6 Dasher - throat movement

[memilanuk]

Been tinkering with my 6 Dasher, and it looks like the throat has moved about ~0.010' or so thus far. I say 'looks like' because a) my digital calipers broke and I'm measuring with a set of 'economy' steel dial calipers and b) to say my earlier record keeping on this gun was lax would be overly generous :,

Going off of memory, I was seated +0.010' into the lands before, and I had a few rounds left over at that seating die setting - they measured 2.752' base-to-ogive,BTO). Just got done taking three readings each on three bullets and the average is 2.751'.

Does ~0.010' worth of throat movement over ~1000rds,340 fire-forming loads of 31+gr of IMR4895, and the remainder almost entirely B105VLD / 33.2gr RE15 / CCI450)? This is my first Dasher barrel so I'm not 100% sure what to expect for barrel life & throat movement.

TIA,

Monte

 

[birdog]

If you do not abuse the barrel by getting it too hot match accuracy will last 1500 to 2000 rounds. My first dasher barrel was rechambered at 2500 rounds. It still shot good scores at 600 yd. but the groups slipped to the 3's and 4's.
At 2500 rounds she was still Prarie Dog worthy.

 

[Fred Bohl]

Monte,

I do not mean to imply any nefarious intent or even intentional error on your part. However, if you have actually had only 0.010' of throat lengthening in 1000 rounds then first call your barrel maker and if he has any of that lot of steel blanks left buy all you can afford. You will be able to finance your retirement selling barrels to the 'upper load window shooters'.

Seriously, from a group of 5 barrels (6PPC) carefully tracked for throat wear, the range was 0.030 to 0.070 over 1000 rounds. These were all shot with jammed bullets in the upper load window.

My own 3 barrels in 6BR are running 0.0015 to 0.0030 per 100 rounds,currently under 1000 rounds each). These are typically loaded in the middle load window except for a few upper window loads for load and/or bullet trials.

 

[JERRYHM]

Monte,

My wife's first dasher barrel was change at 3600-3800 rounds it was still shooting in the high 2s. New the loads were jumped 0.045' and at the end we were jumping over 0.125'. Most of the shooting was at 1000 yards with Sierra 107 and 115.
Jerry

 

[memilanuk]

Thanks for the responses, guys. I'd been doing pretty fair with this barrel in F-Class matches @ 500-600yds this spring/summer, but at the last one,mid June) it seemed like I was having to work a lot harder to put the shots in the middle than I remembered. Didn't have a lot of time to muck about with it at the time, but around the beginning of September I started shooting it again. The groups just seemed to get bigger and bigger - ending up around 3/4-1 moa @ 300yds,I shot a 2.5' 5-shot group from my Dasher followed by a 1.087' 8-shot group from my F/TR rifle with 'left-over' ammo from Bisley... so the problem wasn't entirely the shooter).

I set the gun aside for a few days to mull it over, and then started measuring things,and this time writing them down and sticking them in a binder, instead of my little notepad that lost its way...) After finding that I was basically not in the lands like before, I seated the bullets back out to +0.010', and on a lark, some more @ +0.020' in. The groups tightened up as expected - with the added bonus of some nice chrono strings,several 10-shot strings with SD/ES of 3/12, avg. 3095). Took it to 600yds today,bribed the daughter to pull target for me) and it held good elevation there. Got some matches this weekend to really give it a good 'acid test' - but for now it looks like I'm cooking with gasoline again :thumb:

Fred,

Dunno what to tell ya. It's a 30' Rock 5R 1-7.8' tw SS1000yd contour - my second Rock barrel, but probably not the last. I will have to keep a closer eye on the throat for sure.

Jerry,

I'm hoping that if the throat moves out a bit I might be able to jump these bullets instead of jamming - but the throat started out a tad short.

Thanks,

Monte

 

[Rustystud]

Monte:

There is a magic number somewhere between 3000 fps and 3100 fps that you will find the optimum accuracy with a,107- 108 grain bullet), barrel life and brass life.

If you are lucky/smart you will find this node and you can chase the rifling and get approximately 3000 to 3600 rounds out of a 6mm Dasher. Some folks setback about 2200 rounds, others chase the rifling,adjusting length as they go. You will notice flyers before the barrel completely goes south. A visual inspection will reveal a 8-10,almost smooth bore) infront of the throat when the barrel finaly goes. The rifling is missing or flattened out.

Several of my customers shoot 10 shot reference groups thoughout the life of the barrel. Your rifle should shoot 10 shots at 100 yards into a group between .350' and .450' your extreme spread should be 9fps or less. If your rifle will do this it most likely will be more than competetive at longer distances. Most shooters can't shoot 600 and 1000 yards on a daily basis.

Good Luck
Nat

 

[falconpilot]

My Dasher barrel went to right at 2100 rounds before I notice an unexplained flyer every now and then starting to appear...bear in mind that this rifle is shot strictly F-Class, and if I've got a good puller, I'll shot my 20 rounds string in under 10 minutes..so the barrel does get abused a little due to heating....I had between .15 to .20 thousand 'growth' in the lands...