Barrel Question

constructor said:

paulosantos said:

IMHO, the grooves are not as big of a deal as the Chamber. Now, when you combine everything, they all add up and will make a difference in pressure.

So if you have a 1:11"/6-Groove/SPCII Chamber and a 1:11"/4-Groove/SPCII Chamber, the difference in pressure really aren't tha much, but if you have a 1:10"/6-Groove/SPCII and a 1:12"/3-Groove/SPCII Chamber, then you will have a great decrease in pressure. Remember, the 1:10"/6-Groove/SPCII is the MINIMUM specs for a "C" rating. Anything better than that is just gravy.

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There is a complete 50 some odd page report that Tim wrote with all the proof but your opinion contradicts that even though you have done no testing of your own. So we spent 4 years trying to talk manufactures into building the correct configuration and now we are going backwards because you have a 1-10 twist?

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constructor said:

My DMR chamber is only .030 longer than the SAAMI and .020 shorter than the SPCII, it shoots everything fine as long as it is in a 11, 12 or 13 twist barrel and there are no bad chrome problems. I had a WOA 11 twist with a SAAMI chamber that would also shoot combat loads.
It just my opinion that the bad angle at the end of the case was an issue with the Extreme bullets. The SAAMI chamber was an issue with the 115 Hornady and Extreme bullets because they were loaded out and touched the lands, that raised pressure enough to cause problems.
There are 10 twist barrels with SPC II chambers on the market that still cause swipes with combat ammo, we saw that at the first test at Chris's and again with Marine's barrel.
Both the twist and chambers do make a difference as does the rifling design and bore area.
I have tested 10 twist 6 groove SAAMI, 10 Twist 6 groove SPCII, 11 twist 4, 5 and 6 groove, SAAMI, SPCII and DMR. 12 and 13 twist 3 groove DMR and 11.25 twist Lothar polygonal DMR chambered barrels.
The 12 and 13 twist 3 groove and the Lothar 11.25 twist polygonal will allow me to load at least .5 gr more than the Xtreme barrels which have very thin width lands. The 12 and 13 twist 3 groove and the poly will allow me to load at least a grain more than any other barrel I have tested which has been every barrel that has come through the shop. Stag, LMT, WOA, Noveske, Kotonics, DPMS, Model 1 and a Douglas 10 twist custom. That is why I paid particular attention to the bore area when designing the Xtreme and 12 twist 3 groove rifling buttons.
Paulo your opinion is the chamber makes the biggest difference, My opinion is it may if the bullets are jammed into the lands
but the bore area IMO is what makes the biggest difference. Less chrome that takes up area on every surface, less lands as in not as wide or number of or just barrels with bad specs.
IMO Twist does not have as much influence on pressure as it does velocity but the 13 twist 3 groove and the 11.25 twist Lothar poly shows more velocity consistently with the same loads with bullets up to 110gr.
The Barnes and GS Custom bullets with drive bands reduce pressure in every barrel but when loaded to the maximum allowable pressure the 12,13 and 11.25 twist Lothar polys still allow a stiffer charge and give more velocity.
I cannot stuff enough powder in the case to see any signs of pressure.

So if we go by the KISS principle you can shoot a 110gr Vmax from a 16" model 1 safely at apx 2450fps which will give 1000ft lbs(what most consider adequate to take big game) of energy all the way to 200yds.
Or we can shoot the correct configuration barrel/chamber with handloads at 2750fps safely and extend that 1000ft lbs to 350 yds. It is no doubt up to the purchaser but lets don't dumb it down to help them make a bad choice, put the numbers out there so they can really see the difference. The Vmax has the best BC and shows the best range, that is the only reason I used that as an example. I would not use the Vmax to take deer.
Now some people will go strictly by the load data from powder companies and never load past the max OAL. That will severly limit performance, most manuals show out to the right what pressure that load developed in their 10 twist SAAMI chambered test barrel and the pressures are still like 48000 psi. Not much performance there.

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