Insufficient Headspace on 300 RUM Reloads 3500 fps

crosshair22

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May 18, 2010
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Seattle, WA
I just finished firing about forty of my reloads and six would not even chamber. The other 37 showed signs of pressure spikes with one round reaching 3508 f.p.s. on an average 85.8 grn. of RL22. I full-length sized all these rounds and was wondering if the pressure spikes are really due to insufficient headspace or the chrono. sitting too close to the muzzle giving erroneous readings. I backed the chrono off about two more feet on the last ten and got more consistent readings but that doesn't explain the rounds that would not chamber. BTW the OAL is less than 3.6"" Can Insufficient headspace cause velocities to reach these levels? I have a headspace gauge on order and should not be full length sizing w/o it but thought the die instructions would be sufficient to set headspace. Any advice would be appreciated.
 

The Mechanic

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Re: Insufficient Headspace on 300 RUM Reloads 3500 fps

STOP WHAT YOUR DOING! Step away from the reloading bench! throw away all the rounds that you have or may have loaded. Start the fuck over. With a reloading book, dial calipers, and a good night of reading in the reloading section sticky's. Dude your gonna kill yourself
 

crosshair22

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May 18, 2010
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Re: Insufficient Headspace on 300 RUM Reloads 3500 fps

Besides the go, no-go, and field gauges, where can I find the SAAMI specs. for my caliber's max. headspace? I agree, the remaining rounds will be torn down but I suspect the muzzle blast probably was a factor in the wild velocity variations in the first twenty rounds fired. I had these results for first twenty rounds using 180 grain Barnes TTSX, RL22 @ 85.8 grains: 3107, 3210, 3217, 3254, 3226, 3191, 3287, 3145, 3243, and 3254. The next six rounds got really wild readings climbing in vel: 3257, 3279, 3284, 3343, 3491, and 3508. The last 10 rounds after moving the chrono. only demonstrated an extreme spread of less than 67 fps. with an average velocity of 3146 fps. So my question remains can insufficient headspace cause the extreme pressure spikes by pushing the case necks thus causing higher neck tension on bullets?
 

The Mechanic

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Re: Insufficient Headspace on 300 RUM Reloads 3500 fps

Only doing this so you don't kill yourself. You need to get a reloading book. No I won't work up loads for you. You need to buy a reloading book.
You are at 59314psi Predicted velocity is 3162fps So some of your data seems correct. Your at a 90% fill with that load so I would suggest going with a different powder. I don't have any experience with the .300 so this is just a little bit of QuickLOAD. You may want to just go over to Neco and pick yourself up this program. It may just keep you in one piece instead of experimenting. http://www.neconos.com/category/Software-2
300RUMbmp.jpg
 

madd0c

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Re: Insufficient Headspace on 300 RUM Reloads 3500 fps

I agree with the advice to get a good reloading manual, but going on the assumption you have one and understand what you are doing, your Load of 85.8 gr of RL22 is under the max load of 90gr.
It is very possible you are getting erroneous readings if the chrony is too close.

Also, are you saying that the rounds wouldn't chamber before you fired them, or the spent cases after. Did you have pressure signs on the case? Flattened primers, hard to lift the bolt?

If the rounds wouldn't chamber before you fired them, then yes stop loading and wait for your headspace gauge.

Going by the Alliant website, they list the max charge of 90gr RL22 with a muzzle velocity of 3100FPS. I don't have a 300RUM, so I can't tell you my velocities.

madd0c
 

The Mechanic

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Re: Insufficient Headspace on 300 RUM Reloads 3500 fps

I am going directly off of QuickLoad 3.5
Cartridge : .300 Rem Ultra Mag
Bullet : .308, 180, Nosler BalTip 39583
Useable Case Capaci: 101.544 grain H2O = 6.593 cm³
Cartridge O.A.L. L6: 3.598 inch = 91.39 mm
Barrel Length : 30.0 inch = 762.0 mm

Predicted Data for Indicated Charges of the Following Powders.
Matching Maximum Pressure: 56854 psi, or 392 MPa
or a maximum loading ratio or filling of 100 %
These calculations refer to your specified settings in QuickLOAD 'Cartridge Dimensions' window.
C A U T I O N : any load listed can result in a powder charge that falls below minimum suggested
loads or exceeds maximum suggested loads as presented in current handloading manuals. Understand
that all of the listed powders can be unsuitable for the given combination of cartridge, bullet
and gun. Actual load order can vary, depending upon lot-to-lot powder and component variations.
USE ONLY FOR COMPARISON !

45 loads produced a Loading Ratio below user-defined minimum of 90%. These powders have been skipped.
Powder type Filling/Loading Ratio Charge Charge Vel. Prop.Burnt P max P muzz B_Time
% Grains Gramm fps % psi psi ms
--------------------------------- -----------------------------------------------------------------
Vihtavuori N570 97.2 96.0 6.22 3220 99.1 56855 11996 1.441 ! Near Maximum !
ADI AR 2218 100.0 99.7 6.46 3198 99.2 53571 12171 1.450
Hodgdon Retumbo 100.0 94.1 6.10 3150 100.0 55359 10340 1.449 ! Near Maximum !
Norma MRP 2 96.3 90.2 5.84 3149 100.0 56855 10624 1.452 ! Near Maximum !
Ramshot Magnum (Big Boy) 91.6 91.8 5.95 3148 100.0 56855 10464 1.438 ! Near Maximum !
PB Clermont PCL 517 92.0 91.9 5.95 3147 100.0 56855 10456 1.438 ! Near Maximum !
IMR 7828 93.3 84.9 5.50 3147 100.0 56855 10401 1.422 ! Near Maximum !
SNPE Vectan SP 12 91.8 91.7 5.94 3146 100.0 56855 10431 1.439 ! Near Maximum !
ADI AP 2214 93.2 90.6 5.87 3134 100.0 56855 10146 1.420 ! Near Maximum !
Hodgdon H1000 98.0 90.8 5.88 3131 100.0 56855 10117 1.420 ! Near Maximum !
Alliant Reloder-25 94.2 87.7 5.68 3127 100.0 56855 9871 1.439 ! Near Maximum !
Winchester WXR 91.8 85.0 5.51 3124 100.0 56855 10239 1.440 ! Near Maximum !
Vihtavuori 24N41 100.0 99.7 6.46 3109 95.1 56075 11111 1.439 ! Near Maximum !
Rottweil R905 90.9 84.4 5.47 3106 100.0 56855 10159 1.436 ! Near Maximum !
Hodgdon H870 100.0 96.7 6.26 3085 99.3 50645 11301 1.526
Hodgdon H4831 92.1 83.8 5.43 3079 99.9 56855 9880 1.426 ! Near Maximum !
Vihtavuori N170 100.0 92.6 6.00 3047 97.9 55524 10335 1.472 ! Near Maximum !
Lovex-D1001 98.1 98.9 6.41 3046 95.7 56855 10297 1.450 ! Near Maximum !
Vihtavuori N160 92.4 82.9 5.37 3034 100.0 56855 9314 1.431 ! Near Maximum !
Vihtavuori N165 92.0 85.2 5.52 3031 100.0 56855 9125 1.446 ! Near Maximum !
Accurate 3100 94.9 84.0 5.45 3019 100.0 56855 9005 1.476 ! Near Maximum !
Hodgdon 50BMG 100.0 95.0 6.16 2928 88.3 46698 10713 1.575
Hodgdon US 869 100.0 99.7 6.46 2927 92.4 46948 10572 1.580
SNPE Vectan SP 13 100.0 95.6 6.20 2873 95.8 43966 10235 1.638
Vihtavuori 20N29 100.0 100.7 6.53 2846 93.3 41990 10468 1.676
PB Clermont PCL 513/520/9520 100.0 95.6 6.20 2813 93.7 41187 10107 1.686
Accurate 8700 100.0 95.8 6.21 2798 94.6 39432 10077 1.700
NC A3502 ,test only 100.0 91.6 5.93 2614 72.2 35577 8872 1.759
TLP A 502(RH) ,test only 100.0 91.6 5.93 2582 75.3 34030 8908 1.800
V1734 7-multiperf ,test only 100.0 91.6 5.93 1861 36.1 18382 4428 2.339
 

bigwheeler

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Oct 18, 2008
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Re: Insufficient Headspace on 300 RUM Reloads 3500 fps

I don't see you posting any signs of a hard bolt lift, flattened primers? A chamber
that is small in diameter will cause pressures to rise a lot faster than a short one.
But it will also stick the rounds and make them hard to extract. You need to post
more details of your die setup, how many times fired the brass is etc.. To close to
the chrono will cause false readings and will frequently blow the screens off your
chrono. So again, where are the pressure signs in your brass? Mic them before and
after firing. Do some reading before you load up your next batch on how to set up
your dies. A headspace gauge has nothing to do with sizing your brass.
 

The Mechanic

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Re: Insufficient Headspace on 300 RUM Reloads 3500 fps

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">consistent readings but that doesn't explain the rounds that would not chamber. </div></div>
Just sayin' it is time to get a book and do some more reading before the next round is loaded.
 

The Mechanic

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Sep 9, 2006
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Re: Insufficient Headspace on 300 RUM Reloads 3500 fps

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: madd0c</div><div class="ubbcode-body">I agree with the advice to get a good reloading manual, but going on the assumption you have one and understand what you are doing, your Load of 85.8 gr of RL22 is under the max load of 90gr.
It is very possible you are getting erroneous readings if the chrony is too close.

Also, are you saying that the rounds wouldn't chamber before you fired them, or the spent cases after. Did you have pressure signs on the case? Flattened primers, hard to lift the bolt?

If the rounds wouldn't chamber before you fired them, then yes stop loading and wait for your headspace gauge.

Going by the Alliant website, they list the max charge of 90gr RL22 with a muzzle velocity of 3100FPS. I don't have a 300RUM, so I can't tell you my velocities.

madd0c</div></div>

Went back and looked at the graph again and you are right mad it shows max pressure at 65K psi but when I plug in 90 grains I am getting 68824 psi and 3288 fps
 

ChrisGarrett

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Feb 2, 2007
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Re: Insufficient Headspace on 300 RUM Reloads 3500 fps

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Crosshair22</div><div class="ubbcode-body">Besides the go, no-go, and field gauges, where can I find the SAAMI specs. for my caliber's max. headspace? I agree, the remaining rounds will be torn down but I suspect the muzzle blast probably was a factor in the wild velocity variations in the first twenty rounds fired. I had these results for first twenty rounds using 180 grain Barnes TTSX, RL22 @ 85.8 grains: 3107, 3210, 3217, 3254, 3226, 3191, 3287, 3145, 3243, and 3254. The next six rounds got really wild readings climbing in vel: 3257, 3279, 3284, 3343, 3491, and 3508. The last 10 rounds after moving the chrono. only demonstrated an extreme spread of less than 67 fps. with an average velocity of 3146 fps. So my question remains can insufficient headspace cause the extreme pressure spikes by pushing the case necks thus causing higher neck tension on bullets? </div></div>

Well, to answer your question about headspace, having too little headspace will not allow you to close your bolt, so there's the issue with the six rounds not chambering. You probalby didn't bump those shoulders back enough when you resized them.

Too much headspace, will cause your cases to stretch and possibly lead to case head separation, sooner rather than later.

You need to buy the set of Hornady/Stoney Point headspace gages and measure a fired case, from your chamber and then bump the shoulder back between .001" and .002". Drop in gages are cut to a random spec and are really only good for quick visual cues.

I don't think headspace is the issue with the whacky readings...more likely your chrono was glitching, or your barrel was heating up, expanding and allowing the bullet to pass through the bore with less friction, and hence at a faster velocity.

Chronos can be 'iffy' devices and much like reloading manuals, they're only a guide, not an absolute.

My Sierra V manual, shows their 175 SMK and 180gr class of bullets, including the 180gr SMK and Reloder 22, at 3200 fps and 89.4 grs (max), but Sierra is 'generally' a conservative manual. This is with a 26" Savage 116 LA rifle.

Throw into this mix, the fact that the Barnes are typically 100% copper bullets with 'driving bands' and all bets are off.

Chris

 

crosshair22

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May 18, 2010
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Seattle, WA
Re: Insufficient Headspace on 300 RUM Reloads 3500 fps

Thank you everyone for your contributions and concerns. I did not see any of the typical signs of overpressure (e.g. flattened primers, extractor marks, flattened lettering on head, etc.) I really think the chrono. readings may have been in error due to it being too close (at ten feet). I do remember getting a couple of error readings with it today and have read this is one symptom of having it too close to muzzle blast. When I repositioned it, the readings matched what my Nosler guide and Barnes book is giving me for this charge. However, I think the headspace is still a safety issue and will definitely wait for the gauges to arrive before proceeding with any new loads after tearing these down.
 

crosshair22

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May 18, 2010
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Seattle, WA
Re: Insufficient Headspace on 300 RUM Reloads 3500 fps

"A headspace gauge has nothing to do with sizing your brass." - Big Wheeler. I disagree from what I have read you want to headspace your chamber from fired brass and bump the shoulder back .001 - .002" using full-length sizing die. This is presuming the fired brass is at zero headspace expanding to your rifle's chamber. Does this sound right or do you another method of resizing like just using a collet die. I tried full-length sizing these new Remington brass w/o the gauges and I won't make that mistake again!
 

bigwheeler

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Oct 18, 2008
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Re: Insufficient Headspace on 300 RUM Reloads 3500

If your brass chambers you neck size. When it won't chamber you bump the shoulder as little as possible to get it to chamber. I take my die down 1/16 turn
at a time until the brass will chamber. I sometimes end up going a tad further as
the brass does work a little smaller after a couple of trips through the die and subsequent cases don't size down as much with one trip through the die. Do this
without the expander ball so you aren't working the crap out of the brass while setting the die.
I don't think you are talking about a go no go headspace gauge. You are
referring to the rcbs headspace gauge. I got interested in them several years
back and from talking to fellow shooters they seemed to be less accurate than
setting our dies as I described above. I have never had a need for them. If they help you then by all means use it to learn if nothing else. Eyes and fingers are worth more than 45.00.