Help with 6.5x55 Swede pressures

[webberwood]

Newbie to the forum but I've been reloading for years. I've been tinkering with 6.5 swedes for a few years and recently graduated from an m96 to a tikka t3 w/22" barrel with the idea of maximizing performance of the cartridge. I've been working up a load using RL22, Lapua brass, WLR primers, and 140 grain NPT. I'd rather not post the exact load data but I'm getting around 2950fps without any pressure signs. I'm tempted to press further but I'd like to at least be able to estimate my current pressure before I go any higher. Is there any way to calculate pressure besides Quickload?

[RC20]

Uncleinick will probably weigh in when he sees this.

With a modern gun you can run modern pressures.

That said the new ammo is running 2750 or so.

With 140 grain in this link its not pushed to 2900 fps even with the warning on older guns.

http://www.vihtavuori.com/en/reloadi...ser--skan.html

I don't know if that's a bit of a hedge in case it gets stuck in an old rifle.

I would not push it further, I would do some cross checks on case size expansion and if its chrono out as normal increase in powder vs velocity.

[Unclenick]

NPT is National Pipe Thread. I'm thinking you mean NBT for Nosler Ballistic Tip. If so, QuickLOAD thinks you are running at about 67,000 psi. But that assumes things not in evidence, like your chamber being super tight and not with the actual case water overflow capacity of your fired cases. Assuming your fireformed cases are slightly bigger than as-resized on the inside, then you may be in the 65,000 psi range, about like a .270 Winchester.

To find your case water overflow capacity, weigh a fired case that has not been resized (we nee the size it grows to in the chamber) or deprimed and then fill it with water level with the case mouth (no meniscus and no bubbles inside, which may take some tapping to achieve) and weigh it again. The difference in the two weights in grains or grams is what is needed.

[RC20]

I found one that ran up to 3100 with 6.5, R-22 and 140 grain.

That is well above the 2750 max.

55k seems to be the pressure but not obvious its modern or old.

[webberwood]

NPT can be an acronym for many different things, in this particular instance I was referencing Nosler Partion. My apologies for any confusion. These results did come from fire formed brass neck sized with a lee collet die so I will look into the water capacity further. Accuracy with this load is outstanding so I'm considering backing off a tad and using it as a hunting load.

[webberwood]

Unclenick should I check original case capacity with virgin brass vs fire formed and fired at this velocity since I am neck sizing?

[44 AMP]

Do take pains to see that none of your "modern rifle pressure" ammo winds up in a vintage Swede 96, or any of the old guns.

Coloring the case heads with a distinctive color (sharpie?) can't hurt. Some cartridges you can get nickel plated cases, don't know about the Swede.

[webberwood]

I've heard that the M96's were proof tested at 80,000 psi but I wouldn't dream of firing one of these hot loads in it. I fire form the brass and then neck size so it is kept meticulously separated in to lots that are uniquely labeled and dedicated to each rifle. As an extra precaution I use Lapua in the T3 and Winchester for the M96.

[zeke]

Am reloading for 2 modern 6.5x55's, and would be very hesitant to go over 2800 fps using rl-22 and 140 grain bullets.

[RC20]

Sounds pretty solid setup. A mistake will not wreck a gun. Many mistakes yes.

2900 seems to exceed even modern guns. I sure would not go any higher.

The biggest issue is unsupported case heads and a cracked case.

[azar92]

I'm surprised Unclenick came back with QL stating ~67,000 PSI. I would have expected much higher. Then again, QL's pressure "guesstimate" is just that and is not measured instrumental data. Sometimes it's close, sometimes it's not.

Personally, I agree with Zeke. I would put a safe maximum velocity with that combo closer to 2,800 fps. The Nosler Partition builds pressure faster than many other types of bullets of the same weight.

A respected gunwriter, John Barsness, after crunching lots of numbers from published loading data has developed a rule for comparing cartridges of the same caliber. The "4-to-1 Rule" says that any difference in case capacity results in 1/4 as much difference in potential velocity, with both cases loaded to the same pressure [Emphasis mine].

Alliant Powder shows 46.0 of RL-22 to give 2,701 fps with a 140g Speer SP in the 260 Remington. Unfortunately, Alliant does not list measured pressure for their loads but SAAMI MAP is at 60,000 PSI for the 260 Rem. Hodgdon's data for the 260 shows measured pressure between 57,000 and 59,000 PSI so I would expect Alliant's to be in-line with that.

Using the "standard" case capacities for both 6.5x55 (57 grains) and 260 Remington (53 grains) that gives the 6.5x55 a 7.5% greater case capacity. Using the 4-to-1 rule that means the 6.5x55 has a 1.875% velocity advantage when loaded to the same pressure (which it normally has a ~9,000 PSI disadvantage compared to the 260 Remington).

That would mean the 6.5x55 could achieve ~2,751 fps with a 140g Speer SP when loaded to the same pressure as the 260 (approximately 60,000 PSI). I would imagine getting up to 2,800 and the higher pressure build up from the Partition would eat up most of the "remaining" pressure and put you at or near enough to 65,000 PSI.

No way would I ever consider 2,950 fps with a 140g Partition a safe load even from a modern 6.5x55...

[Unclenick]

Webberwood,

Actually, your well-used cases will be closer to chamber size than a once-fireformed one, so use one of them, but before resizing the neck.

QuickLOAD is an estimate, as Azar92 says, but as you have peak accuracy and assuming you are not getting sticky bolt lift or other excessive pressure signs, you are not likely running too high for the particular gun, even if it actually is nearer 70,000 psi. Some guns can handle that. It is high enough to shorten barrel life, though. If that's a consideration, then you may want to back off some to see if you can't find another accuracy sweet spot with a smaller charge.

[zeke]

From Alliant 1996 reloaders guide, for whatever it may be worth, in 6.5x55 24 in tube.

Speer 140 spitz- cci 200 primer-48.1 grains rl-22-2,700 fps-44,400 cup

yup, it is conservative compared to the 51,800 cup listed for 264 win mag load.

Also likely to be outdated pressure measuring technique.

Am using 48.0 grains under hdy 140 sp for close to 2750 fps from 22 in Win, or CZ. With win brass and col=3.035 in..

Rem factory clocked 2530 fps from 22 inch barrel.

[webberwood]

It took me a while to get around to loading up a few rounds and get to the range. I checked water capacity on ten fired rounds and I’m getting an average of 58.3 grains of water.

[Don Fischer]

I have never cared how much pressure I was getting so long as pressure signs don't show up. Really flat primer, ejector mark on the rim and sticky bolt all spell high pressure to me. The stickier the bolt the higher the pressure. Really flat primer flow's clear to the edge's of the primer pocket, stop's me dead right there and I back off. Flame cutting around the firing pin hole on the bolt is pressure. Keep in mind, the important thing is not how much pressure your getting but weather or not the pressure is safe in that rifle. If your uneasy with it, stop where you feel comfortable. Might get rid of the chronograph too. It can lead you to think your safe when your not. Mod 96 may or may not handle modern pressure, then again it might. Myself I would not try it, get a modern rifle. My 6.5x55 is a mod 70.

[webberwood]

Don,

This load was developed for use in my Tikka T3 in 6.5x55. My Carl Gustaf M96 is currently sending out the partitions at 2750fps.

I'm tempted to push it a little further just to see what happens. I would be tickled if I could hit 3000fps.

[Unclenick]

Webberwood,

Your measured fired case capacity is a grain and a half larger than QuickLOAD's default value (which, for technical reasons, is for an unfired case). With your measured capacity it thinks RL22 can get your bullet to 2950 fps at about 66,550 psi, the lower peak from the previous estimate reflecting that the larger charge, which makes more total gas and therefore does a little more of the bullet acceleration a little further down the tube, relying less for it on the peak value.

This is withing spitting distance of some magnum cartridge loadings. Watch how many loads you get from each case before the primer pocket gets too loose to seat a primer into. That's a good measure of whether the peak pressure is bothering it much. You are right around the European proof pressure for the 6.5×55, which is 68,893 psi.

[ligonierbill]

I am loading 140 SGK for two rifles: Model 70 22" and a rebarreled Mauser 98 24". The Winchester goes 2,725 and the Mauser goes 2,796. The Mauser, in addition to 2 extra inches of barrel, has a SAAMI minimum chamber. I have worked over the 6.5x55 for years, and I would not go above these levels. I'm not particularly conservative. In fact the only time in my "career" I've blown out a primer was with some Woodleigh 160s in the Winchester. Got carried away. Goal setting is mostly a good thing, but it can get you in trouble in this game.

[webberwood]

Thank you for the data Unclenik! The current batch of brass is on their fifth firing and still doing well.

[RC20]

If your accuracy is good I would quit right there.

A couple of weeks back I made a mistake on a load, it was still 3/10 below max but I had not intended to be anywhere near that close.

The low load of a group of 5 had pressure signs (hard bolt life, hint of markings on the case)

As its a modern gun, I had cross checked the book for why and the next load was like 1/10 over, I tried 3 or 4 of those.

Much harder bolt lift, marks on the brass, one blown primer (gone) and when I resized them and put primers in them those last ones were too loose to use again.

Just come up with a shorter measure than 12 inches. Then you can be at 3000 gizawhats a second if round fast numbers are that much appeal.