Vertical Stringing w/ Cast in the M1A

[StrikerOmalley]

I'm hoping someone could point me in the right direction on this issue. I've been loading a 311299 in my M1A for a while now. With the load I use, I've always noticed groups with a degree of vertical alignment. A while back I was shooting from 700 yards and had five shots land with a vertical spread of 25 inches, and a horizontal spread of about 4 inches.

Anyway, I have two copper jacketed bullet loads which I use for this rifle, and both perform well without any noticeable stringing.

Today's series of events:

Two ten round cast bullet groups (H4895) - Vertical stringing in each.
One five round 175 Gr. HPBT group (BLC-2) - Nothing abnormal, good accuracy
One five round 149 Gr. FMJ group (BLC-2) - Nothing abnormal, good accuracy
One five round cast bullet group (H4895) - Vertical stringing

-Alloy is Lyman#2
-I'm shooting with a bipod from a normal bench.
-The load is moving at around 2000 FPS
-1 in 11" twist rate
-I'm using surplus military brass (sorted by manufacturer) and CCI 34 primers
-Powder is H4895
-Annealed .014 Amerimax aluminum gas checks made from a FC III (not possible to remove by hand).
-All bullets were weighed and sorted to within 1/2 grain of the mean (doesn't really seem necessary).

-No buffer, tried adding some and reducing the load then working my way back up. No improvement.
-Tried another type of primer (Fed LR). No improvement.
-I use a rear bag with the bipod but haven't tried shooting from a lead sled or anything like that.

How much truth is there to the idea that slow moving cast bullets are more susceptible to recoil? I'm also trying to understand if it's a powder burn rate or temperature issue. Any ideas or suggestions on what else to try would be great.

Thanks,

[IraqVet1982]

I honestly have no clue what's causing this. How do they group at 25, 50, 100 yards. Just trying to see if this happens at all distances or just long distances.

[StrikerOmalley]

Today I was shooting at 85 yards and the vertical spread was about 4 inches. Most rounds fell within the same 1" grid column on the target. Previously, I was shooting at 700 yards and the vertical spread was about 25 inches.

I'm perfectly fine with the issue being my shooting form or lack thereof (if that's the case). That said, the issue went away entirely once I stopped shooting cast.

[IraqVet1982]

Looks another guy solved a similar problem by adjusting crimp

http://www.marlinowners.com/forum/45-70-govt/73278-cast-vertical-stringing.html#/topics/73278?page=2

[BK7saum]

What are your velocities on those strings. If inconsistent ignition and velocity, then that mat be a factor.

Of course, the longer the dwell time in the barrel, the more lack of form and inconsistency can/wI'll result in inaccuracy.

[Yodogsandman]

Adjust the powder load either up or down just a little. Maybe just a tenth of a grain. You're on the edge of an accuracy node where the bullet leaves the barrel as it is moving up and down. Just a little adjustment will tune and calm the effects, leaving the barrel at the same place in barrel harmonics movement.

[StrikerOmalley]

Thanks guys.

I don't use a crimp but I appreciate the perspective.

Not sure what my velocity is for each shot during those groups, I'll try that next time. I thought the stringing could be a function of velocity.

The accuracy node comment makes sense. I will say that I've seen the stringing with this load on intermittent occasions. when I see it, it's decisive. Perhaps that's related to temperature/velocity which is a factor in some situations and not in others.

[Yodogsandman]

Another thought is that if your H4895 load is a light load, it could be velocity variations from powder position. A light load would be under 80% case fill. You could drop down a grain or two and add Dacron fluff as a filler to keep the powder in place. Be sure to pull the Dacron apart slightly so its a light, fluffy tuft and not a wad. No more dense than the cotton in a pill bottle. Also, completely fill the case from the top of the powder charge to the base of the boolit. That will prevent the filler from becoming your projectile and your cast boolit from being a bore obstruction. Weigh or cut the Dacron so as to use the same amount for each round. Work up the load again with the Dacron filler using normal practices.

[crackers]

I've caught myself with a heavy gun and light load not fully and consistently bracing the butt which allows the back of the gun to slide down (or roll) the rear bag. Depending on the relationship of the bipod attachment point over the feet placement, I could likely make my bad shots worse.

[popper]

+1 ^^^.
I have the vertical problem also, usually just my 'recoil' response. Could be a node problem or 'time in barrel or friction of jacketed vs cast. BL(C) & 4895 are a ways apart in the burn rate chart (depending on which data you use). I use hornady GCs for 'target' work, Josh's Cu checks work ok in less critical shooting. Never used Al. GCs. I shoot ARs, not M1s but both have a gas system and IMHO there is an effect from the 'push' from it on the barrel.

[Larry Gibson]

Your vertical stringing is caused by, as mentioned, inconsistent ignition or inconsistent hold.

Since you apparently do not have a chronograph I suggest the use of a Dacron filler to cure the first. You then may not need to address the second.

[vzerone]

+1 ^^^.
I have the vertical problem also, usually just my 'recoil' response. Could be a node problem or 'time in barrel or friction of jacketed vs cast. BL(C) & 4895 are a ways apart in the burn rate chart (depending on which data you use). I use hornady GCs for 'target' work, Josh's Cu checks work ok in less critical shooting. Never used Al. GCs. I shoot ARs, not M1s but both have a gas system and IMHO there is an effect from the 'push' from it on the barrel.

On an AR with the DI system there is virtually no effect of the gas system working on the pushing the rifle. The gas tube is free floating too and the bullet is gone or just about gone when that gas moves something. This is why DI system AR's generally out shoot piston system ones, that plus there is more "junk" atop the barrel in the piston driven ones. M1 being the gas port hole is so near the barrel I've often wondered what effect it's piston system movement effect is on accuracy. The M 14 and M1A's are a different matter with their gas retrival being further back on the barrel. Interesting note I've notice in shooting AR 15's and AR 10's that their gas system sucks up a lot of gas thus showing lower velocities Even comparing at AR 10 with same barrel length as an M1A shooting the same load there is a big difference in velocity with the AR 10 showing the low figure.

I like the replies so far. Generaly with vertical stringing, assuming the stock is not the culprit, adjusting the powder charge improves it.

[StrikerOmalley]

Thanks again for the perspective. Great feedback.

[Echo]

Thanks guys.

I don't use a crimp but I appreciate the perspective.

Not sure what my velocity is for each shot during those groups, I'll try that next time. I thought the stringing could be a function of velocity.

The accuracy node comment makes sense. I will say that I've seen the stringing with this load on intermittent occasions. when I see it, it's decisive. Perhaps that's related to temperature/velocity which is a factor in some situations and not in others.

I'm just spit-ballin here, but I must ask, DO You Trim Your Cases? If not, the pull will vary, which will vary the pressure, which will vary the velocity, capich? My suggestion is to trim your cases, and put a crimp, mild or otherwise, on the finished product. I have spoken...

[Bama]

Thanks guys.

I don't use a crimp but I appreciate the perspective.

Not sure what my velocity is for each shot during those groups, I'll try that next time. I thought the stringing could be a function of velocity.

The accuracy node comment makes sense. I will say that I've seen the stringing with this load on intermittent occasions. when I see it, it's decisive. Perhaps that's related to temperature/velocity which is a factor in some situations and not in others.

I had same problem with H4895. I resolve it with a factory crimp and a increase in powder. Still get a little with Temp variations with powder and barrel.

[Ford SD]

Your vertical stringing is caused by, as mentioned, inconsistent ignition or inconsistent hold.

Since you apparently do not have a chronograph I suggest the use of a Dacron filler to cure the first. You then may not need to address the second.


Larry is more of a expert on this but
does your strings move up with each shot ?

my thought is vertical stringing is by a velocity change
ps I agree with a dacron filler could fix this

less than 200 fps change in velocity will account for your vertical stringing at 700 yards
recoil could be setting back (shorter oal with each firing of the prevous round ) and increasing pressure = increasing velocity

what size are your cast bullets ?
it could be fixed or reduced by sizing 1 or .002 larger
or by adding a very small crimp

[StrikerOmalley]

All good comments. I think I'm leaning towards stock control as the main culprit. I'll chrono all shots next time to rule out velocity and may follow up with a crimp for additional security.

There was a pause between these two groups, when I went downrange to check my target.

That marked hole was a copper jacketed round at the start of the group.

I do trim all cases and size to .309.

http://i1295.photobucket.com/albums/b639/Strikeromalley/String%202_zpssnlco80v.png

[leadhead 500]

I load and shoot a lot of cast in everything from 223 to 458 win. Mag and from my experience after thousands of cast rifle bullets is you need to use Dacron filler in your loads,when the load density is low I have seen some crazy vertical and horizontal stringing on groups. Dacron is the answer to correct a lot of issues with cast rifle bullets. Larry Gibson is the man to fill you in and get you on the right track