I need some guidance as I develop loads for my new 6.5x55

[Longwalker]

I have just purchased a nice used Merkel drilling in excellent condition, 20 ga. 3" / 6.5x55. I've never owned or hand loaded the 6.5x55 cartridge before. I am a very experienced reloader, but this project has me nervous. I'm trying to create some traditional 160 gr. RN loads which I think will pair nicely with the open sighted drilling for bush hunting for medium sized game. I bought a box of Hornady 160 gr. RN Interlock bullets to start. I have two powders, RL22 and H4831SC that seem to be in the correct slow burn rate suggested by most sources.
But reload data is highly variable depending on the source. For example:

Hornady 8th edition:
H4831 42.3 gr. Max for 2300 fps 29" barrel
No RL 22 Data

Hodgdon 26th ed:
H4831 45gr. Max for 2454 fps 28" barrel
RL 22 47gr. Max for 2605 fps 28" barrel

Lyman 50th ed:
H4831 46gr. Max for 2388 fps 24" barrel
RL 22 46gr. Max for 2361 fps 24" barrel

meanwhile Norma, the Swedish company with what I presume has the most experience with the cartridge, suggests the following with the Hornady 160 gr. RN
Norma MRP ( some sources say it is the same as RL22?) 46 gr. for 2533 fps with no barrel length specified.

I think I trust the Norma data the most but can't get MRP. Various sources say RL22 and MRP are different lots of the same powder from the same factory - but I don't know how differently they burn. In your experience is RL 22 close enough to MRP to substitute?

I'd like to get near maximum performance from the little cartridge, perhaps 2500 fps with the 160 grain, in case I would have an opportunity to use the drilling for moose or bear. But I have no idea how to approach working up towards maximum loads in a break action gun. It would certainly seem different than the usual approach with a bolt action rifle. I'd want to quit increasing the powder charge long before the kind of pressures that would give a bolt action sticky bolt lift or very flat primers. I usually use velocity measured by chronograph as another guide and as an indicator of pressure, but the published velocities are all over the place.

I purchased some Norma "whitetail" ammunition with 156 gr. RN bullet to compare with. Box claims a velocity of 2559 fps, again with no barrel length specified. I will compare that factory load velocity claim with actual results from my rifle and chronograph as a starting point.

Your experienced thoughts please?

 

[375er]

So, a drilling changes the equation due to the shotgun barrels over it. Per standard reloading methods, start low and work up. When you find something that gives you the accuracy you are satisfied with start your chronographing at that load. I have tried hotter loads in drillings to find reduced accuracy.

 

[Frederik]

I doubt you will struggle to get 2500fps with the 160gr Hornady bullet just bear in mind its a non bonded soft.
In my Sweed with 23" barrels I got good results with 44.5gr N560 that was running at 2420fps which is good enough for the soft bullet.
Performed well on game no meat damage and good bullet penetration at that speed.

 

[GuttormG]

Look at loads using Norma MRP, this is the same powder as your RL22.

the RN 160grs is very well talk about among Scandinavian moose-hunters (but now everyone "knows" you need a superdesign expensive bullet to get the job done..).

In your drilling, keep away from the max loads, they have a reputation to getting "loose" if shot much with max.loads.

 

[flatwater bill]

I have loaded 40.0 grains of IMR 4350 under a 156 or 160 RN with good results. This is a mild load, and a good place to start from IMO.........FWB

 

[GuttormG]

In your experience is RL 22 close enough to MRP to substitute?

Very close, it is the same powder; but lot-variations is a thing so do not jump on max-loads.

 

[Longwalker]

Thanks for the advice everyone. I think I'll reduce my velocity goal, and if I get 2400 fps with an accurate load I'll call it "good enough".

 

[Jefferry404]

Longwalker,
In my 6.5x55, I would use H4831SCand the 160gn RN. and 2450fps
Hodgdon reloading website shows max load at 2524fps for the 160gn with a 24" barrel and energy below the CIP proof load.
The short cut reduces the load density to just at 100%, sounds good to me.
The Hornady data used an original swede mauser rifle and hence kept the pressure low.
Steve

 

[Wyatt Smith]

I wonder if the drilling is made for Krag level loads or full power M98 loads.
I think my manual has data for both, I’ll look later when I get home and compare.

 

[Longwalker]

Thanks Jefferry404 that puts some perspective on the various sources of data I was studying. Wyatt, do your manuals publish the pressures generated by the listed loads? That would be very helpful.

 

[Wyatt Smith]

 

[Wyatt Smith]

I thought it had 160s listed, but it just goes to 140. But as you can see there’s a five grain difference with R22.
The military action loads are supposed to be below 51,000 psi, and the strong commercial actions are supposed to be below 58,000 psi.
I know this won’t help much but it might give you some reference.

 

[375er]

In a break action, especially if it is an older one I would keep it on the low end. What year was your drilling made?

 

[Longwalker]

I'm not sure of the year it was manufactured, but it's not extremely old. Perhaps from the 1980's 1990's or so. I'm not even aware of which exact model it is since the sales description was incomplete. I still haven't taken delivery yet. My purchase was at an auction but Canada Post is currently on strike, so I must be patient.

I wish I knew what pressures the manuals are referring to with "military actions" or "strong commercial actions" . Better to be cautious I suppose.

 

[Spacebogan]

I'm not sure of the year it was manufactured, but it's not extremely old. Perhaps from the 1980's 1990's or so. I'm not even aware of which exact model it is since the sales description was incomplete. I still haven't taken delivery yet. My purchase was at an auction but Canada Post is currently on strike, so I must be patient.

I wish I knew what pressures the manuals are referring to with "military actions" or "strong commercial actions" . Better to be cautious I suppose.

Military actions would be Swedish M-96 and Norwegian Krag Jørgensen.

Your intended bullet weight is on the high end for 6.5 ,I don't know anyone using that weight. Having said that 150 grn at a moderate speed is considered enough ,the 156 grn is more for Moose but they are not pushed hard they just don't need to be.

 

[mooze]

I'm not sure of the year it was manufactured, but it's not extremely old. Perhaps from the 1980's 1990's or so. I'm not even aware of which exact model it is since the sales description was incomplete. I still haven't taken delivery yet. My purchase was at an auction but Canada Post is currently on strike, so I must be patient.

I wish I knew what pressures the manuals are referring to with "military actions" or "strong commercial actions" . Better to be cautious I suppose.

If the drilling was originally bored to 20/76 then it is likely later than 1980s.
All the postwar merkels have the often copied double underlock and a Greener Crossbolt. Same lock as the double rifles and the O/U. All in Kalibers pressure rated to 52-58.000 PSI. So strong actions loads should be ok. You can alway check with Merkel, which is better than internet hearsay.