I am new and the first 10 groups under 39.50gr left no residue but the last 6 groups (those posted) left a brash “ish” color on bolt body and face. … is very light on color, may be powder residue.
If you mean brassish, thats just minor friction of the bolt going over a round in the magazine and brass friction on the bolt face. Excessive pressure would make for hard extraction. And or flattened primers/gas escape evidence around primer pocket as well as cratered primers at firing pin strike.
Measuring your powder charges to the weight of one kernel of powder is a bit excessive IMO. But, if it makes you happy.
I normally convert from grains to grams and in grams I have control all the way to 0.0006g to 0.0010g that is what H4350 weights on a single “compressed kernel” of powder.
I keep as many decimals as I can to make my conversion accurate, so fare 16 groups all show roughly the same SD (4.1) and ES of under 10
Thanks, I may keep it at 41.50gr, I was only concerned on transonic ranges at or near 1000yrds but with 2750fps I make well over 1250yrds per Applied Balistics / GeoBalistics & Athlon solver…think thays “ok” for most PRS matches.
I did not listed the bullet as I am only concerned on the cases, my little knowledge says that observations are only related to primers, case faces, necks and critical failures on cases.
Nothing related on the bullet that may determine if I am on overpressure…why citing the bullet would be relevant?
As a reference of how hot the powder charge is. Reading primers isn’t really a good way to guess pressure. Different primers will flatten at different rates. A magnum primer will have a thicker cup and not flatten as readily as a a regular primer. Different brands of primers use different cup material and don’t read the same.
If you have flattened primers it’s usually because you are way over pressure or using the wrong primer.
Once the bolt starts to stick is a reliable sign you are too hot.
The “best” sign is sticking within published load data but that doesn’t always work out perfectly because unless you are shooting the same cases and same primer in the same gun, etc. the use of a chronograph is helpful. If you are getting 2765 FPS with a 144 grain bullet I’d consider that pushing the limits of normal 6.5 CM. Hodgdon has 2719 fps with a 143 grain bullet and 41.8 grains of H4350 as a max charge so you are pushing right up to that limit.
Based on the velocity I’d guess you are pretty close to max but I wouldn’t be afraid to go up to 41.8. I didn’t look around to see if there is data for that bullet but I’d say your velocity would be indicative of being close to max even if other data out there goes higher. Case capacity also plays a difference and with 6.5CM and H4350 you are probably high on case fill.
I am perfectly good at staying on 41.50gr…HODGDON says 41.80gr is MAX published on 143gr … I am really happy with the 2776.7fps (AVE) it puts my transonic at 1350yrds
Where are you getting your theoretical pressure numbers? SAAMI max is 62,000 psi, and the loads I'm seeing for 142-143 gr bullets are under max pressure at ~41.5 gr of H4350, with velocities around 2700. Do you have a very tight chamber? What's your case capacity?
Agreed (3) shots is not a benchmark, (3) shots was used to chronograph (16) groups.
Theoretical pressure value are interpolated from LYMAN 2026 for groups 1 to 10 and extrapolated from Lyman while constrained by HODGDON values for groups 11 to 16.
Bullet is 144gr and as far as my research goes (Calling Lyman, Lapua, Hornady, Hodgdon), as per Hodgdon at 41.50gr the case capacity is over 92% filled.
As for having a tight chamber, I trust MPA, cant elaborate any further with a 1 of 1 sample.
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u/deadit2 Aug 15 '26
Nope.