I am in the process of having a 243AI built to shoot the 69gr absolute hammer solids, going with a 20” 1/10 twist since this will be a Varmint hunting rig. What kind of speeds should I realistically be able to expect? Can I hit 4k? Anyone have approximate barrel life on something like this.
243 AI build going on
- Thread starter Justinmac13
- Start date
swd
Silver $$ Contributor
Can’t help you speed but the last 243AI I built for a good friend went about 750-800 rounds before it was toast as an F Class rifle. It might go double that if you shoot it slower for coyotes and those kind of critters. For ground squirrels and faster action it would probably be under 1K.
From having experience with the .243 & .243AI with lighter and middle weight bullets It is possible to get 4,000 FPS + with the 55 gr. Nosler B T. Not real sure if you will get that with the 69 gr. bullets but if you do the barrel will not last very long if you use that load regularly. Heat is the barrel's enemy and faster loads will build heat quicker and maintain it longer.
It’s primary use will be a night time coyote rig, so if I can get 800 rounds out of it that should last a while for me, after the initial load development the round count should not be terribly high.
That probably will be possible but I would not expect much more from it.
AckleymanII
Gold $$ Contributor
I have shot the throats out of a few 243 AI's, 12T Hart barrels with zero freebore.
My barrels were 29-30" long, and I used Rem brass, CCI 250 primers, AA2700, and Win 760. The never full length sizing load that shot in the low 2's is 48.5g of Win 760 at 3850 on a 29" 12T, zero freebore chamber. I went up to 50.5g of 760 with the 70g Nosler ballistic tip and got 4030 fps.
Now, with 9" less barrel length than I had, You can do some extrapolation.
A stone cold killer bullet for coyotes if you want max speed is the 60g Sierra hp, tough enough for the largest coyotes, super accurate. The 60g Sierra can stand a little jump.
In my experience, those 55g Nosler bt do not like to jump. If you could ever find any, the 75g Sierra hp is a very jump tolerant bullet.
OP, do you know what kind of throat your chamber will have?
Best of luck to you!
My barrels were 29-30" long, and I used Rem brass, CCI 250 primers, AA2700, and Win 760. The never full length sizing load that shot in the low 2's is 48.5g of Win 760 at 3850 on a 29" 12T, zero freebore chamber. I went up to 50.5g of 760 with the 70g Nosler ballistic tip and got 4030 fps.
Now, with 9" less barrel length than I had, You can do some extrapolation.
A stone cold killer bullet for coyotes if you want max speed is the 60g Sierra hp, tough enough for the largest coyotes, super accurate. The 60g Sierra can stand a little jump.
In my experience, those 55g Nosler bt do not like to jump. If you could ever find any, the 75g Sierra hp is a very jump tolerant bullet.
OP, do you know what kind of throat your chamber will have?
Best of luck to you!
Acklyman, thx for the insight, as far as the free bore I am taking a dummy round down to Moon the gunsmith and he will be setting it for me.
I plan on the 69 gr Absolute Hammer solid bullets so I am not sure if they will like jump or not.
I was also thinking about the Hornady 58gr VMAX, just didn’t know how fast you can push them without having issues.
I’ll start my search for win760 as that powder I do not have on hand.
Thanks again
nmkid
Gold $$ Contributor
Max load in your rifle?
AckleymanII
Gold $$ Contributor
No,29-30" Hart bbl, the 48.5g of Win 760 with 70g nosler ballistic tips, Rem 7/08 brass, neck turned, zero freebore chamber, and I have never used the full length sizer on this load, never!
We fire formed with 47 or 47.5g of Win 760 with the cci 250, 70g noslers. I ran the loads up to 50.5g in the Hart 12T with vel over 4000 shooting a tiny bug hole, but wanted to take into consideration the Summer Heat. AA2700 burns about .3g faster than Win 760 with this load, and AA2700 is one of the coolest burning powders you can shoot in this case. We shot as fast as we could load and acquire targets, leade growth was around .070 for 1800 rounds, really abusing the barrels. 150 shot strings were normal.
We rotated guns, but in the Summer heat, barrels never cooled off. We ran water down the barrel to cool them. On our Pandas and Hall M's with McMillen fiberglass stocks, we filled the barrel channel full of water as we started shooting.
Justin, I shot a lot of the Berger 69's at 3850 fps with the same load. The Hammer bullets are supposed to shoot faster due to engraving pressures, so you will have to adjust loads accordingly as this extends the burning chamber.
Hammer bullets are long for the weight, so if you throat accordingly, the 58's will be seated way out of the case neck. This issue does create issues to consider in bullet choices.
Early on with our first 243 Ai's, we went through barrels pretty quick shooting IMR 4064, Varget would do the same thing as would R#15 and xbr8208.
You need to talk to your gunsmith about reamer dimensions and get a print if at all possible. Lapua 243 Win brass does not work well in any SAAMI spec chamber reamer I have ever used, neither does PMC and Norma. Lots of guys have got busted trying to use Lapua brass in SAAMI spec chambers. Lapua, Norma, and PMC are all "fat" in the web.
We fire formed with 47 or 47.5g of Win 760 with the cci 250, 70g noslers. I ran the loads up to 50.5g in the Hart 12T with vel over 4000 shooting a tiny bug hole, but wanted to take into consideration the Summer Heat. AA2700 burns about .3g faster than Win 760 with this load, and AA2700 is one of the coolest burning powders you can shoot in this case. We shot as fast as we could load and acquire targets, leade growth was around .070 for 1800 rounds, really abusing the barrels. 150 shot strings were normal.
We rotated guns, but in the Summer heat, barrels never cooled off. We ran water down the barrel to cool them. On our Pandas and Hall M's with McMillen fiberglass stocks, we filled the barrel channel full of water as we started shooting.
Justin, I shot a lot of the Berger 69's at 3850 fps with the same load. The Hammer bullets are supposed to shoot faster due to engraving pressures, so you will have to adjust loads accordingly as this extends the burning chamber.
Hammer bullets are long for the weight, so if you throat accordingly, the 58's will be seated way out of the case neck. This issue does create issues to consider in bullet choices.
Early on with our first 243 Ai's, we went through barrels pretty quick shooting IMR 4064, Varget would do the same thing as would R#15 and xbr8208.
You need to talk to your gunsmith about reamer dimensions and get a print if at all possible. Lapua 243 Win brass does not work well in any SAAMI spec chamber reamer I have ever used, neither does PMC and Norma. Lots of guys have got busted trying to use Lapua brass in SAAMI spec chambers. Lapua, Norma, and PMC are all "fat" in the web.
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Good to know Acklyman because I have 100 Lapua cases I was planning to use. I’ll get with Moon and get the prints and post them next week.
AckleymanII
Gold $$ Contributor
Justin, I an many others have got busted HARD on this issue of Lapua, Norma, and PMC Web dia at the .200 Mark and also thicker necks than Winchester brass/Rem brass.
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nmkid
Gold $$ Contributor
What about Peterson cases?
Forgive my ignorance, but when you say the .200, is that from the case mouth down .200? I’ll go get a measurement
I’ll get the prints from moon and see if the lapuas will work. If not I may try finding some Peterson. I think I looked for them in SP and they were not available.
swd
Silver $$ Contributor
.200” up from the bottom of the case head.
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