Prior to AIíing, this brand new barrel had just over 600 rounds through it of moderate loads, and throat erosion had already advanced .070Ē.

Now that Iím getting my target velocities with book loads for the parent I know pressures just have to be mild (a goal I increasingly strive for as I get older) and Iím not so worried about those famous kabooms with 100 grain bullets the .243 apparently likes to spring on people as the throat gets all eaten up, Iím a happy camper.


Gunnery, gunnery, gunnery.
Hit the target, all else is twaddle!
CMG 300 BP

#5094088 - 03/29/11 Re: 243 Ackley [Re: darrenk75b]  
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Paul Walukewicz Offline
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finally home in Alaska!!!
From jammed to .03 off. Someone mentioned in another thread that i should try even further. So, i'm going to give that a try and see what happens...


I can't spell... Deal with it...
#5094232 - 03/29/11 Re: 243 Ackley [Re: HuntKY]  
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BradArnett Offline
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Originally Posted by HuntKY
Brad, you said you were on your 3rd barrel on the 243AI. Out of curiosity, how many rounds are you getting before they puke?


Sorry for the confusion. I just meant that this was an older Rem action that I've had 3 barrels on, not all 3 were 243AI's. First was a standard 22-250, then an 1-8"tw 22-250, now the 243AI barrel.


[Linked Image]

#5094339 - 03/29/11 Re: 243 Ackley [Re: BradArnett]  
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HuntKY Offline
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10-4....thanks for the clarification.

I'm sure you shoot the he11 out of your 243AI, but 3 barrels since '08 would be impressive.


Protect WYDAHO fish and game, fence out Utah.
#5094369 - 03/29/11 Re: 243 Ackley [Re: HuntKY]  
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BradArnett Offline
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If the 243AI was my only rilfe I'd be in trouble, 'cause that one is a bunch fun to shoot.


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Alpha

#5094643 - 03/29/11 Re: 243 Ackley [Re: BradArnett]  
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longshot3 Offline
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Lots of good info here! Just ordered my bbl from ER Shaw. 1/10 twist, figured for bullet weight between 85 and 100gr. .600 at the muzzle and 24in long. I have put together 2 remingtons with Shaw bbls and got great accuracy with them.

#5094649 - 03/29/11 Re: 243 Ackley [Re: longshot3]  
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Steelhead Offline
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LUCK


"When I was a kid I thought that quicksand was going to be a much bigger problem than it is."
#5094875 - 03/29/11 Re: 243 Ackley [Re: Jim in Idaho]  
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FVA Offline
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Originally Posted by Jim in Idaho


After fireforming 50 cases this past Sunday, I checked the capacity increase from cases of the same lot. Notes are at home, but the average gain in case capacity (weighing cass water filled to the base of the neck) was about 2 grains of water, or a whopping 3.8% capacity increase.

Using the 1 in 4 rule, that should allow about a 1% increase in velocity. Figuring around 3000-3050 with 100 grain bullets for the parent, that gives us 3030 to 3080 fps. Obviously not something to write home via Priority Mail about.




Funny that the 260 gains a hair over 10% in capacity when AI'n verified pretty thoroughly here.
http://www.24hourcampfire.com/ubbthreads/ubbthreads.php/topics/4686301/all/260_Rem_or_AI


#5094980 - 03/29/11 Re: 243 Ackley [Re: FVA]  
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Jim in Idaho Offline
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Not sure I understand, are you saying that the .260 Remington provides a source of humor that the .243 lacks? wink


Gunnery, gunnery, gunnery.
Hit the target, all else is twaddle!
#5095076 - 03/29/11 Re: 243 Ackley [Re: Jim in Idaho]  
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FVA Offline
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I'm thinking something is off with either your math or your 243AI.
Per http://www.6mmbr.com/243win.html ,"The .243 AI delivers more velocity by virtue of enhanced case capacity--roughly five grains more H20 capacity than a standard .243 Winchester. The .243 AI has a water capacity of approximately 57 to 58 grains, compared to 52-53 grains for the standard .243 Winchester."


Bravo

#5095266 - 03/29/11 Re: 243 Ackley [Re: FVA]  
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Jim in Idaho Offline
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Could be. Here is my raw data if you'd like to check it. All cases were filled with an eye dropper right to the base of the neck as checked under a magnifying glass and strong light. The .243 cases were fired in the previous chamber and had been neck sized only, I inserted a fired large rifle primer in each to keep the water from coming out of the flash hole and to keep that from influencing the weight differences from the fired AI cases.

All cases are Winchester from the same bag, twice fired before forming and trimmed to a uniform length after the first firing.

Formulas here are filled weight - empty weight = weight of water, all weight in grains.

.243
Case 1: 218.3 - 165.3 = 53 grains of water
Case 2: 215.6 - 163.3 = 52.3
Case 3: 217.4 - 164.7 = 52.7

(53 + 52.3 + 52.7) / 3 = 52.66666, called it 52.67 grains average

.243 AI cases
Case 1: 219.4 - 164.7 = 54.7
Case 2: 220.0 - 165.4 = 54.6
Case 3: 220.3 - 165.3 = 55.0
(54.7 + 54.6 + 55.0) / 3 = 54.766666, call it 54.76 average water capacity

54.76 - 52.67 = 2.09 grains increase.

2.09 / 52.67 = 0.0396, or call it 3.96% increase. In my earlier calculation I had used 54.7 instead of 54.76 so that accounts for the extra .16%.

Still, round that up to 4% and apply the 1 to 4 rule, which say that a given percentage increase in case capacity will give you roughly 1/4 that much percentage increase in velocity.

Figure 3000 fps as a nominal velocity for the .243 with 100 grain bullets.

3000 fps * 1% = 30 fps increase.

In the article you cite his fired cases have about 2 to 3 more grains than my Winchester cases so he could certainly have gotten a 5% increase.

5% * 1/4 = 1.25%

3000 fps * 1.25% = 37.5 fps increase. I concede that the author of the article beats me by 7.5 fps.


Gunnery, gunnery, gunnery.
Hit the target, all else is twaddle!
#5095408 - 03/29/11 Re: 243 Ackley [Re: Jim in Idaho]  
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FVA Offline
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As I'm sure you are aware fps as a comparison isn't necessarily the most meaningful as pressure isn't always apples to apples.
Both 308 case based AI's I gave as examples showed about a 5 grain increase in water capacity. Your body shoulder junction measure .460?
With the minimum increase in capacity of your 243AI it sounds like you have a 243AAI-Almost Ackley Improved.


#5095426 - 03/29/11 Re: 243 Ackley [Re: Jim in Idaho]  
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EddyBo Offline
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Hmmm I get 4 grains difference and 125fps difference using vv560 and 115 dtacs. If those are once fired they are possibly not fully formed. Of course not all reamers are created equal.

Last edited by EddyBo; 03/29/11.
#5095767 - 03/29/11 Re: 243 Ackley [Re: EddyBo]  
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longshot3 Offline
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Yeah, Steel. I want another three shot group like this!

#5095900 - 03/29/11 Re: 243 Ackley [Re: FVA]  
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Jim in Idaho Offline
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To answer the dimensional quesetion, three fired cases at random measure .4628", .4621" and .4625" at the shoulder junction. Ha, that beat your quoted figure by an incredibly large (in Lillliputian standards) average .00267"!!!

But before we go any further I have to ask, what is your point? Are you really trying to insult me based on minute differences in my reported results that differ from what you read on the internet?

Really?


Gunnery, gunnery, gunnery.
Hit the target, all else is twaddle!
#5095955 - 03/29/11 Re: 243 Ackley [Re: EddyBo]  
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Jim in Idaho Offline
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That's a valid point. The throat on this chamber is quite short, 100 grain bullets seated to touch the lands still extend quite a bit below the neck junction. This was the very first chamber cut by this Clymer reamer which would make one think it is on the maximum side of spec. I bought it specifically for this job and the probability of creating a few more .243 AI's in the future.

I'll save the before numbers and measure teh cases again on the second firing in the Ackley chamber to see if the average capacity increases.

Still not sure why I was getting almost 135 fps more (3135 fps) with book loads for the .243 and the Sierra 100 Spitzer, that being the 45 gr. of H4350. That same load gave 3096 fps with the 100 grain Hornady. The 100 grain bullets were seated right to touch the lands, that's the only difference I can see.

But getting away from all this ballistic gack and trying to show that 1% of anything is somehow meaningful, I think the .243 loads in manuals were a bit shy of what could be possible simply due to the wider pressure variations in a given string that the parent case shows. They had to keep the average pressure down to avoid the possibility of any one round exceeding the maximum peak pressure.

Since the Ackley shape tames this and makes it behave better (so I have read and shall hopefully prove for myself), I would feel very comfortable running 100 grainers in the 3100 fps range. Especially since this rifle has a 24" barrel - well, about 23.75" since it was set back. wink If one had good pressure testing equipment and could work up loads in an individual rifle to reliably know pressures that figure could probably be exceeded as well.

But again, velocity increase was not my objective in this project. The goals were to tame that propensity for ballistic variation, to keep the throat from eroding so quickly, and to get the added benefit of any AI case to reduce or eliminate trimming.

When I get my .250 Savage AI back from the smith (the barrel is "on the lathe" as of yesterday), then I shall be happy to report capacity increases measured in pints of water and perhaps a few thousand feet per second velocity increases over the parent case. grin


Gunnery, gunnery, gunnery.
Hit the target, all else is twaddle!
#5096607 - 03/30/11 Re: 243 Ackley [Re: Jim in Idaho]  
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FVA Offline
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Originally Posted by Jim in Idaho
To answer the dimensional quesetion, three fired cases at random measure .4628", .4621" and .4625" at the shoulder junction. Ha, that beat your quoted figure by an incredibly large (in Lillliputian standards) average .00267"!!!

But before we go any further I have to ask, what is your point? Are you really trying to insult me based on minute differences in my reported results that differ from what you read on the internet?

Really?


Not trying to insult you at all. Just questioning the 3.8% capacity increase.


#5097476 - 03/30/11 Re: 243 Ackley [Re: longshot3]  
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Ackman Offline
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Amazing how people can bicker so much over stuff that doesn't matter. The .243 is semi-improved already. Blown out to AI the shoulder gets a lot steeper and moves forward, which changes body taper, but shoulder diameter hardly changes at all. I've no idea what that does to internal volume. The only thing that matters is what it does to how it shoots. My first 243AI was a rechambered factory 700 varmint barrel. Comparing accuracy loads......as a 243AI it shot 70's at the same speed it shot 60's before as a std. 243......3800fps. That's a good enough improvement to make it worthwhile. I've had a few re-barrels since then. Accurate velocity from a 25 & 26" barrel with 70's is 3855 + or - depending on which bullet/primer, and which gun. That combo works fine on pds or rockchucks at 500yds.

#5097598 - 03/30/11 Re: 243 Ackley [Re: Ackman]  
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longshot3 Offline
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Thanks Ackman. Looking forward to getting mine together.

#5097790 - 03/30/11 Re: 243 Ackley [Re: longshot3]  
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Steelhead Offline
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Originally Posted by longshot3
[Linked Image]
Yeah, Steel. I want another three shot group like this!


Weren't necessarily about the tube make but about the twist. Going 1-10" twist makes as much sense as screwing together a 22/250 with a 1-14"


LUCK


"When I was a kid I thought that quicksand was going to be a much bigger problem than it is."
#5097992 - 03/30/11 Re: 243 Ackley [Re: Swampman700]  
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Ackman Offline
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Originally Posted by Swampman700
The wildcats are dead and have been for years. They offer nothing. That said if you want to waste your money make it worth your while. The AIs are no better that their factory parents.


More uninformed posting. This and the one about a 50fps increase. You must be trying to look the fool.

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