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Old 05-05-2007, 06:21 PM
scootertrash scootertrash is offline
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Default Sticky reinforcement

I have read two different posts about the "magical" 3800 fps out of 20 VT's in the past two days, and even talk of room to spare.

I'd like to remind the newer members to read the sticky about rifle to rifle differences. Try as I might, I cannot safely reach that speed with my Cooper. Early on I tried H4198 and made it to around 18.5 gr before I got heavy bolt lift. 18.6 blew the primer out of the case.

I've since switched to N120 and have decreased that load twice because I was still getting bolt "click". I'm now using 17.2 gr and the speed is right at 3700. My H2O capacity is 22.6 grains, and using 18.7 grains of H4198 as an example, QL shows a pressure of 50K, and the parent Fireball cartridge is listed at 46K+. The velocity even at the 50K is still only calculated at 3716.

This isn't even considering the burn rate of the powders. The N120 I'm using now has a burn rate 9% faster than the original lot I had.

The spring and summer shooting seasons are upon us, and that means higher temps as well. Use a chrono, and watch for those pressure signs. They appear quickly in these small calibers.

Mike
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Old 05-06-2007, 01:01 AM
Larry in VA Larry in VA is offline
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A good and timely reminder there Scootertrash. Thanks a bunch.
Larry
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Old 05-06-2007, 02:08 AM
sicero sicero is offline
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Default Scootertrash

Mike, Something I would try would be make a few pieces of brass with a good crush fit and try working your loads up again. There shouldn't be enough room for a primer to come out. I am no expert but just a thought. Kenny
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  #4  
Old 05-06-2007, 02:15 AM
Alex Alex is offline
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Default Mike, were you shooting ...

... neck sized brass? If you were shooting FL sized brass, then some of the problem may have been too much head space. Kenny may have the exact diagnosis for it. I've done the same thing, had all sorts of blown primers in loads that weren't in what were supposed to be "hot" loads and found that I had enough head space to put a hat in.

I worry about the seriously fast stuff with the 20VT, too. It was some really hot loads that caused the "sticky" posts to be here in the first place.

Alex
  #5  
Old 05-06-2007, 03:06 AM
scootertrash scootertrash is offline
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Thanks guys. Those loads were indeed neck sized, however the brass was not formed with a crush fit.

Shortly thereafter, I switched to the N120, mainly because I don't like the compressed loads, especially with a stick powder and the small cases.

This was about six months or so ago, and at which time I did not yet have QL.
I liked the performance of the N120 and it shot great using 17.6 grains, but I could tell I was on the ragged edge pressure wise. Since I primarily use this rifle for pdogs, and knowing the temperatures in the summer months, I backed the load down a bit.

After obtaining QL and running numbers, things became much clearer and confirmed what I already suspected. Both the 4198 and the N120 lots I purchased, have very fast burn rates. Regardless, I still could not safely reach that speed.

After decreasing the N120 load, I still experienced not what I'd call hard bolt lift, but difficulty at the top of the bolt lift and the ominous clicking. I had read, perhaps here, that once brass starts the bolt clicking, it will always remain. So, I got new brass and experimented some more. 17.2 grains shoots rather nicely, the bolt opens smoothly, and no clicking. The velocity is just at 3700 in 55° temps, and chrono testing over on the eastern plains a couple weeks ago showed 3732 in 85° temps with no issues.

And I'd like to make it clear, I'm not knocking anyone who choses to run warm, and that has a rifle capable of it. I also shoot some tight necked custom 6 PPC's that are run "over the top". Look in the back of Precision Shooter magazine and some of those loads I don't know how they get the bullet seated.

The point is, some rifles will do it, some won't. Most folks on this forum have a tremendous understanding of small calibers and their little quirks. I've been handloading and shooting right at forty years, am I disappointed I can't get 3800 from my little Cooper? Not at all, it's still a great little cartridge, and ballistically there isn't much difference between 3700 and 3800.

Since a lot of the calibers we deal with here, are a wildcat or some variant, more often than not, you won't find anything in a written manual. I just don't want folks new to the small calibers, and sometimes new to handloading as well, to pick a speed as a specific goal for a given caliber.

I'd also like to take this time to thank the folks here, the knowledge that you share is priceless, and you folks build some mighty awesome rifles.

Mike
  #6  
Old 05-06-2007, 04:57 AM
montdoug montdoug is offline
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Excellent topic.
As we've talked of repeatedly but it can never be too much, not only are rifles all different but lot to lot differences even with the same brand of powder can be "significant".
As I mentioned in the 3,800fps topic which had to do not with a specifically attainable velocity in the VarTarg or any other rifle but how 4 of the small caliber rifles I'm using for gophers and p-dogs this summer are just below or just over that number. That wasn't by design, it's just where they all ended up.
I agree with ST that chasing a specific load in a rifle is big time bad news! In fact I stressed that in the sticky about rifle to rifle differences as I'm the one that started the thread. It wouldn't hurt any of us to read that whole thread from time to time cause a lot of guys posted good stuff in there.
As to my rifle with the batch of powder I'm using I'm well back from a max load but that means nothing with someone else's rifle and powder lots. I'm thinking that there is probably a fair difference between ST's Cooper Chamber and my Greg Tannel chamber as in my fired/neck sized cases 18.7 grains of my batch of H4198 is not a compressed load with where my bullets are seated and in fact comes just below the shoulder neck juncture and my SPL'd V-Max's sit a bit above that and in fact as mentioned have a bit of room left but I stopped at the accuracy point not the velocity limit. Just about perfect load density to me. Not a warm load in my rifle. In Terrific .20's there is what was obviously a safe load for Todd using a "36 grain" Berger and 20.2 grains of H4198 for 3,811fps. My working load is slower than that and use's a 3 grain lighter bullet as well as 1.5 grains less powder in it. They are all different.

I haven't tried N120 cause I have 8lbs of H4198 it's an Extreme powder and it's a bit slower burning than the N120 (cheaper too ).
This batch of cases was weight segregated in 50 round MTM box's and not only have some of them been fired 5 times in temps up to 105ish and still have tight pockets plus as little as I size them I've yet to have to trim them either. Also a 24inch barrel is probably longer than a Cooper barrel.
Larry I wondered what other indications of pressure your using beside bolt lift? My experience is that with the steep angle of the cocking ramp in a Cooper bolt lift is extremely difficult to use as an indicator. Like Kenny if your getting primers blown back in a case it pretty much has to be a headspace issue. I'd try the die set up for a solid crush fit, sure makes good cases.
Regardless of all that one of my personal crusade's is a guy hearing about a specific velocity someone gets in a particular rifle and chasing it with his rifle, it's a recipe for disaster!
An interesting aside.
Dan C. and I have .20 Killer Bee's cut with the same reamer and I believe both are Pac-Nor's as well. He tested his batch of AA1680 in his and was able to use considerably more than I was able to with my batch, he got up to 18.2 grains for 3864 and did that load 10 times in the same cases with primer pockets staying tight. The load I ended up going with was just under 3,800fps with 17.1 grains of 1680. In Dan's it took as I remember more of his lot of 1680 to get to that velocity than mine did, I obviously have a faster lot of 1680 than his.
There are very few constants in reloading.
Good reminder ST we can never be safe enough.
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Last edited by montdoug; 05-06-2007 at 05:37 AM.
  #7  
Old 05-08-2007, 07:07 AM
DittoHead DittoHead is offline
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Quote:
Originally Posted by scootertrash View Post
After decreasing the N120 load, I still experienced not what I'd call hard bolt lift, but difficulty at the top of the bolt lift and the ominous clicking. I had read, perhaps here, that once brass starts the bolt clicking, it will always remain. So, I got new brass and experimented some more. 17.2 grains shoots rather nicely, the bolt opens smoothly, and no clicking. The velocity is just at 3700 in 55° temps, and chrono testing over on the eastern plains a couple weeks ago showed 3732 in 85° temps with no issues.
What is this “clicking” problem?

I think I have seen someone mention it before but I have never read an explanation of the cause. I assume the culprit is pressure, but exactly what part of the bolt or brass is making the clicking sound and why?
  #8  
Old 05-08-2007, 02:18 PM
Dan C Dan C is offline
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Quote:
Originally Posted by DittoHead View Post
What is this “clicking” problem?

I think I have seen someone mention it before but I have never read an explanation of the cause. I assume the culprit is pressure, but exactly what part of the bolt or brass is making the clicking sound and why?
The 'clicking' at the top of the bolt lift, which means when the primary extraction occurs, is usually caused by the cases getting tight at the base and resisting the start of extraction. It can occur with normal, acceptable loads in a chamber that is a little snug at the base for the brass.

Normally when loads are just 'too hot' for the rifle, the bolt lift will be stiff right from the start of the lift. Like montdoug mentioned, on Coopers with their steep cocking ramp this can be hard to feel at times if it's minor.

Personally I've never had a rifle resist primary extraction (causing the 'click') unless the chamber was too tight for the brass. If the body or FL die will reduce the base enough, the click can be made to disappear for a couple of shots with FL sizing but will come back eventually.

I can't imagine a factory Cooper chamber being tight enough at the base to cause this, but my Cooper with it's tight custom chamber is a little snug for my taste and will show the same symptoms as Scootertrash's rifle. Compounding the problem is the poorly designed primary extraction ramp of the Cooper action, it just doesn't do it's job very well.

Scootertrash, I've had QuickLoad for several years now and I just haven't had very good results with the small weird stuff we shoot. Anything very far from the 'standard' (like a 30-06) causes problems with QL. For predicting results it's been practically useless for me. When I plug in tested loads, the velocities are usually not very close unless I adjust the powder burn rate by 10% or more! What good is that? It is a fun tool to play with but hasn't been very useful to me. Perhaps you are just better at running the program and I'm missing some critical piece of information?

Good thread....
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  #9  
Old 05-08-2007, 02:53 PM
scootertrash scootertrash is offline
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Dan,

I typically start with the burn rate adjustment, usually +/- 5% gets me close to matching actual velocity.

I shoot both a known low safe load, and a load a with a heavier charge. After adjusting the burn rate as closely as I can, I then adjust the "weighing factor" in QL until the velocities at both the low and high charge will match very closely to the actual at both ends. For the .20 VT, I have found a weighing factor of .36 works well.

Also I have found if you are loading into the lands, QL's recommended shot start pressure is high. I don't load my .20's into the lands, as I shoot a couple thousand rounds thru each in the summer, and it makes it easier to chase the lands when shooting pdog quantities of ammo. With my 6 PPC's though, somewhere between 5000-6000 on the shot start works well for me and several others on the 6BR forums.

The best way I have found to determine this, is first adjust your burn rate and weighing factor without touching the lands. Now that your parameters are known, chrono the load touching the lands, and then adjust the shot start pressure up until the programs velocity matches your chrono speed.

And thanks for your explanation on the "clicking" question the other poster inquired about. And I agree about the Cooper's extraction system.

Mike
  #10  
Old 05-09-2007, 06:51 AM
DittoHead DittoHead is offline
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Great explanation Dan. Thanks.
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