6.5x55 imp?

[DogBuster]

hard to improve the ole 6.5x55.....grand ole cartridge from way back

often over looked for the new whizz bang 6.5's....mild mannered & accurate

Improving velocity gain ?? 125 fps ? just curious......here's mine

28" Pac Nor 8 twist heavy tube...no throat chamber.....Savage Target action

Bushy 6500 Tact 4-30x50

 

[1shot]

Bear in mind that the rule of thumb for the effect of case capacity change on MV is that all other things being the same (bullet / barrel length / PMax), the % MV change is 25% that of the case capacity % change.

Increasing the standard Ackley upper body diameter at the shoulder by 10 thou' will barely affect the overall capacity, maybe by a mere half-grain water in a fireformed case. Let's be generous and say a full grain of water. As the standard AI holds around 62, 63gn, an extra 1gn = 1.6%. A quarter of that = 0.4%. If the 6.5X55AI can give the 150 SMK 2,900 fps as a guesstimate in a match rifle length barrel, an extra 0.4% equates to 11.6 fps, 12 when rounded. Different barrels even from the same maker often produce greater variances than that! Even if the small difference in case-shape saw an extra 2gn water capacity (which almost takes it to 6.5-284 level) the likely improvement is only 20-25 fps.

If a 6.5X55BJAI reamer and dies are more easily obtained than those of the plain-Jane AI, well and good. If it takes more time, trouble, and money to go that route I for one would need some convincing of its benefits.

Here are a few percentage increase from a straight Swede to some of the variants. I couldn't find the 6.5x55BJAI so if someone has that number, we can add it to the list.

6.5x55 Swede 57.00 H2O
6.5x55AI 62.00 H2O = 8.8% increase
6.5x55GWI 66.65 H2O = 17% increase

Lloyd

 

[JRS]

hard to improve the ole 6.5x55.....grand ole cartridge from way back

often over looked for the new whizz bang 6.5's....mild mannered & accurate

Improving velocity gain ?? 125 fps ? just curious......here's mine

28" Pac Nor 8 twist heavy tube...no throat chamber.....Savage Target action

Bushy 6500 Tact 4-30x50

The improvement with the BJAI version is actually 13%. Depending on the powder used, that's good for an additional 300-350fps.

 

[Bobthenailer]

6.5x55 BJAI built on a Swede small ring mauser M96

 

[DogBuster]

The improvement with the BJAI version is actually 13%. Depending on the powder used, that's good for an additional 300-350fps.

wowzer.......big jump !

 

[rardoin]

6.5 x55 BJ AI Right at 62gr H2O capacity with 4+ fired Lapua brass. Llloyd, are you sure on the GWI capacity? I thought it had a VERY slight reduction in capacity compared to the Jourdan Ackley version due to less taper reduction and less shoulder angle compared to the BJ.

 

[Laurie]

The straight 6.5X55mm will give 140/142s around 2,830-2850 fps in a 30-inch barrel at CIP 6.5X55SE/SKAN MAPs of 3,800 bar / 55,114 psi from a 30-inch barrel. That's the European factory limit for ammunition intended for modern strong rifles and is higher than the US SAAMI standard. A good modern rifle with Norma or Lapua brass will happily and safely run at yet higher pressures, but at the cost of reduced barrel and case life, primer case-heads expanding enough for primer pockets to go slack in a few firings. Run the cartridge through QuickLOAD and you can push it within that (55,114 psi) maximum CIP pressure for the SE version to the 2,950-3,000 fps range in theory with Norma MRP, Alliant Re17 and 22 and other very hot double-based powders. I say in theory, because I've found it difficult to get good results at above 2,850 fps.

Taking the higher end of my own practical 55,000 psi MV range, a 350 fps MV increase is a shade over 12%. From a 13% case capacity increase? When all other things are equal, the quarter rule applies so a 3% MV improvement or around 85 fps would be expected and if pressures are kept constant that's all you're going to get. If we're talking QuickLOAD peak MV models, 350 on 3,000 is still 11.7% and is unachievable at equivalent pressures from a 13% case capacity increase.

Run the straight 6.5X55mm, the Ackley version, or the BJAI version at 6.5-284 pressures though, and you're going to get higher MVs, MUCH higher MVs. At 62,500 psi QuicKLOAD predicts 3,100 fps from the 'straight 6.5X55' and the 142 SMK from Norma MRP, Viht N560, and not that much less from IMR-7828ssc. Go to the standard AI version and it rises to 3,150 fps potential from N570, N560, MRP, Re33 and a bunch of powders in the 3,100-3,150 fps bracket, mostly high energy, hot 'high-energy' or double-based types. Use the 66.65gn BJAI claimed capacity, (which incidentally is greater than that of the significantly fatter bodied 6.5-284 with Lapua brass, so it's a figure which I have some trouble swallowing) you can hit 3,250 in theory with compressed loads of high-energy powder such as N570. That's a 150 fps increase, not 350, from the base cartridge to the BJAI when run at the same (excessive) pressures, or around 5%, the extra amount over the quarter % rule coming from 66.65gn water capacity just allowing yet slower high-energy powders such as N570 to be employed efficiently.

I don't know how the 6.5X55 case compares to that of the 6.5-284, but it certainly won't be any stronger, and is very possibly weaker.

 

[rardoin]

As far as primer pockets holding up....I have just over 1600rds out of one BJAI barrel (30") and its associated Lapua brass with 10+ firings per case minimum running a 142gr at 2950-60 fps using 50.5gr H4831sc then 49.2gr ReLoder 23 and I have not lost a case due to primer pockets opening up. Lloyd is pushing his even harder so it would be interesting to see his experience with the pocket longevity. This barrel/load has cleaned its share of 600yd targets so the load holds well and is competitive against the fast 6's even in mild conditions. I have been very pleased with the cartridge overall.

 

[moondog]

Thanks to everyone who has first hand experience and shared the info.
very helpful.

 

[Mulligan]

Thanks to everyone who has first hand experience and shared the info.
very helpful.

^^^^^What he said^^^^^
CW

 

[Laurie]

As far as primer pockets holding up....I have just over 1600rds out of one BJAI barrel (30") and its associated Lapua brass with 10+ firings per case minimum running a 142gr at 2950-60 fps using 50.5gr H4831sc then 49.2gr ReLoder 23 and I have not lost a case due to primer pockets opening up.

I'm not surprised. QuickLOAD says the 6.5X55AI gives the 142 2,950 fps from a 30-inch barrel at under 54,000 psi, so you are running below peak CIP pressures for the standard version. Nothing wrong with that, very sensible in fact! However, having had the run of the mill SE up to 3,000 fps with the 139 Scenar and Viht N160 out of 30-inches and just starting to show some pressure signs, I certainly wouldn't regard 2,950 from a significantly 'improved' case as anything at all out of the ordinary. As I said previously that the extra case capacity allied to the quarter % rule would add around 85 fps to my standard 2,850 if no pressure change is involved and as I reckon my usual load produces around 52/53,000 psi, an extra 100-110 fps is right where I'd want to be by going to any 'AI type' case-form.

Going back to basics, this shows that if a reamer and dies are readily available, whichever variant of the 40-degree shoulder improved case is available is well worth having if somewhere in the 2,900-3,000 fps MV performance bracket is wanted. It is doing it at modest pressures, so barrel and case life should remain reasonable to good.

When talk of 300-350 fps extra is thrown into the pot though, yes that's likely available, but at a cost - a severe one that people making choices must take into account.

I doubt now if I'll ever build another 6.5X55. The low round-count SE barrel I currently have sits stored while a 31-inch 7-08 is on the rifle for F-Class and by the time I wear that one out, then the 6.5X55 is put back on and it shot out, my shooting days will be over. Still, who knows? If I ever get there, and if the BJAI bits are available, I'd likely go down that route.

 

[Mulligan]

I'm not surprised. QuickLOAD says the 6.5X55AI gives the 142 2,950 fps from a 30-inch barrel at under 54,000 psi, so you are running below peak CIP pressures for the standard version. Nothing wrong with that, very sensible in fact! However, having had the run of the mill SE up to 3,000 fps with the 139 Scenar and Viht N160 out of 30-inches and just starting to show some pressure signs, I certainly wouldn't regard 2,950 from a significantly 'improved' case as anything at all out of the ordinary. As I said previously that the extra case capacity allied to the quarter % rule would add around 85 fps to my standard 2,850 if no pressure change is involved and as I reckon my usual load produces around 52/53,000 psi, an extra 100-110 fps is right where I'd want to be by going to any 'AI type' case-form.

Going back to basics, this shows that if a reamer and dies are readily available, whichever variant of the 40-degree shoulder improved case is available is well worth having if somewhere in the 2,900-3,000 fps MV performance bracket is wanted. It is doing it at modest pressures, so barrel and case life should remain reasonable to good.

When talk of 300-350 fps extra is thrown into the pot though, yes that's likely available, but at a cost - a severe one that people making choices must take into account.

I doubt now if I'll ever build another 6.5X55. The low round-count SE barrel I currently have sits stored while a 31-inch 7-08 is on the rifle for F-Class and by the time I wear that one out, then the 6.5X55 is put back on and it shot out, my shooting days will be over. Still, who knows? If I ever get there, and if the BJAI bits are available, I'd likely go down that route.

Laurie,
The little 7-08 is a great cartridge indeed. Have you ever run the 275AI Rigby in F-Class?
OP, apologize for the slight hijack

CW

 

[SBS]

Having owned several 6.5x55 rifles and being a fan of this caliber, I considered an improved version for a long range prone rifle. I had 3 actions available; Rem. 40X, Wichita BR and RPA 2000. None of the 6.5x55 new brass I had (Lapua, Norma, Win. or Rem) would fit any of the bolt faces, being slightly larger than .308 size. I started searching for a similar capacity case that would have a sharp shoulder, long neck and .308 bolt face. I saw the .257 Ackley was a fit. Didn't know if reamers or dies were available for this case necked up to 6.5, but they were, PTG and Redding. Turned out to be a really good 6.5 round. Measuring water capacity on fired cases, I came up with 62.6 (Nosler), compared to 65.9 for Lapua 6.5-284; 57.5 for Win. 6.5x55 and 53.9 for Hornady 6.5 Creedmoor. I was looking for something better than the CM and less than the 6.5-284 and came up with something very similar in capacity to the 6.5x55 improved cartridges without altering the bolt face. Good brass was the only question here. Currently using Nosler; just have to see how it holds up. Next option would be Norma 7x57 necked down and perhaps turned.

 

[sbhooper]

I have a buddy who has built a couple 6.5x55 AIs, and he really likes them.

 

[Laurie]

Laurie,
The little 7-08 is a great cartridge indeed. Have you ever run the 275AI Rigby in F-Class?
OP, apologize for the slight hijack

CW

It's my short/medium distance match rifle. For longer distance (and 600 yards on 'hairy' days), I use a 284. A fellow club member has the weirdest, clumsiest looking F rifle you'll ever see chambered in 7X57AI ie Rigby in effect. It shot very well with its original barrel, but Number 2 has been a big disappointment to him, so he bought another rifle to supplement it - yes, you've guessed it, a 284 Win which must be rated as the clubman's F/O 'standard' these days. I have three 7X57s - two South American (Chilean) Mauser long rifles and a mid 1950s early BSA Hunter deer rifle with contemporary 4-10X56 Pecar (German) scope. This has always been one of my favourite cartridges and the old Mausers (M1895 and M1912) shoot ridiculously well, especially considering I have real trouble using the iron sights these days.

 

[1shot]

6.5 x55 BJ AI Right at 62gr H2O capacity with 4+ fired Lapua brass. Llloyd, are you sure on the GWI capacity? I thought it had a VERY slight reduction in capacity compared to the Jourdan Ackley version due to less taper reduction and less shoulder angle compared to the BJ.

@rardoin ,
Yes,I'm quite sure of the measurement being accurate using Lapua brass and an FX120 scale.
I talked to Greg Walley sometime ago to verify that the number was accurate and it was.
As several posters have pointed out, the Swede variants are capable of 3,100+ fps with heavy weight bullets but the accuracy and case life will suffer. I have shot loads that were in excess of 3,100 fps, but the brass would have been toast within a couple of re-loads, not to mention the accuracy wasn't anything to write home about.
I hope this helps,
Lloyd

 

[acloco]

Why build a 6.5x55 AI or BJAI? Simple economics.

6.5x55 Lapua brass, is TIED for the CHEAPEST Lapua headstamp brass they manufacture (tied with 223).

Hate trimming cases? Huge advantage of the AI family. Neck size or partial full length size....and load, after your first fireform and trim.

6.5 booooolits - Imagine no discussion is necessary to discuss the benefits of 140 to 150 gr LAWN DARTS in terms of BC and SD and how well these LAWN DARTS really do fly?

Recoil - very reasonable recoil.

Barrel life is excellent. I coat my bullets with WS2 (would switch to nickel boron, but don't think I will ever run out of WS2!!).

 

[moondog]

I'm Sold, now I have to sell so I can Buy

 

[flatlander]

I had a local 'smith do a Krieger med Palma 1-8tw bbl in 6.5x55 for my Nesika K palma rifle in 2002 - didn't have the money to buy & build another complete prone rifle, and had always wanted to try the Swede in a modern action. The load I settled on for 1000yd prone matches was 47.6 of Viht N160/F205/S142MK, which gave 2910fps out of the 30" Krieger, and was very accurate. Eventually, I got tired of trimming cases after every firing, and since I'd always wanted to try the 6.5x55AI, bought a reamer & did a 30" hvy Palma bbl for a BAT 3LL action in a Robertson Composites H&H prone stock. This rifle also shoots very well, but I'm finding best accuracy at only 2950fps with 140-142gr bullets. Over the course of doing a few more AI bbls, I've gotten the same general results, with very modest velocity increases over the original Swede in that first Krieger Palma bbl. Once I got over the minor disappointment of modest velocity increase, the enjoyment of excellent accuracy w/o the need for constant case trimming made it fairly easy to rationalize the need to fireform. I ordered a resize reamer along with the AI finish reamer, so can make my own FL size dies fairly easily on Troy Newlon neck bushing die blanks. However, before doing my own sizing die, I sent a copy of the RZ reamer print & three formed cases to Hornady and had them make a custom FL sizer for me, which I continue to use - it's nice to have a polished & hardened sizer die. One of these days, I'll get around to polishing a Newlon sizer with 800 grit aluminum oxide paste, then send it off to have it nitride hardened - will then have a polished & hardened die with a neck bushing.

 

[Laurie]

Over the course of doing a few more AI bbls, I've gotten the same general results, with very modest velocity increases over the original Swede in that first Krieger Palma bbl. Once I got over the minor disappointment of modest velocity increase, the enjoyment of excellent accuracy w/o the need for constant case trimming made it fairly easy to rationalize the need to fireform.

I don't know what it is about case trimming, but I loathe doing it too. No doubt there are some reading this thread who say "What, go 'improved' just to cut case-trimming out?", but I understand completely.

BTW, that was a hot load / good MV from the standard round! I've stuck to a case-full of N165. I find 2,830 fps from the Berger BT LR suits my shooting style / wind-reading well and hopefully barrel life will be reasonable with this combination.

I'm about to 'play' with a newly rebarrelled long-freebore 260 Rem in a 28-inch heavy profile Bartlein - lots of different brass makes, enough powder grades to shoot half a dozen barrels out ..... and despite my promise never to buy another tub of powder before I use all my old stock up, I see Viht lists N565 loads for both 260 and 6.5X55 with 140s. The latter gives impressive MV improvements over N160 (but not much over N560 unsurprisingly) despite this being in the '6.5X55mm Swedish Mauser' loads table, not the higher pressure SE / SKAN 55,000 psi list. So ... here we go again!