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Joined: 26 Apr 2010 Posts: 3177 Location: NCWa

Under checking for other variables, Do you have access to a different chronograph?

Kennedy,

Did you mean to say 17, 17.5 and 18 grains?

If you are truly loading with only 7, 7.5 and 8 grains of powder, you will most likely not get a sufficient powder burn and pressure to make a usable load.

I'd make double sure my scale is calibrated and load up ten rounds with each different bottle of powder and take notes. Maybe try buying another sleeve of Win primers and shoot more over the chronograph.

I've had a published load with Unique that came back from testing quite a bit higher in pressure and faster velocity from what Alliant shows in their data. I never did nail down the cause of that issue. So I just moved on to other loads.

Lon

Joined: 08 Feb 2009 Posts: 1307 Location: Western WA

What is your crimp? A Hardin crimp or overshot wad can generate spurious chrono data.

oops, yes 17, 17.5 and 18, normal crimp

Joined: 03 Feb 2014 Posts: 325 Location: West Texas

My experience with the Universal 7/8 oz loads was that velocity decreased approximately 50 fps per 0.5 grain reduction, give or take 15-20 fps

I'll be curious to see what you get.

Joined: 15 Dec 2005 Posts: 287 Location: missouri

Member Joined: 16 Nov 2006 Posts: 1338

test results today, average of 2 shots
factory 1225
18 gr 1250
17.5 1225
17 1197

so I am going install a bushing that gives me close from 17 to 17.5gr, load a box and take it to the trap range and see what happens. BTW, the bore was clean, no residue.

Joined: 15 Dec 2005 Posts: 287 Location: missouri

I know that we all have chronographs that are perfect.......but they aren't.

There are a lot of variables here the main one being the chronograph and the fact that you have no way of knowing what the actual velocity is as you arent using ammo with a known velocity to setup the chronograph.

Without some sort of reference ammo everything you are doing is a guess and you are adjusting powder charges. That doesn't make a lot of sense.

Joined: 15 Dec 2005 Posts: 287 Location: missouri

This 10% rule is imaginary.

I have never seen any statement from any powder company claiming any tolerance for their canister powders.

10% is huge, I would like to know the source.

I have to be honest, that I have not seen powders change performance without some change to the data. Steel was changed some years ago, but the data also was changed, as an example.

If your data is correct it means that the loads I just put together and shot with one of the latest lots of Universal powder are now producing close to 1600 FPS. No way is that the case.

However when I get a chance I will reshoot this stuff using Universal for velocity and post the results. I do have the original test sheet from Tom Armbrust and I will post that also.

I will do the same with 700-X.

loaded up a box using 17.4 grs, vel measured 1232 both test shots(factory tested at 1211(1200 on box) and went to the range. I hit less with the 17.4 gr box then with the 18.5 measured at 1338. I think the slower shot made my timing off a little and missed a few more then normal. otherwise it shot good, lighter recoil, clean barrel and did produce some dusted targets.

Joined: 15 Dec 2005 Posts: 287 Location: missouri