.204 load: too much velocity

[scottyd2506]

I bought a 204 a few months back. Just installed a BC medalist stock, spot (lug area etc) bedded the action, it's a cheapo Savage 12FV 12 twist 26 inch bbl.

my loads are 32 Vmax 27.0 of Benchmark or H4895. gets 2 to 2.5 inch groups

The 40 grain Vmax with 27.7 H4895 or 27.6 of 8208 gets around 3/8 to 2/3 inch at 100 and leaves the muzzle at 3905 fps CCI-Br2 or wolf-223 primers

My 39 Sierra Blitzking with 27.7 H4895, 2.380 oal (0.020 off).CCI BR2's and vel is around 3940 fps (85 temp) last group was 0.195 inch 3 shots 100 yards)

I am running low on H4895 and Br2 primers, so I loaded some 39 sierra with 27.4 IMR XBR 8208, wolf-223 primers, 2.38 oal . Mt goal was to back off on the velocity some, but I got 4040 fps and 4037 fps (87 deg temp) and 3/8 inch groups.
No molly or any coatings used. all loads took 7 yards from muzzle. brass is Norma and Hornady.
no ejector marks, primers flatten some but not extreme, slight cratering, extraction is fairly easy. primer pockets are slightly lose when seating primers sometimes.


What I'm wanting to know: is 4000+ fps too dangerous? I like speed, but 3700 fps is plenty enough for 39-40's in a 204. my loads are BOOK LISTED. my powders I used here are not overly FAST in my other guns that use them (223 and 308).
The Chronograph works fine 115 Berger VLD out of my 26 inch 25-06 at 3170-3200 fps, 168 Berger Hunting hybred at 3180 fps out of my 24 inch 300 WM, glock 357 sig underwood 125 at 1450 fps, friends 22 inch bbl 22-250, 40 grn vmax and 39.2 Varget is 4080 fps.

it shoots good, and hate to change load, but I know nothing is free, so this kind of speed has to be pressure or something, tight neck, chamber. etc
any ideas?

 

[scottyd2506]

Solved. Scales was not zeroed right, it is a RCBS 505 beam scale, but with dust collecting on beam, and adjustment on end was off.
32 grain bullet weighed 31.1 grains etc

my load of 27.4 was actually 28.3 avg using 8208. Learn something new everyday. "Always zero scales" pulled bullets on ALL my all my 204 loads today.

I've been shooting those loads for some time now, just when I decided to chrono the loads it raised a red flag. Chronographs are indeed much more useful than just knowing speed. for drop and velocity variations.

 

[Grumulkin]

So, if I'm reading this correctly, you're decreasing the load because you think the velocity is too high?

You should never use velocity as a measure of pressure. Things like sticky bolt lift, primer cratering, pierced primers and blown primers are direct indicators of pressure; velocity is at best a secondary indicator of pressure.

Did you know:

1. As a load is increased to dangerous levels velocity may go down? In fact, in a worst case scenario, the gun will blow up and the bullet won't go far at all; maybe not even leave the barrel.

2. Did you know that shooting identical loads in supposedly identical rifles can be associated with velocity differences even in the 100 to 200 fps range?

 

[skyfish25]

I have a 24" Howa heavy barrel, mine would stick a case when I got near that charge of 8208. And still wasn't getting your velocity. Again 24" barrel and measured 12' from barrel. That was with 40gr V-max. Your col is long, so your adding case capacity.

Just replaced barrel with 1/10 Shilen, seems tighter than stock. Had to back off a bit more. I put several thousand down the stock barrel, but it lost the ability to shoot the 40gr bullets, it would still hold 32gr bullets okay.

 

[scottyd2506]

You should never use velocity as a measure of pressure.

Why not? The 4040 fps with a 39-40 grain bullet is not normal for a 204 in any bbl length.

I was fairly happy with the loads, getting less than 1/2 moa groups.. But the excessive fps raised a Red flag.. I THOUGHT I had my scale zeroed, but I was off. and zero'ed it with 1/10th grain, leading to a grain over max in a 204/223 sized case.

What I thought was 27.4 of 8208 was 28.3 of 8208. 1 grain over max in most 204/223 cases is another 200 fps

Once I reset my scales. the actual 27.4 grain load of 8208 was 3854 fps..
my next 20 I loaded at 27.3 should get me close to 3825 fps depending on temp. I'm happy with this speed at SAFE pressures.

with the 27.4 grain loads and pulled bullets, I shot a few 3 shot groups of 0.540 inch, 0.520 inch, one 0.375 inch group and a 0.095 inch 3 shot group or sub 1/10th of an inch. last week I shot a 0.19 inch 3 shot group and some 3/8 and 1/2 inch groups.. They are only 3 shot groups, not 5, so I really can't brag.. but It is good for me and poor shooting, bad eye's etc

 

[scottyd2506]

I have a 24" Howa heavy barrel, mine would stick a case when I got near that charge of 8208. And still wasn't getting your velocity. Again 24" barrel and measured 12' from barrel. That was with 40gr V-max. Your col is long, so your adding case capacity.

Just replaced barrel with 1/10 Shilen, seems tighter than stock. Had to back off a bit more. I put several thousand down the stock barrel, but it lost the ability to shoot the 40gr bullets, it would still hold 32gr bullets okay.

Sounds like your going to have a shooter. Mine would shoot the 39's the best, the 40 vmax would shoot around 1/2 to 2/3 inch.. but the 32 vmax was all over the place.. 2-3 inches.. 12 twist? Now that I know I was overloaded and 200 fps faster, I may not be able to stablize the 40 vmax, with less bullet rpm's, and the 32's may shoot. I only got around to testing the 39's, got ready to test the 40's and it started to rain. lol

Yes if I was going to re-barrel, I'd go 1:10 or 1:11 I think a 1:11 is just right for thr 40 vmax. But if your shooting the 204 55 bergers,, better get a 10 twist I would think.