Jackpot
03-05-2010, 23:25
I am starting this thread to share my results in coming up with a cast bullet load for my AR-15s. There are two goals for my madness:
1. I want to see if I can do it while retaining all my fingers and not messing up my rifles.
2. It appeals to me to save some money while I work through 100 round close quarters drills. I don't need a whole lot of accuracy while I work over multiple targets at 5 to 25 meters so I'll save my 55, 62 and 69 grain pills for another day.
Disclaimers up front:
1. I realize it is downright heresy to shoot a cast bullet through an AR-15 and it just can't be done anyway. It'll lead the barrel. It'll lead the gas system. The bullets will fragment in flight. The bolt won't cycle. There. I pointed out why this experiment can't possibly work so let's get on with how it did.
2. I will share the loads that I came up with. They worked in my equipment and may not work in yours - may not work in yours in a very loud, surprising and possibly hazardous manner. I do not advocate anyone using these loads - beware loads obtained over the internet!
The Equipment:
Rifle 1 is a RRA Elite Comp which is a 16" midlength DI gas system. The barrel is probably a Wilson tube chambered in 5.56 with a 1:9 twist and is not a chrome bore.
Rifle 2 is a homebrew. Bushmaster upper and lower, 16" carbine length Adams Arms piston system. The barrel is a Daniels Defense tube chambered in 5.56 with a 1:7 twist and is a chrome bore.
Bullet is from Lyman mold #225646 which is a gas check bullet listed at 55gns. I used a lead alloy that is very similar to Lyman #2 and the bullets actually weighed in around 61 grains with the gas check. All bullets were sized to .224 and I used and OAL of 2.100". This OAL is pretty much the only length you can use because #225646 appears to be somewhat tapered in front of the driving bands and the sizing die stops burnishing the bullet just a little in front of the driving bands. Consequently, I had to seat the bullet in the case so that the sized, burnished area was in case neck for bullet tension reasons. This left an OAL of 2.100" wich gave me about .040" freebore which is not too bad for accuracy. Cost of these little bitty bullets with gas check is about 3 cents.
I used the tan colored NRA lube (beeswax and Alox) which many of the cast bullet diehards say is good to 1900 or 2000 fps. Kinda hard to calculate the cost per bullet of lube so I'll say it's 1 cent for arguments sake.
Powder is IMR4895, cases are military (mostly once fired Lake City, prepped by Scharch) and primers are CCI 400. I normally do my own case prep but was having a hard time finding primers so I bought a bunch of cases from Scharch because they graciously stuffed a primer in each case for me. The cost per round for the charge weights I was using is 5 cents. The prepped cases from Scharch ran 15 cents each with 3 cent primer so say 12 per case, fired 4 times each would come in at 3 cents per round.
Added up:
bullet 3 cents
lube 1 cent
powder 5 cents
case 3 cents
primer 3 cents
--------------
grand total is 15 cents per round, $3 for 20 rounds or $15 for a hundred round training session
I think I hit #2 pretty soundly
The Results - I still have all my fingers and the rifle did not blow up
My first series of tests centered around exploring how well the rifle would cycle with the lower power loads. I picked the RRA midlength DI gas gun for the first tests since it is DI and has a 1:9 twist. I'll see how the carbine length piston gun with the fast twist handles cast bullets in later tests.
I began with 18gns of IMR4895 which was a lucky call. All rounds cycled the bolt and there were no FTE/FTFs, but just barely. I noticed that the bolt was not retained after the last round fired because it did not cycle all the way back. Not enough juice. Average fps was 1703 at 7000 feet altitude at 30 degrees F. 50 meter accuracy I though was pretty good at about 1 inch with iron sights. Not a benchrest group but pretty good.
The next set of rounds had 18.5gns which did cycle the bolt all the way for bolt retention. Recoil is VERY light and you do notice a bit of smoke due to the beeswax and Alox bullet lube. Average fps was 1778 at 6500 feet altitude at 35 degrees. Accuracy seemed on par with the 18 gn loads.
The final set of rounds for the cycling test was 19gns again with full cycle on the bolt and not FTEs or FTFs. Average fps was 1864 at 6500 feet at 35 degrees.
Cleaning:
The moment of truth.... I fired no jacketed bullets in either of my two shooting sessions to "clean out the barrel and gas system" as I had seen mentioned in various forums. I am very familiar with what lead-in-the-bore looks like as I have a recalcitrant .357 that leads like crazy and I have gotten to be an expert in cleaning that thing. I saw no lead in the RRA Wilson tube 1:9 bore. Carbon yes, lead no. The bolt appeared to have a bit more carbon build up on it than I'd get for the same number of jacketed rounds. I dunno if the gas tube leaded up or carboned up because I never jam anything into it to clean it - I figure 35000 PSI will keep it fairly well empty.
Future Tests:
My next range session will probably run 19gn loads through the homebrew carbine length piston gun to see how velocities compare to the midlength DI gun. This will also probably tell me whether a 1:7 twist (the carbine length gun) is too much spin for #2 Lyman lead. Another thing I am curious about is wheather the chrome bore will pick up lead as it is somewhat coarser than the chrome moly surface on the midlength DI gun.
Once I have a handle on cycling and stability on both guns I'll publish picts of the groups I get.
Regards,
Jackpot
1. I want to see if I can do it while retaining all my fingers and not messing up my rifles.
2. It appeals to me to save some money while I work through 100 round close quarters drills. I don't need a whole lot of accuracy while I work over multiple targets at 5 to 25 meters so I'll save my 55, 62 and 69 grain pills for another day.
Disclaimers up front:
1. I realize it is downright heresy to shoot a cast bullet through an AR-15 and it just can't be done anyway. It'll lead the barrel. It'll lead the gas system. The bullets will fragment in flight. The bolt won't cycle. There. I pointed out why this experiment can't possibly work so let's get on with how it did.
2. I will share the loads that I came up with. They worked in my equipment and may not work in yours - may not work in yours in a very loud, surprising and possibly hazardous manner. I do not advocate anyone using these loads - beware loads obtained over the internet!
The Equipment:
Rifle 1 is a RRA Elite Comp which is a 16" midlength DI gas system. The barrel is probably a Wilson tube chambered in 5.56 with a 1:9 twist and is not a chrome bore.
Rifle 2 is a homebrew. Bushmaster upper and lower, 16" carbine length Adams Arms piston system. The barrel is a Daniels Defense tube chambered in 5.56 with a 1:7 twist and is a chrome bore.
Bullet is from Lyman mold #225646 which is a gas check bullet listed at 55gns. I used a lead alloy that is very similar to Lyman #2 and the bullets actually weighed in around 61 grains with the gas check. All bullets were sized to .224 and I used and OAL of 2.100". This OAL is pretty much the only length you can use because #225646 appears to be somewhat tapered in front of the driving bands and the sizing die stops burnishing the bullet just a little in front of the driving bands. Consequently, I had to seat the bullet in the case so that the sized, burnished area was in case neck for bullet tension reasons. This left an OAL of 2.100" wich gave me about .040" freebore which is not too bad for accuracy. Cost of these little bitty bullets with gas check is about 3 cents.
I used the tan colored NRA lube (beeswax and Alox) which many of the cast bullet diehards say is good to 1900 or 2000 fps. Kinda hard to calculate the cost per bullet of lube so I'll say it's 1 cent for arguments sake.
Powder is IMR4895, cases are military (mostly once fired Lake City, prepped by Scharch) and primers are CCI 400. I normally do my own case prep but was having a hard time finding primers so I bought a bunch of cases from Scharch because they graciously stuffed a primer in each case for me. The cost per round for the charge weights I was using is 5 cents. The prepped cases from Scharch ran 15 cents each with 3 cent primer so say 12 per case, fired 4 times each would come in at 3 cents per round.
Added up:
bullet 3 cents
lube 1 cent
powder 5 cents
case 3 cents
primer 3 cents
--------------
grand total is 15 cents per round, $3 for 20 rounds or $15 for a hundred round training session
I think I hit #2 pretty soundly
The Results - I still have all my fingers and the rifle did not blow up
My first series of tests centered around exploring how well the rifle would cycle with the lower power loads. I picked the RRA midlength DI gas gun for the first tests since it is DI and has a 1:9 twist. I'll see how the carbine length piston gun with the fast twist handles cast bullets in later tests.
I began with 18gns of IMR4895 which was a lucky call. All rounds cycled the bolt and there were no FTE/FTFs, but just barely. I noticed that the bolt was not retained after the last round fired because it did not cycle all the way back. Not enough juice. Average fps was 1703 at 7000 feet altitude at 30 degrees F. 50 meter accuracy I though was pretty good at about 1 inch with iron sights. Not a benchrest group but pretty good.
The next set of rounds had 18.5gns which did cycle the bolt all the way for bolt retention. Recoil is VERY light and you do notice a bit of smoke due to the beeswax and Alox bullet lube. Average fps was 1778 at 6500 feet altitude at 35 degrees. Accuracy seemed on par with the 18 gn loads.
The final set of rounds for the cycling test was 19gns again with full cycle on the bolt and not FTEs or FTFs. Average fps was 1864 at 6500 feet at 35 degrees.
Cleaning:
The moment of truth.... I fired no jacketed bullets in either of my two shooting sessions to "clean out the barrel and gas system" as I had seen mentioned in various forums. I am very familiar with what lead-in-the-bore looks like as I have a recalcitrant .357 that leads like crazy and I have gotten to be an expert in cleaning that thing. I saw no lead in the RRA Wilson tube 1:9 bore. Carbon yes, lead no. The bolt appeared to have a bit more carbon build up on it than I'd get for the same number of jacketed rounds. I dunno if the gas tube leaded up or carboned up because I never jam anything into it to clean it - I figure 35000 PSI will keep it fairly well empty.
Future Tests:
My next range session will probably run 19gn loads through the homebrew carbine length piston gun to see how velocities compare to the midlength DI gun. This will also probably tell me whether a 1:7 twist (the carbine length gun) is too much spin for #2 Lyman lead. Another thing I am curious about is wheather the chrome bore will pick up lead as it is somewhat coarser than the chrome moly surface on the midlength DI gun.
Once I have a handle on cycling and stability on both guns I'll publish picts of the groups I get.
Regards,
Jackpot