Chrono velocity doesn't match book, what to do?

[adweisbe]

I have been experimenting with Clays and 185 grain bullets in .45. Specifically 185 grain hollow base round nose berries loaded just short enough to fit in the mag. I am starting to find out that this is not a good combination. According to the Hogdgon data I should get 980FPS with a Hornady jacketed SWC and 4.9 grains. I need ~890 to make major. Before the A7 match I chrono'd 5.1 grains and I was getting exactly 890FPS. When the match came I chrono'd 800-850. Initially I thought I had adjusted my powder measure the wrong direction and decreased the charge but that turned out not to be the case.

Does the low velocity indicate that the pressure is low? Is it safe to increase the charge or do I need a heavier bullet or different powder?

I never had trouble making major with titegroup. I spent three weeks working this up trying to get it to make major and ran out of time before the match.

Edited June 9, 2008 by adweisbe

[UW Mitch]

What kind of gun is it? I've had guns with "slow" barrels that required a few tenths of a gain more powder than book to get up to book velocity. I use WST and a 200 grain bullet for 45acp.

~Mitch

[adweisbe]

It's a S&W 1911 with a five inch barrel. I am already .2 grains over max and apparently very far from where I should/need to be so I question whether I should push it further with this combination. If velocity isn't an accurate indication of peak pressure then I will definitely need to switch.

Edited June 9, 2008 by adweisbe

[UW Mitch]

I can't answer your specific question of velocity as an indicator of pressure. How do the primers look? Are they flat? Are they flowing? Or are they just normal looking. I would SUSPECT that one could go some amount over book and still be "safe" but I don't mess with that too often.

If you had no problems making major with Titegroup, why'd you switch?

~Mitch

[Guy Neill]

You have numerous variables that will affect things.

The books list an average velocity either from a test barrel, or from a test gun. Your barrel will be different.

If you don;t have your own chronograph, it's all guesswork.

Different bullets - whether manufacturer or different lots from the same manufacturer will show differences.

Powders have lot to lot variations as well. Canister grades (that we (reloaders) use) are more uniform than non-canister (used by the factories), but there are still variances. Powder in large quantities may also see some settling, showing differences as you work through the keg.

You are seating long, it sounds like. This will reduce pressure - and velocity. Compare your length with the book with the Hodgdon info. You are also using a hollow base - further enlarging the volume - also potentially lowering pressure and velocity.

And so on...

Guy

[revchuck]

In addition to the factors Guy noted, you're working with a significant difference in seating depth and overall length. The SWC is seated to a much shorter overall length, and doesn't have that hollow base, so your load is going to be a much lower pressure one. It might also be that another powder might give you better results.

[Johann the Horrible]

If you have to load over max just to factor(and you should factor at least 165 as chronographs differ) you should possibly look towards another propellant for your gun. The last thing you need is a blown gun and some injuries. It seems that you are shooting Open as a 185gr bullet @ 890 = 164,65PF.

If you are shooting Open you have a compensator and then maybe something fast like Clays is not the best bet in any case.

As I shoot Standard Division I just stick to a 230gr round-nose @ 760FPS for a PF of 174,80. As my bullets normally weigh 232gr I still have a safety net down to 735 FPS.

As a start I would Chrono my loads in another gun. If the velocity stays low you Know it is the propellant. If the velocity suddenly jumps higher you know that you have a "slow" barrel. I am very hesitant to advise a competitor to go over the max load as it normally leads to tears, and sometimes even blood.

[Skywalker]

First: check your handloading book to find out the test barrel lenght and type. It's not unusual to have loads factory tested in longer (manometric) barrels of 7.5" and longer. Try and find this info and compare it to your gun barrel lenght. If the test barrel elnght is longer than your gun one, then you know that with listed loading data you will be getting lower velocities.

Second: check all loading data are exactly what's listed in your literature. C.O.L., bullet weight/profile/type (e.g. 200grs/SWC/Lead), powder charge, primer maker, brass maker. Each of these variables can cause different velocities. E.G. if you load longer than listed, your pressures will be lower (more gas chamber at ignition) and the resulting velocities will be accordingly.

Third: test day temperature, lighting and humidity can play a significant role in measured velocity variations.

Fourth: barrel clean, leaded, fouled usually gives slower readings. Try chronoing your loads always in a clean barrel for consistency sake.

[Joe4d]

your shooting a hollow base bullet, BIG difference in volume, your also long loading for some reason, another big difference in volume, Basic laws of physics, increase volume decrease pressure. I used to run 40 hollow base 155's in my 646 because they were the best speed loading round noses I could find. When I ordered them Berry sent me specific load data including OAL for those bullets. Which by the way work best at higher pressure.

[adweisbe]

A lot of responses here, I will try to address them all.

I can't answer your specific question of velocity as an indicator of pressure. How do the primers look? Are they flat? Are they flowing? Or are they just normal looking. I would SUSPECT that one could go some amount over book and still be "safe" but I don't mess with that too often.

I am loading .45 so there is going to be zero feedback until I am already way over pressure.

If you had no problems making major with Titegroup, why'd you switch?

I bought 8 pounds of Clays to shoot lead/poly bullets. I decided to go exclusively with plated and wanted to start using the Clays and save my Titegroup for 9MM. I think that Clays is not suitable for 9MM with 147 grain bullets.

I'm not shooting open. 890 was just a a reference point for what the bare minimum to make major with 185 grain bullets is. I would actually want an average of 930 to have a buffer for SS division where 165pf is major.

I know that the book is going to be different but I wouldn't expect 150+ fps difference. The test barrel Hogdgon used was five inches, they didn't specify a gun so it was probably in a fixture. I normally ignore the book OAL and instead let bullet profile and magazine dimensions and feeding determine what the OAL will be and that is generally the longest OAL that will fit in the magazine.

I don't work in the dark, I borrow chronos and purchasing my own is first on the list.

Berry sent me specific load data including OAL for those bullets. Which by the way work best at higher pressure.

Sounds like I should email them and ask.

Edited June 10, 2008 by adweisbe

[Carlos]

your shooting a hollow base bullet, BIG difference in volume, your also long loading for some reason, another big difference in volume, Basic laws of physics, increase volume decrease pressure. I used to run 40 hollow base 155's in my 646 because they were the best speed loading round noses I could find. When I ordered them Berry sent me specific load data including OAL for those bullets. Which by the way work best at higher pressure.

It is a REALLY hollow base - guys - these bullets resemble a traditional 12 gauge lead slug or a civil war "minnie ball".

The cavernous hole in the base of this particular bullet REALLY increases the effective case capacity so much so that there is no comparing these to a flat base like a SWC. I would not view the "SWC max load" as bing the same safe max load for the bullet you are actually using here.

[DrShooter]

A buddy used TiteGroup for those open based 185s.

So far, I haven't seen any advantage to the lighter bullets. 230gr+Clays works best for me.