105 AMAX+Retumbo... Primers?

[TannerGun]

Alright, I worked up to Hodgdon's max load of 49 grains of Retumbo yesterday out my 243-no pressure, yada yada, it shot OKAY. I'm getting the classic "2 in 1 out" group. I'm also seeing this over charges of H4350.

I HAVE tried seating to Hodgdons recommended COAL (2.76) and it didn't make a difference. Now, I loaded up some with Retumbo over CCI 250s. Do you guys think this will possibly tighten up the groups, ie more consistent ignition? I have read on the OCW website that a mag primer is needed with Retumbo...

 

[rrflyer]

Re: 105 AMAX+Retumbo... Primers?

If your seeing it with two different powders it may be you or another issue.


Have you let someone else shoot it?

 

[TannerGun]

Re: 105 AMAX+Retumbo... Primers?

I've considered that as well. It just seems so strange that so many of the groups look like that. I'll let someone else shoot it- but I do normally shoot pretty decent groups.

 

[MALLARD]

Re: 105 AMAX+Retumbo... Primers?

have you done a seating depth test ?

 

[TannerGun]

Re: 105 AMAX+Retumbo... Primers?

Yep, I've shot H4350 at 2.81 and 2.72... Pretty much the same groups... I know that's not very extensive testing. Thinking it may be a stock issue or primer.

 

[AzDak]

Re: 105 AMAX+Retumbo... Primers?


What rifling twist rate do you have?

Last weekend I took my first two batches of handloads out to the range in a 700/.243 with a factory SPS heavy profile barrel.

I couldn't get the AMAX 105g to shoot. I was using Fed 210M primers, new Winchester brass and H4350. I ran 5 round groups at 39, 39.5 and 40g. Group size shrunk from 2.5" down to 1.5" as it got faster, but 1.5@100 yards just wasn't what I was looking for. I'm going to try another powder before I give up on them.

Have to say though, the 95g Sierra HPBT over R19 was fantastic. I ran 5 round groups, at 39g, 40 and 41g. The 41g put 5 shots into .45". I'm probably going to stick with this load and try to fine tune it a bit further.

I'll just save the 105g until after I shoot out the factory barrel.

 

[TannerGun]

Re: 105 AMAX+Retumbo... Primers?

It's a Rem 9 1/8 twist.

 

[AzDak]

Re: 105 AMAX+Retumbo... Primers?

From all I've read then, we're in the same boat. Luck of the draw on whether you can ever get the 105g to stabilize in that barrel.

 

[TannerGun]

Re: 105 AMAX+Retumbo... Primers?

I'm at a high elevation, so that's in my favor. I've also heard if about 10 guys that do just fine with the AMAX outta this twist, so I'd venture to say they are stabilizing fine.

 

[boudin]

Re: 105 AMAX+Retumbo... Primers?

I have experienced a load (85 gr SGK + IMR 4064) tightening up approximately 1/8" due to a primer switch (Fed 210 GMM to CCI 200). That being said, I doubt that is your issue here.

If you have worked through a range of powder charges and the best you are getting is "2 in 1 out", then I would take the charge that yielded the best spread and do a more precise seating depth test. You're not going to be able to see the pattern of spread attributed to seating depth changes clearly (or at all) looking at two vastly different OAL's, as you have done.

When I test seating depth I adjust in .005" increments. My guess is that you are outside of the node on each end, with regard to seating depth. I'd load up a batch spanning one of two extremes; either starting around .03" off the lands and working your way to them .005" at a time OR starting at SAAMI spec max (2.71") and gradually seating them longer using the same increment. In my experience, you will want to test an OAL range of .03-.04" to find a node.

For what it's worth, my factory Rem. 700 with a 9.125" twist rate tube stacks the 105's up (.5 MOA or better) at two OAL's using Retumbo and CCI 200 primers. One node is at .02" off the lands (2.284 to the ogive) and one node at 2.182 to the ogive (SAAMI spec max OAL of 2.71). From my experience, magnum primers are not necessary. YMMV though. Good luck.

 

[boudin]

Re: 105 AMAX+Retumbo... Primers?

You didn't say anything regarding this, but I just thought I'd mention the importance of what you are shooting off of/ how you are supporting the rifle. The reason I say this is, when I worked up my first load for my .243, I did so shooting from a bulls bag supporting the rifle under the lug area. After hanging around snipershide for a while, I decided to get a bipod to shoot from. I was stoaked to try out the new piece of equipment, but to my surprise, my groups opened up from 1" or less at 200 yds to about 1.5 FEET! I was baffled... but as it turned out, when the rifle was supported out at the end of the forestock, the pressure pad wreaked havoc on the harmonics of the barrel. Bedding the action, floating the barrel, and reinforcing the forestock alleviated all that. No idea whether this is applicable to your situation, but food for thought.

 

[gvanhyning]

Re: 105 AMAX+Retumbo... Primers?

I saw a couple of things in TannerGun's post. In my opinion, the difference in charge weight between shot test strings is from .5 grains to 1 full grain. One full grain is huge when testing charge weight and even at .5 grains it is possible to miss an accuracy node. I'm not an expert but I go .2 to .3 grains between shot strings and it really makes a difference when trying to dial in a charge weight. Next is the random bullet seating depth. I load all my rounds for use in a magazine and always start my test rounds at that length or the cartridge design OAL which usually correlates to the magazine length. Once I have identified what I believe to be the best group from the charge weight testing, I load up another set of test rounds with the bullets seated incrementally deeper for each shot string. I usually have a load dialed in with only two or three trips to the range. Hope this helps.

 

[TannerGun]

Re: 105 AMAX+Retumbo... Primers?

I derived the 2.81 from the max mag length. I know more extensive testing testing is needed with OCW and COAL but I may just take the groups I'm shooting now and start shooting the loads out to longer distance. Im not an incredible group shooter anyways.

 

[TannerGun]

Re: 105 AMAX+Retumbo... Primers?

And I am shooting off a bipod... I may try off a pack or some bags.this is the first bipod I've ever used.

 

[gvanhyning]

Re: 105 AMAX+Retumbo... Primers?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TannerGun</div><div class="ubbcode-body">And I am shooting off a bipod... I may try off a pack or some bags.this is the first bipod I've ever used. </div></div>
I shoot all mine with a bipod and rear bag. If both are used correctly you'll be rock steady and able to manage the recoil.

 

[TannerGun]

Re: 105 AMAX+Retumbo... Primers?

It's very steady, but I do wonder about the pressure it puts on the forearm.

 

[boudin]

Re: 105 AMAX+Retumbo... Primers?

Tanner, there's nothing wrong with shooting off a bipod, in and of itself. That's pretty much all I shoot off of, unless in a deer stand, even in benchrest matches.

A quick and easy way to tell if the bipod is causing the stock to contact the barrel is to get behind the gun while unloaded, load up the bipod, and have someone cradle the barrel with a dollar bill and try sliding it from in front of the stock to the lug. While the dollar bill is not necessarily the ideal amount of space you want surrounding the barrel, it will do the job in terms of telling you whether or not there is contact anywhere in the barrel channel.

If 2.81 is the max mag length, then you can use the same approach I was describing when approaching the lands, but instead use 2.81 as the maximum OAL you are working up to.

Lastly, don't discount the effect <span style="font-style: italic">you</span> can have on the outcome. It's really common for folks to "pitch" one when they get too caught up staring at that bullseye, wanting to shoot a bughole group. Remember: sight alignment - trigger control - follow through. The moment you get hung up staring at the bull or the two shots you just put on paper, you need to back out of the scope, take a breath, and focus on the fundamentals... at any range.

 

[TannerGun]

Re: 105 AMAX+Retumbo... Primers?

Thanks boudin. I think its shooter error taking hold over anything else.