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Need Help - Sticky Bolt

 
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  #1  
Old 05-31-2003, 03:59 PM
dwm dwm is offline
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Need Help - Sticky Bolt

Have a new 7mm RUM barrel with tight neck and minimum headspace chamber.

First time to the range to break the barrel in everything went well. Cartridges chambered easy, bolt was easy to lift.

Sized the cases with the Redding Body die with the die set all the way down to contact the shell holder. Checked length of the cases, all ok. Neck sized the cases with a Redding Type S Bushing die.

Loaded them with a couple of grains less than max loads, bullets just into the lands. Weighed all charges. Loaded 162 AMAX and 168 Berger VLDs.

All cartridges chambered easy, bolt closed with no resistance on all cartridges.

Things became strange when I fired them.

Some worked as expected, no problems, bolt opened just fine. Some the bolt would lift ok, but would stop just before the top where the bolt cams open. Some were hard to lift and hard to cam open.

All primers looked fine, nothing got flattened. Cases looked ok, nothing out of the norm. The cases have been fired several times.

This is the first time I have ever had a bolt stop at the top and had to be pushed hard/tapped the last bit of rotation.

Any ideas as to whats up?

Doug
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Old 05-31-2003, 05:35 PM
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Re: Need Help - Sticky Bolt

Look at you lugs. are they dented?
I would like to know what is going on also.
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  #3  
Old 06-01-2003, 12:07 AM
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Re: Need Help - Sticky Bolt

IMHO, pressure is too high on both loadings. The first ones were "most likely" FL sized and bolt thrust was ALOT less. If you neck sized or Partial FL sized for minimal headspace on the "next" ones, you just increased the bolt thrust ALOT, only now the brass flowed into the ejector hole/slot where it hadn't before, the case body gripped the chamber wall and lessened the casehead pressure setting it back into the boltface.

This is where your difficult camming action is coming from, the shearing off of the brass in the ejector hole... hense the shinny "spot" you might see on the case head. The increase in overall bolt lift is "tight headspace" and/or heavy web expansion.... FL sizing will make em all better though. [img]images/icons/wink.gif[/img] Primer pockets will likely suffer if you stay at that load...

Back off the load a couple grains would be my suggestion, psi should come down 3-5k and you should be ok and keep your brass healthy.

Just curious, are you using Retumbo on those?
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Old 06-01-2003, 10:35 AM
dwm dwm is offline
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Re: Need Help - Sticky Bolt

baldeagle713 - Lugs look fine, I did check them.

Brent - The first load used to break in the barrel was 98 Grains of WC872 behind a 162 SST. No problems at all.

The two loads used at second time to the range were: 93.5 GR Retumbo behind a 162 AMAX and 92.5 GR Retumbo behind a 168 Berger VLD.

Fed GM 215 Match primers.

Brass neck thickness is 0.013, reamer spec'd at 0.3135 shoulder and 0.3125 at case mouth. A 0.308 bushing was used to size the case necks.

The cases measured to be a bit less than 2.84 inches after sizing. Didn't need tot trim.

I did bump the shoulders back with the body die. Is this not good enough?

I didn't think I had to FL size them if I used the Redding body die.

Headspace seemed fine as they chambered easily.

Doug
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  #5  
Old 06-01-2003, 02:59 PM
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Re: Need Help - Sticky Bolt

DWM,

If you are using a Redding body die... that is an FL die first off, it just doesn't touch the neck portion. The Bushing neck die will take care of that part. It's cut to the same dims as an FL die is.

You don't by chance have a normal Redding FL die for it too do you?

A side note; With .013" thick necks, it may work perfect without using it's expander ball "now." You can theoretically actually increase RO (runout) just using a body die, a die that does the neck and body at the same time won't allow the neck to move over if one side's weaker than the other, hense Reddings FL bushing die. This is where FL sizing has an advantage over NK sizing. If you monitor the RO numbers before and after doing both, you'll see what I'm babbling on about... because it doesn't have anything to do with your problem here though. [img]images/icons/grin.gif[/img]

I believe what I said before concerning NK sizing holds true, "if" you happen to NK size and "don't" bump the shoulder back.

I forgot that you said you used the body die before loading these up. Assuming the body die is set up correctly for minimal headspace, once you "again" size these hard to extract cases you may find they "still" don't chamber easily. These would be good cases to use to set up your body die for minimal headspace, if you haven't already sized them all again. You may have to actually set the die "lower" than it already is to get them to chamber again, a little "cam over" action is "sometimes" what it takes. I set the die down in 1/16 turn increments until they "all" just chamber perfectly, then lock it down there. Cases usually get noticably harder or impossible to chamber right before they finally go in easily.

It's interesting that you're using Retumbo too. With the 300 Ultra, I had "early" hard extractions with top loads using the stuff myself, that's why I asked. Have you used RL25 before and compared MV on your top loads with each? I found RL25 went to 70k psi on the Oehler without any difficult extractions, Retumbo started showing them significantly at just 63k psi though. I could never reach the top loads recommended for Retumbo, pressure would have been way, way high. I have some more testing coming up with Retumbo though. So far, I have gotten a 220 SMK to an even 3000 fps with RL25 at right about 67k psi with exellent accuracy, Retumbo got me to 2920 at 63k psi where extraction became very difficult, accuracy wasn't there at that load level.

Like S1 suggested, the 210's may give you lower pressure at the same velocity.

If your loads are causing stiff extraction, when they chambered easily in the first place, they just simply need to be reduced.

For some reason Retumbo seems to batter up cases at lower pressures than RL25 does at higher levels... this is what I find very strange and will look into further. I wish more people had strain gages hooked up to their barrels and could help draw some serious conclusions about this powder in several cartridges.
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  #6  
Old 06-01-2003, 07:29 PM
dwm dwm is offline
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Re: Need Help - Sticky Bolt

Brent - So if I just happened to have a Redding F/L bushing die, I could stop using the body die/neck size die combination and do it all at one time with the F/L bushing die?

I have a Redding die that says B/FL R1 on it. Got it in a trade from some bullets. It must be the F/L bushing die you are talking about.

I have at least 5-6 pounds of Retumbo left. Although I do use it in the 25-06 with great success I was wishing it would do the job in the RUM.

Have you used WC872? I have a bunch of that also.

Doug
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  #7  
Old 06-01-2003, 11:08 PM
 
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Re: Need Help - Sticky Bolt



[ 07-11-2003: Message edited by: S1 ]
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