How bad is rifling skid really?

[303Guy]

64015

Here one can see the extent of the rifling skid by comparing the width of the groove and land impressions. They should be the same. A bit of detail; that's a 192gr casting fired through my 303 Brit with 35gr W780 which was a 76% load density with wheat germ filler. The boolit was 'lubed' with Autosol Metal Polish (to clean and polish the bore). There is a little base cupping which won't help with accuracy. So the question is - how bad is it for accuracy to have some rifling wear/skid? With lube the conditions would be better but the cupping and a little wear or skid could be expected (I'll fire one to see what happens).

[303Guy]

64016
64017

Well, here's the lubed boolit - pretty much the same as the polishing compound boolit. (The bore looks just as clean).

[44man]

Easy, I see no base skidding and no gas cutting. Cupping is normal as lead is forced back from a good fit.
How much different are the rifling marks from the groove and land marks?
Many of my revolver boolits skid at almost the length of the boolit but stops at the base band because the boolit has taken the twist. Since your boolits are mashed so front skid is not seen, how do you know?
It is at the base that counts so you get a seal.

[cbrick]

Jim is right, I don't see any base band skidding and there is no way from these photo's to know what happened at the ogive where the boolit took the rifling.

You mentioned the bore was clean so there was a gas seal, if "skidding" was an issue with this load you would have leading even if it was caused by tearing lead from the nose when taking the rifling. You didn't mention how the accuracy was.

Rick

[runfiverun]

i don't think he shot these at distance,just in his test tube looking for skidding.

peter,are these with the copper alloy?

[Larry Gibson]

Rifle "skidding" is something that gets a lot of attention from some. However, I pay little attention to it as there's not much you can do about it if it really exists to any great degree. It is simply dealt with as we develop loads with good bullet fit, a GC, a good lube, using softer accelleration with slower powders or harder alloys. Many times we are percieving a problem not really there and looking for an answer that has no question........

Larry Gibson

[montana_charlie]

Does a driven slug come out of that barrel with lands and grooves of equal width?
In some rifling they are equal, but nothing says they have to be.

CM

[Bullshop]

So if it was a problem a gain twist barrel would have serious issues. A gain twist barrel would in effect be skidding the entire length of the barrel.
A key ingrediant to the equasion would have to be sustained pressure. If the sustained pressure is above that required for obturation then it would seem that the area of the boolit where the engraving took place when the boolit started down the barrel as the boolits travel progresses down the barrel the location of engraving on the boolit is constantly changing but the sustained pressure is keeping the obturation adiquate to keep the seal. Wow that was hard to say! Anyway that might be true up to a certain pressure that exceeds the shear limits of the alloy. All I just said might well be BS too but at least in my head it seems possible.

[303Guy]

Thanks for the replies. This is the copper alloy, yes and it was fired into my test tube. I can actually see the nose engraving through the mash but couldn't capture it in the photo. There is no difference between nose and base i.e. no skid as such. I wouldn't have expected any gas leaking as the filler should form a seal. I shall load up and fire a few more and see if I get any leading and if not I'll load some up for range testing. The bore on this rifle is 'dark' but the rifling is well defined and looks shiny when looking down the bore. It's not dark enough for fire-lapping which is why I tried a fire-polishing load. I like the way the rifling engages the boolit over most of its length. To me that means more velocity.

I've wondered about gain twist barrels. I don't think the alloy is being driven past its shear strength. It's wear on the edges of the rifling impression that I'm wondering about.

I haven't tried a slug through the barrel. Perhaps I should.

[detox]

i feel that fire lapping or too much lapping will round off edges of rifling causing more slipage. i have also read that faster twist rate barrels cause more slipage. 1/12" twist rate should be minimum in .308.... 1/15" much better

[.22-10-45]

Hello, 303 Guy..What montana charlie said..not all lands/grooves are equal. The early Colt revolvers have narrow lands. What I do is try to recover a fired slug with a minimum of deformation and compare groove width at base going forward towards nose..any widening of groove indicates skidding.

[Nazgul]

I shot some .458" Barnes solids into newsprint at slow velocity to catch them. There was very obvious "skid" on the leading edge of the rifling. This is with solid brass slugs from a 458 Win Mag. Will try to get pics up.

Don

[detox]

Some criminal investigations fire bullet in large water tank to prevent deformation then match up rifling to gun.

[Oreo]

I hear those rubber mulch trapps are especially good at catching a boolit without deforming it.

[Von Gruff]

I have just put together a bullet trap with 2 pieces of 10x1 and 2 pieces of 8x1 at 6ft long and intend to fill it with pine needles. Will shoot into it from 100 yds and see if I can get an undamaged bullet back for analysis.

[Bullshop]

Snow works good if you happen to have some handy.

[Von Gruff]

Snow works good if you happen to have some handy.
Late summer here so that is out.

[MBTcustom]

Late summer here so that is out.

Maybe Bullshop can send you some LOL!

Incedentally, that is not boolit skid in the OP.
This is boolit skid in all its radiant glory. I drew many a false conclusion from this photo, but its still the most educational picture I ever took:
64087

[longbow]

Well, I am with 303guy.

I found that my PB boolits from home made moulds and boolits from a Lyman 314299 showed wider grooves than lands in the boolits and yes, they are equal width in the bore. I had not had this problem with my .308 and 31141's (lighter boolit though at 170 grs.). I also saw gas cutting in the wider grooves.

Since the boolits were ACWW, I decided to oven heat treat and that made the difference in both the boolits from home made moulds and the 314299.

I figured the main culprit was the 1:10" twist in the Lee Enfield .303 vs a 1:12" twist in my .308. Also, the heavier 200 to 220 gr. boolits might resist the rotational acceleration more than the lighter 170 gr.

In any case, these were not particularly hot loads but as long as I heat treated the boolits, I had no more problem.

Yes Bullshop, I have used snow as a boolit retrieval medium too. It works pretty well if you have lots of it but generally recovering boolits takes a thaw! Sometimes I find some laying on top after they have gone through a lot of snow then maybe bopped off the ground and run out of steam as they popped out on top.

Recovered boolits almost always have a story to tell.

Longbow

[montana_charlie]

Snow works good if you happen to have some handy.
Whatever happened with the cooked rice in the long wooden box. I think it was Buckshot who was working on that one.

CM

[longbow]

I think that was BruceB with the wet rice in the box. Last I recall it was a messy test! I've had a few like that I would rather not talk about too.

I did make up an expansion tester that worked pretty well as a prototype but I haven't tested the final version yet. It is based on eh Glenn Fryxell style end on 2 liter bottle then a bunch of hanging zip lock bags of water and finally a rag bag to catch the expanded boolit.

The prototype used a different and very messy expansion medium (big mistake that!) then the rag bag and that worked not bad.

The idea is that the 2 liter bottle of water provides the "critter" medium per Glenn Fryxell, then the water bags provide some more deceleration and the rag bag makes for a soft landing.

Pretty simple open framework to support PVC pie, wooden end plates and hanging bags. It should work fine with expanding boolits but may not stop a hard cast rifle boolit. We will see!

Longbow

[Bullshop]

I think it was Bruce B and I think he had problems overcomming the hydrolic effect that kept blowing the box apart.

[Von Gruff]

I want to do as undamaged a capture as possible. Have just been and got some pine needles and sifted through them to remove all little sticks etc and will remove the top and tip sideways onto tarpaulin to recover bullet from medium. Have another method for expansion testing where the water containers are held between two boards to stop the hydrolic lift with the intent to keep the bullet tracking straight for recovery.Have 6ft of water container containment so that should be enough for my little 123gn 6.5 bullet at aprox 2300fps. Will not be doing that test till accuracy and velocity testing is complete though.

[303Guy]

I've often wondered about that forensic recovery of bullets fired into water. Myth Busters did some tests firing into water. They borrowed a swimming pool for the tests and were able to recover bullets in small fragments close to the impact point (FMJ's too). Good luck to the forensic boys in trying to match those to a gun!

I had a closer look at those too boolits and there is definitely some skid there (or is it wear). But does it matter? There is no gas erosion, thanks to the fibrous filler wad (I think). What is concerning me is the appearance of the trailing edge of the boolit. It's not symmetrical - that can't be good for accuracy.

Weight retention for both boolits is 95%. That's into rubber grinds.

[detox]

By looking at the excessive mushrooming it looks like your bullets are too soft. I have fired and recovered two lead types of cast bullets shot from my ballard rifled Marlin Guide gun chambered in 45/70. One bullet was cast using standard water quenched wheelweights the other using softer 20/1 lead tin. The harder WW bullet stayed intacked except for nose breaking off and you could see all 1" length of rifling. The softer 20/1 bullet mushroomed like yours in picture and very litle rifling could be seen. Bullets were recovered from soft dirt bank (RCBS .458 Gas Cheacked 405 grain).

[runfiverun]

you have to remember that the boolits get distorted in both directions at impact.
they will get shorter and fatter.
your base distortion [trailing edge failure] is mainly due to the fact that the displaced lead from the smooth sided boolits has no where to go until it gets all the way back there.

[303Guy]

I'm thinking of a cupped base boolit to give the displace metal somewhere to go without dragging it into a feathered edge. An idea stemming from the thread on PP hunting boolit design.

The mushrooming in my case is being caused by fairly high velocity. I fired a lower velocity boolit last night to check the groove impression and it did not expand at all. Instead it transversed the the catch tube into the course rubber grind pot which damaged its sides. The groove-land width is the same as the slower one making me think it's the rifling causing it and not skid. Looking down the muzzle it appears the rifling is not good quality, let alone being 'dark'. I'll go even slower next.

[303Guy]

I tried a 9gr Trail Boss load with the 192gr boolit and that was a failure! There is flame erosion so I cannot 'read' the rifling impressions plus the boolit ran down the side of the test tube and over-travelled again. There was no gas erosion from W748 with Dacron which is interesting. 23gr of W748 is a light load yet burned clean enough ( I should range test that one. I would want to double charge that powder though so I'll use a load that is more than 50% case capacity. 26gr will over overflow with a double charge).

[Von Gruff]

I can tell you that 2meters of pine needles is not enough to catch even a light 123gn bullet at 1750 shot from about 50yds.
http://i667.photobucket.com/albums/vv39/VonGruff/Cast%20bullets/005-1_zps24579660.jpg
http://i667.photobucket.com/albums/vv39/VonGruff/Cast%20bullets/006_zpscf21c6d3.jpg
http://i667.photobucket.com/albums/vv39/VonGruff/Cast%20bullets/007_zps61a30a6f.jpg
http://i667.photobucket.com/albums/vv39/VonGruff/Cast%20bullets/009_zps153e99c7.jpg

[longbow]

Yup! You need mass to slow a boolit and wet anything does a pretty good job but dry most things do not unless they are hard. Ground rubber may be an exception there but then again it has lots of mass.

Glenn Fryxell does expansion testing through an end on filled 2 liter bottle and claims it is fairly representative of "critter" (IIRC) and of course is very repeatable for comparison purposes but he catches the boolits in newspaper after so they still get damaged. My tester will hopefully slow the boolit more then catch in it rags with little damage.

Whatever you use, it has to have considerable mass to slow a boolit. Take a hint though that loaves of bread dough are not good candidates!

Longbow

[303Guy]

Oiled sawdust is said to catch boolits undamaged. It takes a long passage though. Dry bundled rags works fairly well, probably because the layers tug at the boolit, spreading the load over a wider area. Wet bundles rags are more effective but do more damage to the boolit.

[runfiverun]

airc that's what Dr.Mann used.
for all his tests,i think he put cardboard sections in every 2 feet.

[303Guy]

I discovered I found the wrong boolit after the test this morning. I found the real one and the rifling impression is perfect with both groove and land impressions being equal. One of the lands has a small groove in the middle of it and that shows up on the boolit too. It wont be a problem I'm sure. I used Autosol Metal Polish as the lubricant. I tried a fire-lap but I don't actually see any difference. Perhaps a few more will be all it needs. The bore is not too bad really, the rifling is sharp and well defined so there is hope for a good cast boolit shooter with this rifle.

On boolit hardness (or lack thereof) the fact that a fair power load expended so well while a lighter load (likely still supersonic) did not expand, would it be the opinion of this board that my boolits are about right for hunting? I would do most shooting with this gun at targets though.

[Von Gruff]

I decided to redo the test box with the more dense understory from beneath the pine needles and also put in cardboard every 8 inches or so so finding the bullet will be easier.
http://i667.photobucket.com/albums/vv39/VonGruff/Cast%20bullets/010_zps840cf1f3.jpg

[44man]

It is amazing how hard it is to catch a boolit. You would think a revolver would be easy but we had a pass through with 17 gallon jugs of water. Expanding bullets can stop fast.

[runfiverun]

you know paper polishes a barell really well especially ones that are bright white.

an alloy that holds together like that at that velocity should do pretty well in hunting situations.
I don't think you'll have quite the same expansion on game though.