What is the difference?

[mysticplayer]

Been playing with my version of the 260AI called the 6.5 Mystic. Formed from 308 brass, it has a 40deg shoulder with a case shape you would expect for an AI.

I push Lapua 139gr uncoated Scenars with H4831SC lit by a CCI BR2 primer between 2900 and 2950fps to mimic the 6.5-284. I have settled on the slower 2900fps which uses 46.5gr of my lot of powder. Magnum pressures for sure but not excessive,6 reloads per case and counting). 30" barrel.

After shooting 750+rds, I have seen no forward movement in my throat,SS match barrel). I get the same engraving marks on the loaded cartridge as when new.

What will happen when the rd count approaches 2000? Will know next season but for now using that bit less powder seems to have improved barrel wear appreciably. I am comparing notes with a 6.5-284 shooting friend and what I see posted by others.

Reducing the amount of powder burnt will increase throat life. Just as importantly as WHAT type of powder is burnt. I suspect operating pressures matter too but have no way to test that. There certainly are cooler powders and powders that are less 'abrasive'. A lot of balancing to do.

There are about 12 wildcats similar to the XC/47L that I am aware of used in competition. Some are formed from 243 or 22/250 brass. Some are well over 30yrs old. They have long necks, short necks, shoulders of every conceiveable angle and shape.

For the most part, they all provide very similar performance and the accuracy potential has more to do with barrel/bullet/shooter then case design.

Been wildcatting for the last 9yrs and have come up with a number of project rifles/cartridges. There really hasn't been any 'holy grails'. Similar case volume in the same calibre, burning similar amounts of powder ALL perform the same within the vagueries of barrels. Short and fat was no more 'effecient' then long and skinny.

The only thing that mattered was whether there was a powder to optimise that case.

It is alot of fun though and kind of neat winning with your better mousetrap.

Jerry

 

[ghermitage]

... 243 Win and shoot H1000 or N165 ...

What you find out is that your barrel last much longer.

Joe Hendricks

Do these powders require longer barrels to achieve the same velocities as barrel-burning powders? Say we are talking a 24" barrel for other powders, what barrel length is required to get the same velocity with H1000 or N165?

 

[ghermitage]

... 243 Win and shoot H1000 or N165 ... through it

What you find out is that your barrel last much longer.

Are heavier bullets indicated to get best results from these powders?

Is the Ackley Improvement of 243W necessary to make these powders suitable i.e. are they equally advantageous with standard 243W ?

 

[TonyZ]

Mystic, i have just recently finished extensive testing on a 7/08 Improved version of my own having a neck length of 0.300". Based on Lapua cases i am able to achieve 2800 fps with a 175 SMK and 46.5 grains of H4350 and the 215 M. The 162 Amax can be driven to 2930 fps with 47 grains of the same H4350 and the 215M. The 215 M is very important to the developement of this cartridge because when using a 210 M or something similar, there is about 70 fps speed loss. It also happens that the 215 M is giving the lowest ES and best long range grouping. The cartridge runs well short of volume before pressure can really hurt the bullet proof Lapua 308 brass. Taking the 175 SMK and going beyond the 47 grains of H4350 is definetely a surefire way to find the limit of any brass. 20 test cases have fired the 300 rounds through this barrel and are not quite dead yet. One that was sacrificial at 48 grains of H4350 and the 175 SMK is no longer able to hold a primer.
The barrel in this rifle is a 30 inch Krieger in 9.5 twist, but an early sacrificial barrel at 25 inches that was chambered to "lets have a look and see", gave velocities that were only 25 fps shy of what i have stated above. That was what prompted me to continue with a new barrel and i honestly thought that there was a possibilty to go even faster with the extra length, but i am still pleased with the outcome. I have finally found a replacement for my ailing 284 and the poor quality of brass available for it in Aus.
Tony Z.
ps. There are a number of 260s over here that i know of that are consistantly achieving performance levels at around what you have stated, not far away from the 6.5/284, and i will bet that they are using the superior quality Lapua 308 case. Maybe the RWS too.

 

[ghermitage]

Presumably this greatly improved barrel life with H1000 or N165 can be seen in at least some other cartridges as well as 243W.
Under what circumstances is this improvement with these powders not seen in other cartridges?

Do 260 and 7mm-08 like these powders, and with what weight bullets?

 

[TonyZ]

I looked at a number of other powders before i started to configure the reamer dimensions of the intended cartridge,7/08 Imp). Wanting to use the 308 case capacity to keep heat to a minimum during long strings of shots in F Class matches, H4350 was the one that stood out as the best as far as grains used for velocity gained. H1000 is one of the most versitile powders i have struck in recent years and i would have dearly loved to use it in this cartridge, but it is physically impossible to get enough into the case to be of any use. A shame because it has one of the coolest flame temperatures.
I did try Win 748 as another option, dirty and not kind to throats, but it was able to give the best accuracy at the middle distances, although velocity was way down with the pressure way up. Re 19 is another one worth looking at at some time in the future as i feel this is the one that could give even more speed.
Tony Z.

 

[ghermitage]

Does the 260 get good velocity value from H1000, or is it only at 243 that there is no velocity penalty for using H1000?

 

[ghermitage]

Australian Defense Industries lists its AR2217 as equivalent to H1000 and N170.
http://www.adi-limited.com/handloaders-guide/equivalents.asp

Use of AR2217 for 7mm-08 isn't listed, but is for 260R and 243W, and pressures are listed for 260. What's possibly significant about AR2217 is that it develops lower pressure than other powders with maximum loads, even when the other powder has a very similar burn rate
http://www.adi-limited.com/handloaders-guide/burning_rates.asp

There is a significant velocity loss until the bullet weight gets up to 125gr, and the remarkable pressure difference with the lower weights is then moderated.
http://www.adi-limited.com/handloaders-guide/rifle.asp