Gradual increase in group size?

[jhrosier]

I fired ten groups of five shots each from my .308 Win. heavy barreled Remington bolt gun today.
The gun was shooting 1 moa or slightly smaller at the beginning and a little more than 2 moa at the end of fifty shots.
The boolits were reasonably hard 31141s with White label 2500+ lube, over 18 gr of 2400, for an estimated velocity of 1750fps.
The gun was cleaned with Sweets before shooting and I probably got 98% of the metal fouling out of the bore.
There was no visible leading in the bore after fifty shots.
Groups were fired at 50, 100 and 200 yards during the session and the increase in group sizes was consistent at all ranges. The first three groups were at 50 yards, then one at 200 yards, four more at 100 yards, and the rest at 200 yards.
The gun was sandbagged, with a great trigger and a 24 power scope. Recoil was not a factor.
The temperature was about 40 degrees and the barrel never got more than barely warm to the touch.
Some of the groups were fired about two shots per minute and others at about one shot every two minutes. The timing did not seem to affect the group sizes.

The question is, what factor would be most likely to cause the gradual increase in group size?

Jack

[Vly]

Sometimes leading is hard to see in rifle barrels. Run a dry tight-fitting patch through the bore. It will hang up on the lead. Leading is the only explanation I can think of. A distant second choice might be some flavor of shooter fatigue. ( eye strain etc )

[35remington]

Any number of things can cause it. Something is changing about your barrel condition for the worse.

Too much lube. Or not enough, for example. A gradual increase in fouling buildup, maybe.

I presume the rifle doesn't exhibit this tendency with other than lead bullets.

[Leftoverdj]

Your sample is too small to mean anything. Fifty and 100 yard groups are not accurate predictors of 200 yard groups so we discount those for the moment. We are left with three 200 yard groups. The first was the smallest, but we all get lucky groups that are half the size of a rifle's average performance. Also, there was at least half an hour between that group and the next two 200 yard groups. That's plenty of time for light and wind conditions to change, maybe enough for shooter fatique to be a factor.

Your four consecutive 100 yard groups may be a better guide, depending on how pronounced the spread was. I'd consider groups ranging from 1.25 to 1.75 moa to be absolutely normal for a load that averages 1.50 moa.

I'd take 50 more rounds to the range and shoot five consecutive groups at 200 yards, then five more at 100. If the pattern repeats, we'll have some hard info.

[Blammer]

load up more of the same and go shooting again, tell us what happens that time.

[runfiverun]

my 308 is exactly the opposite
it takes at least 5 shots to settle down

[jhrosier]

I found something unusual when cleaning the barrel this eve.
There was a coating in the barrel that made me use a great deal of force to get the first patch, with Kroil, through the bore.
The fouling was jet black and sticky as tar. There were no particles of lead visible on the patch.
I followed up with a couple of patches with Shooters Choice but very little powder fouling was seen on the patches.
A vigourous scrubbing with 3 more patches with Sweets failed to show any sign of metal fouling.
A tight patch pushed through after cleaning showed a perfectly smooth bore from end to end.

I have shot these same boolits, with the same powder, through a number of different 30 caliber rifles and never had this sort of thing happen before.
The only difference that I can think of is that this barrel is stainless steel. I have never had a rifle with a stainless barrel before so I have nothing to compare it to.

Is there anything about stainless that would require a different boolit lube than White Label 2500+ ? It has worked very well in a half dozen other .30s, from about 1200 to 1800 fps.

My intuition tells me that this is going to be a very accurate rifle when I have found the right load combination. Even with this wacky load I have seen a large number of three shot clusters in the 1/2 moa range.

I just ordered a new 311299 mould and a .311 sizer. I think that the longer bore riding nose is going to be easier to get consistent results than the short tapered nose of the 31141.

I haven't even begun to explore slower powders, checking cartridge runout, or the dozens of other variables, but I fully intend to have this gun shooting consistently below 1 moa by the end of the summer.

Thanks for the suggestions and ideas so far. I'm taking notes.:drinks:

Jack

[joeb33050]

When I get leading I get wild shots, it is clear that something has changed-a lot. A little leading does not mean a little bigger groups, not in my rifles. I don't think it's leading.
Five shot groups, shot 5 at a time, will AVERAGE a spread of twice group size. Means that if we shoot 5 five shot groups and measure the group sizes, on average, the largest will be twice the size of the smallest. Not an opinion, statistics at work.
I suspect that you don't have enough groups shot at any of the 3 ranges to draw any conclusions. You're looking at a fluke, so far.
joe b.

[Just Duke]

I was using 2400 with my 629 Classic DX in 1995 and the the gun would get so dirty the cylinder would not spin.
My 300 Ultra mag Police model would shoot really bad after 15 rounds of 95 grains of Retumbo were shot down the bore.
When sighting in I will clean every 5 rounds and leave the bolt out for cooling when possible.
Lead + 2400.... she needs a good cleaning. ;)

I would like to thank you for the detailed range report sir. :) Keep us updated and thanks for sharing.

[Larry Gibson]

jhrosier

MOA groups at 50 yards or even 100 yards do not necessariy equate to MOA groups at 200 yards. You've a 10" twist there and are running 126,000 RPM. You are up into the RPM threshold and any imbalances are begining to be magnified by the RPM. The farther the range the greater the effect on accuracy. Also as you mention you found the lube was "sticky as tar". This also cold be the problem given the colder 40 degree weather. Some lube residue gets hard in the bore in colder weather and causes fliers particularly if we are not cleaning every so often (you make no mention of cleaning the rifle at the range). Since the timing of your shots also varied that also induces another variable as the barrel wasn't warmed up the same during strings.

I've no experience with White Label 2500+ lube but it could be that it just doesn't like cold weather and a mundane 1750 fps. I use Javelina and have little problems with cold weather effect from 35 degrees up and at 2500+ velocity.

Larry Gibson

[jhrosier]

Larry,
I noticed the topics about RPM threshold, but have not taken the time to read them carefully.
I will tend to that soon.
One quick question on the topic:
If I subsitute a heavier bullet, say 200 gr, for the 170 gr, at about the same velocity, will it make the potential for a problem greater or less?
Your expertise and research is appreciated.

Jack

[Larry Gibson]

jhrosier

I see you are interested in the 311299. That is a fine bullet, I use it myself along with 314299. I've had very good accuracy with them in '06 M1903s. The really nice attribute of a heavier bullet is that it provides for more uniform burning of medium and slow burning powders while keeping in the RPM threshold. My limited use of 311299 in the .308 has been for use in M14/M1As, they either had 11 or 12" twists, and a short 18" barreled carbine with a 10" twist. I was using H4895 at the time with a dacron filler and got excellent performance with 28 gr of the H4895. Velocity was 1710 fps in the carbine and 18660 fps in the M14s.

When I get around to the end of the RPM tests I am conducting i will also test with the 311299 in the 3 different twist rifles. Thus I'd suggest you might try exactly what I plan on trying. Take a look at using 4895 starting at 27 gr and work up to 32 gr in 1 gr increments. Use about a 1/2- 3/4 gr dacron as a filler. Then try Varget starting at 29 gr and working up to 36 gr. I don't plan on using the dacron filler with Varget as it is bulkier than H4895. Then I will try RL19 and H4831SC. With both of those I'll be looking for a 80%+ loading density that still keeps the bullet in the 1850-1950 fps range. That is in the upper end of the RPM threshold. I plan on using a #2 type alloy with the bullets WQ'd out of the mould. Sizing will be .31 and lube will be Javelina.

As to a "problem, greater or less I don't know. As I've said I've no experience with the lube you are using but since it gave satisfactory service before that may not be your current problem I do know I've never had a problem with Javelina at the velocities you're talking about. I don't think you will have a problem with well cast 311299s if you keep the velocity in the 1800-1950 fps range using medium or slow burning powders that give you consistant ignition (easy to tell with chronograph as the smaller the ES the more consistant the ignition). Any other questions don't hesitate to ask, always glad to help where I can.

Larry Gibson

[Billwnr]

I shoot 2400 in my .30/06 and after about 25 shots my POI starts to drop down and keeps dropping on each shot until I clean it.. From about shots 8 to 20something it shoots small groups.

Clean your barrel a little more often and use a brass brush when you do.

[jhrosier]

.......

Take a look at using 4895 starting at 27 gr and work up to 32 gr in 1 gr increments. Use about a 1/2- 3/4 gr dacron as a filler. ....

using a #2 type alloy with the bullets WQ'd out of the mould. Sizing will be .31 and lube will be Javelina.

.....

I don't think you will have a problem with well cast 311299s if you keep the velocity in the 1800-1950 fps range using medium or slow burning powders that give you consistant ignition (easy to tell with chronograph as the smaller the ES the more consistant the ignition). Any other questions don't hesitate to ask, always glad to help where I can.

Larry Gibson

Larry,

Your suggestions worked out well for me in the end.

I cast some 311299s from 1 part lino, 2 parts lead and 2 parts WW and water dropped them. They were fited with gas checks and lubed with LLA, but not sized.

My new Lyman mould drops them about .002 small in the nose and just at .3095 in the body. The blocks are also misaligned by about .0015 parallel to the faces, resulting in a casting that measures .3095 x .3115.

The initial results were still complicated by gradual buildup of fouling. I tried loads in .5 gr increments, from 28 to 30 gr. of 4895 and the groups using 29 gr appeared more consistant than the others but it was increasingly obvious that wiping with a dry patch was not removing enough of the fouling.
Fifty rounds were fired, wiping the bore with two dry patches after every five shots.
The groups were all +/- a bit, right around 2 moa. in the beginning, but opening gradually to about 3 moa. At the same time, the effort required to push the patch through the bore steadily increased.

I took Billwnr's advice when I went out the second time and brushed the bore after every ten shots, with a bronze brush, 4 or 5 passes seems to do the trick, then followed with two dry patches. Feeling the resistance of the brush and watching the amount of fouling on the second patch have shown that the fouling is maintained at about the same level as would be left by two or three shots through a clean barrel.

The load that I tried today was:
7.62x51, LC 72 Match brass, trimmed to 2.005"
The cases were neck sized using a Lee collet die, then expanded and lightly flared with a lyman "M" die.
Winchester LR primers, old lot, not the current blue box stuff.
Powder IMR4895, 29 gr +/- 0.2 gr measured, not weighed
3/4" cube of dacron batting, lightly compressed
Lyman 311299 RNGC hard (water dropped), with Lyman (old style) gas checks, used without sizing and lubed with LLA.
The bullet was seated with the case neck flush with the top of the upper lube groove. this puts the gas check base just barely below the neck.

average velocity for 40 shots, 1875 fps, SD 15

The rifle is a Remington 700, heavy barreled, with the kevlar stock and a Burris Signature 8-32x, set at 24x. The shots were fired using front and rear bags for support and allowing 1 minute per shot.

Temperatures were in the low 40s and there were light gusty winds from the rear.

Two five shot and two ten shot groups were fired at 50 yards and one ten shot group was fired at 100 yards.

All of the groups were between 1-1/2 and 2 moa.
Most (80%) of the shots were closer to 1-1/2 moa.
I did not ignore any shots that might have been attributed to shooter error or the light gusty winds in the above results or I might have shaved 1/4 to 1/2 moa off the results.

I continue to be encouraged by the results and believe that I will be able to shoot consistantly below 1 moa, with a little more refinement of my load and cleaning procedure.

It appears that cleaning "dry" greatly reduces the tendency of the first couple of shots to go noticeably out of the group. I am, however, concerned that the amount of brushing may eventuallycause excessive barrel wear.

I remain puzzled by the build up of fouling that has not happened with any of the other half dozen 30 cal rifles that I have fired with similar loads. What is it about this particular barrel that seems to attract and hold the fouling?

My feeling is that effectivley resolving the fouling/cleaning problem will be the key that unlocks sub-moa groups. Aside from this, I am thinking about trying the 314299, sized to .311. I am not eager to spend another $60, unless I have some indication that the extra couple of thou will make a difference.

Jack

http://images36.fotki.com/v1174/photos/5/590147/2786028/targetsm5may08-vi.jpg

(grid is 1")

[runfiverun]

you could try a different lube or thin out your lla with some mineral spirits.
and let it dry well you may just be applying it too heavily and it is catching on a rough spot
in the bbl

[mainiac]

I fired ten groups of five shots each from my .308 Win. heavy barreled Remington bolt gun today.
The gun was shooting 1 moa or slightly smaller at the beginning and a little more than 2 moa at the end of fifty shots.
The boolits were reasonably hard 31141s with White label 2500+ lube, over 18 gr of 2400, for an estimated velocity of 1750fps.
The gun was cleaned with Sweets before shooting and I probably got 98% of the metal fouling out of the bore.
There was no visible leading in the bore after fifty shots.
Groups were fired at 50, 100 and 200 yards during the session and the increase in group sizes was consistent at all ranges. The first three groups were at 50 yards, then one at 200 yards, four more at 100 yards, and the rest at 200 yards.
The gun was sandbagged, with a great trigger and a 24 power scope. Recoil was not a factor.
The temperature was about 40 degrees and the barrel never got more than barely warm to the touch.
Some of the groups were fired about two shots per minute and others at about one shot every two minutes. The timing did not seem to affect the group sizes.

The question is, what factor would be most likely to cause the gradual increase in group size?

Jack

Did you start early in the morning? Are you using wind flags? I think you might be jousting with the wind toward the end of your shooting. First thing in the morning, guns shoot scary accurate, until the sun comes up high,and starts the wind a-blowin again!

[Bass Ackward]

Remember, sizing a lube is impossible because of hydrolics.

So when a bullet has to size down in that throat, it is leaving a substancial amount of lube behind. When any petroleum product is combined with carbon (burnt powder) a tar is the new material. AS this builds up, your bullet must size even more to pass it. Eventually becoming undersized for the application.

If fouling can be shot out with one pass, you get what is called a lube flier. If not, wilder groups will be the result. Chances are you need far less lube than you have previously used or need to size smaller with this one. IMO. I'd bet on both.

[felix]

In general, you want to see a lube star in bright daylight after 7 rounds, and a gray wash at the muzzle should be obvious as well. The gray wash should be there to indicate that enough antimony is being used for the velocity, and the lube had been adjusted properly as to quantity and/or quality. The accuracy should not go downhill enough to warrant cleaning during a day's shoot, provided the gun does not sit for more than 20 minutes (or less) between relays. If shooting for money, then cleaning between relays is a must, and ammo adjusted accordingly. ... felix

[jhrosier]

.... Chances are you need far less lube than you have previously used or need to size smaller with this one. IMO. I'd bet on both.

That's an interesting idea.
I will load another batch to compare the results of LLA with White Label 2500+.

Thanks, Jack

[jhrosier]

... The accuracy should not go downhill enough to warrant cleaning during a day's shoot, ....

I agree, based on my experience with other rifles.
This one is being reluctant to cooperate.[smilie=b:

Jack

[felix]

Do you have a consistent gray wash? ... felix

[jhrosier]

felix,
There is a lube star on the muzzle. As it is the result of more than 40 rounds fired, I don't know how soon it appeared. There is some gray on the lands at the muzzle..

Jack

[Larry Gibson]

jhrosier

I concur with those who say to try another lube. At that velocity with 28-32 gr of 4895 you should not have the residue in the barrel or leading with the bullet and alloy you are using. I'd suggest Javelina or one of the comparable NRA 50/50 Alox/beeswax formulas.

You are getting where you want to be with that rifle, just need to clear up the lube situation.

Larry Gibson

[felix]

Yep, make lube adjustments and don't change anything else for now. Lube star is important as to when it occurs. Too soon equals too much of a good thing. Your gray wash appears to be a little too scarce after 40 rounds especially, which indicates a little too much lube viscosity. Cut back on the same lube, or add some carnauba wax to it. If it were a felix lube, you'd cut back on the lanolin and leave the carnauba the same. ... felix

[Tiger]

jhrosier

Just for heck of it try a tuff of dacron filler. Spread it out do not compact it top of powder. I know you don't need it but try some see what changes and tell here results.

Ralf

[jhrosier]

Thanks guys.
New lube will be the only load change for the next batch.

Jack

[jhrosier]

Thanks to those who suggested changing lubes.
I loaded and fired 100 rounds, lubed with White Label 2500+.
I stayed with 29 gr of 4895, under a hard cast 311299.

Bore fouling is not eliminated, but is greatly reduced and the fouling is more easily removed.

I stayed with brushing the bore dry and following with two dry patches after each ten rounds.

Firing ten round groups, many were the same size at 100 yards that I was getting at fifty yards last time. None were larger than the previous results.

I am seeing the groups grow and shrink and I think that this may be a sign that I am not always getting the bore as clean as I think. I am going to try to work up a more reliably consistent cleaning regimen.

In any case, I am comfortably close to 1-1/2 moa, and greatly encouraged to continue.

I was tickled pink to see that my 100 yard cast boolit groups were just as small as the local swat team guys were getting with their forty-some-odd dollars a box premium grade ammo. We are shooting virtually identical heavy-barrel Remington 700s.

I also fired fifty rounds with home-made aluminum gas checks, otherwise loaded the same. If I didn't mark the targets, I couldn't tell any difference between the groups shot with Lyman checks and the aluminum ones. As time permits I want to try them at 200 yards to see if there is any noticeable difference.

Jack

[Larry Gibson]

Jack

That's great, glad I was one of those who helped. Rifles seldom shoot the same size groups all the time. Some will be smaller and some larger. It's the "average" group size that you should consider. Also as the song goes; "some days are diamonds, some days are stones". Sometimes it's just us and not the rifle or ammo. Keep us posted on your progress.

Larry Gibson