Bullet seating inconsistency

[TKellogg]

I've been reloading for a few years now and have tried all sorts of dies(RCBS, Forster, Hornady, and Redding). With all the different brands and even upgrading to the competition dies I'm still getting a wide variance in the seating depths when measured with a caliper.

Currently I'm trying to get a load worked up for my Tikka T3 Varmint using the Hornady 75gr HP bullet. I'm using a Redding comp seater with either Varget or H4895. I'm getting ok groups but I'd like to make them better.

I'm to the point of trying different seating depths but when I measure the first round(COAL) @ 2.395, then 2.405 then, 2.397 and so on. They are seem to be very inconsistent. Is there something I'm doing, is it a bullet problem or is it a die problem?

 

[coues7]

Re: Bullet seating inconsistency

The first question I'll ask is where are you measuring to? If you are measuring to the tip of the bullet you don't have a shot in hell at getting consistent measurements. If you are measuring to the ogive, then we can talk.

The only time COAL (cartridge over-all length) matters is if you are trying to make sure the loaded cartridge will fit in your mag box or you'll have to single feed.

If you are measuring to the ogive, I'd recommend the Hornady Bullet Comparator or Sinclairs version....they are the same.

 

[Tripwire]

Re: Bullet seating inconsistency

COAL will vary due to manufacturing tolerances and differences in the bullet itself. Measure from a datum point on the ogive and your numbers will clean up. There's more than a few threads here that will tell you this.

Unless you have a very refined skill set measuring with a dial caliper you are going to have inconsistant results due to the inherant misgivings of the design of vernier calipers. Again, there's a few threads here that mention that also.

In practical application to our style shooting here, as it applies to the definition of COAL, the variences you mention are meaningless to all but the most anal retentive OCD sufferers. And yes, that's been well discussed here too.

Hope this helps........

 

[TKellogg]

Re: Bullet seating inconsistency

I'll get one of the above mentioned tools and see what happens. Thanks for the help. I knew there was something I had to be screwing up.

 

[InsidetheStorm]

Re: Bullet seating inconsistency

Another thing that may corrupt your ogive OAL is the wether or not you're using QD die bushings, (Hornady Lock and Load, ect...) I found that using them on my press gave me wildly different measurements, sometimes as much as .003 or more. When I got rid of the bushings, my OAL settled down and now all my cartridges are within .0005.

 

[Jayman_10X]

Re: Bullet seating inconsistency

I would agree - if measuring to tip of bullet vs. to ogive you will experience variations. This is normal. However if you measure to ogive then there is an issue.

Insidethestorm,
Thanks for sharing your experience with the bushing issue. Though unrelated to this post, I am actually experiencing some run out issues with my competition bushings. I have not had time to diagnose the issue further (too busy with work this year), but when I full-length size with my Forester dies I get virtually zero runout. Yet using the same press my competition bushings give about 0.005" to 0.009" runout. Not sure whats going on there.... So much to do so little time.

Jay

 

[wchartz]

Re: Bullet seating inconsistency

I am dealing with a similar issue right now. I do not measure COAL. I measure to a datum line using a custom comparator that my gunsmith made for my rifle using a section of my barrel that was cut off and then reamed with the same chamer reamer. I was getting up to .030" difference in lenghts using that comparator. The difference is much less using the Hornady comparator. I have traced the problem to a varience in the ogive of the bullets. This is strange. The bullets are SMK .308 175's from the same lot. I checked just the bullets in both comparators and found a large variation, up to .052" when using the custom comparator and much less when using the Hornady comparator. I know the reason for this difference. The Hornady comparator seats further up the ogive where a difference in diameter has less effect on the lenght. I am going to make an in depth study of this problem in the next few days and post the results on this forum.

 

[Fuzzball]

Re: Bullet seating inconsistency

Trying all those dies with the same results sorta suggests they aren't causing the problem.

No rifle cares where a bullet tip hangs in space but it will care about the bullet's jump to the rifling. IME, all rifles and well developed loads have a seating 'window' of several thousants OAL in which the specific jump doesn't matter. That window is often as much as 15 thou wide so determing the full range of tolerance and seating in the middle of it makes typical small variations irrelivant.

 

[Jayman_10X]

Re: Bullet seating inconsistency

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: wchartz</div><div class="ubbcode-body">I am dealing with a similar issue right now. I do not measure COAL. I measure to a datum line using a custom comparator that my gunsmith made for my rifle using a section of my barrel that was cut off and then reamed with the same chamer reamer. I was getting up to .030" difference in lenghts using that comparator. The difference is much less using the Hornady comparator. I have traced the problem to a varience in the ogive of the bullets. This is strange. The bullets are SMK .308 175's from the same lot. I checked just the bullets in both comparators and found a large variation, up to .052" when using the custom comparator and much less when using the Hornady comparator. I know the reason for this difference. The Hornady comparator seats further up the ogive where a difference in diameter has less effect on the lenght. I am going to make an in depth study of this problem in the next few days and post the results on this forum. </div></div>

Very interesting. Thanks for passing this information along. I do not own a comparator, but you just educated a lot of shooters here. Looking forward to your test results.