Fps difference by +~ .1 grains varget

[Aimsmall55]

My rcbs chargemaster is acting up and it's a big pain in the ass. Anyone got any guesses as to what the velocity effect would be given .1 grain +~ of varget. Shooting 44.5 grains varget 175 smks , lapua brass, rem 9 1/2 lr primers. At 2.825" Gun is a gap crusader .308

 

[Fuzzball]

Re: Fps difference by +~ .1 grains varget

Differences in cases and primers will likely produce greater variations in speed than .1 grain of Vargit.

 

[madd0c]

Re: Fps difference by +~ .1 grains varget

around 20 FPS per .1 gr in the 43-45gr ranges with a GAP Crusader 24" 1-11.5 twist barrel with 175 SMKs FGMM primers

BTW my go to load is 43.4 with the 175s in this rifle. Also, I would check your OAL with a stoney point or something, not to say your lands aren't .025" farther out than mine, they could be, but mine measures EXACTLY 2.800" with 175 SMKs.

Hope that helps
madd0c

 

[Leaddog]

Re: Fps difference by +~ .1 grains varget

Be careful with that load. You are very close to max pressure. I suggest you start working down towards 43.0 grs.

 

[Boomholzer]

Re: Fps difference by +~ .1 grains varget

Recording MV across a load workup the common result is a a plot that can't be related as a continuious curve. There are often spots where a few tenths of charge show very little change in MV (within the accuracy of the Chrono and sufficient samples). Who knows what the change is in your question, I think it's besides the point. Shoot the ammo and you will have real feedback on results per charge tolerance for that load and your application.


I don't charge cases directly from a CM for same reason.

 

[Aimsmall55]

Re: Fps difference by +~ .1 grains varget

There are no signs of op. Gun loves this recipe. I got it from a real good friend of mine who was told by George of GAP that this load would produce the best results the rifle was capable of. Ex. .991" group at 400 yrds off the tailgate of my truck just last week. Key is just don't go over 2.825"

 

[MALLARD]

Re: Fps difference by +~ .1 grains varget

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Fuzzball</div><div class="ubbcode-body">Differences in cases and primers will likely produce greater variations in speed than .1 grain of Vargit. </div></div>

+1 , variations in CC would probably have a bigger effect

 

[tcasexx]

Re: Fps difference by +~ .1 grains varget

put a mcdonalds straw in the end of youre chargemaster see if that helps

 

[turbo54]

Re: Fps difference by +~ .1 grains varget

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Boomholzer</div><div class="ubbcode-body">Recording MV across a load workup the common result is a a plot that can't be related as a continuious curve. There are often spots where a few tenths of charge show very little change in MV (within the accuracy of the Chrono and sufficient samples). Who knows what the change is in your question, I think it's besides the point. Shoot the ammo and you will have real feedback on results per charge tolerance for that load and your application. </div></div>

^^this

 

[turbo54]

Re: Fps difference by +~ .1 grains varget

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Leaddog</div><div class="ubbcode-body">Be careful with that load. You are very close to max pressure. I suggest you start working down towards 43.0 grs. </div></div>

Why should he back off if no over pressure? That charge, while not light, is totally in the ballpark. I run 45.5 varget under the 175. Its stiff, and almost certainly over SAAMI max, but is safe, and the brass is lasting.

 

[MitchAlsup]

Re: Fps difference by +~ .1 grains varget

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Boomholzer</div><div class="ubbcode-body">Recording MV across a load workup the common result is a a plot that can't be related as a continuious curve. There are often spots where a few tenths of charge show very little change in MV (within the accuracy of the Chrono and sufficient samples).</div></div>

And in particular, the Audett ladder chooses the charge weight where the change in velocity per change in charge weight is smallest. This is also related to the OCW node where small changes in charge weight do almost nothing to the MV.

 

[vman]

Re: Fps difference by +~ .1 grains varget

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Leaddog</div><div class="ubbcode-body">Be careful with that load. You are very close to max pressure. I suggest you start working down towards 43.0 grs. </div></div>

I take it you are reading a Sierra reloading manual? Yeh, I would perhaps look at another brand of manual just to see what they have to say.

 

[Aimsmall55]

Re: Fps difference by +~ .1 grains varget

Yeah , but the manuals' publishers also have another thing in mind..... Lawsuit

 

[Bluesop7]

Re: Fps difference by +~ .1 grains varget

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: turbo54</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Leaddog</div><div class="ubbcode-body">Be careful with that load. You are very close to max pressure. I suggest you start working down towards 43.0 grs. </div></div>

Why should he back off if no over pressure? That charge, while not light, is totally in the ballpark. I run 45.5 varget under the 175. Its stiff, and almost certainly over SAAMI max, but is safe, and the brass is lasting. </div></div>


Ditto, also running 45.1gr varget under the 175SMK with no pressure signs (aside from the time that I left a crapload of oil in the barrel after cleaning and didnt patch it out before firing, but thats a different story). My rifle loves it and so do I.

 

[colt933]

Re: Fps difference by +~ .1 grains varget

Brass makes a big difference. 42.8gr in LC Match = 44.0gr in WIN brass - in my experience.

 

[Bacarrat]

Re: Fps difference by +~ .1 grains varget

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Fuzzball</div><div class="ubbcode-body">Differences in cases and primers will likely produce greater variations in speed than .1 grain of Vargit. </div></div>

Don't tell that to the Prometheus guys, their heads will explode.

 

[Fuzzball]

Re: Fps difference by +~ .1 grains varget

"Don't tell that to the Prometheus guys, their heads will explode."

Yeah. It can get amusing, can't it? But, if they're having fun, I won't bother them!

 

[Big Cal]

Re: Fps difference by +~ .1 grains varget

If it works use it if you start to op back down maybe seating out so far helps give more room and doesant compress the powder so much reducing the chance of op I run 45 grains of 2208/varget with win brass and no problems yet

 

[tcasexx]

Re: Fps difference by +~ .1 grains varget

yes it does!!!!

 

[mdmp5]

Re: Fps difference by +~ .1 grains varget

Of note, there is absolutely no possible way that the velocity difference of 0.1 gr can be measured. I have had loads 0.5 gr stiffer actually chrony slower than the lighter load.

 

[madd0c]

Re: Fps difference by +~ .1 grains varget

palmik, I must respectfully disagree. I am talking about multiple 5 and 10 shot groups approximately ~200 rounds of data with a very tight .1 increment ladder in the 43-45gr Varget range I spoke of in my earlier post.

The averages I got were all in the low double (10-15) or single digit SDs with good extreme spreads. I know the weights were as close as I could get for the loads(scale resolution of 0.1 gr). To improve the resolution, each charge was thrown and trickled up to the next tenth then a scoop used to remove a grain or two from the pan until it settled on the desired measurement. This should put me within 0.05 of the target weight at least, so I do not doubt the 20 FPS steps I was seeing.

That of course is for my rifle. I would suspect other factors if a 0.5 gr difference was not enough to show up consistently on a chrony measurement - unless you are talking about magnum chamberings and 80+ grain loads.

Just my observations, not an attack on Palmik.
madd0c

 

[mdmp5]

Re: Fps difference by +~ .1 grains varget

madd0c, if you did indeed see <span style="font-style: italic">repeatable</span> velocity changes with 0.1 gr increments, then I stand corrected for making such a generalized statement. My statement was not based upon insinuation, but on my actual observations of shooting incremental loads in multiple calibers. But still, I am quite surprised, and I cannot help but be a bit skeptic that you are seeing a difference of 200 fps from 1 grain of powder. Can you post some of your chrony data?

 

[Rthur]

Re: Fps difference by +~ .1 grains varget

I would have to agree palmik. From my experience in my rifle over a oehler 35p it takes .3 gr to get a increase of 15-20 fps on average. While there are spots on my ladder test as high as 25 fps at .3 gr this was not the norm. That still would translate into 8.33 fps at .1 gr. That is also assuming that my charge weight was dead nuts. Something I should mention this is at a higher accuracy node for the 130 berger from a 260. These results are from 42.0-46.2 gr of h4350. As a side note 45.6-46.2 shot 1/2 inch verticle at 300 on this test.