confusing results in 7x64 brenneke

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ackertjosh

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Hey all. So today i thought i would go to the range and test a new load for my Steyr Mannlicher M. Its current load is 175 GS with RL23 @ 2670 fps and shoots it extremally well. The only real reason to test is cost of components and since im using the 160's in the 7-08 i thought id try them in the 7x64 using 280 load data.

What confuses me is the velocity. I cant get them over 2600spf. most landing below or around 2500. load data shows 28-2900 fps... thinking my chrony is having issues i wrote it off and shot for groups and figured i would test velocity again... once complete i grabbed my Sauer 80(carl gustaf 3000) in 30-06 and thought i would test the crony again... to my surprise the crony read what it should.. 2900-2930 for 5 shots and a 165 barns TSX.

So why would my 160,s be going so slow. and i should mention i have played with the 160's in this rifle before usign RL 17,19,22 and 23, IMR 4831 and now AA4350 with no luck on pushing then faster then i can already push the 175's.

Over 15 years of loading, this is a new one for me.
Thanks for any help
Josh
 
I have had several 7x64's, still shoot three. All of them have very long throats. They all do well with 175 grain bullets. A Brno 21H had such a long throat the Nosler Partition 160 gr. wouldn't touch the rifling until it was almost out of the case. Forget about seating 160's near the lands. Your load max over all length will be based on magazine limitations.
The European CIP standard calls for a long throat compared to the USA SAAMI standard .280. Long throats reduce peak pressure compared with otherwise identical chambers with a shorter bullet jump to the rifling. The often quoted load data from the USA claiming similar results for .280 Remington loads in the 7x64 is BS in my opinion. I have to load my 7x64's with a few grains of MORE powder than .280 "book max" to achieve the same velocities. When I do, I get good accuracy, velocity is proper, case life is very good, and all is right with the world. If your velocity is low, pressure probably is too. You can therefore carefully increase powder until the desired standard velocity is achieved.
 
Thanks for you advice Longwalker. It is much appreciated.

I can agree with you about the BS on the 280 load data(even though i just use it as a starting base) my current load for the 175gr Grand slams in full 2 grains over speers listed max. at that point i hit 3/4moa 5 shot groups and pretty decent velocity. I never did see how long the throat is on this steyr as i already new it was more then my Mag would allow so started my load seated out as far as my mag would allow. Still no signs of pressure either.

I was worried i was running into pressure due to "what looked like flatted primers" but these stellor and belleot primers are different in shape and Im not used to looking at them fired. I was getting a ring on the primer which made me wonder.. but no cratering or anything that i have experienced in the past.. stiff bolt lift ext. just funny looking primers. So i errored of the side of caution. The COAL is the same as it is for the 175gr and exact same bullet and profile. just 15gr lighter. Maybe ill use primers im familiar with and work my way up past the listed max, as i did stop at listed max, and see where i go.. i still think 4-500fps is alot to make up but maybe under pressure the gunpowder will act different providing more velocity.

Thanks again for your input. if it dont work out ill just stick with the 175's.
Im working on getting dad outta his 7-08 and into a 7x64 but he shys away from the price tag some of these european rifles wear.

Thanks again!
Josh
 
My experience with the 7x64 is pretty much exactly what longwalker posted. My Zastava has an extremely long throat and I have to load beyond max to get to the velocity it should be producing with any given bullet weight. Accuracy has always been very good.

Obviously this has to be approached with caution and velocity monitored with a chrony, watching for pressure etc.
 
track said:
What manual are you getting the load data? What length of barrel is the rifle?
Click to expand...

Load data comes from a few places. The new Hornady manual has 7x64 in it, Hodgdon data, many places i look but the data im using mainly is the Speer Data only cause its there bullets im using. The rifle has a 24" barrel with a 1-8.7 twist i believe i read it was. never did check it as my understanding more european rifles where set up to shoot heavy for caliber bullets like 175 and were built as such so never did feel the need to check.
 
The Hornady manual I have is a few years old, and is rather confusing. It lists data for 7x65R, NOT 7x64, but fired in a bolt action test rifle. Weird and confusing, since the 7x65R is almost never chambered in bolt action rifles, it is a rimmed cartridge nearly identical to the 7x64, but designed for use in break open single shots and doubles. It is also loaded to lower pressure than 7x64 according to CIP specs. That does not inspire confidence in Hornady's data.
Lee data is even worse, they just used .280 Remington data and REDUCED charges by some arbitrary amount and published it. Makes me shake my head.
I use 7x64 data from Norma, Lapua, and some European sources with good results.
 
jbmauser said:
My experience with the 7x64 is pretty much exactly what longwalker posted. My Zastava has an extremely long throat and I have to load beyond max to get to the velocity it should be producing with any given bullet weight. Accuracy has always been very good.

Obviously this has to be approached with caution and velocity monitored with a chrony, watching for pressure etc.
Click to expand...

Some might faint at that, but was advice given on CGN about "working up a load" that I have followed for many years - I do start at Start level, then typically like 10 increments to past maximum listed - one rifle - Win Model 70 in 338 Win Mag, with 225 grain Accubond, goes a full grain past book's Max - with no difference that I can detect between one grain below Max or one grain above Max. Another similar rifle was a Weatherby Mark V in 7 mm Weatherby Magnum - that series went to 0.5 grain past published "Maximum" without hiccup. Another rifle - a 7x61 Sharpe and Hart - a full 2 grains below Max and the bolt is significantly harder to open than lower levels - no clue about actual pressure, but that tight opening bolt is the limit for me - might be chamber condition, etc. - but is the point of "working up", so far as I am concerned.

Is typical that first 5 increments (of 10) are single rounds, then second five increments (of 10) are two rounds. If on a shooting table, I am usually fussing to get new-to-rifle scope sighted in at same time - or, I have been known to simply fire them off into ditch bank to get pressure test series done- no real clue where sights or scope is set - for some cases, I do not care about that, or the thing may not even have sights on it yet.

Versus a neighbour who froze his bolt shut on his first reloaded round - then used 2x4 wood block and broke the handle off trying to get it to open - that bolt was still frozen shut, now with no handle on it. His notion of not wanting to "waste" components on "working up" a load cost him hundreds of dollars. His rifle and round was a Remington 788 in 22-250.
 
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Potashminer said:
Some might faint at that, but was advice given on CGN about "working up a load" that I have followed for many years - I do start at Start level, then typically like 10 increments to past maximum listed - one rifle - Win Model 70 in 338 Win Mag, with 225 grain Accubond, goes a full grain past book's Max - with no difference that I can detect between one grain below Max or one grain above Max. Another similar rifle was a Weatherby Mark V in 7 mm Weatherby Magnum - that series went to 0.5 grain past published "Maximum" without hiccup. Another rifle - a 7x61 Sharpe and Hart - a full 2 grains below Max and the bolt is significantly harder to open than lower levels - no clue about actual pressure, but that tight opening bolt is the limit for me - might be chamber condition, etc. - but is the point of "working up", so far as I am concerned.

Is typical that first 5 increments (of 10) are single rounds, then second five increments (of 10) are two rounds. If on a shooting table, I am usually fussing to get new-to-rifle scope sighted in at same time - or, I have been known to simply fire them off into ditch bank to get pressure test series done- no real clue where sights or scope is set - for some cases, I do not care about that, or the thing may not even have sights on it yet.

Versus a neighbour who froze his bolt shut on his first reloaded round - then used 2x4 wood block and broke the handle off trying to get it to open - that bolt was still frozen shut, now with no handle on it. His notion of not wanting to "waste" components on "working up" a load cost him hundreds of dollars. His rifle and round was a Remington 788 in 22-250.
Click to expand...

When I was given the advice to load beyond max while watching for the velocity I was supposed to be getting, I will admit I was more than a little nervous about it. It’s definitely not something that should be taken lightly but in some cases can be done perfectly safely. At any rate one should always work up loads with caution and know what to look for as far as pressure goes while monitoring velocity. Of course without real pressure measuring equipment it is impossible to know exactly what’s going on.

Anyway here’s the link to the thread I started about my 7x64. Some good info there.

https://www.canadiangunnutz.com/for...r-than-expected-velocity-from-a-7x64-Brenneke
 
Case capacity between 7x64 and 280 is almost identical, 1gr H20 difference in favor of the 7x64, so 280 Rem data can be used safely, start low and work up of course.
The 7x64 Zastava I have runs into pressure fairly early in load development, but that is how life goes sometimes, one gun to the next can be different.
Due to the faster twist, I stick to heavy for cal bullets, and it seems to really like them.
 
I have several rifles in both 280 Rem and 7x64. They all seem to have a prefered load for best accuracy. Some rifle barrels are faster than others. I have two rifles chambered in 280 that like almost the same load. Barrel length is the same but according to my chronograph one rifle shoots the same bullet and powder combination almost 150 fps SLOWER than the other. I have used the "slow" 280 on several deer and cannot tell any difference between it and the faster 280 or any of the 7x64s. I agree with several comments already made here. Different throats in different rifles will result in different Max loads in different rifles. I work up loads that shoot most accurate in a rifle and care much less about what the velocity is. I have been reloading for almost 60 yrs and one of the first things I learned is that reloading manuals are a guide. They attempt to publish safe reloading data. That will vary from one rifle to another. Yes much of it is a little on the anemic side but that is to keep inexperienced reloaders safe . Bashing the people who publish these manuals wont make your rifle shoot faster
 
Thank you all for your info!!! lots of wisdom here and apprechate all advice!! I was able to make up 4 sets of 3 today to test for pressure/ load development and see where my Velocity ends up. Components are . once fired Lapua brass( neck sized only) CCI 200 primers, AA4350 and 160gr Speer Grand Slam set out as long as my mag would allow.
Last time at the range i stopped at 53gr yielding and average of 2460fps and horrible groups. Im a happy to say i did see improvement and no signs of pressure yet. (funky primers or sticky/heavy bolt lift)
53.5gr yield 2530fps, 54.gr got me just shy of 2600, 54.5 got me to 2635 and 55 got me to a total of 2680.

the 54.5 load placed 3 into a .65 group so cant complain about that, and almost duplicated the velocity im getting outta the 7-08 with the same bullet!!

I feel i could prolly keep waisting components to prolly gain not much in the end.....and i wasnt really looking for VELOCITY like one would suggest but I was looking for ENERGY on target. It doesnt take alot more velocity to gain alot more energy. ( I think its Double the weight Double the Energy, Double the Velocity and Quadrupal the energy). My current 175gr load gives 2791 lbs of ME, if it was achievable to shoot a 160 @ 2800 fps then the energy on target is almost exactly what the 175 produces.

This eliminates ordering 160 and 175gr grand slams and cuts components costs which in isnt cheap any more. This was my ultimate goal, but the cards were not in my hand with this one it seems lol. I really do love shooting the heavies so im completely happy shooting the 175 for moose anyways.

Thanks again for all your input!!
Josh.
 
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