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Originally Posted by Paul Walukewicz
also, the berger bullets are a PAIN to get to shoot for some reason. i've tried them in 243, 6mm, and 308. I'm about to say screw it and just give up on trying them.. only one that had acceptable accuracy was the 243 with the 80's and those are varmint bullets...


Where are you seating them? Many bergers like to be jammed into the lands (not something I'd necessarily want to do for a hunting rifle).

If you have a remington .243, the factory twist should be fine for the 105 AMAXs, but possibly not enough for 105 Bergers.

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My only experience with the Berger's has been w/105's in this 243AI. They shot good for me in the lands and it also looks like they just might work even now that I'm jumping them .040".


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Brad, you said you were on your 3rd barrel on the 243AI. Out of curiosity, how many rounds are you getting before they puke?


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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 24� 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 23.75� barrel gave 3135 fps, it gave 3096 fps with the sierra bullet. That�s cooking. In previous trials with this rifle I�ve 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 it�s propensity for wider pressure swings in any given string. So, I�m using loads that the books claim to give 3000 fps from their 24� 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 I�m unhappy, just cannot explain the increased velocities from this enlarged chamber. Well, maybe � 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 .020� 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 AI�ing the .243 was not for increased velocity anyway. I just wanted to tame it�s internal ballistic weirdness and it�s humongous appetite for eating throats. Prior to AI�ing, this brand new barrel had just over 600 rounds through it of moderate loads, and throat erosion had already advanced .070�.

Now that I�m 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 I�m 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, I�m a happy camper.


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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...


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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.


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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.


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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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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.

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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


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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


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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."


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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.


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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.


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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.

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Yeah, Steel. I want another three shot group like this!

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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?


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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


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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.


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