[PatrickRaymond]

I have a Browning Model 71 in .348 Win caliber and was wondering about getting it re-chambered to .348 Ackley Improved.

Is this an appropriate conversion that would be deemed appropriate and/or be recommended?

I was hoping for a 100 fps velocity increase with a 180 gr Hawk bullet or a 200 gr Hornady bullet. I'm trying to get a flatter trajectory for long shots (200 yds) at deer in open country.

Any comments would be appreciated. What gunsmiths have experience in doing .348 Ackley Improved conversions?

Thanks,
Patrick Raymond
Spokane, WA
[email protected]

 

[leadflinger]

For just 100fps I wouldn't go the cost. Rather for about the same $ I'd buy another rifle/caliber......25-06? 7mm?
But that's just my opinion. LF

 

[dclark1]

I also have the Brownchester Model 71 in .348. I see no need to get an extra 100 fps from a 200 gr bullet. That is not what that rifle/cartridge is designed to do. A lighter bullet will get the extra velocity and kill deer properly, but closer with heavier bullets is where the combination shines. Think elk in heavy cover. 250's. That's the proper use. And it will kill to 250 yards; a lot further than most need to shoot.

dclark

 

[William Iorg]

I agree with DCClark on the use of the .348.
That said... Get a copy of Big Bore Rifles and Cartridges from Wolfe Publishing. This has a collection of past articles from Handloader and Rifle magazine.
Dave Scovill has an excellent article on the basic .348
Jon Kronfeld has an excellent article on the .348 improved. He also has articles on the .416 Alaskan, .416-.348 Improved, .450 Alaskan, and the .50 Alaskan. Good information on the value and usefulness of the various wildcat forms of the .348.
Bottom line is you may well get your 100 fps improvement with an improved chamber. You may also be able to get the additional velocity by switching to the new generation powders. A call or E-mail to Hodgdon may be helpful. We are seeing significant improvement in standard .30-30 performance using Alliant Reloader 15 and Hodgdon Varget. There is little published data for these powders and older cartridges but contacting the powder companies helps. I have never contacted Accurate Arms but I have heard that they are very receptive to enquiries. We are just starting a .30-30 Improved project. Our goal is to compare it to the .307 and to demonstrate to ourselves the improvement in brass life and the ease of loading maximum published charges due to increased case capacity. Remember that with any improved cartridge the reloading die cost skyrockets. A good form trim die is handy also. Perfomance cost money, be prepaired!

 

[Garth]

I have a Browning 71 Carbine and went ahead with the 348 AI rechambering. I puchased the reamer and had a local gunsmith do the work for $75.00. I am very happy with the results and can achieve good velocity from the shorter barrel. My current favorite load is a 220 gr. Barnes X bullet at 2500 fps. The only problem I have encountered is the brass splitting in the shoulder area when fire forming. I solved this by annealing the cases and have not experienced a case loss since. This is probably the most accurate lever gun I have ever owned. I like having the wildcat since it is somewhat different. I need to send a few cases off to Lee to get a factory crimp die made because it is fairly easy to collapse the shoulder when crimpping. I say have some fun and get more velocity if you need it.

Garth

 

[Win71]

Don't hack up a great rifle! The Winchester factory load or anything comparable sighted so as to hit 2" high at 100 yards, will only be a couple of inches low at 200 yards. With that sight setting and a 200 grain Hornady (at factory velocity) I have dropped deer at just under 300 yards. I didn't have to chase after them either, they dropped where they were standing.

 

[axlenut]

The major reason to rechamber to .348 Win. A.I. is to reduce case stretch and bolt thrust. Case life improves along with the more efficient shape. Unfortunately the full value of the increased capacity can't be taken advantage of due to limitations of the barrel shank diameter and the lever action itself. I have a Browning M-71 carbine that came from the factory with defective bolt locking bars, causing the lever to open after every shot. Finally had it repaired this year. If the rifle still has accuracy issues, it will be rechambered to the Ackley version, and then rebarreled if that doesn't solve the problem. Less bolt thrust in a lever action can't hurt.

In fire forming the .35-.348 Win. A.I. I also had problems with split shoulders. Tried anealing the cases and using only starting loads. With 200 gr Remington Cor-loks and 44.0 gr. of IMR 4320 under a case full of Puff-Lon filler, I only lost 3 of 50 cases to shoulder splits. I am going to back off another grain of powder and see if that eliminates the problem. The anealing didn't yield any better results than unanealed cases in my rifle. I am shooting a Siameese Mauser with its stronger action and ridgid lock up. Once formed the cases handle heavier loads with no problems, though some show barely visible stretch marks at the shoulder.

When you look at this fully formed cartridge (the .348 was based on the .50-110 Win. case. It's larger than the .45-70 in front of the rim) the "new" short magnums come to mind. It should be a good choice for those who want something different.

 

[Jack Monteith]

Hi, axlenut:
Mic McPherson had an article on fireforming in Precision Shooting Magazine several years back. The bottom line is, anything less than a full snort load for the standard case will damage cases. I'll try to get it for you if you want it.

Bye
Jack

 

[axlenut]

Thanks Jack, you and McPherson are right about using full power loads, especially in rimless cases. What happens is that the firing pin drives the case forward, the body expands and grips the chamber, but without enough pressure to lengthen the case back against the bolt face they actually shorten up. I have seen this occur leaving the primer protruding substantially. These cases have excessive headspace and can separate with the next firing.

The .35-348 Improved headspaces on the rim and that problem is eliminated. I tried near maximum loads and every one split on fireforming. The starting load for the standard .348 works fine and the cases work normally with subsequent hotter loads. Go figure! Maybe the shock wave is too much for the unsupported brass and it splits at the shoulder before it can contact the chamber wall. Fireforming this cartridge moves a lot of brass around, much more than the .257 Roberts Imp. or the .220 Swift Imp. It's a wonder it works at all! The loading data for this cartridge is 40 years old, so I have to take it slow with freshly manufactured powder to determine maximum loads.

axlenut

 

[Garth]

Axelnut let me know how your loads work out with the newer powders. Need to do that myself but have been way to busy to get much done!!

 

[Sky C.]

Patrick-

If indeed the reason for considering changing the chambering is for flatter trajectory as you mention - I think you may do well to look at the ballistic tables in any of the major reloading manuals. Difference in trajectory for the 100 or so fps you are expecting may not be anywhere close to what you have in mind.

Using the 200gr. Barnes X bullet as an example (with better BC than a 180gr traditional design); at MV 2300fps vs. 2400 fps, the difference in trajectory amounts to less than 3/4" at 200 yds. and less than 3"" at 300 yds. Using iron sights - I think most of us would be hard pressed to hold that difference even shooting off a good bench . Food for thought.

Best regards-

Sky C.

 

[axlenut]

Garth, I shall indeed.

I just picked up a copy of Handloader's Manual of Cartridge Conversions by John J. Donnelly. On Page 404 he states that fireforming the .348 Improved is done with a factory load in the Improved Chamber, or by using 36 grs. of Unique, tissue paper or cormeal filler and a wax wad. He also states that this is a hard case to fireform in this manner and he fireforms each case twice. If that is true for the .348 Imp. then it should also follow for the .35/348 Imp.

So far IMR 4350 seems safe enough, as does IMR 4320. Next comes H380.

BTW, the .348 Imp has a case capacity of 79.87 gns of water, the .35/348 Imp has 77.74 gns., and the 350 Remington Magnum 73.74 gns. my guess is that starting loads for the .350 Rem Mag would be safe in my gun, a Mauser, but be careful with the older lever actions.

Axlenut