Author Topic: 1 load, 2 groups! (Read 1273 times)

Czech_too · « **on:** July 05, 2010, 12:18:50 PM »

OK, I've been working on developing a load for a MGM 14" Contender barrel using lead. I've got an accurate load using jacketed so this seemed to be a natural progression. What I've run into is what seems to be two distinct groups using the same load, fired on the same day no less. All 10 shots were fired off of bags/rest at a distance of 100 yards at maybe 2 minute intervals max., one is a called flier. I tried to hold the pistol in the same way for each shot and yet I have two groups, 4 shots in one and five in another, roughly an inch apart. I can't say for certain but I believe that the upper group, or at least 3 of those shots, were fired 'first', so this may be a heat issue.
I intend to do a repeat of this load, hopefully later in the week, but in the meantime... On the plus side, there isn't any sign of leading, even after 60 rounds!

Brian, in Ohio

DalesCarpentry · « **Reply #1 on:** July 05, 2010, 01:07:33 PM »

I have seen simular things happen with a rifle with a clean bore and a cold barrel to start. Once the barrel fouls a little and warms up it settels in. I don't think it is so much a heat thing as a clean barrel thing. Dale

Grumulkin · « **Reply #2 on:** July 05, 2010, 01:08:06 PM »

A classic example of inconsistent primer ignition of the powder. When the primer lights the powder well, the bullet goes into one group and when not so well, into the other.

What you might to to improve things:

1. Increase the load.

2. Use a hotter primer.

3. Use a tighter crimp.

Czech_too · « **Reply #3 on:** July 05, 2010, 02:30:54 PM »

Thanks for the replies thus far, any input I can get on this is welcome.
Dale, previous to putting the lead downrange I had fired several jacketed rounds and the barrel hadn't been cleaned since the last time out, last Friday. The jacketed load, which I knew was accurate, was dead on.
Grumulkin, when I first started this I loaded some 30 rounds total with 5 rounds per in .2 grain increments and found what I thought were 3 possibles. Those were the ones I tried again today. An increased load didn't improve the group size, quite the contrary. As to the primer, CCI 450's were used. Being a single shot, there was no crimp applied so that is a possibility.

Thanks

jhalcott · « **Reply #4 on:** July 05, 2010, 06:14:32 PM »

Not knowing what powder you used, I'd guess Grumulkin is correct. Waiting till the barrel COOLS instead of watching the clock MIGHT be another thing to try. I've done both and had similar results once. This IS a classic primer/powder mismatch result. A different powder or primer should help.

saddlebum · « **Reply #5 on:** July 05, 2010, 08:56:07 PM »

Because of the consistency of the groups, it looks just like a problem I had with two scopes that would not hold zero. A Leupold 2-8 and a 3-9 Vari x II. They both would go back and forth and make tight groups, but a few inches apart until they settled in at one point or the other. Sometimes took quite a few rounds to settle in. Never knew which group it would settle in and stay.
I don't want to step on any toes but if is an ignition problem would the groups stay that tight and consistent in two different places?
Some say to tap the scope to get it to settle into an adjustment and stay there. Can't remember if that ever worked for me. If it is throwing shots at random from one group to another it might be the scope.....Just a suggestion.

BTW, nice shooting!!!

Lloyd Smale · « **Reply #6 on:** July 06, 2010, 02:30:54 AM »

if you fired those groups at diffent times in the day the way the sun hits your sights can really effect point of aim that only applys though if your using open sights and not a scope.

wncchester · « **Reply #7 on:** July 06, 2010, 02:47:18 AM »

Two distinct groups in different places like that with no "walking" between them suggests Saddlebum is correct, a loose element in a scope.

Czech_too · « **Reply #8 on:** July 06, 2010, 06:47:33 AM »

What I've opted to try first is using different primers under to same load of powder and see what results I get. Loaded 5 rounds each with CCI 400's, 450's, WWSR and CCI 250's. Hopefully I'll hit the range early tomorrow before the temps. gets to high. Being as the rifle portion of the range is down in a hollow, not much of a breeze hits it and it can get a bit warm/er.

A bit more information on the load - 222 Rem., Lyman #225415 (55gr. FNGC), 6.0gr. of Unique, COL 2.100"
The temp. yesterday when all this took place would have been 82+ degrees. It didn't hit the 90's until later in the day.

I realize that 6gr doesn't take up that much space in that case. Maybe it's position sensitive.
Keep you posted on the results.

necchi · « **Reply #9 on:** July 06, 2010, 08:02:16 AM »

Quote from: Czech_too on July 06, 2010, 06:47:33 AM

I realize that 6gr doesn't take up that much space in that case. Maybe it's position sensitive.

I think you just nailed it.

Why not use a more sutable powder,,,,there are many that will get the case to 85% or better. I don't have alliant data at hand nor 222, but the nosler book for 223 show's data similar to rifle for handgun loads in that catridge.

HL · « **Reply #10 on:** July 06, 2010, 08:45:25 AM »

I think Saddlebum's assessment is the correct one. If it were inconsistent primer ignition along with the powder, you would not see the shots grouping that tight. What would be the probability of two separate groups of bad primer ignition where you just happened to pick the same type primer for the two separate groups out of the same batch of primers.

I don't know if I explained myself that well, but I bet the probability of that being bad primer ignition is rather low. I may go play the lottery tonight.

saddlebum · « **Reply #11 on:** July 06, 2010, 03:17:19 PM »

I can't say for certain but I believe that the upper group, or at least 3 of those shots, were fired 'first', so this may be a heat issue.
Quote:

This statement from the original post debunks the heat theory in my mind. I have never heard of point of impact going down when the barrel warms up. Always up or horizontally or a combination there of when the barrel swells and comes in contact with something like the forearm or whatever the barrel is resting on. I have to wonder how much effect that would have on a stiff 14" barrel on a Contender anyway. In any case heat will not make the bullets jump back and forth from one tight group to another.
When talking about inconsistent ignition because of primers or power volume or crimp you have to keep in mind the word "inconsistent". The only thing inconsistent about that target is that the two tight groups are a couple inches apart. Seems to me that the odds on some component of the cartridge making two beautiful groups like that inches apart instead of scattering bullets like a shotgun pattern, would be astronomical. I think HL has that right. Seems a shame to mess with a load that groups that good.
I would be surprised if it was something other than the scope........But some people say I wake up in a new world every day, so who knows!! Best of luck!!!

huntswithdogs · « **Reply #12 on:** July 07, 2010, 07:54:25 AM »

Did you change the way that your gun was rested? When I had my Encore, I'd get different groups, depending on whether I'd rested it on the forearm or back on the receiver. Just a thought...

HWD

Czech_too · « **Reply #13 on:** July 07, 2010, 08:29:55 AM »

First off, I do appreciate ALL of the suggestions received. With that being said...

I was unable do dublicate the previous 'groups' earlier today.

I fired 10 rounds of the jacketed load, which I knew to be accurate, and was able to place all within an 1 1/2". I then fired the other rounds with different primers. No distinct but separate groups were shown in these rounds. What I did find was that the WSR and the CCI 250 primers showed tighter groups than the CCI 400's & 450's. Those two primers will bear further 'testing'.

Since it would appear that it is not the scope which caused the grouping, could it have been my eye placement in relation to the scope eyepiece? This is a pistol grip, not a buttstock, so it's not like I have a cheek weld. I'm using a Burris Timberline 3x9 with a 3.5-4" eye relief I believe.

saddlebum · « **Reply #14 on:** July 07, 2010, 08:46:49 AM »

I give up! But not because I think I'm wrong, yet.

DANNY-L · « **Reply #15 on:** July 07, 2010, 10:06:53 AM »

With the temp. in the 80s maybe you were picking up the mirage from the barrel through your scope, which made the crosshairs look in the proper place on the target but weren't.

Paladin · « **Reply #16 on:** July 07, 2010, 06:30:21 PM »

are your casing all the same?

Czech_too · « **Reply #17 on:** July 08, 2010, 01:17:44 AM »

Quote from: Paladin on July 07, 2010, 06:30:21 PM

are your casing all the same?

Using R-P brass, previously fired in this barrel only, neck sized, trimmed and all that.
I'm gonna load up some more using the 450's, WSR & 250's and see what results I get with them. I would really like to find out why I got those initial groups though.

PawPaw · « **Reply #18 on:** July 10, 2010, 04:32:33 AM »

Not to jack the thread, but I've been having the same problem with a particular load making two different groups, so I conducted an experiment.

I properly prepped the brass, trimmed, camfered, cleaned, etc.

I loaded the brass with exactly the same weight of powder, with four different bullets, from four manufacturers. (Speer, Hornady, Sierra, and Cast).

Three of the four loads fell into nice tight groups. The fourth one fell into two groups, three inches apart. Just like it had always done.

All I can deduce is that this particular barrel doesn't like that particular bullet. That's okay, because I have other rifles that love that particular bullet. They'll shoot it into MOA all day long. For some reason, this particular barrel won't shoot it. Lesson learned.

frankkj · « **Reply #19 on:** July 10, 2010, 05:43:32 AM »

Now, if I am correct, you are using a rifle scope on a handgun. When I tried this (several times) I noticed that the relative position of the head (eye) behind the scope made a great difference where the gun shot. I also noticed (I think) that if I tilted my head down toward the gun, the shots would be higher than if held erect.

XPHunter seems to have studied shooting rifle scopes on handguns for quite awhile and wrote a darn good article for Hangun Hunter magazine, at least I think it was Handgun Hunter.

Anyhow, I never could get very consistent results shooting like this and went to a handgun scope. Best of luck to you.

Frank

revbc · « **Reply #20 on:** July 31, 2010, 03:58:07 PM »

Brian,

You stated that you have neck sized your brass. I personally have never been successful with neck sizing in a break open rifle. Because of frame stretch you need to bump the shoulder back a little until the frame locks up easily. The gun will not lock consistently in the same place with neck sized cases. I didn't see where you said what round you were shooting (could have missed it) but I assume it is a bottleneck case seeing you are only neck sizing.

This is all my opinion from a little experience.

Bobby

Did miss it.............222 rem. Bump that shoulder back and try it.