Tumbling/ Keyholing.

[Mudgegonga]

One reason I think a lot of .17 barrels end up stuffed is because people either dont neutralise the aggressive chemicals they use and or they get them really clean and they corrode especially if they are not used for a long time. The .20 barrels are easier to live with.

[trevort]

One reason I think a lot of .17 barrels end up stuffed is because people either dont neutralise the aggressive chemicals they use and or they get them really clean and they corrode especially if they are not used for a long time. The .20 barrels are easier to live with.

Barry first ever benchrest match I went to I met the current Shooter of the Year and asked how he cleaned. I copied it all. One crucial thing in my kit are two jars of metho. One is clean and a patch soaked in clean metho always follows after I have finished with the sweets to neutralise any residue. The other is to drop the brushes in for a good shake to clean the sweets off the brushes.

Just agreeing with Mudge


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[barryb]

Mudge/Trevort - agree. If I'm using a brush I usually give it a good dip in Shellite to clean up & neutralise. As for the carbon build up I followed a process suggested by Tony Boyer ( Rifle accuracy book) using brushes & working the area through to the neck which has taken a fair bit out -BUT , still getting a percentage of tumbling & smoking primers. At the stage now of leaving it alone till my smithy has a good look at it & whether its worth considering for another barrel. My attention has now been drawn to a Mach1V which unbelievably is having similar problems with pierced primers & tumbling with 20 grain K Kuehn projectiles & BM2 powder. Seems the last of the year 2017 doesn't want to be kind to Barry's rifle purchasing experiences
In closing thanks again for everyones contribution - & all the very best for 2018.

[justjeff]

Guys,
Evinrude engine clean for the carbon, with a bronze brush. sweets with a nylon brush, then with an alloy jag. If this doesn't clean it, 40 or 50 strokes with Bore Bright. TZ has a Swann .17 barrel he seems pretty happy with, and he is very complementary about the service as well.
My two bob's worth is that 17s seem to be very twist sensitive, and also hold to th mantra that cleanliness is next to god, and accuracy.

Jeff

[barryb]

It peeves me to have to reincarnate this topic but it seems this is the year for tumbling for Barry.
We now have a virtually new (maybe 75 round count) through it in a TSE 9 twist tumbling 3 out of 5 shots yesterday at around 90 yards. Previously this little Tikka was shooting 1/2 to 3/4 MOA consistently. Temperature yesterday was around 36/38 , load was 23.2 of 8208 behind Kuehn 24 grain projectiles . Rifle has been properly cleaned after the few outings with Butches BS . I must admit I haven't had the chance to check for carbon build up but wouldn't have though it would have impacted after only about 75 shots.
Photo attached - sorry , have run out of SSAA targets atm

Again , any help , comments , appreciated.
And no !! this fella can't go with the Council cleanup

[trevort]

How long are those pills compared to a 25 gn vmax? Can you measure the twist to make sure the barrel is actually 1 in 9?


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[Tony Z]

It is highly unlikely carbon fouling is the issue if you are using 8208 Barry. This and CFE are the cleanest powders on the shelf at the minute.
Five main causes of destabilation outside of a bullet dynamic balance issue more associated with VLDs.
Incorrect twist rate.
Bullet jacket stripping from acceleration or bullet inertia beyond the ability of the rifling engaging and rotating.
Copper fouling tearing the jacket.
Now this one is hard to measure but twist rate irregularity. By that it means part of the rifling is not constant twist, usually caused by button slippage, whereby the lands have a scissor effect on the jacket compromising its integrity. The longer the bullet shank the more this scissoring effect is accentuated. 6.5s with the old match 155s were terrible for this reason in some button barrels but not so in cut barrels. Unknowingly why so many swear by cut barrels.
Lastly and most common is the crown. A belled crown or unbroken crown edge allows gas to slip past the bullet thus tipping it on exit. My money is on twist rate or crown. New barrel more likely to be twist. Old barrel is the crown 100%.

The attached photo is of a section i cut off from a US made barrel in 17/222 a mate had. You may not see it but the broken edge or 45 degree chamfer is not concentric and the bore is belled for the last quarter inch that was detected after slugging the barrel. Prior to this correction it sent 25 Vmaxes into oblivion and 20 grainers into groups measured in cubits. Now it shoots in the sub half inch area easily and point on no elongated holes.

[barryb]

Trevort -sorry haven't had a chance to follow up on your suggestion as I don't have any 25 gn Vmax on hand . The "Kuehn" projectiles measure 565/566 in length & ogive is 1270 spot on. To measure the twist rate has me buggered as I think it's way outside my salary level & competence but if there is an easy & very simple method some one can point me to I'll certainly give it a go. If we can get a cooler day below bloody 41 I'll pull some of Karls projectiles & try something else.
Tony - I had my local GS have a look at the crown yesterday but he couldn't seem to find anything amiss with it.
I'm going to experiment with some different projectiles when weather & time permits & if I can get someone with much more knowledge than me to have a good look at the twist issue.

PS Thanks for both responses.

Barry

[trevort]

Barry go back to your original 20 gn vm and try them. If they don't work then call the council.

To measure your twist, mark the cleaning rod with something easy to spot and push it in with a tight fitting patch then count the rotations. You know your barrel length so the rest is mathmatics

[barryb]

Barry go back to your original 20 gn vm and try them. If they don't work then call the council.

To measure your twist, mark the cleaning rod with something easy to spot and push it in with a tight fitting patch then count the rotations. You know your barrel length so the rest is mathmatics

Thanks Trevor - I will give the 20 grainers a go & see what happens. & thanks for the tip on the twist measurement.
If I have no luck I guess the timing for the Council is right

[Camel]

Just a heads up for you 17 users, Cleavers have 17cal 20gn Zmax at well under a hundred plus post for 500 projectiles.

[Old Trev-39]

Hi Barryb,
This is how I measure twist rate.
((1) Wipe a rod dry.
(2) With a felt pen draw a line the length of the rod.
(3) Fit a firm fitting patch onto the jag.
(4) Insert into bore a couple of inches and rotate till you can see the line.
(5) Draw a line across this line at rear of action, push rod through till original long line is back to starting position and cross mark again at rear of action.
(6) This gives you one rotation. Withdraw rod and measure between both cross marks, this will give you the distance in 1 revolution which will be your twist rate.
Cheers,
Trevor.

[barryb]

Thanks Trevor.

[stinkitup]

Before chasing crown etc I recomend checking twist. I first got my 222rimmed and tried 50gr vmax's thought they would be perfect!! They went through target side on!!

To test I cut the plastic tip off and almost went through straight lol. Tipped 40's are okay and shoot well, hp and sp 50's okay but just that extra length is no good. I checked it and it was a 1:16. Good luck.

[Shep25]

Had the same problem not long ago and feared that the barrel had seen its day.
Sat down and gave it a thorough clean and is now back to its best with hornady 25gr hp and 21gr of ADI 2206H.

Cleaning process took a while with repeated wet brass brush wet patch and dry patch.
Actually repeated this process about 5 times before I was satisfied.
Wire brush both ways 4 or 5 times before wet patch each time.
Did the trick for me and I am a happy chappy again.