Alum. checks at high pressures.

[JeffinNZ]

Team.

Is anyone shooting alum. checks at top end pressures?

I find that they do not do well when I am getting into the higher range ie: 40K.

Experience thus far is in my .32-20 and .303's but have yet to try the .223 Rem. Home made Cu checks in the same situation do very well.

[Von Gruff]

Jeff, I am away to the gun room shortly to load up a trial batch to test for that very thing.

Have a very sucessful load for my 7x57 of a 160gn lino bullet with Hornady GC over 39gn H4350 for 2400fps and while I dont know pressures have to believe it is getting close to your parematers.

I intend to trial the same load with my .018 al GC (.012 + .006)

Is it an accuracy or leading issue that you have found with the HV with al GC?

My concern (before I do the trial), is that the GC may not remain on the shank and therefore accuracy may suffer. The Hornady GC with the stiffer sidewall seems to hold onto the shank of the bullet more firmly than the al ones even though the thickness is the same.

Will see if I can get out to shoot later in the day.

Von Gruff.

[JIMinPHX]

I ran aluminum checks up over 2300fps out of a .30-30 with good results. The gas checks ended up in the trap with the boolits, so I believe that they stayed on the whole time.

I had a very bad time shooting aluminum checks in a rifle with a chrome bore. the aluminum fouled the bore badly & was very hard to clean out.

[gl89aw]

Where I used to work we used a lot of alum. bearings, when one failed we used plain old oven cleaner to check the shaft to make sure the alum. was all gone or the next bearing would fail, oven cleaner will turn it black so you can see if it is all cleaned off or in the case of a gun barrel, out.

[longbow]

Well then, I will be paying attention here. My plan was to try pushing the NOE 0.314" x 129 gr. pretty hard from my .303.

So far my first attempt failed and gave rather poor accuracy. That was using hefty but not max. IMR4064 under the aluminum gas checked boolit.

I decided to go back to known territory and tried Unique based on the Lyman Cast Bullet Handbook ~ typical fast powder light loads. Accuracy was not bad at all but I am sure velocity was much lower.

I figured if I could demonstrate the the boolit was shooting well then as I increased velocity and charge with slower powders I would have something to compare to.

Now that I have established that the Unique works I will again try to work up higher velocity loads with slower powders.

I had not thought the gas check material would be an issue but obviously it may well be.

I guess now I will have to add that to my list of variables.

Jeff: Do you find any difference in performance throughout the range of loads or just at high pressures of 40k and above?

Now I suppose I have another project too in that I am paper patching in an attempt to get a lightweight boolit to high velocity.

So I guess I had better get organized and load aluminum GC, copper GC and PP boolits to see what works best.

Longbow

[JeffinNZ]

LONGBOW: I am leaning more towards pressure than velocity as I can get very good accuracy out of my .223 at 2100fps burning Green Dot. The problems occur when I am using a full(ish) case of slow(ish) powder for top end loads.

I am wondering if the problem is the lithography alum. I am using. I was reading about printing plates and saw they are engineered to be heat sensitive etc.

I await Von Gruff's results of comparsion from his VERY pretty 7X57.

[Von Gruff]

I did get out to try the different loads and this is how it went.
Usually I shoot with an aperture sight but mounted a scope for this trial to take any sighting variables out of the equation.

First two groups were with the known load of lino bullet and Hornady GC over 39gn ADI 2209 - H4350 with a TCBK wool wad for 2400fps and as usual it performed up to expectations. Was using a different scope so after bore sighting and first group, adjustments were made for the second group and before the third group with the al GC

http://i667.photobucket.com/albums/vv39/VonGruff/001-8.jpg


After second scope adjustment the third group was shot with the same components except for the AL GC, which were the same thickness as the Hornady ones at .018 but obviously not as stiff in the side wall.

http://i667.photobucket.com/albums/vv39/VonGruff/002-4.jpg

I shot many groups with each load but these ones are representative of the results I got with each.
I then tried my plinking load of the same bullet in 50/50 ww/pb and the AL GC over 11.5 gn Red Dot. This is not the most accurate load with this powder as that was at 10 gn neat but it was so light in recoil and sound that it was like not shooting at all. The 11.5gn load gives me 1500fps and plent of accuracy for my steel plate and off hand practice - play

There are 15 rounds in this lot.

http://i667.photobucket.com/albums/vv39/VonGruff/003-3.jpg

Now the trialing begins to see at what velocity the AL GC start to loose out to the Hornady ones. May take a while but will keep plugging away at it. Have a couple of cans of Blue Dot coming for a different project with my 20 VarTarg and intent to give it a try in the 7x57 as well. I understand from the material I have read on the BD that aboyt 50% of case capacity should give about 40K PSI so it will be interesting to compare the H4350 to BD and I can try some ADI 2207 - H4198 as well.

When I got home the barrel looked good but I had put 85 rounds through from a clean barrel with about half and half of the low vel to the higher vel loads. I used one patch of ER and two dry patches. Barrel was clean but I put another ER through but it came out the same as it went in so there was no fouling at all. Have been leaving the ER in after cleaning and like how it helps with the fouling, or rather the lack there of.

Von Gruff.

[JeffinNZ]

Gary, that duplicated what I have found. The AL is not up to the higher pressures. My Mk VI .303 duplicate load is a 220gr bullet over 41gr AR2209/H4350 for 2000fps and pressures I guess to be high 30's. It shoots fine. I reckon over 40K and the alloy chex are toast.

[longbow]

I have to wonder if this is related to the coefficient of friction between the gas check and barrel.

I will take a look in my references tomorrow to see what the difference in dynamic coefficient of friction between aluminum, copper and steel. I am betting that copper has a significantly lower coefficient of friction.

What may be happening here is that at higher pressures there is enough boolit obturation to expand the gas check hard enough against the barrel to cause the aluminum to gall. Plain aluminum sheeting is generally very soft aluminum. I am not sure what alloy pop and beer cans are but will check. I am currently using old gutter material for checks so quite soft.

The aluminum bearing material mentioned by gl89aw is most likely a zinc aluminum alloy which does make good bearings. Soft aluminum however does not.

If this is the case then possibly a change of lube may help. Some form of high pressure grease or oil with EP additive might work if added to lube or lube made with it, or possibly moly or graphite added to the lube.

Another mystery to solve... or I guess just use the aluminum checks within their limitations.

Longbow

[Von Gruff]

I am using the same type of lithographinc plate as Jeff does.

A couple of questions for previous posters.

JIMinPHX got to 2300fps with AL GC in a 30-30 so what powder were you using Jim. You had AL fouling in a chrome bore while I ran to 2400 with no fouling at all which has a CM bore as I suspect your 30-30 did.

JeffinNZ got to 2100with Green Dot in his 223 to shoot good,but that is with Cu GC. The 303 with the 2209 - 4350 load and AL GC shoots worse than with Cu GC as does mine.

Longbow the friction coeficient may have a bearing so will look for your input.

I am going to trial the different powders as in BD, 4198 and further trials with the 4350 to see if I can find a load that will give exceptable velocity with accuracy. I used the same loads so far with the AL GC that worked with the Hornady GC so tweaking the load a bit may bring a better result. See if HOW we get to the higher velocity makes a difference. That will take a while though so will look to the knowledgable for further ideas.

Jeff have you tried the litho plate both ways as so far I have put the shiny side out. I see in the G&H piece you wrote, you had the colour out but they looked like beverage cans rather than the litho plates.

Von Gruff.

[JeffinNZ]

VG: I generally use the 'green' side of the plate on the external surface.

My .223 will shoot equally well on the Green Dot with either Cu or Al.

Possibly harder Al. might the answer for top end loads. Litho plate is pretty soft.

[PatMarlin]

Where I used to work we used a lot of alum. bearings, when one failed we used plain old oven cleaner to check the shaft to make sure the alum. was all gone or the next bearing would fail, oven cleaner will turn it black so you can see if it is all cleaned off or in the case of a gun barrel, out.

That is very interesting.

Thanks for the info gl89aw ...:drinks:

[Bloodman14]

So, what alloy is Al roof flashing? Hey, I found some painted flashing at Sutherlands that is .018! Makes excellent checks! Will let you know what brand.

[Von Gruff]

Gunnerd, what velocity are you running them at. We are able to get good accuracy when vel is down at the 15-1600 fps range but the litho plat al we are using seems to be a bit fussy as the vel and or pressure is pushed a bit.

Von Gruff.

[Bloodman14]

VG, still punching out checks; using them on Lee 150 FN's for my wife's Marlin 30-30 in plinker loads. Have not run them at serious velocities, yet; will do that in my 2 .303's when I get the proper sizer from Lee. The info was for general info for the members. The brand is "Gibraltar". I don't have a chrony, anyway, so I couldn't tell you what the velocity is in anything I shoot; however, I do use J-word starting loads when loading for real boolits, if that helps.

[longbow]

Well then, I got busy at work and forgot to look in my reference books for coefficients of friction (pretty sad when work gets in the way of reloading research!).

I did some internet surfing tonight and came up with:

- coefficient of dry sliding friction for:

aluminum on steel = 0.47
copper on steel = 0.36
lead on steel = 0.95

- coefficient of lubricated sliding friction for:

copper on steel = 0.18
lead on steel = 0.3

So far I have not turned up anything for lubricated aluminum on steel.

The larger the number the more friction. So copper has a significantly lower coefficient of dry sliding friction on steel than either lead or aluminum. I suspect that lubricated aluminum will fall into position between the two as well but that is speculation until I can find documentation.

This is also approximate as the surface finishes and exact alloy also has an effect. This assumes plain old mild steel like cold rolled, soft copper and pure aluminum.

I will see what else I can find but I am guessing lubricated copper will have a lower coefficient of friction than aluminum.

Longbow

[.30/30 Guy]

I have been watching this thread for a while. Might as well step in.

I have been using 26 grains of H335 behind a 170 grain boolit in my .30/30. Guessing the velocity is in the 1900 range.

The 0.014 roofing flashing material gives me 25% smaller groups with the same load than 0.008 lith material. The lith material is much softer.

[JeffinNZ]

The lith material is much softer.

And I believe there in lies the problem.